Quality concerns with surface water sources Which of the following correctly describes typical issues associated with untreated surface water?
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AIt may contain large amounts of impurities (suspended and dissolved).
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BIt may be contaminated by various pollutants.
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CIt may contain disease-producing bacteria and pathogens.
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DAll of the above
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ENone of these
Answer
Correct Answer: All of the above
Explanation
Introduction / Context:Surface waters—rivers, lakes, and reservoirs—are exposed to runoff, discharges, and biological activity. Recognizing inherent risks guides the selection of treatment processes to ensure safe potable water.
Given Data / Assumptions:
- No prior treatment of the raw surface water.
- Catchment activities (agriculture, urban runoff, industry) may affect quality.
- Microbial presence is possible due to animal and human sources.
Concept / Approach:Typical impairments include suspended solids (turbidity), natural organic matter, nutrients, and pathogens (bacteria, viruses, protozoa). Treatment usually requires coagulation–flocculation, sedimentation, filtration, and disinfection, sometimes preceded by pre-oxidation and followed by advanced steps as needed.
Step-by-Step Solution:
Evaluate statements: high impurity loads are common (true).Contamination pathways (urban, agricultural, industrial) exist (true).Disease-producing microbes are frequently present (true).Therefore the comprehensive answer is “All of the above”.Verification / Alternative check:Regulatory standards for potable water focus on turbidity, coliforms, and chemical limits precisely because these risks exist in surface sources.
Why Other Options Are Wrong:Choosing only one aspect ignores the breadth of common surface-water problems.
Common Pitfalls:Underestimating microbial hazards due to clear-looking water; turbidity is not the only indicator of safety.
Final Answer:All of the above