Increasing the environmental sustainability of sewage treatment by mitigating pollutant pathways

The current centralized systems for sewage treatment are highly efficient with respect to the removal of COD and nutrients and the production of an effluent that can be discharged on surface water. However, from an environmental point of view the sewage treatment process is still far from being environmentally sustainable. Based on a desk study, a structural approach is given on how to achieve a more sustainable treatment process. One of the possibilities is to improve the mitigation of toxic pollutants. Using the appropriate treatment steps, including also high-temperature sludge treatment processes and membrane separation processes, it is possible to remove toxic organic pollutants completely. Heavy metals can be immobilized in a solid matrix. N- and P-containing compounds can be recovered for reuse. Other nonpolluting or slightly polluting organic compounds can be beneficially used as energy sources. Furthermore, both the emissions of the greenhouse gas CO2 and of NO2 to the atmosphere can be substantially reduced. It will be evident that further study and research is necessary to develop the mentioned sustainable treatment scenarios to practical application.