Phosphorus Removal and Recovery from Swine Waste: Results of Pretreatment with an Anaerobic Sequencing Batch Reactor

An approach is presented for the on-site treatment of diluted swine waste. The approach (1) incorporates anaerobic digestion with an anaerobic sequencing batch reactor (ASBR) to stabilize waste, reduce odor, and reduce solids and organic compounds, while producing biogas; (2) increases the ortho-phosphate concentration of the anaerobic digester effluent by enhanced biological phosphorus removal; and (3) uses chemical precipitation of struvite. The ASBR accomplishes the necessary pretreatment to release “bound” organic phosphorus as orthophosphate. Preliminary results indicate a fast startup of the ASBR when sludge from a swine waste treatment lagoon was used as the inoculum. The methane yield for an ASBR seeded with lagoon sludge was 0.46 liter methane per g volatile solids (VS) fed. The swine waste fed to the ASBR consisted of a solids concentration of 20 g VS/liter. At a volumetric loading rate (VLR) of 4 g VS/liter/day, the effluent of an ASBR seeded with lagoon sludge, contained approximately 1,500 mg/liter ammonia-N (110 mM) and 125 mg/liter ortho-phosphate (4 mM). Next, a two-sludge biological nutrient removal system is proposed to incorporate phosphate release during the anaerobic phase of an enhanced biological phosphorus removal system, denitrifying dephosphatation, and nitrification. This system can remove nutrients from swine waste and produce struvite with limited amounts of chemical additions.