Seasonal variations in feed-water chemistry and fouling dynamics of reverse-osmosis systems: A global climate lens

Reverse osmosis desalination plants are built for worst-case conditions, yet seasonal variations in feed water quality often outpace their design assumptions, leading to avoidable membrane performance losses. Temperature swings of 10–15 °C, along with changes in salinity, organic matter, and microbial activity, drive predictable membrane fouling dynamics that static protocols cannot accommodate. This review synthesizes RO studies published from 2015 to 2025 across hot-desert, Mediterranean, temperate, and tropical climate zones using Köppen-Geiger climate classification as an organizing framework, the first systematic climate-resolved synthesis of seasonal fouling mechanisms and adaptive responses. Through this review, three principal findings emerge. First, climate-specific seasonal fouling regimes are distinct and mechanistically predictable patterns: arid coasts (BWh) experience summer biofouling synergistically amplified by gypsum scaling; temperate systems (Cfa, Dwa) face winter organic fouling from recalcitrant humics despite reduced microbial activity; and tropical intakes (Aw, Am) endure monsoonal pulses that increase both colloidal fouling and dissolved organics by 5–100× relative to dry-season baselines. Second, static protocols impose severe performance penalties: flux decline rates can reach 70–85 %, membrane cleaning frequency doubling, and energy consumption rising despite viscosity-driven efficiency gains in warm periods, demonstrating that single-parameter optimization fails under coupled thermal-chemical-biological forcing. Third, predictive-adaptive systems demonstrate step-change improvements: predictive models enable accurate, real-time antiscalant dosing, while temperature-responsive pretreatment maintains higher permeate flux and reduces energy demand by up to nearly 20 %; quorum-sensing-inhibitor coatings reduce biofilm thickness by 60–69 %; and ceramic ultrafiltration eliminates harmful-algal-bloom capacity losses that degrade polymeric membranes by 30–40 %. Yet critical gaps persist hot-arid (BWh) and Mediterranean (Csa) zones, most monitoring datasets are short-term, and temperature-dependent fouling relationships remain unclear due to inconsistent findings. Closing these gaps requires multi-year monitoring across all climate zones and economic validation under climate variability. Seasonal adaptation must evolve from reactive adjustment to fundamental design criterion. Future installations should align membrane materials, pretreatment systems, and control algorithms with site-specific hydrological calendars.