Testing in colour
At TasWater, ensuring our systems and treatment facilities across the state are operating appropriately and efficiently is vital.
Throughout the year, testing and maintenance programs continue to be rolled out to help stay on top of any issues, in addition to providing information to inform any future upgrades and projects.
One testing tool used at TasWater is the plume dilution studies dye testing.
TasWater Senior Environmental Scientist Glen Neill is involved in the testing at sewage treatment plants (STPs), and says it helps the environmental performance team see where treated wastewater is entering the environment, where it goes and what happens to it.
“When the dye is discharged at the plant’s outfall point, it generates a plume in the water,” he said.
“Dispersion and dilution of the treated wastewater plume around an outfall helps to assess and determine the potential impact on the receiving environment. The receiving environments includes oceans and rivers.
“It is also used to assess the risk and sustainability of a STP’s discharge in accordance with the Environmental Protection Authority’s requirements.”
The dye mimics what wastewater would do, but the dye is coloured so it can be easily seen and, therefore, assessed.
“Once the dye has been dispersed, we use a drone to capture the dye plumes in the water (as seen in the image),” Mr Neill said.
“We also use this type of dye testing to check for leaks at our outfalls, if dye is seen coming out of anywhere where it shouldn’t, we then know there is a hole that we need to fix.
“This sort of testing helps TasWater identify areas in need of improvement and any leaks we have in our systems, so we can fix them, therefore improving environmental outcomes.”
There are 110 STPs across the state which are operated by TasWater and many of them have had dye testing at some stage since TasWater’s inception, with the testing continuing into the future.
“The dye is not toxic and has no impact on the environment or public health. It is added to the treated water during discharge,” Mr Neill said.
“A small dye plume suggests a small mixing zone into the environment with good dispersion and dilution whereas a large dye plume suggests a larger mixing zone requiring more dispersion and dilution.
“The testing cannot fully inform or verify the mixing zone as dyes do not behave exactly the same as treated wastewater, however they provide a good indication of how treated wastewater behaves in the receiving environment.”
Dye testing at STPs provides valuable information and is an important step in assessing the plant’s impact on the receiving environment. It also helps to identify the need, if any, to upgrade these plants to ensure there is sustainable wastewater discharge in the area.
If the community has any questions on dye testing, they are encouraged to call us on 13 6992 or email:
[email protected].