Carbon materials and inoculum selection for efficient aerobic treatment and reuse of textile effluents

As global populations grow, water reuse is expected to expand due to water scarcity and regulatory and public pressures. Biological treatments are commonly used for textile wastewater treatment, but achieving effluent quality suitable for reuse remains challenging due to the wastewater complexity and the need to balance financial, environmental and social factors. This study aimed to improve the activated sludge (AS) process using carbon-based materials (CBMs)-carbon nanotubes (CNTs) and activated carbon (AC) - to enhance effluent quality for reuse in textile dyeing applications. Three effluents (A, B and C) with distinct physicochemical characteristics were studied. Results showed that CBMs enhanced colour by 1.5 for effluent A and 1.2x for B and C, and improved chemical oxygen demand removal by 1.2x for effluents A and B, compared with controls. The robustness of the aerobic treatment system was investigated over successive cycles using both domestic and textile effluents adapted sludge, with assays performed in the absence and presence of 0.5 g L−1 of CNTs. Although adapted sludge alone had a limited impact, its combination with CNTs led to improved and sustained treatment performance, demonstrating the robustness of the process. CNTs consistently enhanced colour removal across cycles, with Effluent C achieving complete decolourisation and COD of 171–172 mg L−1, while Effluent B reached 209–214 mg L−1. Effluent C treated with CNTs met nearly all reuse standard criteria and was successfully applied in fabric dyeing using a 75% treated effluent and 25% tap water mixture, without compromising dyeing quality. These findings highlight the potential of integrating CNTs into aerobic treatment systems to promote the reuse of treated textile effluent in industrial processes.