Conversion of a decommissioned oxidation lagoon into a functional wetland

This study proposes an ecologically valuable reuse for a decommissioned oxidation lagoon at the Altona Treatment Plant in Victoria, Australia, which could be replicated elsewhere. Previous design attempts for this project had failed due to the potential risk they posed to both the surrounding environment and the Treatment Plant itself. Therefore one of the objectives was to undertake multiple assessments to mitigate these risks. The most important of these, and the focus of this paper, was the determination of the optimal source and quantity of water needed to sustain the wetland. Potential water sources included: water from a nearby estuarine swamp; treated class C or class A effluent from the treatment plant; and rainfall-fed runoff from the treatment plant site. Through an analysis of cost and quality of the available water sources, it was determined that locally captured rainfall-fed runoff with Class-A recycled water as a backup supply was the most feasible. In addition, hydrologic modelling revealed that this source could maintain flow in the wetland year round, even in drought years.