Removal of refractory organics in wastewater by coagulation/flocculation with green chlorine-free coagulants

Huihui Zhang; Hai Lin; Qiang Li; Changkun Cheng; Hui Shen; Zhiyong Zhang; Zhongzhi Zhang; Heming Wang

doi:10.1016/j.scitotenv.2021.147654

Removal of refractory organics in wastewater by coagulation/flocculation with green chlorine-free coagulants

Sci Total Environ. 2021 Sep 15:787:147654. doi: 10.1016/j.scitotenv.2021.147654. Epub 2021 May 8.

Authors

Huihui Zhang¹, Hai Lin², Qiang Li³, Changkun Cheng³, Hui Shen³, Zhiyong Zhang¹, Zhongzhi Zhang¹, Heming Wang⁴

Affiliations

¹ State Key Laboratory of Heavy Oil Processing, Beijing Key Lab of Oil & Gas Pollution Control, China University of Petroleum, Beijing 102249, China; College of Chemical Engineering and Environment, China University of Petroleum, Beijing 102249, China.
² Technology Institute of Drilling & Production Qinghai Oilfield, Dunhuang 736200, China; Unconventional Petroleum Research Institute, China University of Petroleum, Beijing 102249, China.
³ Technology Institute of Drilling & Production Qinghai Oilfield, Dunhuang 736200, China.
⁴ State Key Laboratory of Heavy Oil Processing, Beijing Key Lab of Oil & Gas Pollution Control, China University of Petroleum, Beijing 102249, China; College of Chemical Engineering and Environment, China University of Petroleum, Beijing 102249, China. Electronic address: heming.wang@cup.edu.cn.

PMID: 34000536
DOI: 10.1016/j.scitotenv.2021.147654

Abstract

Coagulation/flocculation is considered an economical and practical technology to remove refractory organic matter from wastewater. Coagulants containing chlorine may release chloride ions into water, thereby resulting in corrosion. A green chlorine-free coagulant of polyaluminum ferric silicate (PSAF) was synthesized to treat non-oily (e.g., humus wastewater) and oily refractory wastewaters (e.g., lubricating oil wastewater). Results showed that the highest removal efficiency of humus substances in non-oily wastewater achieved 96.0% at pH 7.0 using PSAF alone. When treating oily wastewater, the dosage and addition sequence of PAMALAM significantly affected the coagulation performance. The removal efficiencies of turbidity, chemical oxygen demand, and total nitrogen were increased by 0.3, 1.8, and 5.9 folds, respectively, with the optimal adding sequence of PSAF +0.08% PAMALAM. More fulvic acid-like substances can be removed during this process. The analysis of zeta potential and floc properties revealed that charge neutralization, sweep, and adsorption/entrapment mechanisms existed during the single PSAF coagulation process, and PAMALAM mainly improved the adsorption, bridging, and sweep function.

Keywords: 3D-EEM fluorescence spectroscopy; Chlorine-free coagulants; Poly (acrylamide-co-diallyl-dimethylammonium chloride); Polyaluminum ferric silicate; Refractory wastewater.