Wastewater Treatment MCQ with answer and solution

Concept

Anaerobic digestion is a biological process where organic sludges are stabilized in the absence of dissolved oxygen, producing biogas consisting chiefly of methane and carbon dioxide.

Step-by-step solution

1. Understand the anaerobic digestion process which occurs in the absence of oxygen. 2. Identify the breakdown products of complex organic compounds by anaerobic bacteria (acid formers and methane formers). 3. Recognize that the end products include stabilized sludge, water, and biogas. 4. Recall that biogas primarily comprises methane (CH4, 60-70%) and carbon dioxide (CO2, 30-40%).

Explanation

During anaerobic digestion, microorganisms break down organic matter in the absence of oxygen. The primary gaseous end-products of this biochemical process are methane (CH4) and carbon dioxide (CO2), commonly known as biogas.

Why the other options are wrong

A: CO2 is produced, but methane is also a primary constituent. C: Oxygen is absent in anaerobic processes. D: Hydrogen may be produced in trace amounts, but O2 is not produced.

Shortcut

Remember 'Anaerobic = Biogas = Methane + CO2'.

Common mistake

Confusing aerobic digestion (which produces CO2 and water with oxygen consumption) with anaerobic digestion.