Drinking-water nuisances — Iron bacteria in distribution systems and wells can produce which effects?

Introduction / Context:
Iron bacteria (e.g., Gallionella, Leptothrix) oxidize ferrous iron and produce ferric iron deposits. In wells and distribution systems, they are a common cause of aesthetic water quality problems rather than acute health risks, yet they can trigger complaints and maintenance issues.

Given Data / Assumptions:

• Focus is on nuisance effects rather than toxicity.
• Systems affected include groundwater wells, storage tanks, and pipelines.

Concept / Approach:
Iron bacteria form gelatinous, orange-brown biofilms (slime) that can harbor other microbes, clog fixtures, and release compounds causing metallic or swampy odors and off-tastes. They do not directly drive “extreme acidity”; any pH effect is typically minor compared with corrosion chemistry or source water characteristics.

Step-by-Step Solution:

Verification / Alternative check:
Well rehabilitation guides recommend mechanical cleaning and chlorination to remove iron-bacteria slimes and mitigate taste/odor complaints.

Why Other Options Are Wrong:

• Slime alone or odor/taste alone: each is correct but incomplete; both occur.
• Extreme acidity: unrelated to the typical impact of iron bacteria.

Common Pitfalls:
Confusing iron bacteria problems with corrosion-induced low pH; they are separate although they may co-occur in older systems.

Final Answer:
both (a) and (b)