Performances of anaerobic hybrid reactor (AHR) treating salinity wastewater from fermented rice noodle factory

High sodium adversely affects the efficiency of anaerobic treatment treating salinity wastewater due to its toxicity for metabolic function of microbial cell and cell plasmolysis. In this study, the strategy of inoculating the salt-adapted microorganisms during start-up period of an anaerobic hybrid reactor (AHR) for treating salinity wastewater from fermented rice noodle factor was investigated. The fermented rice noodle wastewater contained salt concentration of 16 g/L with COD ranges of 8,000-15,000 mg/L. The AHR was operated with hydraulic retention time (HRT) of 4 days with stepwise increases in OLR until OLR 3.0 g COD/L.d. The results showed that the AHR system could not remove salt content in wastewater. However, with reactor operation conditions of OLR 3.0 g COD/L.d and HRT 4 days with salinity of 16 g/L, AHR showed remarkable results for pH >7.0, T/A ratio < 0.4, COD removal efficiency >80%, methane composition >60% and methane yield >0.30 L CH₄/g COD removed. It indicated that the AHR system tolerated with high salt concentration (16 g/L). These results were also supported with the results of methanogenic activities. The activities of acetoclastic- and hydrogenotrophic methanogens of suspended sludge at OLR 3.0 g COD/L.d were 1.3 and 0.7-folds higher than those in inoculum seed, respectively. Notable results were observed for the activities of acetoclastic- and hydrogenotrophic methanogens in the biofilm (attached) part of AHR which were 3.3- and 1.6- folds higher than those in the suspended sludge at OLR 3.0 g COD/L.d. High values of methanogenic activities (especially at biofilm zone) might be the reason for good operation of AHR treating salinity wastewater. During reactor operation, some microbial groups of salt-adapted microorganisms were probably attached on the attached zone of AHR and continued to grow as salt-resistant biofilm.