Use of halophytes in pilot-scale horizontal flow constructed wetland treating domestic wastewater

Recent findings encourage the use of halophytes in constructed wetlands for domestic wastewater treatment due to their special physiological characteristics as the ability to accumulate heavy metals and salts in their tissues makes them ideal candidates for constructed wetland vegetation. In this particular study, we investigated the application of halophytic plants in a horizontal flow constructed wetland for domestic wastewater treatment purposes. The pilot plant which was situated in Crete (Greece) was planted with a polyculture of halophytes (Tamarix parviflora, Juncus acutus, Sarcocornia perrenis, and Limoniastrum monopetalum). The system’s performance was monitored for a period of 11 months during which it received primary treated wastewater from the local wastewater treatment plant. Results show that halophytes developed successfully in the constructed wetland and achieved organic matter and pathogen removal efficiencies comparable to those reported for reeds in previous works (63% and 1.6 log units, respectively). In addition, boron concentration in the effluent was reduced by 40% in comparison with the influent. Salinity as expressed by electrical conductivity did not change during the treatment, indicating that the accumulation of salts in the leaves is not able to overcome electrical conductivity increasing due to evapotranspiration. The results indicate an improvement in the treatment of domestic wastewater via the use of halophyte-planted CWs.