Cleaner water from sewage

Rainbow Drive Layout, Bhoomi Network for Sustainable Living and Biome Environmental Solutions had together organised a talk by Dr Chandrashekar from Vision Earthcare on May 30th 2010 at the Rainbow Drive Club House on Sarjapur Road.

Dr Chandrashekar articulated the limitations of existing STPs and how an ecological method which is Soil Biotechnology (SBT) based STPs, researched for over two decades at IIT-Bombay, provides clean river quality water at a lower cost. Vision Earthcare, incubated in IIT Bombay, has licensed this method for deployment globally.

Attendees of the talk included ex-panchayat leaders, active citizens from several layouts, chemical and environment engineers and several residents from various communities who are concerned about the current precarious state of water and water bodies.

3 Million Litres per Day (MLD) sewage purification in Corporation of Bombay. Pic credit: Vision Earthcare.

STP treats domestic waste water for disposal. However, apartments and gated communities situated away from the city are totally dependent on bore wells or water tankers. It is mandatory for them to have their own STPs. Cauvery water for these communities is a distant dream at best. Hence, the realities are forcing them to look upon their waste water output as an abundant new source of water. Some communities have started reusing their treated water for flushing and gardening although there are serious problems with the quality of the treated water. Most STPs in communities are Activated Sludge Process (ASP) based.

Conventional technologies

In conventional technologies such as ASP, aeration is achieved mechanically, which is very energy intensive. At higher ambient temperatures (like in India) the solubility of oxygen in water is low, therefore energy requirement increases.

Moreover, air contains only 20% oxygen, the rest being nitrogen that is passed into water wastefully, further adding to process inefficiency. In addition to these inherent limitations of the method, several additional reasons make the reality worse. Treat it somewhat; dump it somewhere is the usual story in most communities.

Several important points were highlighted during the interaction. Some of them were:

1. Conventional STPs are designed for disposal rather than for reuse.

2. They are overloaded, poorly maintained and are prone to frequent breakdowns and are also usually operated by unreliable vendors who employ unskilled labourers as “STP operators”.

3. In addition to a hefty monthly fee, vendors pressurise communities to replace pumps, motors fairly often (to obtain ‘commissions’).

4. There is also significant monthly electricity cost for running STPs.

5. Many communities do not perform an independent quality test of treated water. Vendors usually rig the tests to fake compliance with Karnataka State Pollution Control Board (KSPCB) standards. Foul odour is very common.

Thus STPs in most communities not only consume large amount of resources but pollute surface water bodies and eventually our only source, ground water, when partially treated water is dumped onto open lawns or into storm water drains. Vendors pocket large sums and tanker mafias continue to benefit because of increasing demand for water, while communities grapple with water shortage, pollution and flooding.

Soil Biotechnology (SBT) based STPs

SBT is a major paradigm shift in waste processing. Sewage treatment is just one application among many – it can be used for arsenic/iron removal, hospital waste processing, industrial waste water processing and industrial air purification and so on. Because of its versatility, it revolutionises the way we look at waste water.

SBT treats water for reuse rather than disposal. Since it reinforces the carbon and nitrogen cycles in nature, the quality of the treated water exceeds KSPCB standards reducing Chemical Oxygen Demand (COD) nitrates to very low levels unlike any other STP method. It is highly scalable and can be designed for houses, apartments, gated layouts, towns or cities. The treated water can be reused in many ways:

• Can be sold to constructions/industries who normally purchase tankers. Plant costs can be recovered within a few years depending on the amount of reuse.

• Can be piped back to homes for flushing toilets, gardening, washing yards, cars which can be almost 50% of daily requirements

• It can be used to recharge ground water using rain water harvesting echarge wells. It acts like virtual rain – when you want it, where you want it, how much and at the required rate.

Ecologically safe

SBT is a patented method (US and Indian) developed by Prof H S Shankar, Department of Chemical Engineering, IIT Bombay. It uses only natural materials, natural agents (bacteria culture, worms) and natural processes (respiration, photosynthesis, nitrogen fixation) – it is ecologically 100% safe.

Unlike a conventional STP or septic tank where periodically the sludge has to be offloaded, everything is consumed within the plant in this Soil Biotechnology (SBT) based STP. Raw sewage is pumped to a customised media bed for around 5 hours (dependent on load and capacity) and clean water flows into the collection tank.

It has at most two motors, unlike conventional Activated Sludge Process (ASP) based STPs with numerous motors, stirrer, blower, reverse flush tank, clarifier, sludge pumps and so on. Hence it is energy and cost efficient and requires minimal maintenance while being more reliable.

The recurring cost consists of natural materials used as additives and it can be operated by gardeners rather than environmental engineers. Life of the specially constituted filtering media bed  is long (tens of years) since with time the natural living agents multiply or shrink to optimal levels based on the actual chemical and biological load in the system.  Unlike other ecological STP methods it is far more space and time efficient.

Watch this interview with Professor Shankar, showcasing 3 Million Litres per Day (MLD) sewage purification in the Corporation of Bombay. There have been more improvements to the method since then.

Many communities who have ASP based conventional STPs may hesitate to replace it with a brand new one. Consider these:

1. Your existing STPs are expensive (maintenance, operation) while not providing any water for reuse.

2. Rain water harvesting investment can be leveraged with SBT for storage, reuse and recharge on a daily basis, all year.

3. In our community in Rainbow Drive, if we purchased water tankers for our current consumption, our yearly cost would pay for a new SBT plant.

In conclusion, the fundamental process accomplished by any STP is taking impurities to their highest oxidised state. Since SBT, processes waste on land rather than inside water it is inherently superior to all the current STP technologies in installation, operation, effectiveness and longevity. For water security SBT is a must and a blessing.   ⊕


  1. SBT is surely a today’s need. It is not only cost effective but also environment friendly solution for your sewage management. It is perfect for places where any civil drainage system is not available.

    Sheetal Sharma

  2. In Ahmedabad We was last 20 year manufactured in water treatment system like reverse osmosis plant, water demineralization plant, water purification plants, water filtration plant, water softening plant etc…

    If you are interested our product Please contact to be informed.we are call back as soon as.

  3. In Bangalore, SBT has been installed at the ACCEPT Aids Care Hospice at Doddagubbi (5km from Outer Ring Road Hennur Cross intersection) and is functioning well. Periodic visits to the facility are organised for interested people. Please contact to be informed of the next visit.

    On the occasion of World Water Day, a visit is being planned on 19th/20th March 2011. Please contact above email address for more information.

  4. We have a underground activated sludge process based STP in our apartment that houses 740 flats in South Bangalore. We discharge, on an average 380 to 400 KL effluent per day. I agree 100 % with whatever Mr.Bharadwaj has mentioned in his article.

    Can any one do a quick work out to tell me how much it will cost to change over to a SBT process?


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