Removal of biological organics in high-salinity wastewater produced from methylcellulose production and subsequent changes in the microbial community

The wastewater generated in methylcellulose (MC) production is characterized by high salinity and pH due to the residual sodium and chlorine separated from the methyl group. It is difficult to treat wastewater using the conventional activated sludge method because the high concentration of salt interferes with the microbial activity. This study confirms the biological removal of organic matter from MC wastewater using sludge dominated by Halomonas spp., a halophilic microorganism. The influent was mixed with MC wastewater and epichlorohydrin (ECH) wastewater in a 1:9 ratio and operated using a sequencing batch reactor with a hydraulic retention time of 27.8 d based on the MC wastewater. The removal efficiency of chemical oxygen demand (COD) increased from 80.4% to 93.5%, and removal efficiency had improved by adding nutrients such as nitrogen and phosphorus to the wastewater. In terms of microbial community change, Halomonas spp. decreased from 43.26% to 0.11%, whereas Marinobacter spp. and Methylophaga spp. increased from 0.50% to 15.12% and 7.51%, respectively.