Treating Sewage

Background

When buying the flat, I asked the builder about sewage management. The property is on the city outskirts, right across from a river, with no municipal drainage. Wanting to avoid contributing to river pollution, I pressed for details, but the builder’s response was vague. Apparently, the local municipality had insisted on treating sewage within the campus.

Eventually, the builder made some clever moves and tricked the Resident Welfare Association (RWA) into paying for the plant. By the time I discovered the association existed and had funded the facility, it was too late. Seeing how things were handled, I decided to take over the RWA and manage operations myself

How the Sewage Treatment Plant (STP) Works

Here is a brief look at the design:

• Collection: Wastewater from toilets, kitchens, and greywater drains into two underground tanks before being pumped into the STP.

• Biological Treatment: The STP tanks are primed with bacteria. Air blowers continuously aerate the tanks to accelerate decomposition.

• Separation: The bacteria break down the sewage; sludge floats to the surface while the treated liquid passes through a filtration unit.

• The Goal: In theory, the final filtered water is safe enough to be discharged into the river stream.

Operational Challenges

While simple in theory, running the STP in reality proved highly complex due to several factors:

• The setup relies on multiple paired components running alternately—two raw water pumps, two aeration blowers, two filter feed motors—plus a sludge return motor.

• Combined with an erratic power supply, at least one part of the system would break down every two months.  It will go for repairs or be replaced with a new component.

• The system was built for processing 48,000 liters per day.

• Unmindful water consumption by residents often pushed usage 20% above capacity, stressing the entire setup.

• Filtration is the slowest stage. High inflow meant the filter couldn't keep up, forcing us to bypass sediment filtration just to manage the volume.

• Residents were unaware of how delicate the system was. Items like sanitary napkin shreds and condoms frequently clogged the foot-valves, requiring manual removal and pipe lifting by staff.

As a result, processing was frequently disrupted, occasionally leading to overflows of untreated water or the release of unfiltered water.

Solutions & Results

To fix these recurring issues, we implemented several corrective measures:

• Replaced standard raw water pumps with cutter pumps to handle debris, automated filter feed motors to prevent dry runs, and adjusted foot-valve heights to avoid thick sludge layers.

• Installed an irrigation pipe network across our campus to distribute treated water locally.

• Took advantage of our dry climate, absorbent soil, and spacious grounds by planting high-water-absorbing plants to soak up the water naturally.

The Outcome

The ground absorbed the treated water well, enriching the soil with microorganisms, earthworms, and birdlife, effectively creating a small thriving local ecosystem.

While this issue ended on a positive note, I remain concerned about the fragility of the system and the impact of harsh household cleaning chemicals entering the system.

It is striking how something that wasn't an issue 50 years ago now costs several lakhs of rupees annually just for basic sanitation. Perhaps that is the reality of modern urban living: create a problem, then spend significant time and money trying to solve it.