Tuesday, June 30, 2009
Purpose and Location of the Works
The purpose of the Project is to build Water Treatment Plant based on conventional water treatment technology with the aim to treat raw water from the dam and make it fit for human consumption. The treated water shall be finally supplied to the Mirpur city for use by the residents of the Mirpur City. The project site is located at a distance of 20 Km from the Mirpur City on Mirpur - Kotli Road
Description of the Works
The scope of Contract No LCB/CEM/IT&CM/MP/01 comprises of:
(a) Construction of Civil Works: The civil works shall comprise of two components:
- Intake Structure: comprising Sump & Pump House,
- Water Treatment Plant comprising Reception Tank (1 No), Flash Mixer (1 No), Clarifier Feeding Channel (1 No), Clarifiers Cum Flocculators (2 No), Filter Beds Feeding Channel (1 No), Filtration Plant Building comprising Filter Distribution Channel, Rapid Sand Gravity Filters (8 No), Machine Hall, Pipe Gallery, Filter Control Gallery, Backwash & Service Water Sump, Laboratory & Conference Room, Clear Water Tank (1 No), Chemical House (1 No), Chlorination Building (1 No), Generator Room (1 No), Workshop & Store (1 No), Staff Residences, Development of Parks, Roads Network, Car Parking Shed (1 No) and Barbed wire Fencing.
(b) Providing & laying of Steel Pipes, Galvanized Iron Pipes, High Density Polyethyelene (HDPE) Pipes, Cast Iron Pipes along with specials & accessories which cover Sluice Valves, Butterfly Valves, Check Valves and Electrical Actuators.
(c) Providing & installation of Flash Mixer (1 No), Sludge Scrappers (2 No), Flocculators (2 No), Backwash Pumps (3 No), Service Water Pumps (2 No), Air Blowers (2 No), Compressors (2 No), Hydrophore Tank (1 No), Ultrasonic Flow Meters, Ultrasonic Level Probes, Oriface Flow Meter, Filter Nozzles, Electrical Actuators, chlorinators (3 no), Booster Pumps (3 No), Alum Dosing Pumps (3 No), Lime Dosing Pumps (2 No), Chemical Mixers (3 No), Cranes, Transducers, laboratory equipment, Workshop Equipment and Level Switches etc
(a) Construction of Civil Works: The civil works shall comprise of two components:
- Intake Structure: comprising Sump & Pump House,
- Water Treatment Plant comprising Reception Tank (1 No), Flash Mixer (1 No), Clarifier Feeding Channel (1 No), Clarifiers Cum Flocculators (2 No), Filter Beds Feeding Channel (1 No), Filtration Plant Building comprising Filter Distribution Channel, Rapid Sand Gravity Filters (8 No), Machine Hall, Pipe Gallery, Filter Control Gallery, Backwash & Service Water Sump, Laboratory & Conference Room, Clear Water Tank (1 No), Chemical House (1 No), Chlorination Building (1 No), Generator Room (1 No), Workshop & Store (1 No), Staff Residences, Development of Parks, Roads Network, Car Parking Shed (1 No) and Barbed wire Fencing.
(b) Providing & laying of Steel Pipes, Galvanized Iron Pipes, High Density Polyethyelene (HDPE) Pipes, Cast Iron Pipes along with specials & accessories which cover Sluice Valves, Butterfly Valves, Check Valves and Electrical Actuators.
(c) Providing & installation of Flash Mixer (1 No), Sludge Scrappers (2 No), Flocculators (2 No), Backwash Pumps (3 No), Service Water Pumps (2 No), Air Blowers (2 No), Compressors (2 No), Hydrophore Tank (1 No), Ultrasonic Flow Meters, Ultrasonic Level Probes, Oriface Flow Meter, Filter Nozzles, Electrical Actuators, chlorinators (3 no), Booster Pumps (3 No), Alum Dosing Pumps (3 No), Lime Dosing Pumps (2 No), Chemical Mixers (3 No), Cranes, Transducers, laboratory equipment, Workshop Equipment and Level Switches etc
Mobilization for Construction
The Scope of Works to be done under “Mobilization for Construction of Works” shall consist of the following items:
(a) shipment of Contractor’s Equipment to the Site;
(b) mobilization of Contractor’s personnel and labour at the Site;
(c) provision of camps in compliance with the requirements
(d) provision of such administrative and field offices as the Contractor considers necessary for his organization;
(e) provision of Workshops, warehouses, sheds and storage yards required by the Contractor for the proper and sufficient execution of the Works;
(f) arrangement for supply of water for use in construction, including installation of necessary wells, pumps, pipes, storage tanks, and suitable arrangements for the delivery of water at various points of requirement; and
(g) provision of such roads as may be deemed necessary by the Contractor for the proper execution of the Works.
(a) shipment of Contractor’s Equipment to the Site;
(b) mobilization of Contractor’s personnel and labour at the Site;
(c) provision of camps in compliance with the requirements
(d) provision of such administrative and field offices as the Contractor considers necessary for his organization;
(e) provision of Workshops, warehouses, sheds and storage yards required by the Contractor for the proper and sufficient execution of the Works;
(f) arrangement for supply of water for use in construction, including installation of necessary wells, pumps, pipes, storage tanks, and suitable arrangements for the delivery of water at various points of requirement; and
(g) provision of such roads as may be deemed necessary by the Contractor for the proper execution of the Works.
Duty of Employer
The Employer will be responsible for the design of the Permanent Works and award of other Contracts associated with the Works.
Standards and Codes
Except where otherwise specified plant materials and Workmanship shall comply with the requirements of the relevant British Standards and Codes of Practice (hereinafter referred to as BS or CP) issued by the British Standards Institution, ISO and Amercian Standards. Other authoritative, who ensure an equal or higher quality than the standards and codes specified subject to the Engineer’s prior review and written approval. Differences between the standards specified and the proposed alternative standards must be fully described in writing by the Contractor and submitted to the Engineer at least 28 days prior to the date when the Contractor desires the engineer’s approval. In the event the Engineer determines that such proposed deviations do not ensure equal or higher quality, the Contractor shall comply with the standards specified in the Bid Documents.
All Standards used will be the current version as available on 1st January 2009. A Contractor proposing to use alternative of specified Standards and Codes shall submit the alternative version to the Engineer for approval in accordance with the requirements outlined in the above paragraph.
The Contractor shall obtain at least one copy of each approved standard and reference Work which is referred to in the Specification, and of each other standard which applies to materials which are being supplied to, or Workmanship executed on, the Works. These Standards and Reference Works shall be supplied to the Engineer within 90 days of the Engineer’s Order to commence the Works and will also be available to the Contractor at all reasonable times.
All materials and Workmanship not fully specified herein or covered by an approved standard shall be of such kind as is used in first class Work and suitable to the climate in the Project Area. Where, the requirements of any such standard specification or regulation conflict with the requirements of the specification or any item on the Drawings, then the Contractor should refer to the Engineer for clarification before proceeding with that section of the Works.
All Standards used will be the current version as available on 1st January 2009. A Contractor proposing to use alternative of specified Standards and Codes shall submit the alternative version to the Engineer for approval in accordance with the requirements outlined in the above paragraph.
The Contractor shall obtain at least one copy of each approved standard and reference Work which is referred to in the Specification, and of each other standard which applies to materials which are being supplied to, or Workmanship executed on, the Works. These Standards and Reference Works shall be supplied to the Engineer within 90 days of the Engineer’s Order to commence the Works and will also be available to the Contractor at all reasonable times.
All materials and Workmanship not fully specified herein or covered by an approved standard shall be of such kind as is used in first class Work and suitable to the climate in the Project Area. Where, the requirements of any such standard specification or regulation conflict with the requirements of the specification or any item on the Drawings, then the Contractor should refer to the Engineer for clarification before proceeding with that section of the Works.
Drawings
Drawings which form part of the Contract are included in the Volume of the Contract Documents.
Record Drawings
Within 28 days of the issue of a Certificate of Completion, the Contractor shall provide Record Drawings in black line on transparent film and in AutoCAD format in CD. These Drawings shall include:
(a) General arrangement drawings of the Permanent Works.
(b) Project Components drawings showing equipment installation, piping and pumping machinery shall be drawn to a horizontal scale of 1:1250 or 1:500 and vertical 1:200 or 1:100.
The Title Block shall be that of the Engineer responsible for the supervision.
The Employer will supply one velograph copy of the issued drawings, which the Contractor may use to prepare the Records Drawings.
(a) General arrangement drawings of the Permanent Works.
(b) Project Components drawings showing equipment installation, piping and pumping machinery shall be drawn to a horizontal scale of 1:1250 or 1:500 and vertical 1:200 or 1:100.
The Title Block shall be that of the Engineer responsible for the supervision.
The Employer will supply one velograph copy of the issued drawings, which the Contractor may use to prepare the Records Drawings.
Site Working Hours
The Site shall observe the following Working hours:
Monday to Saturday: 7:30 am to 5:30 pm.
The Contractor shall not increase the Working hours without the prior approval of the Engineer and the Employer.
Monday to Saturday: 7:30 am to 5:30 pm.
The Contractor shall not increase the Working hours without the prior approval of the Engineer and the Employer.
Programme
Before commencing the Works the Contractor shall, in accordance with the relevant clause of the Conditions of Contract, submit to the Engineer for his approval a programme showing the order in which he proposes to carry out the Works. The programme shall be in the form of a bar chart, or any other form as may be agreed by the Engineer, and shall clearly indicate the followings:
(a) The sequence of each activity, the proposed start and completion dates of each activity, the rate of progress and the cumulative quantity or percentage of Work expected to be achieved on each activity by the end of each month.
(b) Dates by which major drawings requiring the Engineer’s approval will be submitted. A period of three weeks shall be allowed from the date of receipt of these drawings for such approval.
(c) The time allocated for Work by others, including those of the Employer and by utility undertakings:
Sufficient space should be provided in the programme for recording the actual progress against the programmed progress for each activity.
The programme shall be submitted with details of the followings:
(i) Work Breakdown Structure (WBS) of Resource and Activities.
(ii) A statement giving the numbers and categories of supervisory and technical staff and skilled and unskilled Workers to be employed on the Works.
(iii) A list and type details of major Constructional Plant (including vehicles), which the Contractor proposes to employ on the Works.
(iv) Details of the Contractor’s methods of Working for all operations.
(v) A statement giving the proposals for location or locations and sizes of base camps, accommodation, offices, Workshops and stores.
(vi) Details of the Contractors programme for submitting catalogues of equipment & machinery along with the date of shipment and installation. The programme must commensurate with the contractor’s construction schedule.
(vii) Details of the programme for the Works from the date of receipt of the Engineer’s order to commence the Works including a complete resource allocation showing the number of units and allotted times for each unit of Constructional Plant, materials and labour allocated to each part of the Works.
(viii) Details of Contractors proposals for Work affecting private property and the dates during which the relevant Work will be undertaken.
The Contractor shall make due allowance in his programme for the provision of any temporary diversions of roads and public inconvenience existing channels which may be necessary.
(a) The sequence of each activity, the proposed start and completion dates of each activity, the rate of progress and the cumulative quantity or percentage of Work expected to be achieved on each activity by the end of each month.
(b) Dates by which major drawings requiring the Engineer’s approval will be submitted. A period of three weeks shall be allowed from the date of receipt of these drawings for such approval.
(c) The time allocated for Work by others, including those of the Employer and by utility undertakings:
Sufficient space should be provided in the programme for recording the actual progress against the programmed progress for each activity.
The programme shall be submitted with details of the followings:
(i) Work Breakdown Structure (WBS) of Resource and Activities.
(ii) A statement giving the numbers and categories of supervisory and technical staff and skilled and unskilled Workers to be employed on the Works.
(iii) A list and type details of major Constructional Plant (including vehicles), which the Contractor proposes to employ on the Works.
(iv) Details of the Contractor’s methods of Working for all operations.
(v) A statement giving the proposals for location or locations and sizes of base camps, accommodation, offices, Workshops and stores.
(vi) Details of the Contractors programme for submitting catalogues of equipment & machinery along with the date of shipment and installation. The programme must commensurate with the contractor’s construction schedule.
(vii) Details of the programme for the Works from the date of receipt of the Engineer’s order to commence the Works including a complete resource allocation showing the number of units and allotted times for each unit of Constructional Plant, materials and labour allocated to each part of the Works.
(viii) Details of Contractors proposals for Work affecting private property and the dates during which the relevant Work will be undertaken.
The Contractor shall make due allowance in his programme for the provision of any temporary diversions of roads and public inconvenience existing channels which may be necessary.
Meetings and Reports
Representatives of the Contractor, approved by the Engineer, shall attend monthly progress meetings on Site or at the offices of the Employer. In addition, approved representatives of the Contractor shall attend further meetings in cases of emergencies or for other reasons when called upon by the Employer.
The Contractor shall submit to the Engineer Daily, Bi-week, Monthly and Quarterly Reports on his progress in the performance of the Contract. The Monthly and Quarterly Reports shall include a copy of the approved programme with the current progress for each activity shown. The Contractor shall provide Monthly and Quarterly Video records of the Works executed during this period.
The Contractor shall submit to the Engineer Daily, Bi-week, Monthly and Quarterly Reports on his progress in the performance of the Contract. The Monthly and Quarterly Reports shall include a copy of the approved programme with the current progress for each activity shown. The Contractor shall provide Monthly and Quarterly Video records of the Works executed during this period.
Temporary Works
Not less than 14 days before commencing any portion of the Works, the Contractor shall if ordered; submit to the Engineer for his approval complete drawings and calculations for all Temporary Works which the Contractor may propose for the construction of that part of the Works.
Notwithstanding approval by the Engineer of any design for the Temporary Works, the Contractor shall be entirely responsible for their efficiency, security and maintenance and for all obligations and risks in regard to such Temporary Works specified or implied in the Contract.
Notwithstanding approval by the Engineer of any design for the Temporary Works, the Contractor shall be entirely responsible for their efficiency, security and maintenance and for all obligations and risks in regard to such Temporary Works specified or implied in the Contract.
Water and Electricity Supply
The Contractor shall make his own arrangements for the supply of water and electricity for the purposes of the Works.
Water and wastewater derived from the construction, testing and completion of the Works shall be disposed of clear of the Site to the satisfaction of the Engineer so as to cause no damage or complaint.
Water and wastewater derived from the construction, testing and completion of the Works shall be disposed of clear of the Site to the satisfaction of the Engineer so as to cause no damage or complaint.
Toilets
Throughout the period of construction of the Works the Contractor shall provide, maintain and cleanse suitable and sufficient toilets and abolition (wazoo) places for use by his employees; he shall ensure that his employees do not foul the Site but make proper use of the latrines.
If practicable these facilities shall be connected to the nearest sewer, or if this is not practicable the Contractor shall provide an adequately sized septic tank and soak away.
If practicable these facilities shall be connected to the nearest sewer, or if this is not practicable the Contractor shall provide an adequately sized septic tank and soak away.
Camps and Accommodation
The Contractor shall construct and maintain a camp to furnished with Mosque provide living accommodation for his staff and operatives. The location of the Contractor’s camp shall be to the Engineer’s approval.
The Contractor shall be responsible for and provide all services to the living quarters and shall see to it that all sanitary laws and other laws and regulations in force in the area are completed with. The Contractor shall be responsible for and provide all necessary fencing and security to these areas.
The Contractor shall be responsible for and provide all services to the living quarters and shall see to it that all sanitary laws and other laws and regulations in force in the area are completed with. The Contractor shall be responsible for and provide all necessary fencing and security to these areas.
Photographs
(i) The Contractor shall supply negatives of color photographs and digital pictures on CDs and uncounted color positive prints not less than 250 x 200 mm of such portions of the Works, in progress and completed, as may be directed by the Engineer and specified herein. The negatives and prints shall not be retouched. The negative of each photograph shall be the property of the Employer and shall be delivered to the Engineer with the color prints. No prints of these negatives shall be supplied to any other person without the written permission of the Engineer.
(ii) If so directed by the Engineer, the Contractor shall supply transparencies and colour prints.
(iii) The photographs shall be of two categories:
(a) Progress Photographs.
(b) Record photographs.
(c) Video Pictures of all major activities and Meetings.
(iv) Both categories of photographs shall be properly referenced to the approval of the Engineer, and on the front and back of each print shall be recorded the date of the photograph, the direction in which the camera was facing, an identifying description of the subject and the reference.
(v) Photographs taken for record purposes as ordered by the Engineer or as specified herein shall be supplied with three prints, having the reverse of one subscribed with the signatures of the Contractor and the Engineer (or their authorized representatives) for the purpose of attestation. If required, the Contractor may at his own expense having an additional print similarly attested for his retention.
(vi) The Contractor shall supply one negative and three prints of each progress photograph and videos each month alongwith each IPC. The submitted IPC will not be entertained without a Monthly Report and Monthly Video Record ordered by the Engineer. He shall supply two additional prints of progress photographs selected by the Engineer for incorporation in albums. He shall supply two sets of albums, mount the prints, and title the prints and albums all to the approval of the Engineer.
(vii) The taking of photographs of the Works by the Contractor for any other purpose whether for use in Pakistan or in AJK shall not be carried out without written approval from the Engineer.
(ii) If so directed by the Engineer, the Contractor shall supply transparencies and colour prints.
(iii) The photographs shall be of two categories:
(a) Progress Photographs.
(b) Record photographs.
(c) Video Pictures of all major activities and Meetings.
(iv) Both categories of photographs shall be properly referenced to the approval of the Engineer, and on the front and back of each print shall be recorded the date of the photograph, the direction in which the camera was facing, an identifying description of the subject and the reference.
(v) Photographs taken for record purposes as ordered by the Engineer or as specified herein shall be supplied with three prints, having the reverse of one subscribed with the signatures of the Contractor and the Engineer (or their authorized representatives) for the purpose of attestation. If required, the Contractor may at his own expense having an additional print similarly attested for his retention.
(vi) The Contractor shall supply one negative and three prints of each progress photograph and videos each month alongwith each IPC. The submitted IPC will not be entertained without a Monthly Report and Monthly Video Record ordered by the Engineer. He shall supply two additional prints of progress photographs selected by the Engineer for incorporation in albums. He shall supply two sets of albums, mount the prints, and title the prints and albums all to the approval of the Engineer.
(vii) The taking of photographs of the Works by the Contractor for any other purpose whether for use in Pakistan or in AJK shall not be carried out without written approval from the Engineer.
Contamination of Water Supplies
Before any person is engaged on Work involving a risk to the purity of potable water supplies or deemed to involve such a risk by the Engineer, he shall be tested to indicate that he is not a carrier of typhoid or other water-borne disease and he shall be informed of the dangers of contamination. The Contractor shall notify the Engineer of any person who has been certified by a doctor as suffering from an illness associated with the looseness of the bowls, and no such person shall be employed on such Work until the employer’s medical advisor is satisfied that it is safe for him to be so employed.
Climatic Data
The Contractor shall take account of the climatic conditions at the Site of the Works both in the design of all plant and equipment, and the construction of the Works.
The following information is provided as a guide to the climatic conditions likely to be encountered on the Site to assist the Contractor in ensuring that the Works are adequate to withstand the effects of the weather, but this shall not relieve him of his responsibility under Clause 11 of the General Conditions of Contract.
(a) Monthly average temperatures:
- Maximum 35 degree C
- Minimum 03 degree C
(b) Extreme Temperatures
- 47 degree C in June
- 2 degree C January
(c) Annual Average Rainfall:
Several times it has been observed that rainfall of 1000 mm did happen, however, 500 mm is Average Annual Rainfall per year and the majority falling in the monsoon months of July and August. On average there are 10 rainy days per year. Storm intensities can be high with storm totals reaching 200 mm with normal durations of 1 to 2 days.
(d) Monthly Average Relative Humidity.
- Maximum = 90%
- Minimum = 40%
The Contractor shall satisfy himself as to the accuracy of the above climatic data, which are based on limited records.
The following information is provided as a guide to the climatic conditions likely to be encountered on the Site to assist the Contractor in ensuring that the Works are adequate to withstand the effects of the weather, but this shall not relieve him of his responsibility under Clause 11 of the General Conditions of Contract.
(a) Monthly average temperatures:
- Maximum 35 degree C
- Minimum 03 degree C
(b) Extreme Temperatures
- 47 degree C in June
- 2 degree C January
(c) Annual Average Rainfall:
Several times it has been observed that rainfall of 1000 mm did happen, however, 500 mm is Average Annual Rainfall per year and the majority falling in the monsoon months of July and August. On average there are 10 rainy days per year. Storm intensities can be high with storm totals reaching 200 mm with normal durations of 1 to 2 days.
(d) Monthly Average Relative Humidity.
- Maximum = 90%
- Minimum = 40%
The Contractor shall satisfy himself as to the accuracy of the above climatic data, which are based on limited records.
Level
The Contractor shall use the benchmarks previously established in the area in connection with the Project. Values of grids and levels have been marked on the benchmarks.
Units of Measurement
All designs, drawings, specifications and manuals shall use FPS units and all measurements dimensions and performance data shall be quoted in those units.
Languages
All drawings, instructions, signs, notices, nameplates, etc for use in the operation and maintenance of the completed Works shall be in English.
Warning signs shall be in Urdu and English.
Warning signs shall be in Urdu and English.
Contract Signboard
The Contractor shall supply and erect one or more Contract signboards at locations to be specified by the Engineer. The signboards shall be of substantial construction to the approval of the Engineer and the lettering in both English and Urdu shall be black on a white background. The layout and dimensions of the signboards shall be in accordance with the relevant Standard Drawing.
Advertising
The Contractor shall not use any part of the Site for any form of advertising without the prior written approval of the Engineer.
Safety Regulations on Site
The Contractor shall comply with all statutory and other regulations concerning the safety and security of his Site staff, operatives, staff of the Employer and Engineer and members of the Public affected as a result of his operations. He shall obtain copies of all the relevant regulations and shall make them available on Site for inspection by the Engineer. The Contractor shall make sure his employees use safety apparatus while working and wear safety glasses, hard hats, hard-toe boots, gloves and belts etc or any other necessary protective gear to be safe from injury or harm.
Protection of Existing Installation
The Contractor shall execute the Works in such a manner as to avoid interruption and interference with the operation of the existing construction activities, to minimize disturbance to those living or occupying properties near the Work and to all existing services within and adjacent to existing facilities. Access to the existing facilities shall be maintained, to the satisfaction of the Engineer at all times.
The Contractor shall apply to the Engineer in writing at least 28 days before starting any Work which involves interference with the existing structures, equipment, etc or otherwise interfere with or interrupt the Employer’s normal construction activities. The Contractor shall not execute such Work until he has received permission to proceed in writing from the Engineer.
The Contractor shall ensure that no earth, debris or rock is deposited on public or private roads or rights of way as a result of the Works and all vehicles leaving the Site shall be cleaned accordingly.
The Contractor shall apply to the Engineer in writing at least 28 days before starting any Work which involves interference with the existing structures, equipment, etc or otherwise interfere with or interrupt the Employer’s normal construction activities. The Contractor shall not execute such Work until he has received permission to proceed in writing from the Engineer.
The Contractor shall ensure that no earth, debris or rock is deposited on public or private roads or rights of way as a result of the Works and all vehicles leaving the Site shall be cleaned accordingly.
Protection of Existing Public and Private Services
The Contractor shall notify all public authorities, utility companies and private owners of proposed Works, which will affect them not less than one week before commending the Works.
The Contractor shall adequately protect, uphold, maintain and prevent damage to all services and shall not interfere with their operation without the prior consent of the public authorities, utility companies, private owners, or the Engineer as appropriate.
If any damage to services results from the execution of the Works, the Contractor shall immediately:
(i) Notify the Engineer and appropriate public authority, utility company or private owner about this occurrence.
(ii) Make arrangements for the damage to be made good without delay to the satisfaction of the public authorities, company or private owner as appropriate. The Contractor shall be liable for all costs for making good such damage.
The Engineer may issue instructions or make other such arrangements as he deems necessary, to repair rapidly and essential services damaged during the execution of the Contract, such arrangement shall not affect any liability to pay for making good the damage, and Contractor shall pay all costs due to this damage.
The Contractor shall adequately protect, uphold, maintain and prevent damage to all services and shall not interfere with their operation without the prior consent of the public authorities, utility companies, private owners, or the Engineer as appropriate.
If any damage to services results from the execution of the Works, the Contractor shall immediately:
(i) Notify the Engineer and appropriate public authority, utility company or private owner about this occurrence.
(ii) Make arrangements for the damage to be made good without delay to the satisfaction of the public authorities, company or private owner as appropriate. The Contractor shall be liable for all costs for making good such damage.
The Engineer may issue instructions or make other such arrangements as he deems necessary, to repair rapidly and essential services damaged during the execution of the Contract, such arrangement shall not affect any liability to pay for making good the damage, and Contractor shall pay all costs due to this damage.
Permits
The Contractor shall be fully responsible for obtaining all necessary permits, Licence and permissions required for the execution of the Works, prior to the commencement of the Works.
Location of the Treatment Units
The location of treatment units comprising the treatment plant, generator room and offices shall be as shown on the drawings.
Notice of Operations
The Contractor shall give full and complete notice of all important operations to the Engineer before starting them and take adequate approval.
Sampling
The Contractor shall provide for the approval of the Engineer samples of all the construction materials and manufactured items required for the Permanent Works, if ordered, all samples rejected by the Engineer shall be removed from the Site. All approved items shall be stored on the Site by the Contractor for the duration of the Contract under conditions which will prevent deterioration of the approved sample. Any material or manufactured item subsequently delivered to the Site for incorporation in the Permanent Works shall be at least equal to the approved sample.
Responsibility for Sampling and Testing
It will be in financial and otherwise the responsibility of the Contractor to collect sampling, testing and the costs thereof under the terms of the Condition of Contract.
Agar Nullah, which flows closely on southern side of the proposed site of this Colony, has much grater perennial flow to meet relatively meagre water demand of this Colony i.e. 65, 000 gallons per day. Incidentally it was a rainy day and water was too turbid on 20-02-2009 when water sample from flow of Agar Nullah was collected, which shows turbidity of 295 PPM Silica Units or N.T. U, refer Chemical Analysis Report of water collected from Agar Nullah at Annexure-III. This turbidity in surface water of Agar Nullah during moderate rains on 20-02-2009 will increase many folds during heavy Monsoon and winter torrential rains requiring a costly water treatment before supply for human consumption. This water source is, therefore, not considered to be suitable and cost-effective.
WATER FROM NATURAL SPRINGS
Water available from this source is relatively of good drinking water quality and cheaper too if such springs exist at higher altitude for conductance of supply through gravity based supply through pipes. Following natural springs were seen in this area which have been considered as water source for C3 Colony.
7.3.2.1 NATURAL bank of Agar Nullah at about 800 ft from its Bridge of Kohala-Muzaffarabad
bank of Agar Nullah at about 800 ft from its Bridge of Kohala-Muzaffarabad Road and just down the Chinese Contractor’s Colony on the outer edge of a katcha track leading to Power House site, refer Plate-V and Figure-II. As per local information this spring has almost perennial flow of 4500 to 5000 gallons per day with small seasonal variations. As seen in the Picture (Plate-V) local residents and even Contractor’s camp have installed pumps for drawing water from this spring for meeting of their drinking water needs. Result of Chemical Water Analysis also declares water from this spring chemically fit for human consumption, refer Annexure-III. This water source is proposed to be used as one of the water source for C3 Colony for which it would be further developed by construction of an appropriate collection chamber (Diggie) with pump house, pumps and rising main for lifting water from this site to the water storage tank on high hill.
NATURAL SPRING-2 NEAR UNDER CONSTRUCTION CABLE TUNNEL
This is natural spring is located on right side of the under construction Cables Outlet Tunnel and its water from it is flowing out of the right front wing stabilized wall of the Cable Outlet Tunnel at about 6 feet height above ground level, refer Plate-VI and VII. Water of the spring is crystal clear and its Chemical Test Report at Annexure-III shows that it is chemically fit w.r.t. WHO Limits for Drinking Water. Discharge of this spring was physically measured during site visit on 21-02-2009 and found to be about .0105 cusecs or 56,700 gallons per day (24 hours). Discharge behaviour of this spring round the wet and dry seasons is, however, not known which should biweekly be monitored by the ARE or his Inspector at C3 to find out its maximum and minimum flow for its final selection as a vitally suitable water source for C3 Colony supplemented by water from sprin-1 discussed above earlier. In case this spring is to be adopted as main water source for C3 Colony care shall be taken while blasting for excavating Cable Outlet Tunnel in its close vicinity to avoid its disturbance, changing its course or closure which happens in case of some natural springs in hilly terrain. For using this spring as main source of water supply to C3 Colony training and collection works, gravity feed line to a low level sump , pump house with pumps and rising mains to the storage tank on high hill shall be planned, designed and constructed to harness this vital water source.
NATURAL SPRING “CHASHMA NOON BAGLA” ON HIGH HILLS NEAR VILLAGE BHANWAN
This system of closely located three natural springs, the bigger one seen in Plate-VIII, called “Chashma Noon Bagla” with total reported discharge of 30,000 to 45,000 gallons per day, is existing in the area of Bhanwan Village on the slopes of high hills on north side of the site of C3 Colony. Water from these springs has already been harnessed by construction of collection chambers (Diggies) and a GI pies gravity based distribution system has been provided by the Local Government & Rural Development Department of AJ&K, for supply of water to the scattered population on down hill slopes. Sufficient quantity of spring water was seen flowing waste during visit to this spring on 21-02-2009, refer Plate-VIII, which can also be tapped and conducted by gravity flow based GI pipe line of appropriate size into the proposed storage tank for C3 Colony on a much low elevation to be used as supplementary emergency supply during acute dry season of low yield from sprongs-1 & 2 discussed earlier.
NATURAL SPRING “CHASHMA NOON BAGLA” ON HIGH HILLS NEAR VILLAGE BHANWAN
Plate-9 Natural Spring called “Chashma Noon Bagla” in the area of village Bhanwan on the slopes of high hills in north of the site of C3 Colony with 30,000 to 45,000 gallons per day yield. GI Pipe of an upper spring bringing water to the main collection chamber (Diggie) is seen entering form right upper corner in the picture.
Plate-10: Another view of natural Spring “Chashma Noon Bagla” in the area of village Bhanwan on the slopes of high hill in north of the site of C3 Colony. Sufficient quantity of spring water is seen flowing waste. Mr. Mukhtar Ahmad, Inspector NJC, who accompanied during visit to this spring, is seen enjoying a nice drink of clean natural mineral water.
Plate-10: Another view of natural Spring “Chashma Noon Bagla” in the area of village Bhanwan on the slopes of high hill in north of the site of C3 Colony. Sufficient quantity of spring water is seen flowing waste. Mr. Mukhtar Ahmad, Inspector NJC, who accompanied during visit to this spring, is seen enjoying a nice drink of clean natural mineral water.
WATER QUALITY AND TREATMENT NEEDED
In view of the above discusse d report about suitability and cost-effectiveness of water source based on natural springs namely Sprin-1. Spring-2 and spring “Chashma Noon Bagla” in village Bhanwan, water being free of turbidity and fit chemically within WHO Permissible Limits for Drinking Water, no mechanical treatment is required. However, disinfection of water to remove bacterial contamination in water with chlorination by calcium or sodium hypochlorite agents is recommended which is also more suitable, easily handle able and non-hazardous and as such preferable for this small scheme.
WATER STORAGE AND DISTRIBUTION SYSTEM FOR C3 COLONY
Normally stock storage of 1/4th to 1/6th of the total maximum day demand is provided for rural water supply scheme. For C3 Colony it is, however, proposed to provide stock storage equal to one day maximum demand i.e. 100,000 gallons due to remoteness of water source and pumping system involved, in order to meet emergency during infrastructure and electricity break downs etc.
PROPOSED SEWERAGE SYSTEM, SEWAGE TREATMENT AND ULTIMATE DISPOSAL
As per design criteria adopted in AJ&K and Punjab Province in Pakistan 80% of the water supplied is taken as sewage generated from households and other consumers. Therefore, 20% of the maximum day water demand i.e. 65,000 gpd, give rise to 52,000
gpd of sewage flow from the entire area of C3 Colony. An appropriate external sewerage system comprising of RCC sewers of 9” diameter (min) and above as per hydraulic design with 2.0 to 2.5 ft/second minimum self-cleansing velocity of flow will be designed and provided with allied appurtenance for trouble free service, operation and maintenance. Sewage will be given anaerobic treatment through community septic tanks of appropriate size before ultimate disposal in to Agar Nullah flowing along southern side of C3 Colony across approach road going to the Power House site. The effluent coming out of septic tanks shall be afforded with further bacterial treatment by natural process of meeting the BOD and dilution of the organic and biodegradable residual load with the rapids generated in water flows due to steep bed slope of Agar Nullah and ultimately in the River Jhelum.
gpd of sewage flow from the entire area of C3 Colony. An appropriate external sewerage system comprising of RCC sewers of 9” diameter (min) and above as per hydraulic design with 2.0 to 2.5 ft/second minimum self-cleansing velocity of flow will be designed and provided with allied appurtenance for trouble free service, operation and maintenance. Sewage will be given anaerobic treatment through community septic tanks of appropriate size before ultimate disposal in to Agar Nullah flowing along southern side of C3 Colony across approach road going to the Power House site. The effluent coming out of septic tanks shall be afforded with further bacterial treatment by natural process of meeting the BOD and dilution of the organic and biodegradable residual load with the rapids generated in water flows due to steep bed slope of Agar Nullah and ultimately in the River Jhelum.
PROPOSED SURFACE AND HILL WASH STORM DRAINAGE SYSTEM AND UTIMATE DISPOSAL.
Collect of storm water from the area of the C1 Colony and hill wash coming down from the hills of northern side of the C3 Colony shall be intercepted by RCC surface drains along the internal roads and at the toe of the hills and disposed off in to the near by Agar Nullah. Proper protection works will be provided for the safety of the storm water collection, drainage and outfall structures. Quantum of rainwater and storm water generated and to be tackled shall be worked out by Rational Method of quantification of storm water runoff based on the maximum intensity of rain fall.
EXTERNAL ELECTRIFICATION OF C1 AND C3 COLONIES
The Consultant will plan and design external eclectic distribution system including external lighting system and requirements of watch & ward and for all the planned houses and the community buildings i.e. mosque, schools and dispensary, in the form of above ground system, complete with transformers, related installations and control switch gear according to agreed load of each house and group of houses/building blocks.. As agreed during Briefing Meetings on 27-10-2008, the Client shall make available the high tension (HT) power supply at the site for each Colony at a suitably located point for stepping down of supply and distribution to the houses and community buildings.
CONCLUSIONS AND FURTHER RECOMMENDED ACTIONS BY THE NJC.
Based on the reconnaissance and information & data collected during the visit and meetings with the field staff of NJC by the Subject Socialists of ACE (Pvt) Ltd from 18 to 21-02-2009 and discussed in detail in this report following conclusions and further actions are recommended to be taken by the NJC for detailed planning and design of the requisite external services including water supply, sewerage, storm drainage and electrification for both the C1 and C3 Residential Colonies: -
I) NJC may approve the design criteria i.e. occupancy, water demand, sewage flow, stock storage etc. and concept design proposed in this report for detailed planning and design of the external services
II) Layouts of both the Colonies be finalized keeping in view the observation listed above and particularly for C3 Colony when most of the area is occupied by the Contractor’s Camp. Consideration may also be given to opinion of the Project Director WAPDA, Neelum Jhelum Hydro-Electric Project, according to whom WAPDA may consider retaining the housing facilities constructed by the Contractor even after completion of the Project.
III) NJC should conduct survey and provide data and survey plan of the proposed small dam to be constructed on Nausadda Nullah for generating domestic water supply source. This information will also require route survey and data for planning and design of gravity transmission main for conducting surface water from the storage of the proposed small dam to the elevated ground storage tank (EGST) proposed to be constructed on higher elevation of the hillocks on southern side of the site for C1 Colony.
IV) WAPDA, the Client and NJC may study and accord approval or suggest amendments, as the case may be, for the Design Criteria for calculation the occupancy, average, maximum day and peak demands of water supply and stock storage for water supply as proposed, and the concept planning and design worked out and discussed at Para 5 above in this Report. Similarly, limit of generation of sewage @ 80% of the water supplied and its anaerobic treatment through community septic tanks before final disposal in the nearest natural water bodies as discussed for both Colonies at Para 6.4 and 7.3.3 above be reviewed and approval thereof accorded.
Subsequent visits of the Subject Specialist of ACE (Pvt) Ltd. shall be required for study of sites for detailed planning and design.
I) NJC may approve the design criteria i.e. occupancy, water demand, sewage flow, stock storage etc. and concept design proposed in this report for detailed planning and design of the external services
II) Layouts of both the Colonies be finalized keeping in view the observation listed above and particularly for C3 Colony when most of the area is occupied by the Contractor’s Camp. Consideration may also be given to opinion of the Project Director WAPDA, Neelum Jhelum Hydro-Electric Project, according to whom WAPDA may consider retaining the housing facilities constructed by the Contractor even after completion of the Project.
III) NJC should conduct survey and provide data and survey plan of the proposed small dam to be constructed on Nausadda Nullah for generating domestic water supply source. This information will also require route survey and data for planning and design of gravity transmission main for conducting surface water from the storage of the proposed small dam to the elevated ground storage tank (EGST) proposed to be constructed on higher elevation of the hillocks on southern side of the site for C1 Colony.
IV) WAPDA, the Client and NJC may study and accord approval or suggest amendments, as the case may be, for the Design Criteria for calculation the occupancy, average, maximum day and peak demands of water supply and stock storage for water supply as proposed, and the concept planning and design worked out and discussed at Para 5 above in this Report. Similarly, limit of generation of sewage @ 80% of the water supplied and its anaerobic treatment through community septic tanks before final disposal in the nearest natural water bodies as discussed for both Colonies at Para 6.4 and 7.3.3 above be reviewed and approval thereof accorded.
Subsequent visits of the Subject Specialist of ACE (Pvt) Ltd. shall be required for study of sites for detailed planning and design.
GENERAL INTRODUCTION
GENERAL INTRODUCTION
1.1. NEELUM JHELUM HYDRO-ELECTRIC POWER PROJECT
Neelum Jhelum Hydro-Electric Project is already under constructed in the vicinity of Muzaffarabad, AJ&K, with its feeding tunnel starting from Neelum River near village Nauseri at about 41 km east of Muzaffarabad to Power Station on right bank of Agar Nullah on north of Chattar Kalas village along Murree-Kohala-Muzaffarabad Road. The Tail Race Tunnel downstream of the underground Power House shall terminate and fall into River Jhelum near Zaminabad upstream of Kohala.
1.1. NEELUM JHELUM HYDRO-ELECTRIC POWER PROJECT
Neelum Jhelum Hydro-Electric Project is already under constructed in the vicinity of Muzaffarabad, AJ&K, with its feeding tunnel starting from Neelum River near village Nauseri at about 41 km east of Muzaffarabad to Power Station on right bank of Agar Nullah on north of Chattar Kalas village along Murree-Kohala-Muzaffarabad Road. The Tail Race Tunnel downstream of the underground Power House shall terminate and fall into River Jhelum near Zaminabad upstream of Kohala.
Friday, June 19, 2009
2.11 Filter Inlet / Backwashing & Drainage Arrangement
The central channel that divides each filter bed in to two parts shall serve as an inlet channel for the clarified water for filtration as well as Backwash channel for discharging backwash water out of the filter bed. Since the volume of backwash water (14.0 Cusecs) is much higher than incoming water (3.0 cusecs), therefore the channel shall be designed for backwash water.
Backwash Flow Rate (q) = 14 Cusecs
(Sum of the Flow Rate of 2 No Backwash Pumps)
No of Troughs for each filter = 1 No
Width of Channel (b) Assumed = 2.0 Ft
Depth of water in the Channel (y) = 1.73 (Q2 / g x b2)1/3
= 1.73 (14.02 / 32.2 x 22)1/3
= 2.0 Ft
Free board = 0.5 Ft
Depth of Washwater Channel at the Upper End = 2.5 Ft
Velocity in the Channel when Flat (v) = 14 / 2 x 2
= 3.5 Ft / s
Find the slope of the Channel using Manning Formula
Roughness Coefficient (n) = 0.013
Hydraulic Radius (R) = 2 x 2 / (2 x 2 + 2)
= 0.67
Slope = (n x v / 1.486 r2/3)2
= (0.013 x 3.5 / 1.486 x 0.672/3)2
= 0.00160 Ft / Ft
= 2 Ft / 1000 Ft (Say)
Length of Filter Bed = 31.0 Ft
Max Possible Friction Losses = 31.0 x 2/1000
= 0.062 Ft
Depth of Wash Water Channel at the lower end = 0.062 + 2.50
= 2.562 Ft
= 2’-7” (2.58’)
2.11.2 Design of Backwash Water Drainage Channels
Backwash Flow Rate (q) = 14 Cusecs
(Sum of the Flow Rate of 2 No Backwash Pumps)
No of Troughs for each filter = 1 No
Width of Channel (b) Assumed = 2.0 Ft
Depth of water in the Channel (y) = 1.73 (Q2 / g x b2)1/3
= 1.73 (14.02 / 32.2 x 22)1/3
= 2.0 Ft
Free board = 0.5 Ft
Depth of Washwater Channel at the Upper End = 2.5 Ft
Velocity in the Channel when Flat (v) = 14 / 2 x 2
= 3.5 Ft / s
Find the slope of the Channel using Manning Formula
Roughness Coefficient (n) = 0.013
Hydraulic Radius (R) = 2 x 2 / (2 x 2 + 2)
= 0.67
Slope = (n x v / 1.486 r2/3)2
= (0.013 x 3.5 / 1.486 x 0.672/3)2
= 0.00160 Ft / Ft
= 2 Ft / 1000 Ft (Say)
Length of Filter Bed = 31.0 Ft
Max Possible Friction Losses = 31.0 x 2/1000
= 0.062 Ft
Depth of Wash Water Channel at the lower end = 0.062 + 2.50
= 2.562 Ft
= 2’-7” (2.58’)
2.11.2 Design of Backwash Water Drainage Channels
2.10.5 Design of Air Scour Pumps & Pipes
Air Scour Rate = 55 M3/M2/H
= 180.36 Ft3 /Ft2/Hr
Area of each Filter Bed = 607.60 Sft
Air Flow Rate = 180.36 x 607.60
= 109587 Cft / Hr
Say = 3200 M3/H
= 53.33 M3 / Min
Provide 2 No Air Blowers (1 operational /1 standby) each having capacity 3200 M3/H @ 650 mbar
Design of Air Flow Pipe
Dia of Air Flow Pipe = 8” (0.20 M)
X- Sectional Area of the Aeration Pipe = 0.350 Sft (0.0325 M2)
Velocity through the Air Flow Pipe = 109587 / 60 x 0.350
= 5218.42 Ft / Min
= 1591.0 M /Min
= 180.36 Ft3 /Ft2/Hr
Area of each Filter Bed = 607.60 Sft
Air Flow Rate = 180.36 x 607.60
= 109587 Cft / Hr
Say = 3200 M3/H
= 53.33 M3 / Min
Provide 2 No Air Blowers (1 operational /1 standby) each having capacity 3200 M3/H @ 650 mbar
Design of Air Flow Pipe
Dia of Air Flow Pipe = 8” (0.20 M)
X- Sectional Area of the Aeration Pipe = 0.350 Sft (0.0325 M2)
Velocity through the Air Flow Pipe = 109587 / 60 x 0.350
= 5218.42 Ft / Min
= 1591.0 M /Min
2.10.4 Capacity of Backwash & Service Water Sump
Backwash & Service Water Sump shall be provided in the Machine Hall. Sump shall be fed from the Filtered Water Channels flowing below the floor of the Pipe Gallery and carrying water from the Filtered Water Outlet Pipes to the Sump. Storage in the Backwash Sump is achieved by building an Over flow weir at the end of the Sump. The level of the weir is so adjusted that the required volume of water for backwashing is always available in the Sump and the surplus water overflows the Weir and goes to the Clear Water Tank through a pipe.
According to Surface Water Treatment for Communities in Developing Countries by Christopher R. Shulz & Daniel A. Okun (1984, P - 161), Wash Water Tank should have sufficient capacity to wash at least two filters for at least 10 minutes at the maximum backwashing flow rate without refilling.
Water required for backwashing of one Filter (From 14.1 above) = 14 Cusecs
Time required for backwashing of one Filter = 10 Minutes
Storage of Backwash Water Sump = 2 x 14 x 60 x 10
= 16800 Cft
Length of the Sump = 54.33 Ft
Width of the Sump = 40.33 Ft
Depth of water to ensure required storage = 16800 / 54.33 x 40.33
= 7.66 Ft
Depth of water below the suction pipe of Backwash Pumps = 2 Ft
Free Board = 2 Ft
Total Depth of Wash Water Sump (7.66 + 2’ + 2’) = 11.67 Ft
Height of Overflow Weir above the floor of the Sump = 9.66 Ft
According to Surface Water Treatment for Communities in Developing Countries by Christopher R. Shulz & Daniel A. Okun (1984, P - 161), Wash Water Tank should have sufficient capacity to wash at least two filters for at least 10 minutes at the maximum backwashing flow rate without refilling.
Water required for backwashing of one Filter (From 14.1 above) = 14 Cusecs
Time required for backwashing of one Filter = 10 Minutes
Storage of Backwash Water Sump = 2 x 14 x 60 x 10
= 16800 Cft
Length of the Sump = 54.33 Ft
Width of the Sump = 40.33 Ft
Depth of water to ensure required storage = 16800 / 54.33 x 40.33
= 7.66 Ft
Depth of water below the suction pipe of Backwash Pumps = 2 Ft
Free Board = 2 Ft
Total Depth of Wash Water Sump (7.66 + 2’ + 2’) = 11.67 Ft
Height of Overflow Weir above the floor of the Sump = 9.66 Ft
Head Loss In Backwashing
During the backwashing process filter media undergoes expansion due to the heavy pressure of the air wash and water wash pumps. Therefore, head lost in the backwashing is the sum of the head loss in the expanded bed, under drains (nozzles) and in the pipes, valves and rate controller.
The equation of head loss in the backwashing process is written as:
H = hf + hu + hp
Where:
hf = Head loss in the expanded bed
hu = Head loss in the under drains (nozzles)
hp = Head loss in the pipe, valves & rate controllers
Head Loss in the Expanded Bed
During the backwashing process, 50 % expansion of the bed takes place as a result porosity of the unexpanded sand bed which is 0.42 increases. The porosity of the expanded bed is worked out from the following relation given Water Treatment Principles & Design by MWH (P -896)
Le/L = 1-e / 1-ee
Where:
Le = Depth of expanded bed
e = Porosity of the unexpanded bed (0.42)
ee = Porosity of the expanded bed
Since provision for 50 % bed expansion has been made, therefore
Le = 1.5 L
1.5 = 1 - 0.42 / 1 - ee
ee = 0.613
Head loss in the expanded bed is given by the following expression:
hf = Le (1 - ee)( Ss - 1)
Le = Depth of expanded bed (1.5 x 4.5 Ft)
P = Porosity of the unexpanded bed (0.42)
Ss = Specific Gravity of the Filtering Media (2.65)
hf = 1.5 x 4.5 (2.65 - 1.0) (1.0 - 0.613)
= 4.3 Ft
Head Loss in the Under Drains (Nozzles)
Head loss in the under drains (nozzles) and is given by the following expression:
hu = (Vb / αβ)2 x 1/2g
Vb = Backwash velocity
α = Orifice Coefficient (0.61)
β = Ratio of the orifice to bed area (normally 0.2 to 0.7 percent)
Area of Orifice = 0.2
g = Acceleration due to gravity
Kawamura (2000) P - 237 has given a head loss range of 4 - 7 Ft for filter nozzles placed 6 - 8 inches apart having orifice size of 0.25 to 0.75 mm.
Therefore, instead of going for detailed calculations upper limit i.e 7.0 Ft given above has been selected as the head loss through nozzles.
Hudson (1981) has reported 1.0 m (3.25 Ft) headloss in the filter under drains (Nozzles) for a backwashing rate of 36 m/h.
Head Loss in Pipe, Valves & Rate Controller
Head loss in the pipe, valves and controller is given by the following expression:
hp = f l/ 2gd x ( 4 Qb/ л d2)2
f = Friction factor (0.01)
l = Equivalent pipe length
d = Pipe diameter (1.5’)
Qb = Backwash flow rate (14 Cusecs)
Calculations of equivalent length of pipe is worked out from the following expression (Ref Wastewater Treatment by Syed R. Qasim:
L = 55.4 C D1.2
L = Equivalent length of pipe fittings for pipe diameter D
C = Factor for equivalent length of pipe
Equivalent length is calculated in the following table:
Fittings
No of Fittings
C value for equivalent pipe length
Equivalent Length
Gate Valve
2
0.25
45.0
Bends
5
0.33
150.0
Tee
1
1.33
120.0
Non Return Valve
1
0.90
81
Length of Pipe
120
Total
516.0 ~ 520
hp = 0.01 x 520 x ( 4 x 14/ 3.14 (1.5)2)2/ 2 x 32.2 x 1.5
= 4.50 Ft
Total Headloss = 4.3 + 7.0 + 4.5
= 15.8 Ft
Delivery Head ( 1034.75 - 1021.5) = 13.25 Ft
Suction Lift = 2.5 Ft
Drawdown = 3 Ft
Total Headloss = 15.8 Ft
Total Head = 34.55 Ft
The equation of head loss in the backwashing process is written as:
H = hf + hu + hp
Where:
hf = Head loss in the expanded bed
hu = Head loss in the under drains (nozzles)
hp = Head loss in the pipe, valves & rate controllers
Head Loss in the Expanded Bed
During the backwashing process, 50 % expansion of the bed takes place as a result porosity of the unexpanded sand bed which is 0.42 increases. The porosity of the expanded bed is worked out from the following relation given Water Treatment Principles & Design by MWH (P -896)
Le/L = 1-e / 1-ee
Where:
Le = Depth of expanded bed
e = Porosity of the unexpanded bed (0.42)
ee = Porosity of the expanded bed
Since provision for 50 % bed expansion has been made, therefore
Le = 1.5 L
1.5 = 1 - 0.42 / 1 - ee
ee = 0.613
Head loss in the expanded bed is given by the following expression:
hf = Le (1 - ee)( Ss - 1)
Le = Depth of expanded bed (1.5 x 4.5 Ft)
P = Porosity of the unexpanded bed (0.42)
Ss = Specific Gravity of the Filtering Media (2.65)
hf = 1.5 x 4.5 (2.65 - 1.0) (1.0 - 0.613)
= 4.3 Ft
Head Loss in the Under Drains (Nozzles)
Head loss in the under drains (nozzles) and is given by the following expression:
hu = (Vb / αβ)2 x 1/2g
Vb = Backwash velocity
α = Orifice Coefficient (0.61)
β = Ratio of the orifice to bed area (normally 0.2 to 0.7 percent)
Area of Orifice = 0.2
g = Acceleration due to gravity
Kawamura (2000) P - 237 has given a head loss range of 4 - 7 Ft for filter nozzles placed 6 - 8 inches apart having orifice size of 0.25 to 0.75 mm.
Therefore, instead of going for detailed calculations upper limit i.e 7.0 Ft given above has been selected as the head loss through nozzles.
Hudson (1981) has reported 1.0 m (3.25 Ft) headloss in the filter under drains (Nozzles) for a backwashing rate of 36 m/h.
Head Loss in Pipe, Valves & Rate Controller
Head loss in the pipe, valves and controller is given by the following expression:
hp = f l/ 2gd x ( 4 Qb/ л d2)2
f = Friction factor (0.01)
l = Equivalent pipe length
d = Pipe diameter (1.5’)
Qb = Backwash flow rate (14 Cusecs)
Calculations of equivalent length of pipe is worked out from the following expression (Ref Wastewater Treatment by Syed R. Qasim:
L = 55.4 C D1.2
L = Equivalent length of pipe fittings for pipe diameter D
C = Factor for equivalent length of pipe
Equivalent length is calculated in the following table:
Fittings
No of Fittings
C value for equivalent pipe length
Equivalent Length
Gate Valve
2
0.25
45.0
Bends
5
0.33
150.0
Tee
1
1.33
120.0
Non Return Valve
1
0.90
81
Length of Pipe
120
Total
516.0 ~ 520
hp = 0.01 x 520 x ( 4 x 14/ 3.14 (1.5)2)2/ 2 x 32.2 x 1.5
= 4.50 Ft
Total Headloss = 4.3 + 7.0 + 4.5
= 15.8 Ft
Delivery Head ( 1034.75 - 1021.5) = 13.25 Ft
Suction Lift = 2.5 Ft
Drawdown = 3 Ft
Total Headloss = 15.8 Ft
Total Head = 34.55 Ft
Design of Backwash Water Pipes
Backwash water pipe shall carry the wash water from back wash pumps to the filter beds. Only one filter bed shall be backwashed at a time:
Proposed Diameter of pipe = 18 “ i/d
X - sectional area of pipe = 1.77 Sft
Velocity = 14/2
= 7 Ft /s
It is proposed to install 18 “ dia MS pipe along the filter beds in the Pipe Gallery to carry wash water from backwash pumps to each filter bed.
Proposed Diameter of pipe = 18 “ i/d
X - sectional area of pipe = 1.77 Sft
Velocity = 14/2
= 7 Ft /s
It is proposed to install 18 “ dia MS pipe along the filter beds in the Pipe Gallery to carry wash water from backwash pumps to each filter bed.
ign of Filtered Water Channels
Two Filtered Water Channels shall flow below the floor of the Pipe Gallery in front of the Filters. Each channel shall collect flow from its respective four Filters Water Outlet Pipes and carry to the Backwash & Service Water Sump located below the Machine Hall. The size of the channels is worked out as follows:
Flow from the four Filtered Water Outlet Pipes = 2.91 x 4
= 11.64 Cusecs
Velocity of Flow through the channel = 3 Ft / s
Crossectional Area of the Channel = 11.64 / 3
= 3.88 Sft
Width of the Channel = 4.0 Ft
Depth of the Channel = 3.88 / 4
= 1.0 Ft
Free Board = 1.5 Ft
Total Depth of the Drain = 2.50 Ft
2.10 Filter Cleaning Arrangement
Filtration of water is stopped due to the clogging of filter by the turbidity causing particles. Filter cleaning shall be carried out through Backwashing. In Backwashing filtered water is allowed to flow upward through the filter beds by pumping huge volumes of water at a certain head. The discharge and head of the flow in backwashing is so adjusted that the flow completely agitates filtration media and removes the clogging material. The process of Backwashing is supplemented by air wash in which air is pumped through the filter media which breaks the layer blocking the filter media. Air wash is carried out prior to the water wash. The entire process of backwashing completes in 20 minutes. Design Criteria governing the design of filter cleaning system is as follows:
Design Parameter
Ref 1
Ref 2
Ref 3
Ref 4
Adopted
Backwashing water Flow Rate
880 - 1200 m / d
25 m3 /m2/hr
5.0 - 6.5 mm / s
30 - 60 m / hr
25 m3/m2/hr
Air Flow rate
55 m3 /m2/hr
1-1.5 m3/m2/min
36 - 72 m / h
55 m3/m2/hr
Duration of washing
8 - 15 minutes
Head at the Pump or elevated tank
10.0 M
10.0 M
1Introduction to Environmental Engineering by Davis & Cornell (P236)
2 Operational Manual of Water Treatment Plant, Rawalpindi
3Water Supply by A.C Twort, F. M. law (P - 278)
4Water Treatment Principles & Design by MWH (P -810)
2.10.1 Design of Backwashing Pumps
Backwash Pumps shall be installed in the Machine Hall and draw water from the Backwash Water & Service Water Sump provided beneath the Machine Hall. The same backwash water rate has been adopted as used in the backwashing of filter beds at the Rawalpindi Water Treatment Plant.
Backwash Water Rate = 25 M3 / M2 / H
= 82.0 Cft / Sft / H
Area of each Filter Bed = 606.81 Sft
Capacity of Backwashing Pumps = 49748 Ft3 /H
= 13.81 Cusecs
No of backwashing Pumps = 2
Capacity of Backwashing Pumps = 13.81 / 2
= 7.0 Cusecs
It is proposed to install 3 no vertical turbine pumps, 2 working and 1 standby to serve as backwashing pumps.
Flow from the four Filtered Water Outlet Pipes = 2.91 x 4
= 11.64 Cusecs
Velocity of Flow through the channel = 3 Ft / s
Crossectional Area of the Channel = 11.64 / 3
= 3.88 Sft
Width of the Channel = 4.0 Ft
Depth of the Channel = 3.88 / 4
= 1.0 Ft
Free Board = 1.5 Ft
Total Depth of the Drain = 2.50 Ft
2.10 Filter Cleaning Arrangement
Filtration of water is stopped due to the clogging of filter by the turbidity causing particles. Filter cleaning shall be carried out through Backwashing. In Backwashing filtered water is allowed to flow upward through the filter beds by pumping huge volumes of water at a certain head. The discharge and head of the flow in backwashing is so adjusted that the flow completely agitates filtration media and removes the clogging material. The process of Backwashing is supplemented by air wash in which air is pumped through the filter media which breaks the layer blocking the filter media. Air wash is carried out prior to the water wash. The entire process of backwashing completes in 20 minutes. Design Criteria governing the design of filter cleaning system is as follows:
Design Parameter
Ref 1
Ref 2
Ref 3
Ref 4
Adopted
Backwashing water Flow Rate
880 - 1200 m / d
25 m3 /m2/hr
5.0 - 6.5 mm / s
30 - 60 m / hr
25 m3/m2/hr
Air Flow rate
55 m3 /m2/hr
1-1.5 m3/m2/min
36 - 72 m / h
55 m3/m2/hr
Duration of washing
8 - 15 minutes
Head at the Pump or elevated tank
10.0 M
10.0 M
1Introduction to Environmental Engineering by Davis & Cornell (P236)
2 Operational Manual of Water Treatment Plant, Rawalpindi
3Water Supply by A.C Twort, F. M. law (P - 278)
4Water Treatment Principles & Design by MWH (P -810)
2.10.1 Design of Backwashing Pumps
Backwash Pumps shall be installed in the Machine Hall and draw water from the Backwash Water & Service Water Sump provided beneath the Machine Hall. The same backwash water rate has been adopted as used in the backwashing of filter beds at the Rawalpindi Water Treatment Plant.
Backwash Water Rate = 25 M3 / M2 / H
= 82.0 Cft / Sft / H
Area of each Filter Bed = 606.81 Sft
Capacity of Backwashing Pumps = 49748 Ft3 /H
= 13.81 Cusecs
No of backwashing Pumps = 2
Capacity of Backwashing Pumps = 13.81 / 2
= 7.0 Cusecs
It is proposed to install 3 no vertical turbine pumps, 2 working and 1 standby to serve as backwashing pumps.
2.9.3 Design of Filter Nozzles
Flow through each Filter = 10017 x 24
= 252000 Ft3 / D
Flow through each Nozzle = 53 Ft3 / D
No of Nozzles in each Filter = 252000/53
= 4755 No
Say = 4800 No
Total No of Nozzles required for 8 Filter Beds = 4800 x8
= 38400 No
4800 Nozzles shall be installed on the perforated RCC slab in each filter at equal spacing. The perforated slab shall comprise of series of slabs placed side by side supported on beams above the Balancing Chamber. Each slab shall be 3’ x 3’ wide. Nozzle shall be of 0.2 mm aperture with 273 mm stem.
= 252000 Ft3 / D
Flow through each Nozzle = 53 Ft3 / D
No of Nozzles in each Filter = 252000/53
= 4755 No
Say = 4800 No
Total No of Nozzles required for 8 Filter Beds = 4800 x8
= 38400 No
4800 Nozzles shall be installed on the perforated RCC slab in each filter at equal spacing. The perforated slab shall comprise of series of slabs placed side by side supported on beams above the Balancing Chamber. Each slab shall be 3’ x 3’ wide. Nozzle shall be of 0.2 mm aperture with 273 mm stem.
2.9.2 Design of Filtered Water Outlet Pipe
Equation governing the flow through the Filtered water Pipe is as follows:
Q = cA (2gh)1/2
Where:
Flow through each Filter = Q (Cusecs)
= 2.91 Cusecs
X - Area of pipe = A (Sft)
Head loss or Differential Head = h (ft)
= 1.6 Ft
Acceleration due to gravity = g (Ft /s2)
Coefficient of Discharge = c (0.6)
X- Area of Pipe (A) = Q / c x (2gh)1/2
= 2.91 / 0.6 x (2 x 32.2 x 1.6) ½
= 0.48 Sft
Dia of Pipe = (A x 4 /3.14) ½
= 0.78 Ft
= 10 “
It is proposed to install 10 “ dia Filter Water Outlet Pipe fitted with a butterfly valve in Balancing Chamber of each filter bed to carry water from filter beds to the Filtered Water Collection Channel.
The operation of butterfly valve installed on the Filtered Water Outlet Pipe is controlled by the ultrasonic level gauge installed above the filter bed to measure the water level in the bed. As the water level rises due to clogging of filter bed, ultrasonic level gauge sends message to the controller for opening butterfly valve installed on the Filtered Water Outlet Pipe for opening valve proportionate to the rise in water level. This operation maintains a constant water level on the filter bed. It is this very reason this type of filtration is called Constant Rate Filtration. The automatic operation of the level gauge and butterfly valve takes place through electric actuation and the three components together are called Rate Controller.
Q = cA (2gh)1/2
Where:
Flow through each Filter = Q (Cusecs)
= 2.91 Cusecs
X - Area of pipe = A (Sft)
Head loss or Differential Head = h (ft)
= 1.6 Ft
Acceleration due to gravity = g (Ft /s2)
Coefficient of Discharge = c (0.6)
X- Area of Pipe (A) = Q / c x (2gh)1/2
= 2.91 / 0.6 x (2 x 32.2 x 1.6) ½
= 0.48 Sft
Dia of Pipe = (A x 4 /3.14) ½
= 0.78 Ft
= 10 “
It is proposed to install 10 “ dia Filter Water Outlet Pipe fitted with a butterfly valve in Balancing Chamber of each filter bed to carry water from filter beds to the Filtered Water Collection Channel.
The operation of butterfly valve installed on the Filtered Water Outlet Pipe is controlled by the ultrasonic level gauge installed above the filter bed to measure the water level in the bed. As the water level rises due to clogging of filter bed, ultrasonic level gauge sends message to the controller for opening butterfly valve installed on the Filtered Water Outlet Pipe for opening valve proportionate to the rise in water level. This operation maintains a constant water level on the filter bed. It is this very reason this type of filtration is called Constant Rate Filtration. The automatic operation of the level gauge and butterfly valve takes place through electric actuation and the three components together are called Rate Controller.
2.9.1 Composition of Filter Bed
Filter bed shall comprise a Balancing Chamber (5’ depth) with perforated slab fitted with nozzles placed on it. A 4.5 Ft deep filtration media i.e sand shall be placed on the perforated slab. Filter Media shall have the following characteristics;
Depth of Filter Media Sand = 4’ - 6”
Water Depth over Filter Bed = 3’ - 3”
Silica Sand Effective Size (95 % Silica) = 0.85 mm
Uniformity Coefficient = 1.3 -1.7
Density = 2.65 mg /l
Porosity = 40 - 43 %
The source of the filter media will be selected after investigating various sites to suite the requirement.
Depth, size and other characteristics of the filter media has been selected based on the experience of Water Treatment Plant, Rawalpindi, where sand has been used as filter media having bed depth of 4.5 Ft and effective media size of 0.85 without any gravel base. Kawamura (2000), P- 231 has given the following relationship between bed depth and the size of the filter media:
l/de ≥
1000
For ordinary mono sand & dual media filters
1250
For regular trimedia (coal, sand & garnet) beds
1250 - 1500
For most coarse deep monomedium beds
(de is 1.2 to 1.4 mm)
1500 - 2000
For very coarse monomedium beds)
(de is 1.5 to 2.0 mm)
Note: l is a depth of filter bed in mm & de is an effective size of the media in mm
L / de = 4.5 x 1000 / 3.28 x 0.85
= 1614
Water after passing through the sand bed and nozzles shall be collected in the Balancing Tank and shall come out of the Filter Bed through a Filtered Water Outlet Pipe which discharges in Filtered Water Collection Channel flowing in the Pipe gallery below the ground. The Filtered Water Channel shall discharge in to Backwash Water Sump. The capacity of the Backwash Water Sump will be slightly more than the requirement of cleaning of one Filter bed. The excess water shall move in to the Clear Water Tank after flowing over a Weir through a pipe.
Depth of Filter Media Sand = 4’ - 6”
Water Depth over Filter Bed = 3’ - 3”
Silica Sand Effective Size (95 % Silica) = 0.85 mm
Uniformity Coefficient = 1.3 -1.7
Density = 2.65 mg /l
Porosity = 40 - 43 %
The source of the filter media will be selected after investigating various sites to suite the requirement.
Depth, size and other characteristics of the filter media has been selected based on the experience of Water Treatment Plant, Rawalpindi, where sand has been used as filter media having bed depth of 4.5 Ft and effective media size of 0.85 without any gravel base. Kawamura (2000), P- 231 has given the following relationship between bed depth and the size of the filter media:
l/de ≥
1000
For ordinary mono sand & dual media filters
1250
For regular trimedia (coal, sand & garnet) beds
1250 - 1500
For most coarse deep monomedium beds
(de is 1.2 to 1.4 mm)
1500 - 2000
For very coarse monomedium beds)
(de is 1.5 to 2.0 mm)
Note: l is a depth of filter bed in mm & de is an effective size of the media in mm
L / de = 4.5 x 1000 / 3.28 x 0.85
= 1614
Water after passing through the sand bed and nozzles shall be collected in the Balancing Tank and shall come out of the Filter Bed through a Filtered Water Outlet Pipe which discharges in Filtered Water Collection Channel flowing in the Pipe gallery below the ground. The Filtered Water Channel shall discharge in to Backwash Water Sump. The capacity of the Backwash Water Sump will be slightly more than the requirement of cleaning of one Filter bed. The excess water shall move in to the Clear Water Tank after flowing over a Weir through a pipe.
2.9 Design of Rapid Sand Gravity Filters
The processes of coagulation, flocculation and subsequent settlement have considerably reduced the turbidity of water, but it still has a turbidity of 40 - 50 NTU and is undrinkable. According to the WHO Guidelines for the Drinking water, the turbidity of drinkable water should be less than 25 NTU. The situation demands that water should be subjected to further treatment in order to make it drinkable. The next treatment unit is Rapid Sand Filter in which water passes through a bed of sand for further cleaning. The process is called Rapid Sand Filtration.
Overall the plant will have the capacity to treat 18 MGD of water. But initially it has been planned to construct plant that can cater to 12 MGD demand of water. Therefore, Rapid Sand Gravity Filters shall be developed to fulfill the water need of 12 MGD leaving space for extension by 6 MGD in future.
Design Criteria
Design Parameter
Ref 1
Ref 2
Ref 3
Ref 4
Adopted
Filtration rate
5.0 m/h
120 m/d
5 - 15 m/h
120 – 235 m3/m2/d
5.4 m/h
Media Diameter
0.5 - 1.2 mm
0.35 - 0.55
0.8 mm
Bed Depth
0.6 - 1.8 m
1.4 m
Uniformity Coefficient
1.3 – 1.7
1.4
Required Head
1.8 - 3.0 m
3.0 m
1Water Supply & Sewerage by E.W Steel & Terence J.McGhee (P -233)
2Hand Book of Environmental Engineering Calculations by C. C. Lee & Shun Dar Lin (P - 1.363)
3. Water Treatment Principles & Design by MWH (P -743)
Design
Flow = 12.0 MGD
Add 5 % water losses in backwashing = 0.6 MGD
Total Flow requirement = 12.6 MGD
= 2019230.8 / D
= 23.37 Cusecs
Time Required for Filter Cleaning = 0.5 Hrs
Filtration Rate = 17.7 Cft / Sft / Hr
Area of Filter Required = 2019230.8 / 17.70 x23.5
= 4854 Sft
No of Filter Beds = 8
Area of each Filter Bed = 4854/8
= 606.81 Sft.
Length of each Filter Bed = 31.0 Ft
Width of each Filter Bed = 19.57 Ft
A channel shall pass through the center of each filter bed to serve as a feeding channel as well as backwashing channel. This channel shall divide each filter bed in to two parts, the width of each part shall become 9’ - 10”.
Overall the plant will have the capacity to treat 18 MGD of water. But initially it has been planned to construct plant that can cater to 12 MGD demand of water. Therefore, Rapid Sand Gravity Filters shall be developed to fulfill the water need of 12 MGD leaving space for extension by 6 MGD in future.
Design Criteria
Design Parameter
Ref 1
Ref 2
Ref 3
Ref 4
Adopted
Filtration rate
5.0 m/h
120 m/d
5 - 15 m/h
120 – 235 m3/m2/d
5.4 m/h
Media Diameter
0.5 - 1.2 mm
0.35 - 0.55
0.8 mm
Bed Depth
0.6 - 1.8 m
1.4 m
Uniformity Coefficient
1.3 – 1.7
1.4
Required Head
1.8 - 3.0 m
3.0 m
1Water Supply & Sewerage by E.W Steel & Terence J.McGhee (P -233)
2Hand Book of Environmental Engineering Calculations by C. C. Lee & Shun Dar Lin (P - 1.363)
3. Water Treatment Principles & Design by MWH (P -743)
Design
Flow = 12.0 MGD
Add 5 % water losses in backwashing = 0.6 MGD
Total Flow requirement = 12.6 MGD
= 2019230.8 / D
= 23.37 Cusecs
Time Required for Filter Cleaning = 0.5 Hrs
Filtration Rate = 17.7 Cft / Sft / Hr
Area of Filter Required = 2019230.8 / 17.70 x23.5
= 4854 Sft
No of Filter Beds = 8
Area of each Filter Bed = 4854/8
= 606.81 Sft.
Length of each Filter Bed = 31.0 Ft
Width of each Filter Bed = 19.57 Ft
A channel shall pass through the center of each filter bed to serve as a feeding channel as well as backwashing channel. This channel shall divide each filter bed in to two parts, the width of each part shall become 9’ - 10”.
2.8 Design of Filter Feeding & Filter Distribution Channels
The Filter Feeding Channel shall collect the clarified water from the launders of the three Clarifiers and carry it to the Filter Distribution Channel. Dimensions of the Filter Feeding Channel shall remain the same as of the Clarifier Feeding Channel, both being designed for 35 cusecs capacity. The channel connecting the Clarifier Launder and the Filter Feeding Channel shall be 5’-0” long. The design of connecting channel is as follows:
Flow under extreme conditions = 23.33 Cusecs
Flow under normal operating conditions = 11.67 Cusecs
Design of Connecting Channel
Flow through the Channel = 23.33 Cusecs
Velocity through the Channel = 3 Ft / s
Crossectional Area = 7.78 Sft
Width of the Channel = 4 Ft
Depth of the Channel = 2 Ft
Provide Free Board = 1 Ft
Dimensions of the connecting channel are 4’-0” Wide and 2’-0” deep.
Since Connecting Channel will discharge in to the Filter Feeding Channel, it is necessary to determine the difference of levels of the water surfaces of the two channels. Difference of water levels of the two channels is worked out below:
∆H = (Q / Cd x A x (2xg)1/2) 2
Where :
∆H = Difference of water level between Connecting Channel & Filter Feed Channel
Q = Flow through the Connecting Channel
A = Crossectional Area of the Connecting Channel
g = Acceleration due to gravity
Cd = Coefficient of Discharge
∆H = (23.33 / 0.61 x 2 x 4 x (2 x 32.2) 1/2) 2
= 0.370 Ft
= 0.67 Ft (Say)
Connecting Channel and the Filter Feeding Channel are so adjusted that the vertical distance of their water surfaces should be 0.5 Ft.
Design of Filter Distribution Channel
The design basis of Filter Distribution Channel is that it should be able to uniformly distribute clarified water in the filters. Kawamura (2000), P - 229 has recommended a minimum velocity of 1.5 Ft / s to be maintained in the Filter Distribution Channel.
Flow through the Distribution Channel = 35.0 Cusecs
Velocity through the Channel = 1.5 Ft / s
Crossectional Area = 23.33 Sft
Width of the Channel = 4.5 Ft
Depth of the Channel = 5.20 Ft
Channel has been designed for an ultimate flow of 18 MGD. Under the present phase of facility development when the flow would be 12 MGD, the velocity in the channel will be around 1 Ft /s.
Flow under extreme conditions = 23.33 Cusecs
Flow under normal operating conditions = 11.67 Cusecs
Design of Connecting Channel
Flow through the Channel = 23.33 Cusecs
Velocity through the Channel = 3 Ft / s
Crossectional Area = 7.78 Sft
Width of the Channel = 4 Ft
Depth of the Channel = 2 Ft
Provide Free Board = 1 Ft
Dimensions of the connecting channel are 4’-0” Wide and 2’-0” deep.
Since Connecting Channel will discharge in to the Filter Feeding Channel, it is necessary to determine the difference of levels of the water surfaces of the two channels. Difference of water levels of the two channels is worked out below:
∆H = (Q / Cd x A x (2xg)1/2) 2
Where :
∆H = Difference of water level between Connecting Channel & Filter Feed Channel
Q = Flow through the Connecting Channel
A = Crossectional Area of the Connecting Channel
g = Acceleration due to gravity
Cd = Coefficient of Discharge
∆H = (23.33 / 0.61 x 2 x 4 x (2 x 32.2) 1/2) 2
= 0.370 Ft
= 0.67 Ft (Say)
Connecting Channel and the Filter Feeding Channel are so adjusted that the vertical distance of their water surfaces should be 0.5 Ft.
Design of Filter Distribution Channel
The design basis of Filter Distribution Channel is that it should be able to uniformly distribute clarified water in the filters. Kawamura (2000), P - 229 has recommended a minimum velocity of 1.5 Ft / s to be maintained in the Filter Distribution Channel.
Flow through the Distribution Channel = 35.0 Cusecs
Velocity through the Channel = 1.5 Ft / s
Crossectional Area = 23.33 Sft
Width of the Channel = 4.5 Ft
Depth of the Channel = 5.20 Ft
Channel has been designed for an ultimate flow of 18 MGD. Under the present phase of facility development when the flow would be 12 MGD, the velocity in the channel will be around 1 Ft /s.
2.7.3 Design of Clarifier Effluent Launder
Effluent Launder shall also be designed for the extreme condition i.e closure of one Clarifier for repair. In this condition all the flow shall pass through one clarifier. Design of effluent launder is as follows:
Width of launder (b) = 2.625 (Assumed)
Flow through the Launder = 23.34 Cusecs
Gravity (g) = 32.2 Ft / s2
Depth of Flow at the lower end (h) = (Q2/ b2 x g)1/3
= ((11.67)2/ (2.625)2 x 32.2)1/3
= 0.85 Ft
Circumference of each Clarifier = 3.14 x 91.5
= 287.31 Ft
Half Circumference of each Clarifier = 143.66 Ft
Depth of Flow at the Upper End (H) =√(0.850)2+ 2(0.0789)2((143.67)2/32.2(0.850)(2.625)2 = 1.42 Ft
Friction Losses (Say) = 0.33 Ft
Depth of Flow in the Launder = 1.75 Ft
Free Board (15 %) = 0.2625 Ft
Add 0.15 Ft to ensure Free Fall = 0.15 Ft
Total Depth of Launder (1.75 + 0.2625 + 0.15) = 2.16 Ft
Say = 2.25 Ft
A channel / launder 2’- 7.5” wide and 2’ - 3” deep shall be provided around the Clarifier. Depth of the channel / launder shall be measured 2 - 3” below the crest level of the weir. A 1’-0” vertical space shall be provided between the weir crest and bottom of the beam supporting the bridge.
Width of launder (b) = 2.625 (Assumed)
Flow through the Launder = 23.34 Cusecs
Gravity (g) = 32.2 Ft / s2
Depth of Flow at the lower end (h) = (Q2/ b2 x g)1/3
= ((11.67)2/ (2.625)2 x 32.2)1/3
= 0.85 Ft
Circumference of each Clarifier = 3.14 x 91.5
= 287.31 Ft
Half Circumference of each Clarifier = 143.66 Ft
Depth of Flow at the Upper End (H) =√(0.850)2+ 2(0.0789)2((143.67)2/32.2(0.850)(2.625)2 = 1.42 Ft
Friction Losses (Say) = 0.33 Ft
Depth of Flow in the Launder = 1.75 Ft
Free Board (15 %) = 0.2625 Ft
Add 0.15 Ft to ensure Free Fall = 0.15 Ft
Total Depth of Launder (1.75 + 0.2625 + 0.15) = 2.16 Ft
Say = 2.25 Ft
A channel / launder 2’- 7.5” wide and 2’ - 3” deep shall be provided around the Clarifier. Depth of the channel / launder shall be measured 2 - 3” below the crest level of the weir. A 1’-0” vertical space shall be provided between the weir crest and bottom of the beam supporting the bridge.
2.7.2 Design of V - Notch (To be installed on the periphery of Clarifier)
Design
Circumference of each clarifier = 3.14 x 91.56
= 287.31 Ft
Columns (1’ x 1’) shall be provided at every 12’ interval for supporting a beam on which one end of the Scrapper Bridge shall be placed. Therefore space for the installation of the notch shall be reduced compared to the circumference of the Clarifier.
Length of Span = 12’
No of available spans for the installation of notch = 287.31 /12
= 24
Size of columns = 1’ x 1’
No of Columns = 25
Length of Effective Spans for installation of notch = 287.31 -25
= 262.32 Ft
Center / Center spacing of notch = 1’
No of Weirs = 262
Flow per Notch (q) = 23.34 / 262
= 0.089 cusecs
Coefficient of Discharge (Cd) = 0.60
Gravity (g) = 32.2 Ft / s2
Depth of water over V - Notch =(15 x q / 8 x Cd x (2g)0.5)0.4
=(15x 0.089 / 8 x 0.60(2 x 32.2) 0.5) 0.4
= 0.26 Ft
= 3.15“
Add safety Allowance against submergence = 1.61 “
Total Depth of V Notch = 5”
Width of V- Notch at the top = 2 x .0
= 10.0 “
Under normal operating conditions when flow through each Clarifier shall be 11.67 cusecs, depth of flow over each notch shall be 2.36 “.
Circumference of each clarifier = 3.14 x 91.56
= 287.31 Ft
Columns (1’ x 1’) shall be provided at every 12’ interval for supporting a beam on which one end of the Scrapper Bridge shall be placed. Therefore space for the installation of the notch shall be reduced compared to the circumference of the Clarifier.
Length of Span = 12’
No of available spans for the installation of notch = 287.31 /12
= 24
Size of columns = 1’ x 1’
No of Columns = 25
Length of Effective Spans for installation of notch = 287.31 -25
= 262.32 Ft
Center / Center spacing of notch = 1’
No of Weirs = 262
Flow per Notch (q) = 23.34 / 262
= 0.089 cusecs
Coefficient of Discharge (Cd) = 0.60
Gravity (g) = 32.2 Ft / s2
Depth of water over V - Notch =(15 x q / 8 x Cd x (2g)0.5)0.4
=(15x 0.089 / 8 x 0.60(2 x 32.2) 0.5) 0.4
= 0.26 Ft
= 3.15“
Add safety Allowance against submergence = 1.61 “
Total Depth of V Notch = 5”
Width of V- Notch at the top = 2 x .0
= 10.0 “
Under normal operating conditions when flow through each Clarifier shall be 11.67 cusecs, depth of flow over each notch shall be 2.36 “.
2.7.1 Design of Sludge Pit
Two categories of solids form sludge. The solids contained in the raw water which are a cause of turbidity in water and the solids of Aluminium Hydroxide. The volume of Sludge Pit depends on the rate of sludge generated. Following parameters and their typical values are given in the literature for the estimation of sludge produced from the use of Alum as coagulant:
Design Parameter
Range
Adopted
Kg of Dry Sludge / Kg of Coagulant (Alum)
Range
0.33 - 0.44
0.40
Turbidity Removal
Mg of TSS / NTU Removed
0.9 - 1.5
1.40
Sludge Solids Concentration (%)
5
Specific Gravity of Sludge
1.05
Ref: Water Treatment Principles & Design by MWH (P -1659 )
Estimation of Sludge Solids
The rate of sludge generation is estimated as follows:
Flow through each Clarifier = 11.67 Cusec
Turbidity of the incoming water = 100 NTU
Turbidity of the water leaving Clarifier = 40 NTU
Turbidity that forms part of the sludge & collected in Sludge Pit = 60 NTU
The relation between turbidity and the suspended solids is described by the following equation
TSS (mg / l) = 1.40 x NTU
= 84 mg / l
= 84 /1000
= 0.084 gm / l or 0.084 Kg / M3
Sludge generation rate from Turbidity causing Solids = 0.084 x 11.67 x 3600/ 35.28
= 100.0 Kg /Hour
Alum when added in raw water forms Aluminium Hydrooxide flocs which settle down on the floor of the Clarifier carrying turbidity causing solids with it. Sludge generation rate due to addition of alum has been worked on the basis of addition of 60 mg /l of Alum concentration in the raw water.
Hourly consumption of Alum = 60 x 11.67 x 3600 / 1000 x 35.28
= 71.45 Kg / Hr
Sludge generated due to Alum addition is calculated as follows:
Sludge production from Alum (Kg/Hr) = 0.40 x 71.45
= 28.60 Kg / Hr
Total Sludge (Kg / H) = 100.0 + 28.60
= 128.60 Kg / H
Estimation of Sludge Volume
Volume of Sludge shall be computed from the following expression:
V= Ws / ρw Ssl Ps
Where:
V = Volume of Sludge
Ws = Weight of Total Dry Solids
ρw = Density of water
Ssl = Specific Gravity of Sludge
Ps =Percentage Solids expressed as solids
Volume of Sludge = 128.60 / 1000 x 1.05 x .05
= 2.45 M3 / H
= 2.45 x 35.28
= 86.44 Cft / H
Volume of Sludge generated per day = 86.44 x 24 x 3 = 6223.70 Cft /D
(From 3 Clarifiers)
Total Flow Per Day = 11.67 x 3 x3600 x24
= 3024864 Cft
Volume of Sludge as (% of total flow) = 6223.70 x 100/ 3024864
= 0.20 %
Ref: Water Treatment Principles & Design by MWH (P -1646) states that Underflow from sedimentation tanks typically contain on the order of 0.1 to 0.3 percent of the plant flow but contains most of the solids removed.
Sizing of Sludge Pit
Two Sludge Pits shall be provided in each Clarifier. Sludge pit shall be sized to store one hour of the sludge generated and shall be cleaned every hour by opening valves installed on the Sludge Pipe connecting Sludge Pit with the outer manhole.
No of Sludge Pits = 2
Volume of Sludge Pit = 86.44 /2
= 43.22 Cft
Bottom width of the Sludge Pit = 2.0 Ft
Top Width of the Sludge Pit = 4.5 Ft
Average Width of the Sludge Pit = 3.25 Ft
Depth of Sludge Pit = 43.22 / 3.25 x3.25
= 4.0 Ft
Sludge Draw-Off Pipe
Water Treatment Principles & Design by MWH (P -814 ) recommends a minimum diameter of 6 “ for sludge draw - off pipe to prevent clogging. Sufficient head (16.5’) will be available for the quick removal of sludge from the sludge pit. It is therefore proposed to provide 3 Sludge Draw - Off pipes each of 6“ diameter in each clarifier from Sludge Pit to manhole. A Flow Control Valve along with actuator and timer shall be provided on the Sludge Draw - off for the automatic removal of sludge after a fixed interval of time. Time interval between the two sludge removals shall be fixed by the operator. Sludge Draw Off pipes shall be Polyethylene pipes.
Design Parameter
Range
Adopted
Kg of Dry Sludge / Kg of Coagulant (Alum)
Range
0.33 - 0.44
0.40
Turbidity Removal
Mg of TSS / NTU Removed
0.9 - 1.5
1.40
Sludge Solids Concentration (%)
5
Specific Gravity of Sludge
1.05
Ref: Water Treatment Principles & Design by MWH (P -1659 )
Estimation of Sludge Solids
The rate of sludge generation is estimated as follows:
Flow through each Clarifier = 11.67 Cusec
Turbidity of the incoming water = 100 NTU
Turbidity of the water leaving Clarifier = 40 NTU
Turbidity that forms part of the sludge & collected in Sludge Pit = 60 NTU
The relation between turbidity and the suspended solids is described by the following equation
TSS (mg / l) = 1.40 x NTU
= 84 mg / l
= 84 /1000
= 0.084 gm / l or 0.084 Kg / M3
Sludge generation rate from Turbidity causing Solids = 0.084 x 11.67 x 3600/ 35.28
= 100.0 Kg /Hour
Alum when added in raw water forms Aluminium Hydrooxide flocs which settle down on the floor of the Clarifier carrying turbidity causing solids with it. Sludge generation rate due to addition of alum has been worked on the basis of addition of 60 mg /l of Alum concentration in the raw water.
Hourly consumption of Alum = 60 x 11.67 x 3600 / 1000 x 35.28
= 71.45 Kg / Hr
Sludge generated due to Alum addition is calculated as follows:
Sludge production from Alum (Kg/Hr) = 0.40 x 71.45
= 28.60 Kg / Hr
Total Sludge (Kg / H) = 100.0 + 28.60
= 128.60 Kg / H
Estimation of Sludge Volume
Volume of Sludge shall be computed from the following expression:
V= Ws / ρw Ssl Ps
Where:
V = Volume of Sludge
Ws = Weight of Total Dry Solids
ρw = Density of water
Ssl = Specific Gravity of Sludge
Ps =Percentage Solids expressed as solids
Volume of Sludge = 128.60 / 1000 x 1.05 x .05
= 2.45 M3 / H
= 2.45 x 35.28
= 86.44 Cft / H
Volume of Sludge generated per day = 86.44 x 24 x 3 = 6223.70 Cft /D
(From 3 Clarifiers)
Total Flow Per Day = 11.67 x 3 x3600 x24
= 3024864 Cft
Volume of Sludge as (% of total flow) = 6223.70 x 100/ 3024864
= 0.20 %
Ref: Water Treatment Principles & Design by MWH (P -1646) states that Underflow from sedimentation tanks typically contain on the order of 0.1 to 0.3 percent of the plant flow but contains most of the solids removed.
Sizing of Sludge Pit
Two Sludge Pits shall be provided in each Clarifier. Sludge pit shall be sized to store one hour of the sludge generated and shall be cleaned every hour by opening valves installed on the Sludge Pipe connecting Sludge Pit with the outer manhole.
No of Sludge Pits = 2
Volume of Sludge Pit = 86.44 /2
= 43.22 Cft
Bottom width of the Sludge Pit = 2.0 Ft
Top Width of the Sludge Pit = 4.5 Ft
Average Width of the Sludge Pit = 3.25 Ft
Depth of Sludge Pit = 43.22 / 3.25 x3.25
= 4.0 Ft
Sludge Draw-Off Pipe
Water Treatment Principles & Design by MWH (P -814 ) recommends a minimum diameter of 6 “ for sludge draw - off pipe to prevent clogging. Sufficient head (16.5’) will be available for the quick removal of sludge from the sludge pit. It is therefore proposed to provide 3 Sludge Draw - Off pipes each of 6“ diameter in each clarifier from Sludge Pit to manhole. A Flow Control Valve along with actuator and timer shall be provided on the Sludge Draw - off for the automatic removal of sludge after a fixed interval of time. Time interval between the two sludge removals shall be fixed by the operator. Sludge Draw Off pipes shall be Polyethylene pipes.
2.7 Design of Clarifier with Concentric Flocculation Tank
Design Criteria
Standard design criteria for Clarifiers following coagulation and flocculation with alum are as follows:
Design Parameter
Ref 1
Ref 2
Ref 3
Ref 5
Ref 6
Ref 7
Ref 8
Adopted
Detention Time
2-8 Hrs
2.5 - 3.0 Hr
1.5 - 4.0 Hr
1.5 - 4.0 Hr
2 Hr
Overflow Rate following Coagulation & Flocculation
20-33 m3 /m2/d
40 - 60 m3 /m2/d
1-1.2 m3/m2/h
20 - 40 m3/m2/d
1.25 - 2.5 m3/m2/h
2.3 m3/m2/hr
Water Depth
3-5m
4.35 m
Bottom Slope
1:600
¾ - 2 inches /Ft
1/2 inch / Ft
Weir Overflow rate
250 m3 /m/d
6 – 14 m3/m/h
9-13 m3/m/h
13 m3/m2/hr
1Water Supply & Sewerage by E.W Steel & Terence J.McGhee (P -234)
2Hand Book of Environmental Engineering Calculations by C. C. Lee & Shun Dar Lin (P - 1.370)
3 Environmental Engineering, A Design Approach by ArcadioP.Sincero & Gregoria A. Sincero (P 267)
4Introduction to Environmental Engineering by Davis & Cornell (P227)
5Water Supply Engineering by BC. Punmia, Ashok jain & Arun Jain (P - 282)
6 Water Supply by A.C Twort, F. M. law (P - 268)
1. Water Treatment Principles & Design by MWH (P -810)
2. Wastewater Engineering by Metcalf & Eddy (P – 477)
Ref 4 recommends the following:
Types of flocs
Type of Waters
Weir Overflow Rates (m3/m/d)
Light Alum Flocs
Low turbidity waters
143 - 179
Heavier Alum Flocs
Higher Turbidity Waters
179 – 268
Typical Sedimentation Tanks Overflow rates
Application
Type of Tanks
Sedimentation Tanks Overflow Rates (m3/m/d)
Turbidity Removal
Long Rectangular or circular
40
Color Removal
“
30
High Algae
“
20
Source: American Water Works Association, Water Treatment Plant Design
Design
In addition to the above mentioned references, experience has been drawn from the Rawalpindi Water Treatment Plant, where an Overflow rate of 2.3 m3 /m/hr has been adopted and the Clarifiers are successfully functioning. Design calculations proceed as follows:
Flow = 35.0 Cusecs
O. F. R = 7.544 Ft3 / Ft2 / H (2.30 m3/m2/h)
No of Clarifiers = 3
Flow through each Clarifier = 35.0 /3
= 11.67
Area of each Clarifier = 11.67 x 3600 / 7.544
= 5567.34 Sft
Diameter of Flocculation tank = 33.15 Ft
Area of Flocculation tank = 862.65 Sft
Let thickness of the Diffuser wall = 1’-0”
Area of the Diffuser Wall = 3.14 (35.152 - 33.152) / 4
= 107.231 Sft
Total Area of each Clarifier cum Flocculator (5567.34 + 862.65 +107.231) = 6537.221 Sft
Dia of each Clarifier with Concentric Flocculation Tank = (6537.221 x 4/3.14)1/2
= 91.26 Ft
= 91’ - 6”
Floor of the Flocculation tank shall be flat, whereas floor between the diffuser wall and the Clarifier Wall shall be sloped at a rate of 1/2 inch / Ft for the smooth sliding of sludge to Sludge Pits.
Floor width between Diffuser Wall & Clarifier = 91.50 - 33.15 - 2
= 56.35 Ft
Proposed Slope = 1/2 inch / Ft
Difference of Floor Level between outer & inner walls of the Clarifier = 0.5 x 56.35
= 28.175 inches
= 2.34 Ft
Water Depth in the Flocculation Tank = 16.5 Ft
Side Water Depth in the Clarifier = 16.5 - 2.34
= 14.16 Ft
= 14’ - 2”
Check for Detention Time in the Clarifier
Average Water Depth in the Clarifier = (16.5 +14.17) / 2
= 15.335 Ft
Effective Volume of Clarifier = 5567.34 x 15.335
= 85375.16 CFt
Detention Time = 85375.16 /11.67
= 7317.9 Seconds
= 2.04 Hrs (Okay)
Provide 3 no Clarifiers cum Flocculators each having diameter of 91’- 6” with concentric flocculation tank having 33’ - 2” diameter. Two Clarifiers cum Flocculators will be developed under Ph I & II whereas 3rd will be developed under Ph III.
Sludge Scrapper
Clarifier shall be fitted with a Sludge Scrapper. The flocs formed shall settle down on the floor of the Clarifier to be scrapped by the Sludge Scrapper towards the sludge pits. Two Sludge Pits have been provided in each Clarifier. A Sludge Pipe shall connect the Sludge Pit to the outer Manhole for the removal of the sludge. Sludge shall be intermittently removed by opening valves installed on the Sludge Pipe. A Sludge pit shall also be provided in the Flocculation Tank for the removal of the sludge particles if settled in the Flocculation tank.
Standard design criteria for Clarifiers following coagulation and flocculation with alum are as follows:
Design Parameter
Ref 1
Ref 2
Ref 3
Ref 5
Ref 6
Ref 7
Ref 8
Adopted
Detention Time
2-8 Hrs
2.5 - 3.0 Hr
1.5 - 4.0 Hr
1.5 - 4.0 Hr
2 Hr
Overflow Rate following Coagulation & Flocculation
20-33 m3 /m2/d
40 - 60 m3 /m2/d
1-1.2 m3/m2/h
20 - 40 m3/m2/d
1.25 - 2.5 m3/m2/h
2.3 m3/m2/hr
Water Depth
3-5m
4.35 m
Bottom Slope
1:600
¾ - 2 inches /Ft
1/2 inch / Ft
Weir Overflow rate
250 m3 /m/d
6 – 14 m3/m/h
9-13 m3/m/h
13 m3/m2/hr
1Water Supply & Sewerage by E.W Steel & Terence J.McGhee (P -234)
2Hand Book of Environmental Engineering Calculations by C. C. Lee & Shun Dar Lin (P - 1.370)
3 Environmental Engineering, A Design Approach by ArcadioP.Sincero & Gregoria A. Sincero (P 267)
4Introduction to Environmental Engineering by Davis & Cornell (P227)
5Water Supply Engineering by BC. Punmia, Ashok jain & Arun Jain (P - 282)
6 Water Supply by A.C Twort, F. M. law (P - 268)
1. Water Treatment Principles & Design by MWH (P -810)
2. Wastewater Engineering by Metcalf & Eddy (P – 477)
Ref 4 recommends the following:
Types of flocs
Type of Waters
Weir Overflow Rates (m3/m/d)
Light Alum Flocs
Low turbidity waters
143 - 179
Heavier Alum Flocs
Higher Turbidity Waters
179 – 268
Typical Sedimentation Tanks Overflow rates
Application
Type of Tanks
Sedimentation Tanks Overflow Rates (m3/m/d)
Turbidity Removal
Long Rectangular or circular
40
Color Removal
“
30
High Algae
“
20
Source: American Water Works Association, Water Treatment Plant Design
Design
In addition to the above mentioned references, experience has been drawn from the Rawalpindi Water Treatment Plant, where an Overflow rate of 2.3 m3 /m/hr has been adopted and the Clarifiers are successfully functioning. Design calculations proceed as follows:
Flow = 35.0 Cusecs
O. F. R = 7.544 Ft3 / Ft2 / H (2.30 m3/m2/h)
No of Clarifiers = 3
Flow through each Clarifier = 35.0 /3
= 11.67
Area of each Clarifier = 11.67 x 3600 / 7.544
= 5567.34 Sft
Diameter of Flocculation tank = 33.15 Ft
Area of Flocculation tank = 862.65 Sft
Let thickness of the Diffuser wall = 1’-0”
Area of the Diffuser Wall = 3.14 (35.152 - 33.152) / 4
= 107.231 Sft
Total Area of each Clarifier cum Flocculator (5567.34 + 862.65 +107.231) = 6537.221 Sft
Dia of each Clarifier with Concentric Flocculation Tank = (6537.221 x 4/3.14)1/2
= 91.26 Ft
= 91’ - 6”
Floor of the Flocculation tank shall be flat, whereas floor between the diffuser wall and the Clarifier Wall shall be sloped at a rate of 1/2 inch / Ft for the smooth sliding of sludge to Sludge Pits.
Floor width between Diffuser Wall & Clarifier = 91.50 - 33.15 - 2
= 56.35 Ft
Proposed Slope = 1/2 inch / Ft
Difference of Floor Level between outer & inner walls of the Clarifier = 0.5 x 56.35
= 28.175 inches
= 2.34 Ft
Water Depth in the Flocculation Tank = 16.5 Ft
Side Water Depth in the Clarifier = 16.5 - 2.34
= 14.16 Ft
= 14’ - 2”
Check for Detention Time in the Clarifier
Average Water Depth in the Clarifier = (16.5 +14.17) / 2
= 15.335 Ft
Effective Volume of Clarifier = 5567.34 x 15.335
= 85375.16 CFt
Detention Time = 85375.16 /11.67
= 7317.9 Seconds
= 2.04 Hrs (Okay)
Provide 3 no Clarifiers cum Flocculators each having diameter of 91’- 6” with concentric flocculation tank having 33’ - 2” diameter. Two Clarifiers cum Flocculators will be developed under Ph I & II whereas 3rd will be developed under Ph III.
Sludge Scrapper
Clarifier shall be fitted with a Sludge Scrapper. The flocs formed shall settle down on the floor of the Clarifier to be scrapped by the Sludge Scrapper towards the sludge pits. Two Sludge Pits have been provided in each Clarifier. A Sludge Pipe shall connect the Sludge Pit to the outer Manhole for the removal of the sludge. Sludge shall be intermittently removed by opening valves installed on the Sludge Pipe. A Sludge pit shall also be provided in the Flocculation Tank for the removal of the sludge particles if settled in the Flocculation tank.
2.6 Design of Diffuser Wall
Diffuser wall divides the flocculation tank from the clarifier. Suitable numbers of openings are provided in the diffuser wall through which water after flocculation enters the clarifier. Design criteria governing the design of Diffuser Wall and the values adopted are as follows:
Design Parameter
Ref 1
Adopted
Opening Area
(As percentage of flow Crossection)
2 – 5
Velocity through Orifice
- Dividing ist & 2nd Floc Basin
- Dividing Floc & Sedimentation Basin
0.55 M/s
0.35 M/s
0.35 M/s
Headloss Across Baffle
- Dividing ist & 2nd Floc Basin
- Dividing Floc & Sedimentation Basin
7 - 9 mm
3 – 4 mm
4 mm
Submergence of highest port
15 mm
Clearance below baffle for sludge
25 mm
1. Water Treatment Principles & Design by MWH (P -765)
Design
Velocity through orifice = 1.15 Ft /s
Flow = 11.67 Cusecs
Total Flow Area = 11.67 /1.15
= 10.14 Ft2
Area of each opening = 5 % of the flow Area
= 0.05 x 10.14
= 0.507 Sft
Diameter of each opening = (0.507 x 4 / 3.14)1/2
= 0.80 Ft
= 9.5 “
No of diffuser openings = 10.14 / 0.49
= 21
Perimeter of the Clarifier = 3.14 x 33.17
= 104.15 Ft
Spacing between the diffuser openings (Center / Center) = 104.15 / 21
= 4.95 Ft
= 5.0 Ft
21 diffuser openings each of 9.5“diameter shall be provided all around the diffuser wall at 5.0 Ft Center to Center. All diffuser openings shall be located 7’-0” above the floor of the Flocculator.
Design Parameter
Ref 1
Adopted
Opening Area
(As percentage of flow Crossection)
2 – 5
Velocity through Orifice
- Dividing ist & 2nd Floc Basin
- Dividing Floc & Sedimentation Basin
0.55 M/s
0.35 M/s
0.35 M/s
Headloss Across Baffle
- Dividing ist & 2nd Floc Basin
- Dividing Floc & Sedimentation Basin
7 - 9 mm
3 – 4 mm
4 mm
Submergence of highest port
15 mm
Clearance below baffle for sludge
25 mm
1. Water Treatment Principles & Design by MWH (P -765)
Design
Velocity through orifice = 1.15 Ft /s
Flow = 11.67 Cusecs
Total Flow Area = 11.67 /1.15
= 10.14 Ft2
Area of each opening = 5 % of the flow Area
= 0.05 x 10.14
= 0.507 Sft
Diameter of each opening = (0.507 x 4 / 3.14)1/2
= 0.80 Ft
= 9.5 “
No of diffuser openings = 10.14 / 0.49
= 21
Perimeter of the Clarifier = 3.14 x 33.17
= 104.15 Ft
Spacing between the diffuser openings (Center / Center) = 104.15 / 21
= 4.95 Ft
= 5.0 Ft
21 diffuser openings each of 9.5“diameter shall be provided all around the diffuser wall at 5.0 Ft Center to Center. All diffuser openings shall be located 7’-0” above the floor of the Flocculator.
2.5.5 Sizing of Paddle Flocculator
Flocculation Tank shall be provided with a flocculator, which shall comprise of a number of paddles fitted on shafts. These shafts shall hang from the rotating arms of a bridge in to the flocculation tank. The rotation of the paddles and shaft shall carry out the gentle mixing necessary for the formation of settleable flocs. Bridge shall be rotated through a central gear motor drive placed on the center of the bridge. Outer ends of the bridge shall move on the walls of the Flocculation Tank. In this section energy required for the gentle mixing of the alum mixed water and the size of the paddles shall be worked out.
Power Input by Paddle Flocculator
Dynamic Viscosity (µ) =2.050 x 10-5 lb.s/ft2
Volume of Flocculator Tank (V) =14004 Cft
Velocity Gradient (G) =50 1/s
Power of Agitator (P) = G2 µV
=(50)2x2.050x10-5x 14004
= 717.70 ft - lb /s
= 717.70/550
= 1.30 Hp
= 1.0 Kw
Efficiency of Motor Power to Water Power = 0.9
Motor Power of the Mixer = 1.0/0.9
= 1.15 Kw
Check for GT
Velocity Gradient (G) x Detention Time = 50 x 20 x 60
= 60000 (Okay)
Provide one variable speed Paddle Flocculator with motor capacity 1.15 Kw and rotational speed of 2 - 10 Rev per Min.
Size of Paddles
The area of paddles is worked out from the following expression:
P = Cd ρ A (V – v)3/2
ρ = 1000 Kg /M3
V (Velocity of tip of the paddle) = 0.5 M /s
v (Velocity of water at paddle tip) = 25 % of V
V - v = 0.5 - 0.25 x 0.5)
= 0.30 M / s
Cd (Coefficient of Discharge) = 1.8
P is a power input by paddle flocculators calculated above.
1000 x 2 = 1.8 x 1000 x A x 0.303
Area of paddles = 1000 x 2 / 1.8 x 1000 x 0.303
= 21 M2
= 226.7 Sft
Provide 2 shafts for supporting paddles and 4 paddles supported by each shaft
Thus total number of paddles = 8
Area of each paddle = 31.84 /8
= 4 Sft
Length of each paddle = 8 Ft
Width of each paddle = 4/8
= 0.5 Ft
Provide 8 paddles each of 8 Ft x 0.5 Ft size
Power Input by Paddle Flocculator
Dynamic Viscosity (µ) =2.050 x 10-5 lb.s/ft2
Volume of Flocculator Tank (V) =14004 Cft
Velocity Gradient (G) =50 1/s
Power of Agitator (P) = G2 µV
=(50)2x2.050x10-5x 14004
= 717.70 ft - lb /s
= 717.70/550
= 1.30 Hp
= 1.0 Kw
Efficiency of Motor Power to Water Power = 0.9
Motor Power of the Mixer = 1.0/0.9
= 1.15 Kw
Check for GT
Velocity Gradient (G) x Detention Time = 50 x 20 x 60
= 60000 (Okay)
Provide one variable speed Paddle Flocculator with motor capacity 1.15 Kw and rotational speed of 2 - 10 Rev per Min.
Size of Paddles
The area of paddles is worked out from the following expression:
P = Cd ρ A (V – v)3/2
ρ = 1000 Kg /M3
V (Velocity of tip of the paddle) = 0.5 M /s
v (Velocity of water at paddle tip) = 25 % of V
V - v = 0.5 - 0.25 x 0.5)
= 0.30 M / s
Cd (Coefficient of Discharge) = 1.8
P is a power input by paddle flocculators calculated above.
1000 x 2 = 1.8 x 1000 x A x 0.303
Area of paddles = 1000 x 2 / 1.8 x 1000 x 0.303
= 21 M2
= 226.7 Sft
Provide 2 shafts for supporting paddles and 4 paddles supported by each shaft
Thus total number of paddles = 8
Area of each paddle = 31.84 /8
= 4 Sft
Length of each paddle = 8 Ft
Width of each paddle = 4/8
= 0.5 Ft
Provide 8 paddles each of 8 Ft x 0.5 Ft size
2.5.4 Diameter of the Flocculation Tank
Thickness of the Inlet Pipe = ½”
Dia of the inlet Pipe = 2.5 Ft
Thickness of concrete wall = 12”
Outside diameter of concrete wall (Dp) = (30”+ 1”+24”)
= 4.5 Ft
Let inside diameter of Flocculation Tank = D
Area of Flocculation Tank = 848.73 Sft
3.14 (D2 - Dp2) /4 = 848.73
3.14 (D2 - 4.502)/4 = 848.73
D2 = 848.73 x4 / 3.14 + 4.252
Diameter of the Flocculation Tank = 33.15 Ft
= 33’- 2”
Each Flocculation Tank shall be provided with 2 No Slow Speed Paddle Mixers called Flocculator each mounted on a central rotating double arm bridge.
Dia of the inlet Pipe = 2.5 Ft
Thickness of concrete wall = 12”
Outside diameter of concrete wall (Dp) = (30”+ 1”+24”)
= 4.5 Ft
Let inside diameter of Flocculation Tank = D
Area of Flocculation Tank = 848.73 Sft
3.14 (D2 - Dp2) /4 = 848.73
3.14 (D2 - 4.502)/4 = 848.73
D2 = 848.73 x4 / 3.14 + 4.252
Diameter of the Flocculation Tank = 33.15 Ft
= 33’- 2”
Each Flocculation Tank shall be provided with 2 No Slow Speed Paddle Mixers called Flocculator each mounted on a central rotating double arm bridge.
2.5.3 Sizing of Outlet Openings
Outlet velocity through the openings = 2.5 Ft /s
Total Openings Area = 4.452 Sft
Size of openings = 8” x 8”
Area of each opening = 0.44 Sft
No of openings = 4.452 / 0.44
= 10
Provide 10 openings each of size 8 “x 8” in the inlet pipe and the concrete wall.
Total Openings Area = 4.452 Sft
Size of openings = 8” x 8”
Area of each opening = 0.44 Sft
No of openings = 4.452 / 0.44
= 10
Provide 10 openings each of size 8 “x 8” in the inlet pipe and the concrete wall.
2.5 Design of Flocculation Tank
The design of Flocculation Tank is also governed by the Velocity Gradient (G) and Detention Time (t). Varying values of G and t given in the literature and the values adopted are given below:
Design Criteria
Design Parameter
Ref 1
Ref 2
Ref 5
Ref 6
Ref 7
Adopted
Velocity Gradient (G)
20 – 65
20 - 70 1/s
20 - 75 1/s
20 – 75
10 – 80
50
Detention Time (t)
20 – 30 Min
20 - 30 Min
10 – 30 Min
10 - 60 Min
20 - 30 Min
20 Min
Gt
-
-
20000 – 60000
12000 - 270000
60000
Drive
Variable Speed, variation of G value by a factor of 2 to 3
Turbine Type variable speed Flocculator
Rotational Speed
2 - 15 rpm
10 - 30 rpm
1Water Supply & Sewerage by E.W Steel & Terence J.McGhee (P -233)
2Hand Book of Environmental Engineering Calculations by C. C. Lee & Shun Dar Lin (P - 1.363)
3 Environmental Engineering, A Design Approach by ArcadioP.Sincero & Gregoria A. Sincero (P 267)
4Introduction to Environmental Engineering by Davis & Cornell (P203 - 205)
5Water Supply Engineering by BC. Punmia, Ashok jain & Arun Jain (P - 278)
6Water Supply by A.C Twort, F. M. law (P - 252)
7. Water Treatment Principles & Design by MWH (P -743)
Ref (3) recommends the following G & t values:
Type of Raw Water
G (1/s)
(Gt) - Dimensionless
Low Turbidity, Color Removal Coagulation
20 – 70
50000 - 250000
High Turbidity Solids Removal Coagulation
70 -150
80000 - 190000
Ref (4) recommends the following G & t values
Type of Raw Water
G (1/s)
(Gt) - Dimensionless
Low Turbidity
20 – 70
60000 - 200000
High Turbidity Solids Removal
30 – 80
36000 - 96000
2.5.1 Sizing of Flocculation Tank
Design Flow = 35.0 Cusecs
No of Flocculators = 3
Flow per Flocculator = 11.67 Cusecs
Detention Time = 20.0 Min
Volume = 14004 Cft
Water Depth = 16.50 Ft
Crossectional Area of each Flocculation Tank = 848.73 Sft
2.5.2 Sizing of Inlet Pipe
Velocity through inlet Pipe = 2.5 Ft /s
Crossectional Area of inlet pipe = 11.67 Ft /s
= 4.67 Sft
Dia of inlet pipe = 2.43 Ft
= 2.5 Ft (Say)
Pipe shall be wrapped around with a concrete wall (12” thick). The objective of this wall is to serve as a support for the scrapper bridge. Openings shall be provided in the inlet pipe and the concrete wall from where the water will enter the flocculation tank.
Design Criteria
Design Parameter
Ref 1
Ref 2
Ref 5
Ref 6
Ref 7
Adopted
Velocity Gradient (G)
20 – 65
20 - 70 1/s
20 - 75 1/s
20 – 75
10 – 80
50
Detention Time (t)
20 – 30 Min
20 - 30 Min
10 – 30 Min
10 - 60 Min
20 - 30 Min
20 Min
Gt
-
-
20000 – 60000
12000 - 270000
60000
Drive
Variable Speed, variation of G value by a factor of 2 to 3
Turbine Type variable speed Flocculator
Rotational Speed
2 - 15 rpm
10 - 30 rpm
1Water Supply & Sewerage by E.W Steel & Terence J.McGhee (P -233)
2Hand Book of Environmental Engineering Calculations by C. C. Lee & Shun Dar Lin (P - 1.363)
3 Environmental Engineering, A Design Approach by ArcadioP.Sincero & Gregoria A. Sincero (P 267)
4Introduction to Environmental Engineering by Davis & Cornell (P203 - 205)
5Water Supply Engineering by BC. Punmia, Ashok jain & Arun Jain (P - 278)
6Water Supply by A.C Twort, F. M. law (P - 252)
7. Water Treatment Principles & Design by MWH (P -743)
Ref (3) recommends the following G & t values:
Type of Raw Water
G (1/s)
(Gt) - Dimensionless
Low Turbidity, Color Removal Coagulation
20 – 70
50000 - 250000
High Turbidity Solids Removal Coagulation
70 -150
80000 - 190000
Ref (4) recommends the following G & t values
Type of Raw Water
G (1/s)
(Gt) - Dimensionless
Low Turbidity
20 – 70
60000 - 200000
High Turbidity Solids Removal
30 – 80
36000 - 96000
2.5.1 Sizing of Flocculation Tank
Design Flow = 35.0 Cusecs
No of Flocculators = 3
Flow per Flocculator = 11.67 Cusecs
Detention Time = 20.0 Min
Volume = 14004 Cft
Water Depth = 16.50 Ft
Crossectional Area of each Flocculation Tank = 848.73 Sft
2.5.2 Sizing of Inlet Pipe
Velocity through inlet Pipe = 2.5 Ft /s
Crossectional Area of inlet pipe = 11.67 Ft /s
= 4.67 Sft
Dia of inlet pipe = 2.43 Ft
= 2.5 Ft (Say)
Pipe shall be wrapped around with a concrete wall (12” thick). The objective of this wall is to serve as a support for the scrapper bridge. Openings shall be provided in the inlet pipe and the concrete wall from where the water will enter the flocculation tank.
2.4 Design of Clarifier cum Flocculator Feeding Channel
Alum mixed raw water after passing through the Flash Mixer needs to pass through the Flocculation Tank for the gentle mixing and agglomeration of the flocs before entering the Clarifers for their removal through settlement. The flocculation tank is located at the center of the Clarifer and is treated as one unit called Clarifier Cum Flocculation tank. The size and shape of the land provided for the construction of the treatment plant is such that Flash Mixer and Clarifier Cum Flocculation Tanks are located at a distance from one another. Therefore, a channel will be constructed to serve as a Feeding Channel for the Clarifier Cum Flocculation tanks. The Feeding Channel shall collect chemical mixed water from the Channel / Launder built around the Flash Mixer and distribute equally between the three Clarifier Cum Flash Mixers. The design of the Clarifier Feeding is as follows:
Flow through the channel = 35.0 Cusecs
Velocity through the channel = 3.0 Ft / s
X Sectional Area of Flow = 35 / 3
= 11.66 Sft
Width of the Channel = 3- 4” Ft
Effective Water Depth of the Channel = 3’ - 6”
Free Board = 1.0 Ft
Total Depth of the channel = 4.5 Ft
Water shall enter the Flocculation Tanks through their respective Inlet Pipes. One end of the Inlet pipe shall be connected to the Feeding channel (3’- 4” W x 4’ -6” D) through a Valve Chamber and the other to the Flocculation Tank at its center. The valve shall serve to stop the flow in the Clarifier cum Flocculation Tank during breakdowns. The design of the inlet channel is given under the Design of Flocculation Tank.
Flow through the channel = 35.0 Cusecs
Velocity through the channel = 3.0 Ft / s
X Sectional Area of Flow = 35 / 3
= 11.66 Sft
Width of the Channel = 3- 4” Ft
Effective Water Depth of the Channel = 3’ - 6”
Free Board = 1.0 Ft
Total Depth of the channel = 4.5 Ft
Water shall enter the Flocculation Tanks through their respective Inlet Pipes. One end of the Inlet pipe shall be connected to the Feeding channel (3’- 4” W x 4’ -6” D) through a Valve Chamber and the other to the Flocculation Tank at its center. The valve shall serve to stop the flow in the Clarifier cum Flocculation Tank during breakdowns. The design of the inlet channel is given under the Design of Flocculation Tank.
2.3.3 Design of Channel / Launder around Flash Mixer
Raw water and Chemicals (Alum) after being mixed in the Flash Mixer shall over flow a rectangular weir installed on the periphery of the Flash Mixer. A channel provided all around Flash Mixer shall receive water and transfer to Clarifier Feeding Channel. The design of channel around the Flash Mixer is as follows:
Diameter of the Flash Mixer = 7.5 Ft
Circumference of the Flash Mixer = 3.14 x 7.5
= 23.55 Ft
Half Circumference of each Clarifier = 11.775 Ft
Head over the Rectangular Weir
H = (3 x Q/2 x Cd x L (√2g))2/3
Flow over the wier (Q) = 35.0 Cusecs
Coefficient of Discharge (Cd) = 0.60
Length of the weir (L) = 23.55 Ft
Gravity (g) = 32.2 Ft / s2
Head over the weir (H) is worked out as follows:
H = (3 x 35 / 2 x o.6 x 23.55 x 8.024) 0.666
= 0.60Ft
Depth of water over the weir shall be 0.6 Ft. A metallic rectangular weir shall be installed on the periphery of the Flash Mixer over which the water will flow before falling in the Channel / Launder provided around the Flash Mixer. The metallic rectangular weir shall project 2 “ above the concrete weir crest.
Design of Channel / Launder Around the Flash Mixer
Width of launder (b) = 3.0 (Assumed)
Flow (Q), In Launder flow splits in to two halves = 35 /2 Cusecs
= 17.5 cusecs
Gravity (g) = 32.2 Ft / s2
Depth of Flow at the lower end (h) = (Q2/ b2 x g)1/3
= ((17.5)2/ (3.0)2 x 32.2)1/3
= 1.0 Ft
Depth of Flow at the Upper End (H) = √(1.0)2+ 2(1.486)2((11.775)2/32.2(1.0)(3.0)2
= 1.76 Ft
Depth of Flow in the Launder = 1.76 Ft
Add friction allowance of 25 % = 0.44 Ft
Add 1.0 Ft to ensure Free Fall = 1.0 Ft
Total Depth of Launder (1.76 + 0.44 + 1.0) = 3.2 Ft
Say = 3.25 Ft (Say)
A rectangular channel 3 Ft wide and 3.25 Ft deep shall be provided around the Flash Mixer. The depth of the channel is measured from the weir crest feeding the channel.
Diameter of the Flash Mixer = 7.5 Ft
Circumference of the Flash Mixer = 3.14 x 7.5
= 23.55 Ft
Half Circumference of each Clarifier = 11.775 Ft
Head over the Rectangular Weir
H = (3 x Q/2 x Cd x L (√2g))2/3
Flow over the wier (Q) = 35.0 Cusecs
Coefficient of Discharge (Cd) = 0.60
Length of the weir (L) = 23.55 Ft
Gravity (g) = 32.2 Ft / s2
Head over the weir (H) is worked out as follows:
H = (3 x 35 / 2 x o.6 x 23.55 x 8.024) 0.666
= 0.60Ft
Depth of water over the weir shall be 0.6 Ft. A metallic rectangular weir shall be installed on the periphery of the Flash Mixer over which the water will flow before falling in the Channel / Launder provided around the Flash Mixer. The metallic rectangular weir shall project 2 “ above the concrete weir crest.
Design of Channel / Launder Around the Flash Mixer
Width of launder (b) = 3.0 (Assumed)
Flow (Q), In Launder flow splits in to two halves = 35 /2 Cusecs
= 17.5 cusecs
Gravity (g) = 32.2 Ft / s2
Depth of Flow at the lower end (h) = (Q2/ b2 x g)1/3
= ((17.5)2/ (3.0)2 x 32.2)1/3
= 1.0 Ft
Depth of Flow at the Upper End (H) = √(1.0)2+ 2(1.486)2((11.775)2/32.2(1.0)(3.0)2
= 1.76 Ft
Depth of Flow in the Launder = 1.76 Ft
Add friction allowance of 25 % = 0.44 Ft
Add 1.0 Ft to ensure Free Fall = 1.0 Ft
Total Depth of Launder (1.76 + 0.44 + 1.0) = 3.2 Ft
Say = 3.25 Ft (Say)
A rectangular channel 3 Ft wide and 3.25 Ft deep shall be provided around the Flash Mixer. The depth of the channel is measured from the weir crest feeding the channel.
2.3.1 Sizing of Flash Mixer
Design Criteria
Governing parameters in the design of Flash Mixer are Velocity Gradient (G) and the Detention Time (t). Varying, values of G and t have been recommended in the literature. The values recommended for the design of Flash Mixer along with their reference and the values adopted are given below:
Design Parameter
Ref 1
Ref 2
Ref 4
Ref 5
Ref 6
Adopted
Velocity Gradient (G)
500 – 1000 1/s
600 – 1000 1/s
300 or More
500 - 600
1000
Detention Time (t)
10 - 20 Sec
60 - 120 Sec
1 - 10 Sec
30 - 60 Sec
20 -30 Sec
10 Sec
Power Requirement
2 – 5 Kw /M3/Min
1-3 Watt/M3/Hr
4-10 Kw/M3/Sec
10.9 Kw/M3/Sec
Depth /Dia Ratio
0.5 - 1.1
0.2 to 0.4
1.0
1. Water Supply & Sewerage by E.W Steel & Terence J.McGhee (P-232)
2. Hand Book of Environmental Engineering Calculations by C. C. Lee & Shun Dar Lin (P - 1.363)
3. Environmental Engineering, A Design Approach by ArcadioP.Sincero & Gregoria A. Sincero (P 267)
4. Introduction to Environmental Engineering by Davis & Cornell (P203 – 204)
5. Water Supply Engineering by BC. Punmia, Ashok jain & Arun Jain (P – 277)
6. Water Supply by A.C Twort, F. M. law (P – 252)
In addition Ref (3) recommends the following G & t values:
Detention Time (t) – Sec
Velocity Gradient (G) - 1/Sec
0.5
4000
10 – 20
1500
20 – 30
950
30 – 40
850
40 -130
750
Design
Design Flow = 18.9 MGD
= 35.0 Cusecs
Detention Time = 10 Sec
Volume = 350 Cft
Average Depth = 8.0 Ft
Area = 43.75 Sft
Diameter = 7.5 Ft
Depth /Dia Ratio = 7.5/8
= 0.94
Provide Flash Mixer Tank 7.5 Ft diameter and 8 Ft deep fitted with vertical shaft mounted high speed Agitator Mixer.
2.3.2 Sizing of Rapid Mixer
Temperature = 20 0C ( 68 0F)
Absolute Viscosity (µ) = 0.00098 N-s/m2
= 2.050 x 10-5 lb.s/ft2
Design
Dynamic Viscosity (µ) =2.050 x 10-5 lb.s/ft2
Volume of Flash Mixer (V) =350 Cft
Velocity Gradient (G) =1000 1/s
Power of Agitator (P) = G2 µV
=(1000)2x2.050x10-5x 350
= 7175 Ft lb / s
= 7175 / 550
= 13.05 hp
= 13.05 x 0.746
= 9.73 Kw
Efficiency of Motor Power to Water Power = 0.9
Motor Power of the Mixer = 9.73/0.9
= 10.81 Kw
Provide 1 No Mixer with output power of 10.81 Kw at rotational speed of 110 - 175 Rev / Min.
Governing parameters in the design of Flash Mixer are Velocity Gradient (G) and the Detention Time (t). Varying, values of G and t have been recommended in the literature. The values recommended for the design of Flash Mixer along with their reference and the values adopted are given below:
Design Parameter
Ref 1
Ref 2
Ref 4
Ref 5
Ref 6
Adopted
Velocity Gradient (G)
500 – 1000 1/s
600 – 1000 1/s
300 or More
500 - 600
1000
Detention Time (t)
10 - 20 Sec
60 - 120 Sec
1 - 10 Sec
30 - 60 Sec
20 -30 Sec
10 Sec
Power Requirement
2 – 5 Kw /M3/Min
1-3 Watt/M3/Hr
4-10 Kw/M3/Sec
10.9 Kw/M3/Sec
Depth /Dia Ratio
0.5 - 1.1
0.2 to 0.4
1.0
1. Water Supply & Sewerage by E.W Steel & Terence J.McGhee (P-232)
2. Hand Book of Environmental Engineering Calculations by C. C. Lee & Shun Dar Lin (P - 1.363)
3. Environmental Engineering, A Design Approach by ArcadioP.Sincero & Gregoria A. Sincero (P 267)
4. Introduction to Environmental Engineering by Davis & Cornell (P203 – 204)
5. Water Supply Engineering by BC. Punmia, Ashok jain & Arun Jain (P – 277)
6. Water Supply by A.C Twort, F. M. law (P – 252)
In addition Ref (3) recommends the following G & t values:
Detention Time (t) – Sec
Velocity Gradient (G) - 1/Sec
0.5
4000
10 – 20
1500
20 – 30
950
30 – 40
850
40 -130
750
Design
Design Flow = 18.9 MGD
= 35.0 Cusecs
Detention Time = 10 Sec
Volume = 350 Cft
Average Depth = 8.0 Ft
Area = 43.75 Sft
Diameter = 7.5 Ft
Depth /Dia Ratio = 7.5/8
= 0.94
Provide Flash Mixer Tank 7.5 Ft diameter and 8 Ft deep fitted with vertical shaft mounted high speed Agitator Mixer.
2.3.2 Sizing of Rapid Mixer
Temperature = 20 0C ( 68 0F)
Absolute Viscosity (µ) = 0.00098 N-s/m2
= 2.050 x 10-5 lb.s/ft2
Design
Dynamic Viscosity (µ) =2.050 x 10-5 lb.s/ft2
Volume of Flash Mixer (V) =350 Cft
Velocity Gradient (G) =1000 1/s
Power of Agitator (P) = G2 µV
=(1000)2x2.050x10-5x 350
= 7175 Ft lb / s
= 7175 / 550
= 13.05 hp
= 13.05 x 0.746
= 9.73 Kw
Efficiency of Motor Power to Water Power = 0.9
Motor Power of the Mixer = 9.73/0.9
= 10.81 Kw
Provide 1 No Mixer with output power of 10.81 Kw at rotational speed of 110 - 175 Rev / Min.
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