466 / 2018-09-05 21:59:06

Towards understanding the stabilization process in vermicomposting of excess sludge under copper oxide nanoparticles stress using PARAFAC analysis of fluorescence spectra

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ABSTRACT

Due to extensive applications of copper oxide nanoparticles (CuO NPs), the discharge in wastewater has increased in recent years. This has also resulted in their enrichment in excess sludge. In this study, growth status of earthworms and physico-chemical properties of substrates were studied to investigate the feasibility and stabilization performance on vermicomposting of excess sludge contaminated with CuO NPs. Experiments using four groups of CuO NPs concentrations (0, 400, 800, 1600 mg/kg-SS) in the substrates were conducted using Eisenia fetida. The results showed that earthwoms could survive and play the positive role in sludge stabilization in the four groups of vermicomposts. Moreover, the degradation of TOC and DOC in the substrates was slightly decreased with the increasing of CuO NPs concentration in the substrates. Furthermore, a three-component model containing two humic acid-like materials (C1 and C3) and a soluble microbial by-product-like material (C2) was successfully developed using PARAFAC analysis. C2 and C3 could be used to track the organic transformation and assess the maturity of vermicompost. The decrease of the relative contents of the three components was observed with the increasing of CuO NPs concentration in the substrates, which might due to the complexation with cupric ion released from CuO NPs during the vermicompost. Overall results suggested vermicompost could be a feasible and effective treatment method for excess sludge polluted by CuO NPs.
Key words:
Vermicomposting; Copper oxide nanoparticles; Excitation-emission matrix (EEM); Parallel factor analysis (PARAFAC); Excess sludge