Comparative assessment of PACl variants and clarifier sludge for textile wastewater treatment: A grey water footprint approach

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Textile wastewater poses significant environmental risks due to high loads of dyes, heavy metals, and organic compounds, requiring effective treatment solutions. This study evaluated polyaluminum chloride (PACl) variants and water treatment clarifier sludge (CLS) for textile wastewater treatment, using grey water footprint reduction efficiency (GWF%) as a holistic performance metric. Five scenarios (Sce-1 to Sce-5) were tested via jar tests, combining powdered/liquid PACl, CLS, sodium hypochlorite (NaOCl), and calcium oxide (CaO) under optimal dosages: 0.7 g/L powdered PACl, 3.0 mL/L liquid PACl, 75 mL NaOCl, and 1.0 g/L CaO. High removal efficiencies were achieved for COD (80-95%) and TSS (94-98%). Thallium and zinc were reduced by up to 99%, while aluminum removal varied from 0.0% to 99% depending on treatment. Overall, GWF was reduced by 83% (Sce-4) to 93% (Sce-2). Liquid PACl with NaOCl and CaO (Sce-2) was identified as the most effective based on GWF% analysis. Statistical analysis confirmed Sce-2 as the top performer (Group A), with Sce-3 statistically comparable (Group AB), followed by Sce-1 and Sce-5 (Group B), and Sce-4 (Group C) (p < 0.05). Excessive PACl dosing destabilized pollutants, with aluminum removal collapsing to 0% in Sce-5, highlighting the need for optimized coagulant application. As a waste-derived material obtained at no cost, CLS offers economic and environmental benefits for targeted applications like aluminum and color removal, despite limited standalone performance. These findings confirm PACl-based coagulation, particularly liquid PACl, as highly effective for textile wastewater treatment, while GWF% proved a robust multi-pollutant indicator for identifying sustainable treatment strategies.