Sewage Treatment Methods and Inherent Problems

Sewage treatment is the process of removing contaminants from wastewater, primarily from household sewage. There are several sewage treatment methods available, each with its own advantages and disadvantages. In this question, we are asked to identify the sewage treatment method that has inherent problems of odour, ponding, and fly nuisance. Let's take a closer look at each of the options provided:

a) USAB system - The Upflow Anaerobic Sludge Blanket (UASB) system is a type of anaerobic digester that is used to treat wastewater. It is designed to treat high-strength organic wastewater streams and is particularly useful in developing countries where electricity is limited. However, this system does not have inherent problems of odour, ponding, and fly nuisance.

b) Activated Sludge Process - In the activated sludge process, sewage is mixed with a microbial culture in a tank. The microbes consume the organic matter in the sewage, and the resulting sludge settles to the bottom of the tank. This process is effective in removing organic matter and nutrients from wastewater, but it does not have inherent problems of odour, ponding, and fly nuisance.

c) Trickling Filters - A trickling filter is a fixed-bed, biological reactor that is used to treat wastewater. In this system, wastewater is distributed over a bed of rocks or other media, and microorganisms attached to the media consume the organic matter in the sewage. This system has inherent problems of odour, ponding, and fly nuisance because of the following reasons:

- Odour: Trickling filters produce a lot of odours due to the decomposition of organic matter by microorganisms. The odour can be particularly strong if the system is not properly ventilated.
- Ponding: Trickling filters require a constant flow of wastewater to function properly. If the flow rate is too low, the wastewater can accumulate on the surface of the media, leading to ponding.
- Fly Nuisance: Trickling filters can attract flies, which can be a nuisance to people living nearby. Flies are attracted to the decomposing organic matter in the system.

d) Stabilization Ponds - Stabilization ponds, also known as lagoons, are shallow ponds that are used to treat wastewater. In this system, wastewater is held in the pond for an extended period of time, allowing natural processes to break down the organic matter in the sewage. This system does not have inherent problems of odour, ponding, and fly nuisance.

Conclusion

In summary, the sewage treatment method that has inherent problems of odour, ponding, and fly nuisance is the trickling filter. While this system is effective in removing organic matter from wastewater, it can produce a lot of odours, lead to ponding, and attract flies.