Sustainable approaches in textile dyeing sludge management: A review of emerging technologies and future perspective

Abstract

The textile dyeing sector produces a significant amount of sludge from Effluent Treatment Plants (ETPs), leading to serious environmental issues due to ineffective traditional disposal practices. This research reviews the sustainable approaches for the sludge management of bio, salt, and lime sludge generated during effluent treatment. A detailed characterization of all the sludges was done using CHNS, TGA-DTA-DTG, ICP-MS, SEM-EDS, XRD, and FTIR analysis. Bio-sludge showed high carbon, 25.86%, in comparison to other sludges. The salt-sludge showed significant levels of sulfur 5.45% and sodium, 21.95 wt.%, whereas the lime-sludge was alkaline in nature with pH 10.02 and increased calcium levels, 22.2wt.%. The ICP-MS results showed that salt-sludge contained high levels of heavy metals, particularly Cu (1038.44 ppm), Zn (103.10 ppm), and Hg (284.30 ppb), which highlights issues related to potential toxicity. The TGA exhibited multi-stage decomposition for all samples, with considerable weight loss recorded in bio-sludge, consistent with its volatile content. SEM-EDS showed porous carbonaceous structures in bio-sludge, in contrast to the crystalline salt clusters in salt-sludge and layered mineral formations in lime-sludge. These results establish bio-sludge as a promising option for pyrolytic conversion due to its rich organic content and energy potential. Although salt sludge has a lower organic fraction, it is suitable for controlled gasification if heavy metals are carefully monitored. Lime-sludge, with its inorganic stability and low moisture content, can act as a co-feed in thermal processes or co-processing in cement manufacturing. Hence, the sludges demand customized treatment strategies to transform them into energy, biochar, or industrial raw materials, fostering the principles of a circular economy and reduced environmental impacts.