Sludge digestion converts organic solids mainly into:
Choose the correct answer
Sludge → water only
Organic solids → biogas (mainly methane + CO2) + stabilised sludge
Sludge → nitrogen gas
Sludge → pure CO2
Correct Answer
B. Organic solids → biogas (mainly methane + CO2) + stabilised sludge
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Anaerobic sludge digestion (mesophilic, 35°C): organic sludge → CH4 (methane, 65–70%) + CO2 (30–35%) + H2O + digested sludge. Methane used as energy source. VSS reduction 50–60%. Digestion time 20–30 days. Advantages: volume reduction, pathogen reduction, energy recovery. Digested sludge: stable, less odorous, can be used as fertiliser.
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