Ammonia-methane two-stage anaerobic digestion of dehydrated waste-activated sludge

概要

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In repeated batch-wise thermophilic anaerobic digestion of dehydrated waste-activated sludge with 80% (w/w) water content (DWAS), although methane production reached 30 % of total organic carbon in DWAS in the first run of 15d, it gradually decreased and finally stopped in the subsequent runs together with an increase in ammonia concentration. When the loading of DWAS on anaerobic digestion was investigated, methane production at 30d significantly decreased with the increase in the amount of organic matter per kg wet sludge while enormous proportion of organic nitrogen in the DWAS was converted to ammonia within 5d. The addition of ammonia to sludge significantly decreased methane production rate. When ammonia was removed from the DWAS using a physicochemical method after 10d of ammonia production and it was applied to semi-continuous anaerobic digestion, stable methane production was observed.