In wastewater oxidation processes (natural or engineered), which compounds are typically formed as the end products of oxidizing organics and reduced species?
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ACarbon dioxide (from carbonaceous oxidation)
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BNitrates (from nitrification of ammonia)
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CSulphates (from oxidation of sulphides)
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DAll the above
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ENone of the above
Answer
Correct Answer: All the above
Explanation
Introduction / Context:Biochemical and chemical oxidation in wastewater treatment converts reduced compounds into more oxidized, stable forms. Recognizing the typical products helps in interpreting plant performance and effluent characteristics.
Given Data / Assumptions:
- Presence of organic carbon, ammonia, and sulfide species in sewage.
- Oxidation can be biological (aerobic) or chemical (e.g., with oxidants).
- Complete oxidation end products considered.
Concept / Approach:
Carbon in organics is oxidized to carbon dioxide; ammonia is converted to nitrite and then nitrate (nitrification); sulfides/sulfur are oxidized to sulfate. These transformations lower BOD and toxic odors and stabilize the wastewater.
Step-by-Step Solution:
Carbonaceous oxidation → CO2 and water.Autotrophic nitrifiers oxidize NH3 → NO2- → NO3-.Sulfur species (H2S, S2-) oxidize to SO4^2-.Verification / Alternative check:
Stoichiometric equations and process monitoring (CO2 evolution, nitrate increase, reduction in sulfide odors) support these end products.
Why Other Options Are Wrong:
Each individual option describes a real oxidation product; therefore the aggregate choice (all the above) is correct.
Common Pitfalls:
Confusing denitrification (which reduces nitrate to nitrogen gas) with oxidation; ignoring partial oxidation intermediates.
Final Answer:
All the above