Question

Spent wash is highly polluted effluent released from

• A. Pulp and paper industry
• B. Tannery
• C. Sugar industry
• D. Distillery industry

Hint:

Spent wash = Molasses + Yeast + Distillation.
Industry = Distillery.
It is "spent" because all the sugar has been turned into alcohol and removed.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks to identify the specific industrial sector responsible for the production of "spent wash," a notoriously problematic wastewater.
Detailed Explanation:

• Definition of Spent Wash:
Spent wash (also known as vinasse or distillery slop) is the dark brown, acidic liquid residue left after the distillation of alcohol (ethanol).
It is produced primarily during the fermentation of molasses in the distillery industry.

• Pollution Characteristics:
It is one of the most polluting industrial wastes.
- High BOD and COD: Levels can reach $50,000$ to $100,000$ mg/L.
- Color: Very dark due to melanoidin pigments.
- Odour: Very unpleasant and persistent.
- Chemicals: Contains high concentrations of potassium, chlorides, and sulfates.

• Environmental Impact:
Direct discharge into water bodies causes immediate oxygen depletion and fish kills. If used on land without treatment, it can lead to soil salinity and groundwater contamination.

• Treatment:
It is often treated through anaerobic digestion to produce biogas or concentrated to make fertilizer (biocompost).

Step 2: Final Answer:
Spent wash is the characteristic effluent of the distillery industry.