Question

What do you mean by activated sludge in an STP?

Hint:

Include a relevant concept, shortcut, or useful trick related to solving this type of problem. Give useful quick tips for the question. Also properly format the text in quick tip as per latex. \textbf{Quick Tip (a):} Think of activated sludge as a concentrated community of beneficial microbes that are the workhorses of secondary wastewater treatment, responsible for breaking down organic pollutants. \textbf{Quick Tip (b):} Understand that anaerobic digestion of sludge is a multi-stage process involving different groups of bacteria that ultimately convert organic waste into biogas and a more stable, smaller volume of sludge. This process is crucial for both waste reduction and energy recovery in STPs.

Answer 1

Activated sludge is a flocculent mass of microorganisms, primarily bacteria, along with fungi, protozoa, and other aerobic microbes, that develops in the aeration tank of a Sewage Treatment Plant (STP) during the biological treatment of wastewater. This sludge is called ”activated” because the microbial community within it is highly active in consuming and oxidizing the organic pollutants present in the sewage. The process involves aerating the wastewater in the presence of this microbial floc. The microorganisms utilize the organic matter as their food source, metabolizing it and converting it into microbial biomass (more sludge), carbon dioxide, and water. The flocs of activated sludge have a spongy structure that allows for efficient adsorption and degradation of organic pollutants. After the aeration tank, the activated sludge is allowed to settle in a settling tank (secondary clarifier). Most of this settled sludge is then recycled back into the aeration tank to serve as an inoculum, ensuring a continuous and efficient biological treatment process.