Utilization of treated swine wastewater for greenhouse tomato production

An integrated system has been developed to recycle waste organics and treated wastewater from a swine farm to make value-added products and to protect the environment from potential contamination. The farm is a farrow-to-wean swine operation with approximately 4,000 sows. A high-strength wastewater (chemical oxygen demand, 18,000 mg/l; total Khejdal nitrogen, 1,600 mg/l; total phosphorus, 360 mg/l) is produced from the swine operation. An ambient-temperature anaerobic digester has been used to treat the swine wastewater and to produce biogas (from an average 475 m3/day in winter to 950 m3/day in summer). The biogas is combusted in an engine to produce electricity (around 900 kW-hr/day). The digester effluent that is rich in nutrients (N, P, and minerals) is then utilized for fertigation for greenhouse tomato production. A trickling nitrification biofilter has been developed to convert ammonium in the effluent into nitrate. The nitrified anaerobic effluent is used as both fertilizer and irrigation water for approximately 14,400 tomato plants in greenhouses. Experimental data indicate that the tomato greenhouses have used approximately 12 m3 of the effluent and 3.84 kg nitrogen per day. At the same time, the greenhouses have a daily yield of 520 kg (37 g/plant) of marketable fruit.