Question

Why is secondary treatment also called biological treatment? What is the principle involved? What are the two alternative techniques used?

Short answer

Secondary treatment is called biological treatment because it uses microbes to decompose organic materials in wastewater. The key principle involved here is the conversion of organic matter into harmless by-products by these microorganisms. The two alternative techniques for this process are aerobic and anaerobic treatment.

Step-by-step solution

Understanding Secondary Treatment

Secondary treatment, also known as biological treatment, involves the use of microbes to remove organic materials from wastewater. This stage comes after primary treatment where large solids are removed by sedimentation.

Principle Involved in Secondary Treatment

The principle involved in secondary or biological treatment is the breakdown of organic matter into harmless end products. Microorganisms consume organic material as food, thus cleaning the water.

Alternative Techniques Used in Secondary Treatment

Two major techniques used in this process are Aerobic and Anaerobic treatment. In Aerobic treatment, microorganisms that need oxygen break down waste. In the Anaerobic process, bacteria that function without oxygen convert organic matter into biogas.