Effect of organic loading rate and effluent recirculation on biogas production of desulfated skim latex serum using up-flow anaerobic sludge blanket reactor

High sulfate contents in skim latex serum (SLS) can be reduced by rubber wood ash (RWA). Subsequently, the desulfated skim latex serum (DSLS) can be further anaerobically treated more effectively with the accompanying generated biomethane. In this study, DSLS was treated using an up-flow anaerobic sludge blanket (UASB) reactor operated at 10-day HRT and under mesophilic (37 degrees C) conditions. The effect of organic loading rates (OLR) at 0.89, 1.79 and 3.57 g-COD/L-reactor.d on DSLS biodegradability was investigated in Phase I-IV using NaHCO3 as an external buffering agent. Maximum methane production yield of 226.35 mL-CH4/g-CODadded corresponding to 403.25 mL-CH4/L reactor.d was achieved at the suitable OLR of 1.79 g-COD/L-reactor.d. UASB effluent recirculation which was then applied to replace the NaHCO3. It was found that with 53% effluent recirculation similar to an OLR of 2.01 g-COD/L-reactor.d, an average of 185.70 mL-CH4/g-CODadded corresponding to 371.40 mL/L reactor.d of methane production was reached. The dominant bacteria in UASB reactor were members of Proteobacteria, Bacteroidota, Firmicutes, and Desulfobacterota phyla. Meanwhile, the archaeal community was majorly dominated by the genera Methanosaeta sp. and Methanomethylovorans sp. The study clearly indicates the capabilities of UASB reactor with effluent recirculation to treat DSLS anaerobically.

Automated summary

Rubber wood ash can reduce high sulfate contents in skim latex serum and effectively treat desulfated skim latex serum (DSLS) with the generated biomethane. The study used an up-flow anaerobic sludge blanket (UASB) reactor to treat DSLS under mesophilic conditions. The organic loading rates (OLR) and effluent recirculation in the UASB reactor were found to significantly affect DSLS biodegradability and methane production. The dominant bacteria in the reactor were Proteobacteria, Bacteroidota, Firmicutes, and Desulfobacterota, while the archaeal community was mainly composed of Methanosaeta sp. and Methanomethylovorans sp.