Role of Iran Pseudacorus plant in removal of bacteria in subsurface constructed Wetland

Background and Removal of bacteria by macrophytes in wetland system had been reported by many researchers. This study was designed and performed to determine the efficiency of sub-surface constructed wetland in removal of coliform bacteria from sewage. We have used 4 plastic reactors in Bench-Scale in two series. Ïn each serie and to the three reactors were added 1,2 and 3 plants respectively and the fourth reactor was kept as control (without plant). Gravel media was used in both series of reactors with the effective size of 5mm and porosity coefficient of 2.2 and 33 percent respectively. Çoncentration of coliform to act as MPN/100 ml in influent sewage was 2000-9200000 (4.3-7.96 Log). Detention time applied in the reactors was 1-10 days. Flow pattern of reactors was intermittent. Sewage samples were injected to the reactors on certain time interval, Samples were collected from the reactors and the standard method number of coliform was counted. Çoliform removal efficiency was obtained 91.7%, 92.5%, 95.8%, 99.7% in first reactor series and 99.29%, 99.97%, 99.99%, 99.999% in second reactor series with 0,1,2,3 plant respectively. There was no significant relationship between the reactors in first seri (P>0.05), but was significant in second series (P<0.05). The results showed optimum detention time for removal of coliforms in constructed wetland in 5-6 days. Çonclusion: This study indicates Subsurface-constructed wetland with gravel media and Ïris-pseudacorus plant in 5-6 days detention times has the efficiency to remove coliform of influent sewage.