AN ON-FARM SWINE WASTE MANAGEMENT-SYSTEM IN HAWAII

A prototype of a swine waste treatment system for a 20-25 sows operati on was investigated for its potential of odor control, byproduct utili zation and treated wastewater reuse. The high solid portion of the swi ne waste ranging from 4% to 8% TS was treated and stabilized by the an aerobic process with an HRT (hydraulic retention time) of 32 days. The dilutea liquid portion from raw and anaerobically digested swine wast ewater was effectively treated by the aeration and sedimentation units with the HRT of 3 and 4 days, respectively The overall removal effici ency of 89-95.4% for TCOD, 82.3-88.5% for TKN and 81.2% for T-P was ac hieved. The treated effluent was reused for irrigation of pasture with out any negative impact of odor problems. Also, it meets the requireme nts of the wastewater reuse criteria, R-3, issued by the State of Hawa ii, Department of Health. The economic analysis was conducted by calcu lating the NPW (net present worth). It was found that the capital cost is the major cost for the proposed treatment system. The reuse of bio gas as energy and sludge as fertilizer are the key factors as to wheth er or not it will turn the treatment system into a profit. More than 8 30 pigs (or approximately 80 sows) are required to achieve the break-e ven point for the application of the swine waste treatment system. Thu s, a profit could be made with the application of this treatment syste m to more than 830 pigs if the comprehensive utilization of methane ga s and stabilized sludge could be realized. (C) 1998 Published by Elsev ier Science Ltd. All rights reserved.