Efficiencies of solid-liquid separators applied to pig farm slurry

H.K. Ong, P.Y. Choo and M. Suhaimi

Abstract

Protection of the environment demands that the tremendous quantity of manure in today’s intensive livestock farms be managed properly. In the Malaysian context, the most sensitive problem is in pig farms, where manures are turned into slurries due to farmers’ practice of washing barns daily. The slurry formed would eventually find their way into the country’s waterways, treated or otherwise. One of the problems in treating and handling pig slurry is the accumulation of solids. The accumulated solids often cause stratification and short-circuiting problems during treatment. This could be partly overcome by separating it into a solid and a liquid component. The solid fraction, composed of undigested grain, roughages, hair and bedding materials, is readily stabilized by composting. The separated liquid is less voluminous and more easily pumped. Besides it does not form crusts. Mechanical separators are employed for this purpose. This paper reports on the efficiencies of two types of separator applied to pig farm slurry, namely a screw-press separator and an inclined-screen separator. Efficiency was measured in terms of reductions in total solids (TTS), total volatile solids (TVS), total suspended solids (TSS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and total phosphorus (TTP) after mechanical separation. Removal efficiencies of the screw-press were found to be 54, 46, 58, 21, 36, 33 and 31%, for TTS, TVS, TSS, BOD, COD, TKN and TTP, respectively. The case of inclined-screen separator, removal efficiencies were 33, 44, 41, 20, 35, 25 and 21%, respectively. The throughputs were 5.2 and 13.9 m³/h; and the dry matter of separated solids was 28.7% and 18.5% for screw-press and inclined-screen separator respectively. The advantages and disadvantages of solid separation are discussed.

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