Katherine’s emergency water treatment plant will be shut down over the next week for maintenance.
Power and Water staff will be replacing the resin which is used to clean the PFAS chemicals from contaminated bore water.
The water authority has been busy topping up the town’s storage tanks during this low demand time of year to assure safe water supplies are maintained during the shutdown.
It will be the first time the synthetic resin, now saturated with dangerous PFAS, has been replaced since the plant was installed as an emergency measure in September 2017.
This smaller plant, manufactured in the US, will eventually be replaced by a larger plant capable to treating all of Katherine’s drinking water.
Contracts for the new plant, an upscaled version of the existing plant, have still not been signed even though the Defence Department has agreed to pay the almost $15 million price tag.
Katherine Times was again told earlier this month there would be no delay with the expected installation of the new plant by the end of this year.
Katherine will remain on water restrictions until the new plant is operational.
The existing PFAS water treatment system filters contaminated groundwater, removing PFAS, before it enters the surface water treatment plant.
The plant reduced PFAS levels below the Australian limit of 0.07 micrograms per litre.
Regular testing shows the bore contamination ranges between 0.2-0.3 micrograms per litre.
Senior engineer water and wastewater treatment, Skefos Tsoukalis, says the interim pilot treatment plant has been successfully operating in Katherine since October 2017 and has treated more than 400 megalitres of groundwater.
About 10 megalitres of treated water is supplied to Katherine each day, one megalitre per day from the PFAS treatment plant.
“The treatment process is in three stages,” Mr Tsoukalis said.
“Groundwater passes through a filter for pre-treatment while removing organic matter. An antiscalant is then added to reduce the amount of calcium in the water.
“The water is then passed through a series of filters containing a synthetic resin. These small plastic beads of resin have a unique chemical holding capacity that removes PFAS from the water.
“The filtered water is then blended with the treated Katherine River water. A small amount of chlorine is added to keep your water safe all the way to your tap,” Mr Tsoukalis said.
When the resin becomes fully saturated with PFAS, it is removed and replaced with new resin.
“We monitor the resin to determine when it has become saturated and requires changing.
“We anticipated it would be within 12 to 18 months of use and the resin is now due to be replaced.
“This process will take place over the next week while water use is low. We will fill the storage tanks to capacity to maximise our supply capability during the changeover.
“The PFAS treatment plant will be taken offline and river water will be used to maintain the water supply for the duration of the maintenance work.”
A Power and Water spokeswoman said 10 cubic metres of the PFAS saturated resin will be removed from the plant.
A standard sized shipping container has a capacity of about 33 cubic metres.
The spokeswoman said the resin would be stored securely onsite before half is transported by Defence to the Tindal RAAF Base for regeneration.
The NT Environment Protection Authority has previously said it did not have oversight on the PFAS disposal as the base was located on Commonwealth land.
PFAS extracted in the process, will be later disposed of at an authorised interstate facility, the spokeswoman said.
The other half of the resin, which is non-regenerable, will be transported by Defence to a licensed waste facility interstate for destruction, in accordance with state and federal environmental regulations.
Since the interim pilot treatment plant has been operational, based on regular testing results, there have been no detectable levels of PFAS in Katherine’s treated water supply derived from Power and Water’s facilities.
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