Balancing ecological risk and economic feasibility: A marginal-cost optimization framework for textile effluent recovery

The textile sector faces increasing pressure to align stringent effluent controls with economic viability. This study develops a marginal-cost optimization framework to identify the dynamic equilibrium recovery level at which incremental treatment expenditure equals marginal environmental benefit. Techno-economic data from membrane-based and ecological treatment trains were integrated with life-cycle damage monetization, and an NSGA-II multi-objective optimization framework was used to derive Pareto-optimal recovery levels. Life-cycle assessment showed that reclaimed effluent had a GHG intensity of 5.70 kg CO 2 eq/m 3 , versus 3.66 kg CO 2 eq/m 3 for standard discharge, with electricity accounting for 49% of emissions; the indicated optimal recovery levels were 55–82%, with elasticities of 0.38 for water tariffs, −0.42 for electricity prices, and −0.15 for carbon taxation. A tiered strategy combining Class I-A discharge, constructed wetland polishing (0.1–0.23 CNY/m 3 ), and small-scale membrane recovery (15–25%) was identified as optimal. Comparative analysis of water-scarce Aksu showed that zero-liquid-discharge pathways with 50–60% recovery are justified by water-security imperatives despite higher costs. Carbon pricing shifts the equilibrium recovery level downward by 3–5 percentage points, highlighting region-specific water–carbon trade-offs that require coordinated policy design.