Constructed wetlands for the Mediterranean countries: Hybrid systems for water reuse and sustainable sanitation

One of the main problems in adopting extensive treatment for wastewater purification in hot climate countries, when also the effluent reuse is aimed, is the high evapotranspiration rate. This factor can play a key role in reducing the water output, a desirable effect in some cases but completely adverse when water reuse is a primary resource for the area. Constructed wetlands have an higher evapotranspiration rate in comparison with ponds or lagoons but they also have the shortest hydraulic retention time (HRT) amongst the whole group of extensive treatment techniques. The water loss can also be minimised using a particular design and configuration of the constructed wetland system. The most powerful combinations seems to be the coupling of horizontal and vertical submerged flow beds, called hybrid systems, which performances are analysed in the present paper. In terms of overall performances the following mean removal rates were obtained: COD 94%, BOD5 95%, total suspended solids 84%, NH4+ 86%, total nitrogen 60%, total phosphorus 94%.