Treatment of Swine Wastewater with Biological Conversion, Filtration, and Reverse Osmosis: a Laboratory Study

The performance of a bench-scale integrated swine wastewater treatment system was evaluated on the basis of energy recovery, fertilizer production, and water reclamation. The system consisted of one anaerobic sequencing batch reactor (ASBR), one or two aerobic sequencing batch reactors (SBR1 and SBR2), one sludge settling tank, one sand filter, and one reverse osmosis (RO) unit. The system was tested with swine wastewater (approximately 15,000 mg/L volatile solids). The chemical oxygen demand (COD) and solids in the wastewater were reduced by 89% to 97%, and total coliforms and E. coli were reduced by 1 log CFU after treatment with the ASBR and SBRs. The oxidized nitrogen (NO2 -N and NO3 -N) was 14% or 53% of total nitrogen in the wastewater after it passed through SBR1 or SBR1 and SBR2, respectively. The sand filter was used to further reduce the COD and solids, especially suspended solids, prior to RO treatment. Two types of spiral-wound RO membranes were tested and compared. The RO was found to be highly effective in separating nutrient and salt elements from water. After RO treatment, over 70% of NH3 -N, NO2 -N, and NO3 -N and over 90% of other elements, such as P, K, Cl, Ca, Mg, Na, Zn, Fe, and Cu, were concentrated in a liquid effluent with one-tenth the original volume. The reclaimed water needs to be further evaluated for its uses. Various operational cost and maintenance issues associated with individual processes and the overall system need to be addressed when the treatment system is scaled up and evaluated for farm applications.