Ahydrogeological characterization of the Ezousas alluvial aquifer, located in SW Cyprus, has been conducted to assess its suitability for groundwater recharge with 5 Mm3 a−1 of chlorinated disinfected tertiary treated sewage effluent from the Paphos Municipality Wastewater Treatment Plant. We present results from a 3 year field study conducted to establish the regional groundwater regime and to define the aquifer hydrology. New drillings at selected locations were made to provide reliable information about the aquifer dimensions and boundaries. Pumping and constant-head permeability tests were used to estimate the key hydraulic properties of the aquifer system. The storage capacity was assessed to be 4.2 Mm3. The bedrock of the aquifer, in its approach to the sea, was found to be some 40 m below sea level, thus indicating the potential for seawater intrusion. A monitoring programme consisting of recording piezometric heads and electrical conductivities was used to observe the position of the seawater–freshwater interface, so that rates of abstraction and recharge could be determined, to maintain a stable interface. The quality of the treated sewage effluent, and of native and abstracted groundwater, was continuously assessed in terms of salinity, heavy metals, persistent organic compounds and microbiota, to optimize the quality of the downstream groundwater used for local irrigation.