Solids Reduction Process for Agricultural Effluent – A Laboratory Feasibility Study

Process steps of flocculation, filtration and centrifugation are investigated to better utilizing existing storage capacity of agriculturally based effluents and at the same time minimize the environmental impact of agricultural operations. As flocculant Ca(OH)2 as a 20% solution, FeCl3 as a 30% solution, and Al2(SO4)3 as a 20% solution were used. The solids content of the liquid manure, having a preadjusted pH of 9.5, resulted in a solids reduction of up to 46.8% with centrifugation. For all flocculants, the 20% Ca(OH)2 solution, the 30% FeCl3 solution, and the 20% Al2(SO4)3 solution resulted in a decrease of the solids content of the liquid manure. FeCl3 as flocculant reduced the solids content by 45%, Al2(SO4)3 and Ca(OH)2 as flocculant by 21.0% after the second centrifugation process. Filtration as the fourth process step reduced the solids content further by 31.6% for the Ca(OH)2 flocculant, whereas for FeCl3 and Al2(SO4)3 as flocculant and increase of the solids content by 18.2% and 2.5% respectively resulted. The flocculant Ca(OH)2 outperformed FeCl3 and Al2(SO4)3 by 71.2%, 65.4%, and 56.9% respectively. A Maximum COD removal rate of 47/8% could be realized without flocculant and 70.6% COD removal rate could be utilized using FeCl3 as flocculant applying a second centrifugation process.