Treatment of wastewater containing linear alkylbenzene sulfonate by bacterial-microalgal biological turntable

Linear alkylbenzene sulfonate (LAS), which is widely used as detergent, is a common toxic pollutant in wastewater. Generally, biodegradation process is applied to remove LAS. However, the efficiency of traditional wastewater treatment cannot meet the growing demand. In this study, an improved biological turntable with a symbiotic system of bacteria and microalgae was primarily used to enhance the biodegradation efficiency of LAS from wastewater. The symbiotic system of bacteria and microalgae was mainly composed of Scenedesmus dimorphus and three LAS-degrading bacteria Plesiomonas sp. (L3, L7) and Pseudomonas sp. (H6). The average removal rate of LAS was up to 94.6%. The LAS concentration of the effluent of the system decreased by 81.7% after the bacterial-microalgae inoculation (the inoculation temperature was 25 oC; microalgae were inoculated at a concentration of 10% only at the start of the system; bacteria were continuously inoculated at 1‰ concentration). After bacterial-microalgae inoculation, the average effluent concentration of COD Cr in the tertiary reaction tank was 24.3 mg/L, the average membrane effluent concentration was 15.8 mg/L, and the average removal rate was 90.5%. Compared with the control group without inoculation, the concentration of COD Cr in the tertiary reaction tank and membrane effluent decreased by 55.7% and 46.4%. The denaturing gradient electrophoresis (DGGE) pattern analysis of the systemic flora showed that there were two dominant species of high LAS degrading bacteria. They were identified to belong to Plesiomonas sp. and Pseudomonas sp., respectively.