Anaerobic digestion of sewage sludge
2010
Dubrovskis, V., Latvia Univ. of Agriculture, Jelgava (Latvia) | Plume, I., Latvia Univ. of Agriculture, Jelgava (Latvia) | Kotelenecs, V., Latvia Univ. of Agriculture, Jelgava (Latvia) | Zabarovskis, E., Latvia Univ. of Agriculture, Jelgava (Latvia)
Utilization of sewage sludge causes environmental problems in Latvia; therefore anaerobic digestion of sludge was investigated as the treatment method. Sludge from the wastewater plant ''Jurmala'' was processed at temperature 38 °C ± 1.0 deg C in laboratory bioreactors operating in batch mode. The investigated differences between total solids and organic solids contents were 2.0 % for fresh sludge, 2.1 % for old sludge, 3.6 % for sludge stored for a long period and 4.2 % for sludge from a ditch overgrown with vegetation in the wastewater treatment plant ''Jurmala''. The average biogas yield obtained from the sludge samples was varying from 233 l•kgVSdE-1 for sludge from the ditch overgrown by vegetation to 397 l•kgVSdE-1 for fresh sludge. The average methane yield from fresh sludge was 233 l•kgVSdE-1 and average methane yield from long time stored sludge was 122 l•kgVSdE-1. The investigated average methane content was 59.0 % in biogas from fresh sludge, and the methane content was 46.1 % in biogas from sludge located for a long storage period. Co-digestion of sludge stored for years with fresh sludge or with agricultural biomass is recommended to increase the methane content in biogas.
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