Techno-economic and emissions assessment of renewable-energy integration into textile wastewater zero liquid discharge

Textile wastewater zero liquid discharge (ZLD) reduces freshwater use and saline effluent discharge but is associated with high energy demand and operational emissions. This study assessed renewable-energy integration into a closed-loop reverse osmosis (CLRO)–osmotically assisted reverse osmosis (OARO)–crystalliser process chain in Tiruppur, India, at plant-feed capacities of 500, 920, 1000 and 2400 m 3 /d. Grid supply, photovoltaic (PV) generation with grid support, PV with process-load shifting, and hybrid PV–wind generation with battery energy storage (BESS) were evaluated. The hybrid system was assessed using representative-day and continuous 8760 h dispatch. PV with grid support gave the lowest net ZLD cost among the simplified scenarios, whereas load shifting produced the lowest calculated emissions but required additional membrane capacity, intermediate storage and PV capacity. For the 1000 m 3 /d reference plant, the continuous 8760 h hybrid configuration with a 60:40 PV–wind generation share and 5 h BESS achieved a renewable-electricity share of 76.2%, operational emissions of 0.84 kg CO 2 /m 3 and a net ZLD cost of approximately 1.33 €/m 3 . This represented an approximately 80% emissions reduction relative to the grid–coal reference while maintaining a similar net cost. Storage beyond 5 h provided limited additional benefit. Among the evaluated PV–wind allocations, the 60:40 share provided the highest renewable utilisation and the lowest emissions and net ZLD cost. These results show that renewable-energy integration can substantially reduce the operational CO 2 emissions of textile wastewater ZLD while maintaining a similar net treatment cost under the assessed conditions.