Comparative Life Cycle Assessment of Management Strategies for Municipal Wastewater Reclamation: Disposal, Zero Liquid Discharge, and Selective Resource Recovery

Abstract

Water reclamation from municipal wastewater treatment plants is a critical strategy for addressing freshwater scarcity in water-stressed regions. This study presents a comparative cradle-to-grave Life Cycle Assessment of three treatment configurations applied to tertiary-treated effluent from a wastewater treatment plant (WWTP) in Cyprus. The three studied systems comprise a conventional single-pass reverse osmosis (RO) unit, serving as the baseline and resulting in salt disposal (Scenario I); an integrated Zero Liquid Discharge (ZLD) system, combining membrane (nanofiltration and reverse osmosis) and thermal (multi-effect distillation and vacuum crystallization) units, resulting in NaCl recovery (Scenario II); and a selective resource recovery configuration combining chemical precipitation (with the recovery of CaCO3, Mg(OH)2, and NaCl), RO, and a low-temperature crystallizer unit (Scenario III). The environmental impacts were assessed in SimaPro 10.3 using EF 3.1 across 16 midpoint categories with a defined functional unit of 1 m3 recovered water. Based on the SimaPro results and the conducted analysis, Scenario II performed worst in 13 of 16 impact categories, with increases up to +395% (human toxicity, non-cancer) relative to Scenario I, driven by its high thermal electricity demand (12.21 kWh/m3, over four times the baseline’s) under the fossil fuel-dominated Cypriot grid. Scenario III’s Module D credits (recovered NaCl, Mg(OH)2, CaCO3) reduced burden by up to 96% in individual categories but did not reverse any impact category to net-negative values. On the weighted single score, the baseline (280 µPt) outperformed both Scenario III (345 µPt) and Scenario II (1038 µPt), a nearly fourfold gap between the best and worst configurations. Sensitivity and Monte Carlo analysis confirmed this ranking as robust, while showing that a 20% increase in recovered-product credit is sufficient to reverse ionizing radiation to net-negative in Scenario III. Overall, selective resource recovery narrows, but does not reverse, the environmental burden of advanced brine treatment relative to conventional disposal.