PROJECT DESCRIPTION
BACKGROUND
The lack of a legislative framework for wastewater reuse, and delays in technology development, are the two main reasons for the limited development of wastewater reuse techniques in Greece. In addition, the unsustainable use of water resources along the extensive coastline of Greece is the principal cause of seawater penetration into groundwater aquifers, as well as the decrease of ground water levels. These phenomena are observed in all Mediterranean coastal areas and especially in the areas targeted by this pilot project (Prefectures of Thessaloniki and Chalkidiki).
OBJECTIVES
The objectives of the project were the determination of guidelines for wastewater reuse in Greece, and the evaluation in real conditions of the most appropriate methods based on pilot scale experiments. A pilot plant was to be implemented at the secondary wastewater treatment plant of Thermi. The existing treatment plant had been designed to service about 12.000 inhabitants and had operated for the last five years. An advanced treatment unit was to be designed, constructed and made operational during the project for the removal of suspended solids, biological, organic and inorganic pollutants from the secondary effluent. The treated effluent, ranging in quality from drinking water to effluent from the secondary treatment plants, was to be used for irrigation and direct injection to the groundwater aquifers, so that the impact on the environment could be monitored. The pilot-project was to be an innovative approach to the replenishment of the groundwater aquifers and the control of salt intrusion. The project's results would be used for the development of a framework for wastewater reuse in Greece supporting the strategy for the sustainable use of natural resources. It was expected that the results could be applied to other EU countries and countries of the Mediterranean region facing similar hydrological problems, and that the techniques could be used for the control of other environmental problems observed in basins, sea and drinking water sources.
RESULTS
The stated objectives have been met: the project demonstrated a successful application of reused wastewater for the artificial enrichment of aquifers and for salt-water intrusion control. In combination with the reduction/elimination of water consumption, the solutions for depleted and/or degraded groundwater sources were demonstrated. One of the technical problems faced during the pilot implementation, was maintaining the quality of the wastewater that was intended to be used in order to avoid adverse environmental impacts. Future uncertainties include : possible failure in preventing salt water intrusion due to the low level of reclaimed water inflows and the possible phenomenon of plant growth and clogging which could result in a periodic reversal of the operation of the recharging basins. A final limiting factor in the application of the technology is the existence of different scientific approaches concerning wastewater reuse in Greece, which must be coordinated in order to formulate a national legislative framework.The stated objectives have been met: the project demonstrated a successful application of reused wastewater for the artificial enrichment of aquifers and for salt-water intrusion control. In combination with the reduction/elimination of water consumption, the solutions for depleted and/or degraded groundwater sources were demonstrated. One of the technical problems faced during the pilot implementation, was maintaining the quality of the wastewater that was intended to be used in order to avoid adverse environmental impacts. Future uncertainties include : possible failure in preventing salt water intrusion due to the low level of reclaimed water inflows and the possible phenomenon of plant growth and clogging which could result in a periodic reversal of the operation of the recharging basins. A final limiting factor in the application of the technology is the existence of different scientific approaches concerning wastewater reuse in Greece, which must be coordinated in order to formulate a national legislative framework.
