SWINE WASTEWATER TREATMENT IN ANAEROBIC DIGESTERS WITH FLOATING MEDIUM

A 20L attachedgrowth anaerobic system with floating plastic Ballast rings as a medium has been studied forswine wastewater [chemical oxygen demand (COD) = 1,925 to 2,033 mg/L; total suspended solids (TSS) = 1,051 to 1,184mg/L] treatment at the mesophilic temperature of 35C. The plastic Ballast rings had a specific surface area of 108 m 2 /m 3and a density of 0.98 g/cm 3 and filled the upper half of the anaerobic digesters. The porosity of the filled portion of the digesterswas 0.86. Performance of the anaerobic digesters was evaluated for organics decomposition and methane production withtwo different hydraulic retention times (HRTs): 10 days and 5 days. When HRT was 10 days in the anaerobic digesters, removalof COD, total organic carbon (TOC), TSS, and volatile suspended solids (VSS) was 65%, 55%, 69%, and 70%, respectively.Methane yield was 0.23 m 3 CH4 per kg COD removed. As the HRT was reduced to 5 days, the removal of COD, TOC, TSS,and VSS decreased to 55%, 48%, 57%, and 60%, respectively. Methane yield was 0.24 m 3 CH4/kg CODrem. Higher HRT inthe anaerobic digester resulted in higher organics degradation efficiency. However, higher rates of methane production andorganics decomposition were obtained in the digester with lower HRT.