What gases are produced in anaerobic sludge digestres

Options

A. Hydrogen Sulphide and `CO_2`
B. Methane and `CO_2` only
C. Methane, Hydrogen Sulphide and `CO_2`
D. Methane, Hydrogen Sulphide and `O_2`

Answer

### Step-by-Step Solution:

1. **Understanding Anaerobic Sludge Digestion**:
- Anaerobic sludge digestion is a biological process that occurs in the absence of oxygen. It is used for the treatment of wastewater and the stabilization of organic matter.

2. **Phases of Anaerobic Digestion**:
- The anaerobic digestion process consists of four main phases:
- **Hydrolysis**: In this phase, complex organic materials are broken down into simpler compounds by the action of water and enzymes.
- **Acidogenesis**: The simple molecules produced in hydrolysis are further broken down by acidogenic (fermentative) bacteria into volatile fatty acids and other compounds.
- **Acetogenesis**: In this phase, the products of acidogenesis are converted into acetic acid, along with hydrogen and carbon dioxide.
- **Methanogenesis**: This is the final phase where methanogenic bacteria convert acetic acid and other substrates into methane (CH₄), carbon dioxide (CO₂), and sometimes hydrogen sulfide (H₂S).

3. **Gases Produced**:
- The primary gases produced during anaerobic sludge digestion are:
- **Methane (CH₄)**: This is the main product of the methanogenesis phase and is a valuable energy source.
- **Carbon Dioxide (CO₂)**: This gas is produced alongside methane during the methanogenesis phase.
- **Hydrogen (H₂)**: This gas can also be produced during the acetogenesis and methanogenesis phases.
- **Hydrogen Sulfide (H₂S)**: This gas may be produced in smaller amounts and is often associated with the breakdown of sulfur-containing compounds.

4. **Conclusion**:
- In summary, the gases produced in anaerobic sludge digesters include methane (CH₄), carbon dioxide (CO₂), hydrogen (H₂), and hydrogen sulfide (H₂S).