Which of the following is not a typical method of performance evaluation of a wastewater treatment plant?

Question

Which of the following is not a typical method of performance evaluation of a wastewater treatment plant?

1. A. Comparing design discharge with personal opinion (Correct answer)
2. B. Checking percentage removal of BOD, COD, SS and nutrients
3. C. Monitoring effluent discharge against standards (e.g., CPCB)
4. D. Recording operating parameters (F/M ratio, SRT, DO, sludge volume index)

Correct Answer

Option A — Comparing design discharge with personal opinion

Detailed Solution & Explanation

The correct answer is Comparing design discharge with personal opinion.

Key Points

• Performance evaluation must rest on measured, comparable evidence. The three legitimate methods listed are:
  • percentage removal of BOD, COD, SS and nutrients across each unit,
  • effluent quality checked against statutory discharge standards,
  • operating parameters recorded — F/M ratio, SRT, DO, sludge volume index.
• Comparing design discharge with personal opinion is not a method at all. It substitutes subjective judgement for measurement, so it is neither reproducible nor auditable.

Additional Information

• Removal efficiency is computed as (influent − effluent) / influent × 100, and doing it unit by unit rather than only across the whole plant is what localises a problem to a particular tank.
• The operating parameters are the leading indicators. A rising SVI warns of bulking before the effluent deteriorates; a falling DO or a drifting F/M ratio explains a loss of treatment before the monthly compliance sample is even drawn.
• Compliance monitoring in India is against the Environment (Protection) Rules, 1986 schedules and the consent conditions issued by the State Pollution Control Board.
• A sound evaluation also includes a mass balance across the plant — flow and load in against out plus sludge wasted — which exposes measurement errors that percentage removals alone can hide.