Performance evaluation of floating wetland with emergent macrophytes for treatment of domestic wastewater

Author: Vidalath Vongnalaysane

Vongnalaysane, Vidalath, 2019 Performance evaluation of floating wetland with emergent macrophytes for treatment of domestic wastewater, Flinders University, College of Science and Engineering

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Floating wetlands are considered an alternative treatment by using the root-bed to purify and remove the pollution compounds from wastewater. Studies in Australia specifically use floating treatment wetlands for stormwater, which leads to the question as to; whether this application can remove contaminants from domestic wastewaters. Therefore, the objective of this study was to evaluate the effectiveness of floating wetlands for domestic wastewater treatment using native South Australian aquatic species. The floating wetland application was investigated at the mesocosm scale during winter, when the growth rates of wetland plants are likely low. The wastewater source for this study was from the pond storing wastewater treated by the High Rate Algal Ponds (HRAPs) at the community wastewater treatment scheme at Kingston on Murray, South Australia. The major aim of the study was to compare growth parameters of four emergent aquatic macrophytes, which were; bare-twig rush (Baumea juncea), stiff-leaf sedge (Cyperus vaginatus), common sedge (Carex tereticaulis), and tall sedge (Carex appressa) in domestic wastewater. Comparisons were made any measured changes in wastewater quality in the presence and absence of macrophytes. The results showed that all emergent wetland plants were able to survive in the wastewater environment in winter. The growth rates of the common sedge and tall sedge suggested they were the more suitable species to apply in the treatment of HRAP effluent rather than bare-twig rush and stiff-leaf sedge. There was a strong correlation between the increase in plant biomass production and nitrogen content in plant tissue, which indicated the capacity for nitrogen removal by floating wetlands. At the end of the trial, the water quality in the tanks within the floating wetland system showed a slight decrease in ammonium, BOD5 and organic carbon. There was, however, a statistically significant increase in the removal of suspended solids and chlorophyll-a in the tanks containing wetland plants compared to the control tank containing wastewater only. This resulted in a notable improvement in wastewater clarity following treatment by floating wetland plants. Therefore, floating treatment wetlands are not only beneficial in wastewater treatment and water management but also provide economic value, environmental services and sustainability benefits.

Keywords: Floating wetland, Domestic wastewater treatment, Emergent macrophytes

Subject: Water Resources Management thesis

Thesis type: Masters
Completed: 2019
School: College of Science and Engineering
Supervisor: Howard Fallowfield