Effects of iron dosing used for phosphorus removal at wastewater treatment works; impacts on forms of phosphorus discharged and secondary effects on concentrations and fate of other contaminants

Iron dosing for phosphorus reduction during wastewater treatment is wide practised across the globe. However, impacts of this in terms speciation discharged and secondary effects on removing or introducing other trace elements from into effluent have not been studied. Results are presented concentrations a range contaminants over 600 works, reported as mean concentration values derived 20 samples taken period two years. Approximately half works employed iron to reduce effluents. In addition expected level surface waters, it shown that these measures unintended beneficial consequences several constituents wastewater. Reductions more than 40% dissolved metals (copper, lead) benzo(a)pyrene hexabromocyclododecane observed. Lower but still significant decreases (>30%) evident cadmium, fluoranthene cypermethrin biochemical oxygen demand. Small less environmentally important increases seen nickel, case latter presumably because nickel contaminant reagent used dosing. These reductions offer benefits levels entering waters relating in-river environmental quality standards.