Adding Value to Reclaimed Water from Wastewater Treatment Plants: The Environmental Feasibility of a Minimal Liquid Discharge System for the Case Study of Larnaca

Abstract

The escalating water demand in Cyprus has necessitated the exploration of alternative water resources. The available water, which relies on rainfall and dam storage supplemented by methods such as desalination and aquifer enrichment, is inadequate to meet the current water demand. As a solution, Cyprus is utilizing reclaimed water for irrigation, in full compliance with both local and EU regulations. To address sustainable water management in Cyprus, a minimal liquid discharge (MLD) system is assessed for its environmental feasibility. A system incorporating reverse osmosis (RO), a multi-effect distillation (MED) evaporator, and a vacuum crystallizer (VC) is proposed for treating reclaimed water from the wastewater treatment plant (WWTP) in Larnaca. The proposed system aims to control the salinity (2500 mg/L) that limits the use of recovered water to the irrigation of non-sensitive types of crops, while recovering salt (sodium chloride). A life cycle assessment (LCA) was conducted, comparing the proposed MLD system with a reference system based on RO technology, where water is recovered, and brine is rejected back into the sea. The environmental feasibility was assessed via comparing 16 different environmental impact categories. Based on the analysis, the reference study provided a positive numeric value for most of the impact categories that were examined. Thus, it was concluded that the reference study has an overall negative impact on the environment, whereas the proposed MLD system demonstrated an overall positive impact, mainly due to low ecotoxicity.