Title: Extent of degradation in three stage co-composting of faecal sludge and solid waste

Abstract

Co-composting of Faecal Sludge (FS) and Solid Waste (SW) allows recycling of essential nutrients into agriculture thereby closing the nutrient circle. In this study, temperature variation, the mass balance of forced and passively aeration on composting process, and the extent of degradation with different stages were investigated. The extent of degradation was determined through the different composting process in the first, second and third stage with different mix proportion of Faecal Sludge. Four sets of the initial waste mixture were prepared using SW and FS. SW and FS were mixed at four different ratios for four sets namely 90:10, 85:15, 80:20, and 75:25 (SW: FS). Forced aeration and passively aeration composting tests were done using series of reactors as described above according to a planned experimental program. The results show that (i) the mean maximum temperature of the first and second stage were 65 oC and 56 oC of passively, 67 oC and 60 oC of forced aeration respectively which raised within 7 days. (ii) According to the mass balance, total mass, moisture content, and volatile solids were always decreased at every stage for passive and forced aeration process, the degradation of the volatile solid in composting process using forced aeration was more than passively aeration process. (iii) For the passively and forced aeration process, the total BVS degradation of were ranged between 82 % to 89 %, and 73% to 91% respectively after 60 days. Therefore, it can be concluded that the percentage of BVS degradation in forced and passively aeration was not significantly different.