Wastewater Treatment MCQ with answer and solution

Concept

Biological removal of organic matter in attached growth systems occurs through microbial action within the biofilm formed on the filter media.

Step-by-step solution

1. Understand the working principle of a trickling filter: it is an attached-growth aerobic biological process. 2. As wastewater trickles over the filter media, a biological slime layer (biofilm) develops. 3. Microorganisms (bacteria, fungi, protozoa) present in this biofilm consume the organic matter (BOD) as food under aerobic conditions.

Explanation

A trickling filter is an attached growth biological treatment process. Wastewater is sprayed over a bed of media (such as rocks or plastic) coated with a biological slime layer (biofilm) consisting of aerobic and facultative bacteria, which metabolize and remove the organic matter (BOD) from the wastewater.

Why the other options are wrong

A: Sedimentation only removes suspended solids, not dissolved or colloidal BOD. B: Anaerobic digestion occurs in the absence of oxygen, whereas standard trickling filters are aerobic processes. D: Coagulation is a chemical treatment process used to destabilize colloidal particles, not the primary mechanism of biological filters.

Shortcut

Trickling filter = Attached growth = Biofilm microbial action.

Common mistake

Confusing trickling filters with suspended growth systems like Activated Sludge Process (ASP) or mistaking them for simple physical straining/sedimentation processes.