Passive constructed wetlands and small municipal wastewater systems. An approach for meeting national effluent regulations.

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Canadian municipalities have a variety of processing options to treat and discharge wastewater. One such technique is the use of passive waste stabilization ponds (WSP) for the treatment and polishing of wastewater. This method is one of the least energy intensive treatment options available and, conceivably, has the potential to be the least costly. However, conventional WSPs often have certain performance issues which have made their performance more variable. In order to overcome concerns associated with these issues, further research is required to develop energy and cost efficient WSP treatment systems can be brought forward. The research objectives of this project are to (I) conduct an extensive characterization of the background physical, chemical and biological conditions found with a typical, temperate-climate sewage WSP system; (II) design and create a new, natural attenuation constructed wetland system to augment the performance of an existing WSP, using native Canadian wetland species which are specific to the characterizations realized in objective I; and (III) undertake an intensive monitoring program over a two year period to document and assess the ability of the combined WSP and constructed wetland system to fulfill its intended role to enhance effluent quality. The WSP system to be studied is indicative of those in Ontario using Great Lakes' derived municipal water systems, although the findings are expected to be either directly applicable to jurisdictions across Canada. This project is expected to make a substantial contribution to the state of the art in using natural passive systems to treat and polish wastewater from a WSP setting by providing the evidence base for natural attenuation within the chemical, physical and biological interplays present in Canadian systems. It is expected to provide answers and/or guidance to many municipalities facing costly upgrade dilemmas for aging or inadequate wastewater WSP systems while at the same time, it is anticipated that the knowledge developed through this project can be transferred to industry so that future WSP and constructed wetland development can follow an evidence-based method, one which leads to effective treatment systems.