Municipal Wastewater Treatment Using Reed Bed Eco-Technology

Abstract

The treatment of municipal wastewater using engineering constructed Reed Bed wetland system was investigated in this research work at Al-Nahrain UniversityA reed bed pilot plant, for treating 2m3/day of municipal wastewater has been designed, constructed and is being running for 12 months now. The system is based on the principles of sub-surface flow constructed wetlands. It consists of two beds (two steps), filled with gravel and sand layers as filter media. The first and second bed were designed to give 2 and 5 days retention time respectively and are capable of handling hydraulic surface flow up to 170 l/m2.day. The two beds were planted with Phragnmites communis (common reed).The general aim of this research work was to start implementing this new technology, for the first time, in Iraq and put the basis for future research work on this promising eco-technology in attempts to overcome the problems facing the wastewater treatment sector in general and the existing conventional treatment system in particular and to find the right solution for healthy environment.The findings of this research work can be summarized as follow, the improvement of the pollutant removal was proportional to the maturity of reed plants and the results obtained after running the pilot plant for nearly 12 months were, 95% for BOD5, 97% for TSS, 65% for TP, 41% for NO3-N, 39% for NH4-N and with no pathogenic (disease-causing) organisms found in the treated wastewater, were obtained. The results were good and the design is expected to give better results when the reed plants reach their maturity state. During the hot and dry season the evapotranspiration rate was higher than the influent rate and, as set by the reed bed design, a stage was reached where a complete dry out of the system occurred. Better pollutant removal results were obtained during the hot and dry season when high rate of evapotranspiration causes high pollutant concentration inside the reed bed. This finding indicates that high pollutant concentrations are generally advantageous for such treatment system. Moreover, periodically drying the system is the ideal condition for aerobic bacteria to increase in quantity and diversity which resulted in higher removal of organic pollutants.