Effect of physical conditioners (sawdust) on the dewatering of faecal sludge using unplanted filter beds

Abstract

Abstract

The study was conducted at Kwame Nkrumah University of Science and Technology, Kumasi on bench scale, using drying beds to determine the effect of different percentages of sawdust as a bulking agent for the dewatering of faecal sludge. Different percentages of sawdust, 50%, 100%, 150% and 0% (control) by weight of TS of the faecal sludge, with TS of 26.93 g/l which was selected in previous studies, were mixed with the faecal sludge. The sawdust-faecal sludge mixture of 50%, 100%, 150% and 0% TS of faecal sludge dewatered at 5.3, 4.9, 3.9 and 5.6 days respectively with 150% being fastest to dewater. The 150% sawdust-faecal sludge treatment was most efficient with respect to removal of contaminant loads like TVS, SS, COD and NH₃-N, but was least in TS and EC removal. The 150% sawdust-faecal sludge mixture showed the least organic matter accumulation rate in the top 10cm of the filter media, whereas the 0% was the highest. The percentage TVS of the biosolids produced were 70.1, 77.3, 80.6 and 66.3 for 50%, 100%, 150% and 0% sawdust-faecal sludge mixtures, leading to annual organic matter estimation of 359, 567, 987 and 225 (kg TVS/m²/year) respectively