Removing Organic Matter and Nutrients from Swine Wastewater after Anaerobic–Aerobic Treatment

Abstract

Anaerobic digesters generate effluent containing about 3000 mg L−1 of organic matter in terms of chemical oxygen demand (COD). This effluent must be treated before being reused or discharged into the environment. The objective of this study was to evaluate the efficiency of a trickling filter packed with red volcanic rock for the treatment of anaerobic digester effluent with COD concentrations of around 3000 mg L−1. The trickling filter consisted of an aluminum cylinder, 2 mm thick, 3 m high, and 1 m in diameter. To evaluate the efficiency of the treatment system, there were three experimental runs, each lasting 20 days (d). The predictor variable was the initial COD concentration, which ranged from 2002 to 3074 mg L−1. The hydraulic retention time was 9 h. The influent flow was 2.2 L min−1, which amounts to a hydraulic load of 4033 m3 m−2 day−1 and an organic load of 0.006342 to 0.009738 kg m−3 day−1 of COD. Independent of the initial concentration, COD removal efficiency was very high, varying from 90 to 96%. Final effluents met all the maximum permissible limits to be used as irrigation water, as well as for its release into natural or artificial water reservoirs, stored for agricultural crop irrigation.

Keywords

• trickling filter
• anaerobic digester
• swine wastewater
• organic matter
• COD