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Volume and load of sewage treatment plants

Key finding

The annual volume and load of nitrogen and phosphorus released from coastal sewage treatment plants into waterways in Queensland has remained relatively constant since 2010, apart from a significant reduction in volume and some nutrient loads in 2014 and 2016. The annual volume and loads of nitrogen and phosphorus released from coastal sewage treatment plants in Great Barrier Reef catchments have reduced over the reporting period, particularly since 2013.

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Queensland

Most effluent released directly into waterways from sewage treatment plants in Queensland comes from the more populated coastal areas in South East Queensland (SEQ) and from coastal Great Barrier Reef catchments.

The combined volume of treated sewage released to coastal waterways has been relatively steady since 2010 at around 790 to 830 megalitres per year. Noticeable volume drops in 2014 and 2016 are most likely attributable to the absence of large storms, particularly in SEQ, with less inflows to the sewage treatment plants.

Nitrogen and phosphorus are present in treated sewage and can impact on waterways, particularly in promoting excessive plant and algal growth.

The total load of nitrogen released from sewage treatment plants to coastal waterways in Queensland has been relatively steady since 2010 at around 1,200t to 1,300t per year. Significant drops observed in 2014 and 2016 can be attributed to lower treatment plant volumes, particularly for those plants in SEQ.

The total load of phosphorus released from sewage treatment plants to coastal waterways in Queensland has been relatively steady since 2010 at around 620t per year, with a significant reduction in 2016 due to lower loads from SEQ.

South East Queensland

In South East Queensland (SEQ), the combined volume of treated sewage released to coastal waterways varied around 630 megalitres since 2010 —up 10% in 2012, 2013 and 2015 and down 10% in 2014. The reduction in 2014 was most likely attributed to the absence of large storms and a subsequent reduction in inflows to the sewage treatment plants from infiltration.

Nitrogen and phosphorus are present in treated sewage and can impact on waterways, particularly in promoting excessive plant and algal growth. The total load of nitrogen released from sewage treatment plants to coastal waterways in SEQ has varied from about 870t to 990t per year since 2010. A significant drop to 780t in 2014 is attributed to lower inflows to SEQ plants that year, resulting in lower release volumes.

The total phosphorus load released from sewage treatment plants to coastal waterways in SEQ has been relatively steady since 2010, at around 510 to 550t per year. Despite reduced release volumes in 2014, the phosphorus load increased by more than 5% in 2014 compared to 2013. In 2016, the phosphorus loads reduced to 450t due to increased phosphorus removal and lower than average release volumes.

Great Barrier Reef

In the Great Barrier Reef (GBR) catchments, the combined volume of treated sewage released to coastal waterways has gradually reduced since 2010 from 160 to 130 megalitres per year. The volumes released from sewage treatment plants in GBR catchments generally make up less than 20% of the total volume released from plants in Queensland.

Nitrogen and phosphorus are present in treated sewage and can impact on waterways, particularly promoting excessive plant and algal growth. The total load of nitrogen released from sewage treatment plants to coastal waterways in the GBR was relatively steady from 2010 to 2013, at around 320t to 350t per year, falling significantly by about 30% (240t annually) since 2014. This appears to be due to improved treatment performance and some reduction in release volumes.

The load of total phosphorus released from sewage treatment plants to coastal waterways in GBR was relatively steady from 2010 to 2013, at around 90 to 100t per year. A significant drop of about 20% (to less than 80t per year) has been observed since 2014. As with nitrogen load reductions, this appears to be the result of improved nutrient removal at certain sewage treatment plants and some reduction in release volumes.

More information:

Indicator: Current volume and load, and change over time of discharge from sewage treatment plants into waterways

Annual volume and load of nitrogen and phosphorous released from sewage treatment plants into waterways for the South East Queensland and Great Barrier Reef catchment areas for the period 2010-2016.

Download data from Queensland Government data

Last updated 8 January 2019