VOLATILE SOLIDS REDUCTION IN 2-PHASE AND CONVENTIONAL ANAEROBIC SLUDGE-DIGESTION

Success of two-phase anaerobic systems for primary and secondary sludg e treatment has been reported based on both directly and indirectly me asured volatile solids (VS) reduction, total gas and methane generatio n, COD reduction, etc. The objective of this research was to determine whether phase separation increases directly measured VS reduction com pared to conventional anaerobic sludge digestion. Two-phase and conven tional digesters were operated with sludge feeds from three sources; b oth 1:1 sludges (primary:waste activated, solids basis) and 100% waste activated sludges (WAS) were studied. The maximum difference between VS reductions in conventional and two-phase systems was about 8.7% wit h waste activated sludge. The increase in volatile solids reduction in two-phase systems with the 1:1 sludge ranged from 1.9 to 6.0% as comp ared to conventional systems. This relatively small increase in VS red uction may not be worth the additional cost of operating two-phase dig esters at full scale. Copyright (C) 1996 Published by Elsevier Science Ltd.