Transforming Sewage into Usable Water: A Tour of a Sewage Treatment Plant
Every day, each one of us generates about 200 liters of sewage. In this article, we will take you on a fascinating journey to explore how 90% of this sewage is converted into usable water. Aditya, from Greentivity, will guide us through their sewage treatment plants (STPs) in Bangalore. Astoundingly, they generate a whopping one crore liters of water every single day.
The sewage treatment process begins in the bar screen chamber, the first destination for all waste from the apartment. Here, a mechanical filter screens out all unwanted materials such as condoms, pet hair, human hair, sanitary parts, pregnancy test kits, and other debris that residents might irresponsibly flush down their drains. These materials, if not removed, could potentially damage the plumbing and clog the motors and pumps.
The bar screen chamber also features an oil and grease trap. Despite the fact that kitchen oils, fats, and greases are not meant to be flushed down the drain, they often find their way there. These substances are skimmed away in this chamber.
After passing through the bar screen chamber and the oil and grease trap, the sewage flows into the raw sewage tank. Here, the varying sewage load is equalized, ensuring consistent quality of sewage for further treatment. The term "sewage load equalization" refers to the process of standardizing the biological load of the sewage, which changes throughout the day depending on various factors such as bathing, toilet usage, or operation of washing machines and dishwashers.
One of the unique aspects of Greentivity's STPs is the absence of odor, vapor, or gas from the raw sewage tank onwards. The specifics of how they achieve this remain a proprietary secret.
From the raw sewage tank, the sewage moves into the anoxic zone. This is a recommended addition under BS6 regulations for the removal of excess nitrogen, ammonia, and phosphorus—collectively known as biological nutrient removal (BNR).
Following the anoxic zone, the fluids move into the aeration tank, the heart of any sewage treatment plant. In this tank, millions of tiny microbes digest the sewage, aided by the introduction of oxygen. This biological process, similar to the role of earthworms in composting, essentially treats the sewage as food for the microbes, resulting in clear water and some amount of sludge as byproducts.
The subsequent stage of the process takes place in the secondary clarifier, where the sewage flows by gravity, and the sludge is transferred back to the anoxic zone. Clear water then flows over this chamber and moves to the filter feed tank.
In the filter feed tank, the water is pumped through a sand and carbon filter under pressure. The sand filter removes any residual organic matter, while the carbon filter eliminates odor and color. The water is also disinfected through chlorination.
Finally, the treated water emerges, colorless and odorless. It is a testament to the effectiveness of the sewage treatment process, transforming waste into a vital resource.
Greentivity, through its STPs, serves Bangalore and the entirety of South India. If you have any questions about STPs or are interested in their services, feel free to reach out to them.
Let's continue striving for sustainable and responsible water management practices. Our actions today will determine the availability and quality of water for future generations.