Question

The two stage anaerobic process of dairy effluent treatment allows ________.

• A. higher retention times and shorter loading rates
• B. shorter loading rates and nil retention
• C. higher loading rates and shorter retention times
• D. nil loading and shorter retention times

Hint:

Two-stage treatment = Efficiency. By splitting the "acid-makers" from the "methane-makers," the system can work faster (shorter retention) and harder (higher loading).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Dairy effluents have high organic loads (BOD/COD). Anaerobic digestion is a common treatment method.
Anaerobic digestion occurs in four stages: Hydrolysis, Acidogenesis, Acetogenesis, and Methanogenesis.

Step 2: Detailed Explanation:
In a conventional single-stage reactor, all these processes happen in one tank. However, acid-forming bacteria grow faster and prefer lower pH, while methane-forming bacteria grow slower and need neutral pH.
By using atwo-stage process:
1. The first stage (Acidogenesis) is optimized for fast growth.
2. The second stage (Methanogenesis) is optimized for slower growth.
3.Benefit: This separation prevents the "souring" of the reactor and allows the system to process much more waste in a smaller volume.
4.Result: It allows forhigher organic loading rates (more waste added per day) andshorter hydraulic retention times (the effluent stays in the system for less time) compared to single-stage systems.

Step 3: Final Answer:
The process allows higher loading rates and shorter retention times.