Nutrient removal mechanisms in constructed wetlands and sustainable water management

Constructed wetland systems are used to treat domestic and industrial wastewaters and agricultural runoff. The capacity of five constructed wetland systems to remove phosphorus (P) and nitrogen (N) and factors influencing removal processes were examined for experimental constructed wetland systems at Richmond, near Sydney, Australia. The influence of hydraulic loading, retention time, water column depth and P concentrations of influent wastewater on P and N removal were studied. Results showed that P concentrations of water from outlets at all five units decreased( from 11% for unit 1, which received wastewater with an average P concentration of 8.18 mg P L-1 water to 48.9% unit 3, which received wastewater with an average P concentration of 3.58 mg P L-1 water) The nitrogen concentrations in the effluent water were also decreased at all five units (from 26.3% for unit 1 to 77.5% for unit 4). The P and N in the soil increased in the first year at all five units (increased from an initial P level of 23.4+/-4.5 kg unit(-1) to 30.4+/-5.0 kg unit(-1) for unit 3 and 33.6+/-10.3 kg unit(-1) for unit 4 respectively) but unchanged at the end of second year. The study showed that low hydraulic loadings and greater retention times positively enhanced removal of P and N from wastewater in constructed wetland systems.