Author: Nosheen Mohsan
Mohsan, Nosheen, 2018 Design performance evaluation of Oaklands Park wetland through water quality analysis, Flinders University, College of Science and Engineering
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In order to overcome the water insecurity issues, managed aquifer recharge schemes (MAR) have been gaining interests of Australian States and Territories. South Australia has implemented such schemes after going through severe water crises during the Millennium drought. There were several MAR schemes constructed after 2010 to secure and reuse stormwater which was previously discharged to sea. The MAR schemes in South Australia, are recharging aquifers by intercepting stormwater in to wetlands to be treated and then recharged into the aquifer for later use when needed. In order to reduce and prevent the risks associated with water recycling, Australian guidelines For Managed Aquifer Recharge have been developed (NRMMC-EPHC-NHMRC 2009), which are part of National Water Quality Management Strategy. These guidelines provide guidance for practitioners in order to reduce the environmental and public health risks associated with water recycling.
There are several schemes established in South Australia. Oaklands Park wetland and MAR scheme was established in 2014. The water injected into the ASR wells has been used for irrigation of North and South public reserves by Marion City council. The scheme has been functioning for past four years. Although these schemes have been implemented there are few evaluation studies conducted to determine the performance of these systems. This project is the first to evaluate the performance of the Oaklands Park wetland.
This study was conducted between May and August, 2018 and determined the performance of this wetland in terms of water quality and treatment. The impact of rainfall on water quality of the wetland was evaluated by monitoring performance over 3 storm events. Microbiological, physical and chemical analysis were conducted. Online water quality monitoring data and climate was collected and analysed. These parameters were analysed at inlet and outlet pond as well as through the whole wetland system. Increases in concentrations of nutrients and E.coli were recorded from in outlet pond, Pond 2 and 3, Pond 5 than the inlet pond following passage through the wetland. Wetlands systems are complex and each pond behaviour in treating water quality was not consistent during the whole study period. There are some linkages of these contaminations with wetlands internal bio geophysical activities inside the wetland. The increased concentrations of Total Suspended Solids (TSS) were observed in the outlet pond as compare to the inlet pond where the average concentrations of TSS suggests that water is of low quality as per guideline value of Australian Guidelines for Managed Aquifer Recharge. The numbers of E.coli observed in the outlet pond and 2/3 was higher than those of the inlet pond and faeces of ducks/birds (present in wetland) are the likely cause of this contamination. The number of E.coli further increased during rainfall events in all ponds of the wetland. The increase in number of E.coli have shown clear linkage with rainfall events. The cause of the increase in concentration of TSS and TOC concentrations in Ponds 2, 3, 5, and outlet pond is due to the movement of ducks, birds, and fish present inside these ponds which causes the resuspension of particulate pollutants through their movement. The nitrate concentration was less in outlet pond as compare to inlet pond whereas ammonia concentration was more in the outlet pond. The increase in ammonia concentrations could be resulted through denitrification process as nitrates concentrations decreased in the outlet pond or due to ducks/birds feaces which contain high concentrations of ammonia. Further research is required to analyse the impacts of rainfall on water quality improvement by considering different parameters like rainfall duration and intensity, volume of inflow into the wetland. It has been recommended to increase the residence time of the wetland and conduct research to analyse the impacts of increased residence time on water quality improvement.
Keywords: water quality, wetland performance, managed aquifer recharge, water recycling
Subject: Water Resources Management thesis
Thesis type: Masters
Completed: 2018
School: College of Science and Engineering
Supervisor: Howard Fallowfield