When a city hits a plateau with regard to water availability it perforce needs to become innovative in identifying alternative options. Right now many problems exercise the minds of citizens and institutions; garbage, sewage in stormwater drains and lake destruction are on top of them.
As you drive west out of the city on Magadi Road, a little after Sunkadakatte Cross you see a tank on your right. This is Herohalli tank, with a water-spread of about 14.50 hectares. The Bruhat Bangalore Mahanagara Palike (BBMP) has been working to restore it. The tank has been fenced to protect it from encroachment; a bund has been created to enable walkers to go around it. A major stormwater drain brings in water mixed with sewage as well as debris including plastic. An underground sewage line runs across the periphery of the tank too. This sewage line carries about 6 to 8 million litres of waste-water daily. The water from the storm drains is not enough to fill the tank.
A quite but dedicated team of engineers from the BBMP and a competent and young team of designers are working to resuscitate this water body. A new technology called Soil Bio-technology or SBT is being applied for the first time in Karnataka at a scale of 1.50 million litres per day treatment.
Use of strainersUsing the concept of sewage mining, the SBT system taps into the sewage line and draws 1.50 MLD into a small wet well. From here the water is strained using 20 mm and possibly 10 mm strainers to remove solids, plastics, grit and large sediments. This will be collected and removed separately. The remaining waste-water is then allowed to percolate gradually through a specially prepared bed of soil and stones which harbour million of good bacteria. These bacteria eat away at the carbon in the sewage and also change the composition of nitrates and adsorb phosphates to clean up the water.
As the water trickles down the special medium, it is collected at the bottom. If necessary it can be re-circulated to allow the bacteria to have another go at cleaning it up. The treated sewage that comes out of the system is crystal clear and meets the requirement necessary to be led into the tank.
From the top the SBT plant looks like a garden, beautifully landscaped and full of colourful flowers and grass. There is no smell and no unsightly scenes. The SBT plant occupies 2,000 square metres as a foot-print, a really small component of the tank. Eventually Herohalli tank will receive treated waste-water and will be full. This water, cleaned by nature, will in turn recharge the surrounding aquifers and be available as additional supply to the local residents. Bangalore will have converted sewage water into usable water using the SBT and the tank as nature’s kidneys.
Sewage flowing in the stormwater drains can also be diverted to the SBT plant and then allowed into the tank. The design provides for it.
There are problems though. Plastics and garbage thrown into the storm drains end up clogging the bars and creating a backflow in the drains. These also end up in the tank. Sewage flow is sometimes mixed with industrial waste-water. This is highly toxic and cannot be treated. What the SBT plant does for now is to allow this water to flow past and then pick up only domestic sewage.
None of the problems are of a nature that cannot be overcome. All we need is community participation and institutional responsibilities. What the city now realises is that everything is tied up — garbage management, stormwater management, sewage management, lake restoration and groundwater recharge. Citizens and others should visit the SBT plant and Herohalli tank, understand how an eco-system can be managed and try to do the same for the water bodies in their neighbourhood. The time to seize this challenge and overcome it is now or else we will have lost our lakes and will run out of water for the city.
