AERATED STATIC PILE COMPOSTING OF MUNICIPAL SOLID-WASTE (MSW) - A COMPARISON OF POSITIVE PRESSURE AERATION WITH HYBRID POSITIVE AND NEGATIVE AERATION

A hybrid mode of aeration using ''suck'' and ''blow'' with temperature feedback control was used In a static pile composting process. Its pe rformance was compared with the classical aerated static pile process using positive pressure aeration (blowing) based on temperature feedba ck control including low rates of fixed aeration, The two piles used i n the trial each used shredded municipal solid waste (MSW) as the subs trate. The characteristic temperature/time profiles for both control s trategies were monitored alongside other physico-chemical parameters i ncluding volatile solids content (and extent of reduction), CIN ratio, moisture content, pH, and electrical conductivity. Specific oxygen up take rate (SOUR) was also measured to determine the stability of the c ompost. The indicator organisms for faecal contamination, faecal colif orms and faecal streptococci were monitored to determine the extent of sanitisation of the compost. In both piles, thermophilic temperatures were reached within one day, but the hybrid pile had higher temperatu res and a more even distribution than the classical aerated static pil e (ASP) which showed low temperatures at the base throughout the compo sting period. The SOUR rest showed that the extent of stability for bo th piles was very similar, dropping from an initial value of 18.92 mgO (2)/(gVS.h) to 1.81 and 1.37 mgO(2)/(gVS.h) for the hybrid pile and th e brow pile, respectively, at the end of the composting period. Moistu re removal was faster for the classical pile than for the hybrid pile, but the hybrid pile showed better sanitisation due to the high temper ature coverage for most of the File's material. Differences in other p arameters such as pH, electrical conductivity, NH, and NO between the two piles were negligible.