Novel bio-filtration method for the removal of heavy metals from municipal solid waste

Fast urbanization, and agricultural escalation produce a lot of municipal solid wastes (MSW). There is need to recognize economically practical innovations to debase substantial metals to an innocuous state. The present investigation aimed to recognize proficient fungi and develop bio-filtration strategy utilizing them for expulsion of substantial heavy metals (HMs) from tainted MSW compost (MSWC). Six fungi were isolated from sewage sludge, namely, Trichoderma viride, Aspergillus heteromorphus, Rhizomucor pusillus, Aspergillus flavus, Aspergillus terreus, and Aspergillus awamori. Growths of all these fungi were highly susceptible to Cd at 5 ppm. Trichoderma viride, Aspergillus awamori, and Rhizomucor pusillus were highly susceptible to Cu at 50 ppm. Aspergillus flavus and Aspergillus heteromorphus could tolerate Cr below 50 ppm. The varying degree of HM tolerance by different fungi may be due to diverse strategies to dodge HM toxicity. Functional groups like amide (-NH2), hydroxyl (-OH), carboxylate anions (-COO), carbonyl groups (-CO), C-F and C-Br were responsible for bio-sorption of heavy metals by fungi through chelation with HMs. We found Trichoderma viride and Aspergillus flavus based bio-filters were capable to remove the highest amount of Pb (>40%) and Cd (>20%). Aspergillus heteromorphus based bio-filters was the most efficient to remove Cu and Cr from MSWC (∼20%). Trichoderma viride, Aspergillus heteromorphus, Rhizomucor pusillus and Aspergillus flavus based bio-filters were equally effective for elicitation of Zn (∼30%) and Ni (>30%) toxicity. Differential minimum inhibitory concentration, uptake of HMs, bio-sorption capacity of HMs by fungi resulted in unequal efficacy of fungal bio-filters.