DIFFERENCES IN DEHYDRATION EFFECTS DEPENDING ON MIXING CONDITIONS IN THE DEHYDRATION OF SEWAGE SLUDGE MIXED WITH PLANT BIOMASS

Abstract

 This study involved the introduction of a sludge dewatering system mixed with plant biomass in a sewage treatment plant. The purpose of the study was to collect information to inform the selection of plant biomass mixing points. The investigation items were the mixing conditions of digested sludge, the flocculant, and the plant biomass. Mixing the plant biomass with the sludge first, compared to mixing with the flocculant first, was more effective at reducing the water content of the dewatered cake, suppressing the outflow of the plant biomass into the filtrate, and reducing the amount of dewatered cake. In addition, the results suggested that the condition at which the plant biomass was most effectively mixed in the sludge occurred around the lowest level at which the sludge flocculates. The optimal mixing ratio of the plant biomass was 15% solids, but a wide range from 5% to 15% was effective. In the selection of plant biomass, it is important to investigate the water absorption rate as one of the factors influencing water content reduction.