HIGH-SOLIDS AEROBIC DECOMPOSITION - PILOT-SCALE REACTOR DEVELOPMENT AND EXPERIMENTATION

Pilot-scale reactors have been constructed to mimic the central core o f an aerated static bed or in-vessel composting process. The 770 litre reactors were instrumented to measure temporal and spatial variations in temperature, oxygen and moisture content. Experiments were perform ed with a synthetic food waste (SFW) and digested biosolids using four different aeration rates and two initial moisture contents. An analys is of the temporal and spatial temperature and oxygen profiles has sho wn the systems replicate well and represent a process with one-dimensi onal spatial variation. An analysis of oxygen gradients has shown that cumulative oxygen depletion and oxygen depletion rates within the bed increased with increasing aeration rate in the SFW experiments, howev er, they decreased with increasing aeration rate in the biosolids expe riments. The SFW studies showed that a 10% variation in initial moistu re content had little influence on cumulative O-2 consumed, but had a significant influence on the location of maximum biological activity w ithin the bed. Maximum temperatures varied from 58 to 74 degrees C in the SFW experiments and from 43 to 60 degrees C in the biosolids exper iments. In all experiments the maximum temperatures and the positions where they occurred varied with initial moisture content and aeration rate. In the SFW experiments maximum axial temperature differences coi ncided with significant axial differences in moisture content, while i n the biosolids experiments maximum axial temperature differences coin cided with minimal axial differences in moisture content. (C) 1997 Els evier Science Ltd.