An on-farm swine waste management system in Hawaii

Abstract

A prototype of a swine waste treatment system for a 20–25 sows operation was investigated for its potential of odor control, byproduct utilization and treated wastewater reuse. The high solid portion of the swine waste ranging from 4% to 8% TS was treated and stabilized by the anaerobic process with an HRT (hydraulic retention time) of 32 days. The diluted liquid portion from raw and anaerobically digested swine wastewater was effectively treated by the aeration and sedimentation units with the HRT of 3 and 4 days, respectively. The overall removal efficiency of 89–95·4% for TCOD, 82·3–88·5% for TKN and 81·2% for T-P was achieved. The treated effluent was reused for irrigation of pasture without any negative impact of odor problems. Also, it meets the requirements of the wastewater reuse criteria, R-3, issued by the State of Hawaii, Department of Health. The economic analysis was conducted by calculating the NPW (net present worth). It was found that the capital cost is the major cost for the proposed treatment system. The reuse of biogas as energy and sludge as fertilizer are the key factors as to whether or not it will turn the treatment system into a profit. More than 830 pigs (or approximately 80 sows) are required to achieve the break-even point for the application of the swine waste treatment system. Thus, a profit could be made with the application of this treatment system to more than 830 pigs if the comprehensive utilization of methane gas and stabilized sludge could be realized.