From Treated Wastewater to Alternative Water Resources in Semi-Arid Regions

MEWWC's wastewater treatment unit (WTU) is the only one in Greece that has been given a license for reusing 100% of its effluent. This practice is currently allowed only for tree irrigation. The WTU has a capacity of 40 000 people-equivalent, but is only fully used during the tourist season (June-August). In winter, the WTU serves 2 000 local residents. The system needs upgrading for a number of reasons: there is no monitoring of the quality of the treated wastewater, or of its effects on soil, plants and people; poor infrastructure means that the treated wastewater is not fairly or equally distributed (enhanced controls could result in an estimated 30-35% increase in the area irrigated); there is no information about how to safely use the treated wastewater; and there is no pricing for this alternative water resource, resulting in a lack of funds for maintenance of the distribution system. Therefore, there is a need for Providing Upgraded REuse (PURE), not just for the local community but also for similar applications in Greece and Southern Europe. The main objective of the PURE project was to transform an existing network of pipelines, for distributing treated wastewater for irrigation in an uncontrolled way, into an upgraded system that provides high-quality alternative water resources for irrigation in accordance with the principles of the Water Framework Directive. The proposed upgraded wastewater distribution system comprised over 30 000 metres of pipelines, at least three advanced wastewater treatment units, and a complete online monitoring system. The aim was to make a socially-fair system – especially in economic terms – for distributing this important alternative water resource. The project aimed to produce detailed planning, financial and management information for the future implementation of similar systems elsewhere. Overall, the project planned to produce and disseminate a prototype approach and management plan for a sustainable, environmentally-significant, safe, publicly-accepted wastewater reuse and utilisation system that could be applied in all semi-arid areas. The PURE project upgraded the infrastructure and management of an existing wastewater treatment and irrigation network in Chersonissos, Crete. Prior to the project, treated wastewater was distributed with no control, monitoring, pricing or management plan. The project firstly determined the technical characteristics of the system and undertook a technical-economic feasibility study. The network was upgraded and tested in 2012, and has since been operating at full scale, distributing treated wastewater for the irrigation of olive groves. Optimal operating conditions were reached in autumn 2013. The project team addressed issues that arose during the upgrade to significantly improve the required deliverables, including two LCA (Life Cycle Assessment) reports on the wastewater reuse system, a monitoring protocol and a business plan. A new department was established within coordinating beneficiary MEWWC, with responsibility for the management of the upgraded wastewater distribution system. The main direct and quantitative environmental benefits are the treatment and utilisation of 2. 400 000 m3/per year of wastewater for crop (tree) irrigation. This will contribute significantly to addressing the impact of growing water scarcity and drought in the region, which is expected to worsen due to climate change, and the decrease and salination of aquifers from over-pumping, especially in coastal areas. Before the PURE project, the reuse schemes in the project area were based on a simple reality: farmers or other end-users struggling to find water for irrigation purposes were using water of disputable quality. The PURE project provided the necessary tools for turning wastewater into a preferable solution both economically and for the local environment. A monitoring protocol was established for assessing water quality, and the environmental status of soils and plants. Forty sampling locations were established in olive groves. The beneficiary presented monthly data for biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended solids, nitrogen, ammonia, nitrate, E. coli and other water quality parameters. Associated beneficiary Technological Education Institute of Crete (TEIC) will continue monitoring the soil and plants in the area where the wastewater has been utilised. The project tested several different irrigation systems along rows of olive trees. The project team collected questionnaire responses (1 749 in total) concerning attitudes to wastewater reuse from four main target groups: farmers, local authorities, the local population and tourists. The project also produced a list of the farmers using reclaimed water. In addition to questionnaires, the project’s information and awareness-raising campaign utilised a website, newsletters and leaflets, and an environmental educational programme in local schools. There are two main social benefits from the PURE project. Firstly, the improved safety and efficiency of wastewater reuse practices facilitates sustainable agricultural production, and through that economic benefits for farmers. Secondly, the awareness-raising and education programmes make the local population more accepting of wastewater reuse and of related issues and projects.