Department of Civil Engineering

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Author: search.filters.author.Singhal, AnupamSubject: search.filters.subject.Municipal solid waste (MSW)

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    Bio-chelation for sustainable heavy metal remediation in municipal solid waste compost: a critical review of chelation technologies
    (Springer, 2025-04) Singhal, Anupam; Srinivas, Rallapalli
    Municipal solid waste (MSW) compost is a promising solution for sustainable urban waste management, widely used as a soil amendment and for carbon sequestration. However, heavy metals in MSW compost pose risks to ecosystems, food safety and human health. This review critically examines three decades of research (1994–2024) on heavy metal contamination in MSW compost and household hazardous waste (HHW), identifying gaps in managing these pollutants, particularly regarding hazardous waste co-disposal. It evaluates existing remediation strategies for heavy metal removal, with a focus on chemical-assisted leaching using chelating agents. Key treatment parameters—such as chelating agent concentration, pH, contact time, liquid/solid ratio, temperature and flow rate—are analysed in both batch and continuous modes. The study advocates for biodegradable chelating agents as an effective approach to enhancing MSW compost quality, with applications in landfill reclamation and agriculture. Emphasizing the need for eco-friendly heavy metal mitigation, the review underscores the importance of safe urban composting practices. The findings contribute to the circular economy and Sustainable Development Goals by promoting sustainable and safe MSW compost applications, fostering environmental protection and public health and guiding research and industry toward scalable, marketable remediation solutions.
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    An Assessment of Qualitative and Quantitative Municipal Solid Waste City Compost by Indexing Method
    (Springer, 2023-09) Khare, Srishti; Singhal, Anupam
    Globally, the disposal of municipal solid waste (MSW) is a significant environmental challenge. The production of MSW is continuous in megacities, small cities, and large villages, and if wastes are not managed properly, they can have a detrimental effect on both the environment and human health. Processes such as incineration, anaerobic digestion, and composting are widely adopted. The MSW city compost (MSWCC) generated poses significant challenges due to the presence of a high amount of residual metal toxicity. Therefore, the researcher examined the material's physical and chemical properties, as well as its heavy metal content and spectral characteristics were investigated to assess the applicability of its use for different purposes generated from MSW dump yards. For this purpose, spectral characterization including mineralogical analysis with X-ray diffraction (XRD) was used to determine the presence of heavy metals; topographical imaging and elemental mapping with a scanning electron microscope and energy dispersive X-ray analysis were carried out (FESEM-EDX). Current investigation shows that (i) XRD, SEM–EDX confirms the evidence of HMs in MSWC; (ii) In terms of Zn, Cu, Cd, Pb, and Ni, MSW compost did not meet the quality control guidelines of ‘The Fertilizer (Control) Order 1985.’ (iii) Using the Indexing method, the Fertilizing Index (FI) of compost was found to be 4.4, which means it has a high potential to fertilize. The Clean Index (CI) of compost, on the other hand, was found to be 1.7, which means it has a high potential to pollute with heavy metals; (iv) The compost sample belongs to RU-3 (Restricted Use category 3) class and, hence, has been found unsuitable for any kind of use.
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    Heavy metal remediation using chelator-enhanced washing of municipal solid waste compost based on spectroscopic characterization
    (Springer, 2023-04) Singhal, Anupam; Srinivas, Rallapalli
    Due to high metal toxicity, mixed municipal solid waste (MSW) compost is difficult to use. This study detected the presence of heavy metals (Cd, Cu, Pb, Ni, and Zn) in MSW compost through mineralogical analysis using X-ray diffraction (XRD) and performed topographical imaging and elemental mapping using a scanning electron microscope and energy dispersive X-ray analysis (SEM–EDX). Ethylenediaminetetraacetic acid (EDTA), a typical chelator, is tested to remove heavy metals from Indian MSW compost (New Delhi and Mumbai). It deals with two novel aspects, viz., (i) investigating the influence of EDTA-washing conditions, molarity, dosage, MSW compost-sample size, speed, and contact time, on their metal removal efficiencies, and (ii) maximizing the percentage removal of heavy metals by determining the optimal process control process parameters. These parameters were optimized in a batch reactor utilizing Taguchi orthogonal (L25) array. The optimization showed that the removal efficiencies were 96.71%, 47.37%, and 49.94% for Cd, Pb, and Zn in Delhi samples, whereas 45.55%, 79.52%, 59.63%, 82.31%, and 88.40% for Cd, Cu, Pb, Ni, and Zn in Mumbai samples. Results indicate that the removal efficiency of heavy metals was greatly influenced by EDTA-molarity. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of hydroxyl group, which aids heavy metal chelation. The results reveal the possibility of EDTA to reduce the hazardous properties of MSW compost.