Algae control in water sources and treatment works: Which chemical is most commonly used for controlling algal growth in reservoirs, intakes, or filters?

Introduction / Context:
Algal blooms can produce taste, odor, and filter-clogging problems. Chemical control measures complement watershed management and operational strategies such as mixing or shading.

Given Data / Assumptions:

• Application in raw-water reservoirs, intake structures, or on filter beds.
• Objective is to suppress algal proliferation safely and cost-effectively.

Concept / Approach:
Copper sulphate (CuSO4), dosed carefully based on algal species and water chemistry, is a standard algaecide. It disrupts algal metabolism and is effective at low concentrations. Alum aids coagulation but does not directly control living algae; lime adjusts pH/alkalinity; bleaching powder disinfects but is not the primary algaecide of choice for blooms.

Step-by-Step Solution:

Verification / Alternative check:
Combine with physical measures (hypolimnetic withdrawal, mixing) and activated carbon to address taste/odor compounds.

Why Other Options Are Wrong:
Alum and lime treat coagulation/pH; bleaching powder targets pathogens rather than algal bloom control; permanganate is an oxidant for taste/odor or iron/manganese but not the primary algaecide here.

Common Pitfalls:
Overdosing copper; applying during fish spawning; not accounting for hardness, which affects copper efficacy.

Final Answer:
Copper sulphate