Volume and load of sewage treatment plants

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Key finding

The volume and load of nitrogen and phosphorus released from coastal sewage treatment plants into waterways in Queensland has remained relatively constant since 2010, with the exception of a significant reduction in both volume and nitrogen loads released in 2014. Phosphorus loads increased in South East Queensland in 2014, most likely due to reduced water recycling from advanced water treatment plants.

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Queensland

The majority of 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, except for about a 13% drop in 2014. This was most likely attributed to the absence of large storms in 2014, particularly in SEQ, and a subsequent reduction in 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 1,200 to 1,300t per year. A significant 20% drop in 2014 can be attributed to lower inflows to SEQ that year and improved nitrogen removal for some plants in Reef catchments.

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. There was no decrease in 2014: phosphorus loads from SEQ plants increased, outweighing a reduction in phosphorus loads from plants in Reef catchments.

Southeast Queensland

In South East Queensland (SEQ), the combined volume of treated sewage released to coastal waterways varied around 630 megalitres since 2010 with an increase of 10% in 2012 and 2013 and a drop of 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 870 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 load of total phosphorus 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. This may be attributed to less use of advanced water treatment for water recycling.

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 140 megalitres per year. The volumes released from plants in GBR catchments generally made up about 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 has been relatively steady since 2010, between 320 to 350t per year. A significant drop of about 20% was recorded in 2014. This appears to be attributed to better treatment performance or upgrades and some reduction in release volumes.

The load of total phosphorus released from sewage treatment plants to coastal waterways in GBR has been relatively steady since 2010 at around 90 to 100t per year. A significant drop of about 20% in 2014 may be the result of improved treatment and phosphorus removal at certain 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 2010-2015.

Download data from Queensland Government data