Valorisation of toxic paper mill waste through vermicomposting: An insight towards cleaner engineering through alleviation of wastes

Abstract

Valorisation involves conversion of toxic compounds into value added products. The present study has tried to evaluate the potential of vermicomposting in management of different types of toxic paper mill wastes such as primary waste (VCP) and secondary waste (VCS) using Eisenia fetida for 60 days. The procedure was performed using sundried samples of paper mill wastes, cow dung and straw in different trial sets using different ratios. The study had revealed that the trial sets (VCP1 and VCS1) using ratio of paper mill waste: Cow dung: Straw (5:4:1) were effective in maintaining physiochemical parameters and different population attributes of earthworm. The present study had also demonstrated the enzymatic enrichment of vermicompost in terms of 19 enzymes such as α-Glucosidase, lipase, leucine aminopeptidase etc. in maintenance of C/N ratio of the compost. A significant reduction of heavy metals were noticed in vermicomposting of primary waste (VCP1) as Zn (40%) ​> ​Pb (36%) ​> ​Cr (28%) ​> ​Cu (25%) and secondary waste (VCS1) as Zn (44%) ​> ​Pb (41%) ​> ​Cu (19%) ​> ​Cr (13%). Such reduction of heavy metal was highly correlated with the reduction of C/N ratio of the vermicompost. The process of bioremediation was further manifested through the regular monitoring of bioaccumulation factor (BAF) among earthworm population in vermicomposting of primary waste (VCP1) as Zn (0.40) ​> ​Cu (0.23) ​> ​Cr (0.18) ​> ​Pb (0.11) and secondary waste (VCS1) as Zn (0.47) ​> ​Cu (0.25) ​> ​Cr (0.21) ​> ​Pb (0.14). Therefore, the study concludes that the ratio of paper mill waste, cow dung and straw (5:4:1) can be an efficient formulation in qualitative enrichment of different toxic organic paper mill wastes through vermicomposting. • Valorization of solid paper mill wastes through vermicomposting ensures qualitative enrichment. • Ratio of paper mill sludge: Cow dung: Straw (5:4:1) supports earthworm growth in an organic rich environment. • Moulding of an organic waste into an enzyme rich compound through the turnover of carbon and nitrogen turnover enzymes. • Reduction of several toxic heavy metals and its bioaccumulation within earthworms. • C/N ratio of vermicompost can determine the extent of metal removal and enzyme enrichment.