Abstract

Heat integration and waste heat recovery have become critical strategies in enhancing the energy efficiency and sustainability of industrial water reclamation processes. As industries face growing pressure to minimize environmental impact and operational costs, the adoption of advanced thermal management techniques has gained momentum. This systematic review evaluates recent advancements in heat integration and waste heat recovery technologies applied within water reuse systems across sectors such as petrochemical, food processing, textile, and power generation. The review explores how various thermal integration strategies such as pinch analysis, exergy analysis, and heat exchanger network (HEN) design optimize the reuse of thermal energy during processes like membrane filtration, thermal evaporation, and multi-effect distillation. Emphasis is placed on the recovery of low- to medium-grade waste heat from unit operations including cooling towers, condensers, and steam discharge lines, and its reintegration into upstream or parallel processes for energy conservation. Advanced technologies such as heat pumps, thermoelectric generators, and membrane distillation driven by residual heat are also examined for their ability to reclaim thermal energy while supporting water recovery. Additionally, the integration of combined heat and power (CHP) systems with water treatment facilities is discussed as a viable pathway for cogeneration and energy autonomy. The review highlights both centralized and decentralized frameworks for waste heat management and their effectiveness in process optimization. Key performance indicators such as thermal efficiency, recovery factor, and energy intensity are assessed across case studies. Barriers including heat exchanger fouling, corrosion in high-salinity streams, and the intermittent nature of waste heat availability are addressed, along with emerging solutions such as self-cleaning surfaces and hybrid energy systems. Overall, the findings underscore the critical role of thermal integration in reducing the energy-water nexus footprint, with recommendations for industrial adoption, lifecycle cost analysis, and policy support. These insights contribute to designing future-ready industrial water systems that are both economically and environmentally sustainable.