Nitrification in biological wastewater treatment is the conversion of:
Choose the correct answer
Nitrate to nitrogen gas (denitrification, not nitrification)
Ammonia (NH4⁺) → nitrite (NO2⁻) → nitrate (NO3⁻) by aerobic autotrophic bacteria
Organic carbon to CO2 (carbonaceous BOD removal)
Sulphate to hydrogen sulphide
Correct Answer
B. Ammonia (NH4⁺) → nitrite (NO2⁻) → nitrate (NO3⁻) by aerobic autotrophic bacteria
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Nitrification: aerobic, autotrophic bacteria (Nitrosomonas: NH4⁺ → NO2⁻; Nitrobacter: NO2⁻ → NO3⁻). Requires oxygen (4.57 g O2/g NH4-N oxidised). Slow-growing nitrifiers require: long SRT (> 8–10 days at 20°C), adequate oxygen (DO > 2 mg/L), alkalinity (consumes 7.14 g alkalinity as CaCO3 per g NH4-N). Followed by denitrification for N removal.
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