Issue 12, 2019

Application of composite flocculants for removing organic matter and mitigating ultrafiltration membrane fouling in surface water treatment: the role of composite ratio

Abstract

Coagulation prior to the ultrafiltration (UF) process was implemented to improve natural organic matter (NOM) removal and membrane permeability. Polyaluminum chloride (PAC), polyferric chloride (PFC), and composite flocculants polyaluminum chloride–polydimethyldiallylammonium chloride (PAC–PDMDAAC) and PFC–PDMDAAC were used for comparison for treating HA-simulated water, FA-simulated water, Yellow River water and Yangtze River water. The comparative experiments showed that PAC–PDMDAAC achieved the best C-UF performance among the flocculants PAC, PFC, PFC–PDMDAAC and PFC–PDMDAAC due to its highest charge density. With an increase in the PDMDAAC content, the ability of the charge neutralization and adsorption bridging of PAC–PDMDAAC improved. PAC–PDMDAAC (5 : 1) contributed to the highest NOM removal efficiency and the formation of amorphous flocs with the lowest density and the most open structure because PDMDAAC as high positively charged organic matter quickly neutralized the negative charges on the micro-flocs and swept them to form highly branched flocs. In membrane experiments, PAC–PDMDAAC with a high content of PDMDAAC mitigated membrane fouling due to the formation of a cake layer with high porosity and less blockage in the membrane pores. With an increase in the PDMDAAC content in PAC–PDMDAAC, Rcs decreased and the cake layer resistance still accounted for the majority of the total resistance when an RC membrane was used. These results demonstrate that PAC–PDMDAAC with a high PDMDAAC content is effective in alleviating membrane fouling by reducing pore blockage and forming a porous cake layer, which is attributed to flocs with a large size and open structure.

Graphical abstract: Application of composite flocculants for removing organic matter and mitigating ultrafiltration membrane fouling in surface water treatment: the role of composite ratio

Supplementary files

Article information

Article type
Paper
Submitted
23 Jun 2019
Accepted
12 Oct 2019
First published
15 Oct 2019

Environ. Sci.: Water Res. Technol., 2019,5, 2242-2250

Application of composite flocculants for removing organic matter and mitigating ultrafiltration membrane fouling in surface water treatment: the role of composite ratio

X. Shen, B. Gao, K. Guo and Q. Yue, Environ. Sci.: Water Res. Technol., 2019, 5, 2242 DOI: 10.1039/C9EW00528E

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