Insight into removal TOC and NH4+ from mature landfill leachate using coupled bio-coagulation from Moringa oleifera seeds and ZVI/H2O2 process

Abstract

In this research, protein was extracted from Moringa oleifera (MO) seeds using protease from Bacillus licheniformis and evaluated for effectiveness as a bio-coagulant to be applied in leachate pretreatment. Leachate samples were collected from part of a closed municipal landfill with total organic carbon (TOC) of 1465 mg/L and ammonium ion (NH4+) of 1245 mg/L. A Fenton-like reaction with a mediated zero-valent iron (ZVI) system was applied to the leachate after coagulation. A response surface methodology (RSM) based on a Box-Behnken design (BBD) was adopted to optimise the Fenton-like process. A quadratic polynomial model was used on the data, with R2 of 0.996 and 0.998 for total organic carbon (TOC) and NH4+ removal, respectively. Influence of three main factors was investigated, namely pH, molar ratio of H2O2/ZVI, and concentration of H2O2 for TOC and NH4+ removal. In optimum conditions of 30 min reaction time, pH = 3, [H2O2] =43.82 mM, molar ratio H2O2/ZVI of 3.89, effectiveness of elimination of TOC and NH4+ was 59.98 % and 98.3 %, respectively. Combined technology of bio-coagulant and Fenton-like reaction was confirmed to be a competent process for treating leachate, with 72.6 % TOC and 98.98 % NH4+ removal. Supposed operation costs for the coupling of treatments can be estimated at 5.67 $/m3. Thus, reductions in NH4+ and mineralization were achieved cost-effectively by combining bio-coagulation with protein extracted from MO seeds and a Fenton-like process activated by ZVI.