Studies on sodium linear alkylbenzenesulfonate (LAS) II Form and distribution of LAS in wastewater treatment plant.

Abstract

The amounts of homologous series of linear alkylbenzenesulfonates (LAS) in the wastewater treatment plant were measured as free and complex LAS by using methylene blue colorimetry and high-performance liquid chromatography. The concentration of free LAS in the influent was found at levels varying 0.34 to 0.54 mg/l, with an average value of 0.43 mg/l, and complex LAS was found at levels varying 1.7 to 2.4 mg/l, with an average value of 2.0 mg/l. The removing efficiencies in the primary sedimentation tank were 58% for free LAS and 0% for complex LAS, and those in the aeration tank and the secondary sedimentation tank were 16% for free LAS and 87% for complex LAS. There was no clear tendency that both free and complex LAS with longer C chain length were more effectively removed than those with shorter ones in the effluent and the sludge. Free LAS remained in the raw sludge was 73% to the amount (30 kg/d) treated in the primary sedimentation tank, whereas free and complex LAS and in the excess sludge was 2% and 0.06%, respectively, to the amount (9 kg/d for free LAS and 210 kg/d for complex LAS) treated in the aeration tank and the secondary sedimentation tank. The results obtained in this work suggest that free LAS is preferentially removed in the primary sedimentation tank to be in the raw sludge, whereas complex LAS is biodegradated in the aeration tank and the secondary sedimentation tank.