Ecological outcomes of wastewater discharges in contrasting receiving environments

PROJECT 2.4

With about 85% of Australians living near a coast, the chemicals we use on land can pollute our estuaries and oceans. Household wastewater is cleaned by wastewater treatment plants before being discharged to the ocean. No treatment system is perfect, however, and residual chemicals can persist in discharged water. Depending on the prevailing ocean currents and water residence time, they may accumulate and reach concentrations that can reduce water quality and affect the health of the marine ecosystem.

Currently, we have little understanding about which contaminants are entering our oceans, what concentrations they are found in, and what effects they have on marine plants and animals.

This project aims to determine the concentration of emerging pollutants in different wastewater outfall settings, and assess where environmental impacts are greatest. It follows a Marine and Coastal Hub scoping study (Project 1.16) that engaged stakeholders from around Australia in identifying and prioritising concerns about threats to water quality, including chemicals of emerging concern. The study identified a need for data on environmental concentrations of emerging contaminants and an assessment of their impact on ecological communities.

Understanding chemical pollution in the marine environment

To better understand how pollution affects Australia’s marine environments, this project will:

• Apply hydrodynamic modelling to understand water residence time in key locations near wastewater treatment plant outlets.
• Sample marine environments with different hydrodynamics and determine concentrations of four key chemicals of emerging concern: microplastics, heavy metals, Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) and antibiotics.
• Assess whether the concentrations of marine pollutants detected are affecting marine water quality and the ecological health of the lower marine food web.

Continuing the National Outfall Database

This project will also continue the National Outfall Database (NOD), which was developed under the NESP Marine Biodiversity Hub, a forerunner of the Marine and Coastal Hub. The project team worked with 42 water authorities, and state, Northern Territory and local governments, to develop agreements and standard protocols for collecting and publishing discharge data.

The resulting NOD website presents a national inventory of 194 coastal outfalls that users can search by location, or browse via an interactive national map, or by state and locality. Tables and charts summarise monthly discharges by volume and composition, including pollutants (oil and grease, E. coli and enterococci) and nutrients (nitrogen and phosphorus).

It was the first attempt in Australia to provide all stakeholders with ready access to quality coastal wastewater data, consolidated at a national level and provides a transparent evidence base for considering risks and investments in sewage infrastructure and wastewater recycling, and a model for standardised, national reporting.

Project location

National

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