This story emphasizes what Ecotech has maintained through the years—the classic Extended Aeration Activated Sludge (EAAS) system is still the best STP Technology for micro, mini, and small STPs in residential apartment complexes, commercial office buildings, hospitals and colleges, etc.
The small little town of Kuppam with a population of 20,000 is best categorized as a Tier 4/Tier 5 town. Kuppam lies in the neighbouring state of Andhra Pradesh, roughly 130 Km East-South-East of Bangalore. It can be reached in about three hours by car on fairly well-tended roads. Ecotech had occasion today to visit this little town on an invitation from the prestigious PES group of institutions which runs a medical college, and a hospital attached to the college in Kuppam.
Our brief was to inspect, study, and solve the riddle of excessive loss of water in their Water Treatment Plant (WTP), which was in excess of 30%. This was when nearly 600 KLD of water extracted from their borewells was treated through a Pressure Sand Filter and a water softener. Our first thought was that the Ion Exchange resin in the softener may have outlived its usefulness and therefore was calling for frequent regeneration with common salt, followed by rinse operations which might explain the losses. However, we reserved judgement until we did a Gemba walk and an onsite physical inspection.
The puzzle was solved easily enough within minutes when the WTP operator on site confessed that he did a backwash of the sand filter once every three hours, for 20 minutes on each occasion. The backwash water was then wasted out into an adjacent open field. This practice was based on some sort of Standard Operating Procedure (SOP), possibly shared with him by the vendor who installed the unit. We showed the operator the quality and clarity of this “Backwash Waste” and his folly in blindly following the vendor’s advice and gave him a fresh SOP based on the scientific principles of pressure loss across the filter measured by two pressure gauges, one fitted before and one after the filter. The small-town boy was beaming with pleasure, nodding his head at this simple, logical, common sense explanation when we left him to inspect the Sewage Treatment Plant (STP) on the other side of the campus.
Not one, but two STPs we were told were on campus; one rated at 200 KLD and the other at 400 KLD. Having seen the status of the WTP operation, we trudged along towards the STPs, expecting the worst.
To our pleasant surprise, both STPs were in perfect working condition, each receiving the design quantity of wastewater and producing treated water of excellent quality. This was not unlike any STP that we at Ecotech operate and maintain. The secret of this success was not a mystery—both STPs were built on the classic EAAS (Extended Aeration Activated Sludge) technology, and were designed and engineered well.
In the remote little town of Kuppam we saw a 100% success rate of STPs. If Bangalore enjoyed the same success rate, the lakes of our city would not have to suffer.
This story of Kuppam would be incomplete without a final piece of teaching and learning. When we asked the young lad how many times he backwashed the filter in the STP, he very respectfully replied that he did this procedure two times a day. Given this, do you really need to backwash the filter in the WTP—which is handling much cleaner borewell water compared to the sewage water handled in an STP—every three hours?
Good environmental engineering is 50% knowledge, expertise and experience; the other 50% is common sense.