Tertiary treatment of domestic wastewater for reuse: Implementation and evaluation in a rural context in Chile

Water scarcity in arid and semi-arid regions of Chile is intensifying demand for safe irrigation water sources. This study assesses a modular tertiary treatment train for rural wastewater reuse based on fixed-bed polishing with natural zeolite and activated carbon, followed by UV-C disinfection. Pilot-scale implementation at the La Higuera wastewater treatment plant confirmed robust field performance, reducing TSS by ≈ 70%, BOD₅ by ≈ 56%, and fecal coliforms by 99.9%, enabling compliance with Chilean irrigation reuse criteria (NCh 1333; DS 90/2001). Average salinity indicators during monitoring were EC = 1774 μS/cm and TDS = 964 mg/L, suggesting moderate irrigation restrictions and practical suitability mainly for moderately salt-tolerant crops under appropriate management (e.g., leaching and drainage). Because the pilot evaluation covered only ∼3-4 months, long-term performance claims remain preliminary, and seasonal variability and fixed-bed media breakthrough/saturation should be validated through extended multi-season monitoring. Persisting limitations include dissolved solids control and maintaining nitrogen removal during extended operation. Overall, the proposed low-energy, locally adaptable train provides a pragmatic and transferable pathway for decentralized water reuse in arid rural settings, with site-specific adaptation mainly required for influent nitrogen loading/speciation, background salinity/TDS, and local reuse regulations, supporting circular water management aligned with SDG 6 and SDG 12.