A breif Overview

Hooghly River is the main source of potable surface water for the city of Kolkata supplied from the age-old Palta Water Works now rechristened as Indira Gandhi Water Treatment Plant. The Palta Water Works ,spreading over a sprawling strechh of 480 acres,was the first intake point constructed during 1864-1870 for generation and supply of water . Initiated with a humble capacity of 6 mgd (million gallon per day),filtered water was generated through sedimentation in pre and final settling tanks and slow sand filteration in the Old Series of 12 filter beds. Further addition of 24 beds with a capacity of 1 mgd per bed,was made during the period 1888-1893. In 1905,filter beds with 2 mgd capacity ,called New Series was started . Further addition took place in between 1920 and 1936 when 17 nos.of 3mgd capacity and 1 no.of 2mgd capacity filter beds,called Extension Series were introduced.

It is said that old is gold and the relentless service of this age-old pumping station is certainly proving the point. With an output of 130 mgd,the plant seems to have perenial capacity to serve.

The slow sand filternation system is an effective and reliable system which does not required daily washing. A single bed can work upto 100 to 120 days.Formation of a biological mat soon after effective charging removes turbidity,colour and microoraganisms,by 95%. Due to this process,requirement of chlorine as a disinfectant of about 10 to 20 mm of top sand layerr every 100 day,make the bed ready for reuse.

Further development took place with the introduction of rapid gravity filter with 12 beds and 20 mgd capacity during 1952. This process helped in reducing the sedimentation time. In 1968,another 60 mgd rapid gravity filteration unit was added.

The present arrangement did not however,seem to suffice the demand level. In 2002,KMC supplied 281 mgd of water,falling short of the demand by almost 50 mgd. However,in 2003,the average supply rose to 334 mgd, meeting nearly 90% of requirement. Keeping in tune with the growing rate of population and proportionally accelerating rate of demand,KMC has undertaken several capacity enhancement and upgradation programmes and hopes to exceed the demand by 2005.

New Palta Water Wokrs at Indira Gandhi Water Treatment Plant,is a notable step in this development process. It is a 100 mgd water generation project. This scheme,which is to be commissioned on 29th July 2004,further augments the capacity of Palta by 60 mgd,taking the already commissioned 20 mgd treatment plant,out of the planned 100 mgd additional supply. This ,along with the increased supply from Garden Reach Water Works,will increase the per capita water supply to 234 liters per day from the present 202 liters per day. This would indeed be a feather in the cap of KMC,as it benchmarks the highest water supply level in the country.

Intake Jetty

New Palta is a completely self-sustained water treatment plant capable of suplying 100 million gallon water per day. In addition to the two old jetties,it has a new jetty to draw unpurifed river for treatment. The delivery process is aided by three 72" suction mains,that end in underwater bellmouths.

Intake Pumping Station

The intake pumping is equipped with six pumps of 42 mgd capacity ,each having motor units. The intake station has 100% standby capacity. Collectively,only 3 pump- motor stes are capable of drawing 100mgd water from the river. The pumping station ,equipped with modern state-of-the-art control pumps,controls all the operations of the pumps. The impure water extracted from the river consits of suspended purification.

*mgh : million gallon per hour
Treatment Plant

The treatment plant is equipped with five modules eachh of capacity 20 mgd for the purification of the 100 mgd intake. Out of these five,three have already been constructed and will commence operation from the day of inauguration. Built with modern French technology of pulsator clarifier,the treatment modules treat water through a sludge blanket created through upward flow of alum mixed water. The five modules around the central administrative building resemble the design of a fan. The construction of two remaining modules will be completed by 2005.

Pulsator Clarifier

This is a reactor type clarifier having inflow of water through bottom. While allowed to get through the bottom,it gets thoroughly mixed up with induced alum solution and chlorine gas. Moreover the sludge formed out of coagulation is also getting a boost for floating due to upward pressure. The sludge floating scatteredly forms a thick blanket and floats little below the clarified water face at 5. When this blanket is thick , it is supported through supplemented thrust of pulsator plates at 4. When it is furtehr thicker it spills through the drain at 10. Thus raw coagulated and disinfected water passes throough the sludge blanket field and clarified water is collected through the gutters at 2 fro passing it to filter. The turbidity of the clarified water achieved in this process is below 10 NTU.

Pressure Station

The water purified at the treatment plant,needs to be trasmitted to the city at a distance of almost 40 km. To precisely conduct the task,a new pressure station equipped with six pump-motor sets has been constructed. While three of these pumps are sufficient to create the pressure for transmission of 100 mgd water, the remaining three provides 100% standby for any emergency situation is powerful enough to create a water jet of 110 feet height,equal to that of a ten-storied building.

Pipeline

62" HDPE pipes,extending for 3.5 km have been laid down to carry the entire capacity of 100 mgd water from Palta to Tallah. The diameter of existing pipelines were 48",54" ,60" and 72". KMC ,for the first time in India,rehabiliated the one km 62" corroded HDPE ( High Density Poly Ethylene) pipes. With the help of this new technology,the completion of work was possible within a record time of 29 days, without disrupting traffic or damaging the roads.

Electrical Sub-station

One 33 KV electrical sub-station has been commissioned to receive the direct high tension power from CESC source for the augmented electricel installations including existing electrical installations. Another 6KV electrical sub-station with necessary network has been commissioned to step down th ehigh tension dedicated servial to suit the input requirement of all new existing electrical prime movres and other ancillaries.

Future Treatment Plant

While 60 mgd treatment facility has been commissioned,work has already started for construction of another 49 mgd treatment plant.

This treatment plant would be built on Settler Technology. This will imply that the entire Palta facility would be a mix of old and reliable,maintenance free slow sand filter,more advanced rapid gravity filter,state-of-the-art pulsator and relatively low O&M based plate Settler Technology.

The 40 mgd treatment plant is planned to get ready by April 2005.

Also in order to improve the availability and quality of water supply in the city ,construction of water treatment plants at Jorabagan and Watgunj has been undertaken.

Watgunj
This 5mgd water treatment plant cum booster pumping station is being constructed with the aid of new technology at Watgunj Square to supply water from Palta Water Works and meet the requirement of filtered water for th eresidents of Watgunj and Hastings area.

Jorabagan
This 8mgd water treatment plant and 3.5 mgd underground reservoir cum booster pumping station will filter and supply water generated at Mullick Ghat Pumping Station to the water scare area of Chitpur,Nimtala,Sovabazar and adjoining areas of North Kolkata.

Reservoir and Booster Pumping in Offing

Bagmari
This 6mgd underground reservoir cum booster pumping station ,which is to be commissioned in August ,is one of the largest boosting sations in the city. With a total of 29.36 km of distribution line,it shall supply water from Palta Water Works to the residents of Maniktala,Ultadanga,Bagmari and adjoining areas thus substantially reducing the dependence on ground water in these areas.

Ranikuthi
This 3.5 mgd underground reservoir cum booster pumping station is ready to serve the residents of Tollygunge,Dhakuria and adjoining areas. Located by the side of Ranidighi in Tollygunge,this station would supply filtered water of Garden Reach Water Works through an elaborate distribution pipeline network.

Kasba
This 3.5 mgd underground reservoir cum booster pumping station ,which is to be commissioned by the end of this year,will get water from Palta. The citizens of the fast growing area of East Kolkata shall be receiving treated water from this booster station. This will also substantially reduce the dependence on ground water in these areas.

Kalighat
This 4 mgd underground reservoir cum booster pumping station is being constructed at Kalighat Park to supply water to a vast area of South Kolkata. The dedicated supply line to bring water from Garden Reach Water Works is beign laid down to meet the completion deadline of the project of 31st december 2004.