With increasing human populations in coastal regions, there is growing concern over the quality of wastewater treatment plant (WTP) discharge and its impacts on coastal biodiversity, recreational amenities, and human health. In Australia, the current system of WTP monitoring and reporting varies across states and jurisdictions leading to a lack of data transparency and accountability, leading to a reduced ability to comprehensively assess regional and national scale biodiversity impacts and health risks. The National Outfall Database (NOD) was developed to provide a centralized spatial data management system for sharing and communicating comprehensive, national-scale WTP pollutant data. This research describes the structure of the NOD and through self-organizing maps and principal component analysis, provides a comprehensive, national-scale analysis of WTP effluent. Such a broad understanding of the constituents and level of pollutants in coastal WTP effluent within a public database provides for improved transparency and accountability and an opportunity to evaluate health risks and develop national water quality standards.

This report primarily targets water authorities and state/territory-based environmental protection agencies. It provides a pathway forward for establishing a national standard for reporting outfall wastewater treatment plant data. Key findings from our survey of water treatment authorities (WTAs) are:  (1) the majority of WTAs agreed on participating in further discussions to develop standards, (2) WTAs supported the concept of annual reporting used for the National Outfall Database (NOD), and (3) WTAs are willing to collaborate to develop outfall report cards. The pathway forward is to establish a consultative process with key stakeholders to develop and implement the second phase of the NOD. Establishing a network of key stakeholders in the national wastewater sector will be important for developing a national reporting standard.  

This report provides an analysis of the Australian coastal outfalls and ranks them according to the total flow volume and nutrients load to prioritize the potential degree of impact of each source to the environment and human health. The pollutant contribution index, based on nitrogen and phosphorous loads, was calculated for each outfall. Outfalls were ordered from lowest to highest index value to rank them according to their relative pollutant contribution to the coastal and marine environment. The index is based on a total nutrient load discharge using the variables of flow, nitrogen and phosphorous. The ranked loads throughout Australia were mapped by quartiles. The top quartile (lowest nutrient load) of outfalls seem to be more prevalent in regional areas and discharge less nitrogen and phosphorus loads into the coastal and marine environment. The bottom quartile, on the other hand, with higher nutrient loads principally occur around the major cities. This ranking of nutrient loads from Australian outfalls by site at a national scale can therefore be useful in prioritizing treatment upgrade resources to manage biodiversity impacts and human health concerns.