Question

In anaerobic wastewater treatment the microorganisms present are?

• A. methane formers and acid formers
• B. actobacillus
• C. Nocardia
• D. Ecoli

Hint:

• Anaerobic digestion is a multi-stage process driven by a diverse microbial community.
• Key stages include hydrolysis, acidogenesis, acetogenesis, and methanogenesis.
• Acid formers (acidogens) are crucial for producing volatile fatty acids.
• Methane formers (methanogens) are crucial for producing methane, the final product.
• These two groups represent essential functional roles in the process.

Answer 1

The Correct Option is A

Anaerobic wastewater treatment, also known as anaerobic digestion, is a complex biological process involving a consortium of different types of microorganisms that work synergistically to break down organic matter in the absence of oxygen. The process generally occurs in four main stages, each carried out by distinct groups of microbes: Option (A) Hydrolysis: Hydrolytic bacteria break down complex organic polymers (e.g., carbohydrates, proteins, fats) into simpler soluble monomers (e.g., sugars, amino acids, fatty acids). Option (B) Acidogenesis (Acid Formation): Acidogenic bacteria (acid formers) ferment the products of hydrolysis into various volatile fatty acids (VFAs) such as acetic acid, propionic acid, butyric acid, as well as alcohols, CO$_2$, and H$_2$. Option (C) Acetogenesis: Acetogenic bacteria convert the VFAs and alcohols produced during acidogenesis into acetate, CO$_2$, and H$_2$. Option (D) Methanogenesis (Methane Formation): Methanogenic archaea (methane formers or methanogens) utilize acetate, H$_2$/CO$_2$, and other simple compounds (like formate, methanol) to produce methane (CH$_4$) and CO$_2$. Thus, the key functional groups of microorganisms essential for the complete anaerobic digestion process are acid formers (acidogens) and methane formers (methanogens), along with hydrolytic and acetogenic bacteria. Options (b) Lactobacillus, (c) Nocardia, and (d) E. coli are specific genera or species of bacteria. While some might be present in anaerobic environments or even participate in certain steps (e.g., E. coli can perform fermentation), they do not represent the broad, essential functional groups that define the entire anaerobic digestion process as comprehensively as "methane formers and acid formers." Nocardia are typically aerobic. \[ \boxed{\text{methane formers and acid formers}} \]