Question

Comment upon sewage treatment.

Hint:

Remember the 3 stages of sewage treatment: Primary (physical), Secondary (biological), and Tertiary (chemical/advanced).

Answer 1

Step 1: Introduction.
Sewage treatment is the process of removing contaminants, organic matter, and harmful microorganisms from wastewater before releasing it into the environment. It protects human health and maintains ecological balance.

Step 2: Stages of sewage treatment. \begin{enumerate} \item Primary treatment: Involves physical removal of large particles through filtration, sedimentation, and grit chambers. Removes about 30–40% of organic matter. \item Secondary treatment (Biological treatment): Utilizes microbes (bacteria, fungi, protozoa) to decompose organic matter. \[\begin{array}{rl} \bullet & \text{Aerobic process: Uses aeration tanks and activated sludge.} \\ \bullet & \text{Anaerobic process: Produces biogas from sludge digestion.} \\ \end{array}\] \item Tertiary treatment: Advanced stage involving chemical treatment, disinfection (chlorination, UV light), and nutrient removal (phosphates, nitrates). Ensures water is safe for release. \end{enumerate}

Step 3: Importance.
\[\begin{array}{rl} \bullet & \text{Prevents spread of water-borne diseases.} \\ \bullet & \text{Reduces environmental pollution.} \\ \bullet & \text{Produces useful by-products like biogas and treated water for irrigation.} \\ \end{array}\]