The effect of pH/PAC on the coagulation of anionic surfactant wastewater generated in the cosmetic production

Abstract

The wastewater generated from the production of cosmetic raw materials contained a large number of anionic surfactants, which could hardly meet the wastewater discharge standards in China when biological technology was employed as a sole treatment strategy. Coagulation pretreatment was one of important operation units of wastewater treatment, and it could greatly reduce the burden of subsequent biological treatment and improve the efficiency of wastewater treatment. The pH value of the wastewater directly affected the hydrolysis intermediates of the coagulants, thereby influencing the performance of the flocculation reaction. In this study, the effects of adjusting the pH value of raw wastewater on the removal efficiencies of the pollutants, dissolved organic matter and sludge morphology were discussed. The changes of coagulation performance and group structure and thermal stability of flocculated sludge under the coupling action of pH/polyaluminum chloride (PAC) were studied. The results showed that only adjusting the pH of raw wastewater could promote removal efficiencies of chemical oxygen demand (COD) and linear alkylbenzene sulfonate sodium (LAS) and enhance the conductivity of actual cosmetic wastewater, but could not remove the aromatic proteins. The highest coagulation efficiency was achieved under PAC concentration of 2.6 g/L and the pH value of 6. The molecular weight distribution of organics after coagulation was mainly concentrated in the range of> 100 kDa and< 3 kDa, and medium molecular weight organics were mainly removed. It was expected to provide strategies for improving the coagulation performance of actual cosmetic wastewater.