Landfill leachate pretreatment effects on nanofiltration and reverse osmosis membrane performance

Abstract

The present study investigates the effects of landfill leachate pretreatment by coagulation-flocculation (C/F) on the performance of nanofiltration (NF) and reverse osmosis (RO) membranes by comparing permeate flux, fouling resistance, and leachate quality. Pretreated leachates were produced by applying the C/F with ferric chloride (FeCl3) and alum sulfate (Al2(SO4)3), named P1 and P2 leachates. Raw leachate (RL), P1, and P2 samples were treated using five different polymeric membranes termed NP030, NP010, XN45, BW30, and X201. The C/F pretreatment with FeCl3 or Al2(SO4)3 increased XN45's permeate flux by more than 80%. In this case, fouling median resistance values were 2.13e+ 08, 0.96e+ 08, and 1.02e+ 08 m−1 for RL, P1, and P2, respectively. Kruskal-Wallis test showed a significant difference between RL and pretreated leachate groups (p-value < 0.05). No significant difference between P1 and P2 was identified by the Dwass-Steel-Critchlow-Fligner test run for pairwise comparisons. These results indicate that the leachate pretreatment reduced membrane fouling by more than 50%, independently of the coagulant employed. Although higher removals of organic contaminants were, on average, obtained by membrane treatment for RL than for P1 and P2 samples, membranes that operated for RL treatment presented the worst performance in terms of permeate flux and fouling resistance. Therefore, NF and RO processes are not advisable as a single step in a landfill leachate treatment train, and a pretreatment step is recommended. This research makes a major contribution to the field by providing quantitative data for the conceptual premise that leachate pretreatments mitigate membrane fouling. Our findings help elucidate pretreatment effects on membrane performance and determine the preferable leachate treatment layout.