Authors: ABEBE ABERA
Abstract: The Ethiopian textile industry has experienced rapid expansion as a key focus for industrialization and export. However, this growth has generated substantial wastewater volumes, with over 60% of effluent treatment plants failing to meet national discharge standards for BOD, COD, and TSS. Inefficient coagulant-flocculant dosing practices, often based on trial-and-error approaches, remain a primary contributor to this non-compliance.
This study aimed to optimize coagulation-flocculation dosing for the removal of TSS, BOD, and COD from textile wastewater at Arbaminch Textile Share Company, Ethiopia, to achieve compliance with MoEFCC discharge standards.
Wastewater samples were collected from primary and secondary treatment units. Jar test experiments were conducted to determine optimal pH (5.5–8.0) and coagulant (alum) to flocculant (PAM) dosing ratios (0:0 to 30:8 mL). Treatment efficiency was evaluated through physicochemical analysis of TSS, BOD, and COD before and after optimization.
Initial wastewater characterization revealed pollutant concentrations substantially exceeding permissible limits. Optimal conditions were identified at 160 mg/L alum, 8 mg/L PAM (20:4 mL ratio), and pH 7.5. These conditions achieved exceptional removal efficiencies: 100% TSS, 90.8% COD, and 92.2% BOD, improving from baseline removals of 82.6% and 87.4% for COD and BOD, respectively. Overdosing provided marginal gains but reduced post-treatment pH below 5.0, increasing costs and sludge production.
Optimized coagulation-flocculation with precise pH control and chemical dosing provides a cost-effective, technically viable primary treatment solution for Ethiopian textile wastewater. The findings offer an evidence-based framework for improving ETP performance, achieving regulatory compliance, and supporting sustainable industrial development.
Keywords: Textile wastewater, effluent treatment plant, coagulation-flocculation, optimization, pollutant removal efficiency