Anaerobic Baffled Reactor in Treatment of Natural Rubber Processing Wastewater: Reactor Performance and Analysis of Microbial Community

Wastewater discharged from the coagulation process of natural rubber contains high concentrations of organic compounds, mainly formic or acetic acid, and residual rubber particles. These compounds pose serious issues during the high-rate anaerobic digestion without pH adjustment and solid removal in advance. In this study, an anaerobic baffled reactor (ABR, working volume of 68 L, ten compartments) was investigated for the treatment of such wastewater with a HRT of 3.5 ± 0.9 days. The performance of the ABR was evaluated with the stepwise increase in COD influent during a period 224 days. The microbial community in the sludge from each compartment of the ABR on the 143rd day was analyzed. Under an OLR of 1.4 ± 0.3 kg-COD/(m3·day), the highest COD and total suspended solid removal efficiency of 92.3 ± 6.3% and 90.0 ± 5.6%, respectively, were observed. Sequencing of 16S rRNA genes using MiSeq revealed the difference acetogen communities in each compartment. Most of the methanogens, particularly acetate-utilizing methanogens, were predominantly distributed in the 3rd, 4th, and 5th compartments, where volatile fatty acid concentration considerably decreased and the highest biogas production was observed. These results indicated that the ABR is a potential alternative for the treatment of this wastewater.