Phytoremediation of domestic wastewater for reducing populations of Escherichia coli and MS-2 coliphage

Sub-surfaceflow constructed wetlands enhance water quality of domestic wast ewater by decreasing biochemical oxygen demand and the survival of enteric pathogens. Wetlands contain plants for aesthetic reasons and for phytoremed iation. Glasshouse experiments were conducted during February and May to ev aluate the role of four aquatic plant species, Cyperus alternifolius, Cyper us isocladus, Typha latifolia, and Iris sp. in reducing the populations of E. coil and MS-2 coliphage, indicators of bacterial and viral pathogens, re spectively over 2-3 days retention. Plants were grown in 5-1 buckets contai ning washed gravel and domestic wastewater. Phytoremediation reduced popula tions of E. coli and MS-2 coliphage in February, but not in May. In Februar y, plants reduced populations of E. coil by approximately 1.5 log 100ml(-1) in 2 d, compared to 0.2 log 100 ml(-1) reduction by the control without pl ants. In February, C. alternifolius, C. isocladus and T. latifolia decrease d populations of MS-2 coliphage by approximately 1.5 log ml(-1) in 3 d comp ared to 0.4-log ml(-1) reduction by the control without plants and Iris sp. During May, C. isocladus reduced E. coli populations from 4.5 log 100 ml(- 1) to 1.85 log 100 ml(-1) in 2 d while populations in other treatments rema ined approximately 0.5 log 100 ml(-1) higher. Survival of E. coli and MS-2 in May was confounded by high temperature in microcosms without plants beca use of lack of shading, which led to poorer survival of the indicators. Phy toremediation may be one mechanism through which populations of enteric mic roorganisms are reduced in wetlands and may be enhanced by selection of pla nts for the wetland.