Oral Presentation SETAC Asia-Pacific Virtual Conference 2022

Toxicants in constructed stormwater wetlands and associations with landuse and other catchment characteristics (#28)

Kathryn Hassell 1 , Daniel MacMahon 1 , Milanga Walpitagama 1 , Claudette Kellar 1 , Erica Odell 1 , Rhys Coleman 2 , Vincent Pettigrove 1
  1. RMIT University, Aquatic Environmental Stress Research Group (AQUEST), Bundoora, Vic, Australia
  2. Melbourne Water Corporation, 990 La Trobe Street, Docklands, 3008, Victoria, Australia

In Melbourne (Victoria, Australia), the major water utility is Melbourne Water, and together with stakeholders including local government and developers, manage hundreds of constructed stormwater treatment wetland systems across Greater Melbourne.  Collectively, these wetlands represent the biggest investment in improving stormwater quality in the region.  As well as treating sediments and nutrients, stormwater wetlands are designed to capture and treat toxicants such as metals and pesticides that may be present in stormwater. Metals may cause direct toxicity to biota as well as accumulating in plants and sediments, and if concentrations exceed waste disposal guidelines, it creates large, additional costs for sediment disposal. Herbicides can cause plant dieback and alterations in algal communities, and fungicides and insecticides can be toxic to biota and interfere with microbial processes relating to carbon and nitrogen cycling. 

The aims of this 5-year study are to characterise toxicant levels in several constructed wetlands around the Greater Melbourne Area, with the expected outcomes including:

  • comprehensive understanding of problematic contaminants in wetlands (including emerging contaminants), in particular contaminants that impact wetland performance
  • inform cost-effective monitoring of stormwater wetland performance to underpin asset management programs
  • guide the optimization of stormwater wetland maintenance (e.g., desilting operations)
  • inform future stormwater management policy, guidelines and standards
  • support the possible refinement of stormwater wetland modelling tools to incorporate toxicants
  • establish a better understanding of the effectiveness of WSUD treatment trains to remove toxicants to inform stormwater harvesting risk-based approaches and advanced treatment requirements for stormwater harvesting schemes

Here we will present findings from the first three years of water and sediment sampling in constructed wetlands across Greater Melbourne, including the identification of the most important toxicants in terms of impacts on wetland function (toxicity) and wetland maintenance (waste disposal costs).