Which of the following observations most strongly suggests that equalization alone will not be sufficient as a pre-treatment for an industrial effluent?
- ASignificant diurnal variation in flow and COD
- BHigh variability in pH and intermittent discharge of inhibitory compoundsCorrect
- CUneven hourly discharge but stable biodegradability and pH
- DModerate fluctuation in suspended solids with no evidence of toxicity
Solution
Concept
Limitations of flow equalization in industrial wastewater pretreatment
Formula
NONE
Step-by-step solution
1. Flow equalization dampens hydraulic peaks and smooths average concentration. 2. Simple blending cannot eliminate toxic or biocidal chemicals that inhibit downstream microbes. 3. If inhibitory compounds and wide pH swings persist even after mixing, additional chemical neutralization or detoxification is required. 4. Hence, presence of inhibitory compounds and high pH variability shows equalization alone is insufficient. Answer: B
Explanation
Equalization basins dampen fluctuations in hydraulic flow and pollutant concentration by blending batches over time. However, if an industrial effluent contains intermittent discharges of inhibitory/toxic compounds or extreme pH swings that equalization cannot neutralize, biological treatment will be poisoned unless specialized chemical neutralization, detoxification, or advanced pretreatment is implemented.
Why the other options are wrong
A) Diurnal variation in flow and COD is the classic problem that equalization basins solve. C) Uneven discharge with stable pH and biodegradability is ideally handled by equalization. D) Moderate solids fluctuation without toxicity is easily handled by equalization and primary settling.
Shortcut
Equalization buffers flow & peaks; it cannot neutralize severe toxicity or persistent extreme pH.
Common mistake
Assuming flow variations (Option A) overwhelm equalization basins, whereas smoothing flow variations is precisely their primary function.
Correct answer: B) High variability in pH and intermittent discharge of inhibitory compounds