The Mediterranean is a semi-enclosed sea and by being oligotrophic is also highly susceptible to eutrophication problems. Discharges of wastewater (treated or untreated) are a major cause of eutrophication which results in imbalance of the ecosystem and encourages the spread of invasive species.
Cyprus, since the early 1980s has taken the political decision to eliminate all treated and untreated wastewater discharges in the sea, reducing therefore the risks of eutrophication and its negative effects.
Since then all successive governments have adhered to the policy not a drop of water in the sea and the program for the construction of sewerage networks and treatment facilities for all agglomerations with population equivalent greater than 2000 population equivalent (p.e.) was systematically implemented. Efforts were concentrated on the five coastal towns, namely Limassol (165.000 p.e), Paphos (100.000 p.e), Larnaca (80.000 p.e), Paralimni (53.500 p.e) and Ayia Napa (37.500 p.e), with a generated waste water load of 436,000 p.e.
In all these agglomerations sewerage networks and tertiary treatment facilities, utilizing the latest technology in the field, have been constructed . The treated effluent requirements are of the highest international standard and include nutrient removal. Specifically the treated effluent standards are BOD 10 mg/l, Suspended Solids 10 mg/l, Phosphorus 10 mg/l, Nitrogen 15 mg/l).
In the coastal towns of Paralimni, Ayia Napa and Larnaca the treated effluent is stored in lagoons and used for irrigation via dedicated irrigation networks. In Limassol the treated effluent is either used directly for irrigation or stored in an aquifer and is abstracted for irrigation. Similarly for the town of Paphos all the treated effluent is stored in an aquifer and is abstracted for irrigation.
Currently about 3% of the treated effluent of Limassol and Larnaca during winter, when demand for irrigation is low, is discharged to the sea through an appropriately designed and constructed sea-outfalls. In order to eliminate completely all marine discharges, the treated effluent irrigation networks are currently under expansion, are expected to be completed by the end of 2020 and all effluent discharges will seize. The cost of these remaining networks is expected to be in the range of 35 million USD.