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Colloque avec actes et comité de lecture. Internationale.; International audience

Colloque avec actes et comité de lecture. internationale.; International audience; Many regulatory authorities set water quality objectives or thresholds based on nutrient concentrations to safeguard aquatic ecosystem health. But do these criteria adequately assess the biological and ecological status? Our research has been focussing on the performance of constructed wetlands for water quality improvement and ecosystem health. In this paper we present data on macroinvertebrate species richness from two wastewater treatment wetlands and two stormwater treatment wetlands. Despite nutrient concentrations exceeding water quality objectives all four wetlands supported a diverse assemblage of macroinvertebrates, including sensitive taxa. From our study we concluded that water quality objectives may be too stringent and that aquatic plants are more important for macroinvertebrate richness. Thus, constructed wetlands are effective for both water quality improvement and aquatic biodiversity.

Colloque avec actes et comité de lecture. Internationale.; International audience

Colloque avec actes et comité de lecture. Internationale.; International audience

Sediment basins, wetlands and ponds are commonly used in subtropical Australia for stormwater storage and water-quality improvement. A crucial question is: \342\200\234How effective are these stormwater treatment devices?\342\200\235. Wetlands and ponds, being \342\200\234natural systems\342\200\235, also have the potential to enhance aquatic biodiversity. Our research efforts have focussed on monitoring water quality and macroinvertebrates in a wetland system consisting of a sediment basin and two wetlands, and a pond system consisting of a sediment basin (Pond 1) and five ponds. Reductions in TSS occurred in the wetland system during short, intense events but increased in longer, more intense events due to resuspension. Reductions in TSS in the pond system largely occurred in Pond 1. TSS increased in both systems in dry weather due to resuspension by ducks. NO3 decreased in both systems in wet and dry weather. NH4 increased, probably due to ammonification of organic matter. PO4 decreased in both systems, but removal was highest in the pond system. Neither system achieved TN and TP Water Quality Objectives on a regular basis, due to NH4, organic N and P. Macroinvertebrate species richness increased in both systems.

Many councils and management authorities within Australia are beginning to take steps to ameliorate downstream ecosystem affects of stormwater by creating treatment systems within individual catchments and sub-catchments. Commonly, detention ponds and wetlands are used in subtropical Australia as a means of both storing and treating stormwater before in reaches downstream receiving waters. The ability of detention ponds to store and treat stormwater is well document, but past research lacks the insight into how detention ponds treat the stormwater. This research paper investigates questions of how, where and why inorganic nutrients are removed in stormwater detention ponds. Phytoplankton and Bacterioplankton were found to remove a significant amount of inorganic nutrients from the water column within the studied detention basin, with large bacterioplankton productivity indicating a huge internal nutrient source. While the stormwater detention pond studied showed considerable amount of treatment during a monitored flood event, it also showed a considerable amount of \342\200\230un traced\342\200\231 inorganic nutrient sources and sinks. These un traced sources and sinks essentially cloud the true removal potential (or performance) of detention ponds, making it difficult to assess the true inorganic nutrient removal ability of stormwater detention ponds.