The water we drink.

Bangalore is a city which is growing very fast, thanks to the influx of people from all over the world, for it has made a name as the Education and IT hub of the country. One can find people of all kinds of ethnicity and religion on the streets of Bangalore. And guess what, the probability of you finding a person who shares the local tongue and dialect is very less, not to mention a particular category of people who fake their ignorance of the local language.

The point I am trying to make is that being a rapidly growing city in terms of area as well as population, Bangalore has got its share of problems. Some of the problems everyone experience is traffic, then comes water, power and also the ever increasing cost of living. There are times when the water supply won’t be regular; sometimes people may have to manage without the regular water supply by the municipal body. When we face these kinds of problems, it is a natural reaction for the citizens to get angry and blame the water supply board. Even I was among one of them until recently but my views changed a bit after I visited the water treatment and pumping station run by Bangalore Water Supply and Sewage Board (BWSSB) which is the government body which is responsible for the water supply and other related operation.

The water we get in the taps is sourced from the river Cauvery which is one of the major rivers in the country and flows across the southern Deccan plateau. This water treatment and pumping station is about 85kms away from the city and the river flows another 20 -25kms away from this. The water from the river is diverted from Shiva Anicut (Dam/ reservoir) which is situated near Shivanasamudra which is known for being the first hydroelectric power station in Asia. The water diverted from there makes use of the height (head) difference and flows until it reaches the Netkal Balancing Reservoir (NBR) from where it flows to the treatment plant situated in T.K halli (Torekadahalli) which is 9kms away from the NBR. In the T.K Halli facility, they treat the raw water from the NBR and then is pumped further towards the city. This facility is the first pumping station along the supply line which is followed by 2 more pumping stations before the water reaches Bangalore. This plant has 4 stages and the 5th one is under construction. The first stage, commissioned in the year 1974 has an output of 135 MLD, the second stage commissioned in 1982 has the same output of 135 MLD. Third stage came into operation in 1993 and has the capacity of around 330-350 MLD and the most recent one being the stage 4 plant, which started in 2002 operates at 330 MLD at the moment.

I had the privilege to visit the stage 4 plant recently and was surprised to find the whole operation automated and they recover as much water as possible during the operation of this plant. The water flows in from NBR and it is subjected to aeration in a cascade aerator where the water is made to flow down stepwise and this improves the contact with the atmospheric oxygen and brings about aeration. This aerated water then flows to the next section of the plant where it is subjected to pre chlorination. The chlorine gas is mixed with liquid phase (water) and is fed to the pre chlorination section. The chlorine levels are maintained at 1 ppm in order to bring about the disinfection of water. Then the raw chlorinated water is checked for turbidity and pH. This water source is found to have a constant pH of 8, so eliminating the need to regulate the pH but still the checks are carried to for variations. The turbidity is treated by using alum as a flocculating agent. The dosage of alum depends upon the turbidity of water. Compared to summer, the turbidity will be more in rainy season. This alum brings about flocculation of the suspended solids in water and in turn undergoes sedimentation in the pulsator clarifiers where the water is retained for around 20 minutes or more depending upon the amount of suspended particles present. The clean water obtained is made to flow into the filtration section where it gets filtered in Rapid sand filters. Once the filtration is done the water flows to the pumping station from where it is pumped towards Bangalore. The sludge formed in the clarifiers are pumped into a Sludge thickener where the sludge is thickened and the remaining water is removed and pumped back to the first step of treatment process again. The filters are backwashed once after every shift using air and water at pressure from below. The plant operates round the clock with three 8 hour shifts per day.

The treated water is again recharged with chlorine and pumped using huge centrifugal pumps. The water pumped has to pass through 2 more pumping stations before it reaches the city. The water is recharged with chlorine at every station and again once in the city before distribution. The water from all the 4 stages of this plant amounting to around 950 MLD is pumped using around 20 pumps making this the main source of water for the city. Around 190 MLD is sourced from one more river Arkavathy through another 2 pumping stations situated in Hesarghatta and T.G Halli near Bangalore.

That was a detailed description of the things I managed to remember, and the engineer there also made it a point to inform us that in case if they have to carry out any maintenance work, the plant has to be shut for a day or so, and this leads to a drastic reduction in the amount of water pumped and hence the interruption of regular supply of water in many areas of Bangalore.

But can’t we make use of the recycled/treated water from many sewage treatment plants set up in and around Bangalore to meet our non-potable requirements and reduce the demand thereby conserving water and saving the energy required to purify and pump water from far off places?? Think about it and work towards it.