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How City West Water enabled returns on water treatment processes

With recycled water a key factor in managing Australia’s water security requirements, one utility has optimised salt-reduction processes to ensure maximum return with reduced costs.

Presenting at this year’s Ozwater’18 in May, City West Water Process Engineer Shanli Zhang said the utility’s Altona Salt Reduction Plant (ASRP) has successfully applied reverse osmosis in pre-treatment to enable a higher and more cost-effective return on water treatment processes.

“ASRP is a dual-membrane recycled water plant for reducing the pathogen and the salt content in the water to produce fit for purpose recycled water. The reverse osmosis [RO] membrane is our key technology for reducing salt,” Zhang said.

“Our feed water is effluent water from the Altona sewage treatment plant, which means that naturally there will be some amount of organic residuals from the biological process.

“The RO membrane is very good at reducing the salt content, but we needed pre-treatment to reduce the pollutants as RO may be fouled quickly by the organic and biological substance.”

Zhang said to achieve optimised RO performance, the plant investigated microbial control, UF performance and cartridge filters.

“We use biocide as microbial control method and keep monitoring the microbial condition. There are not many plants adopting the biocide shock dose as biological control regime,” he said.

“There were not a lot of references for us to learn from. We tried different scenarios and initially it was hard to make an assessment for the results.

“Last year, we applied some new technology, based on Adenosine Triphosphate (ATP), which is present in all living cells. This lab technology can extract the ATP from the living cell of the bacteria and then test and quantify the amount of ATP.

“This gives us an idea of total microbial condition is in our water and feedback for how well we are controlling it.”

Ultrafiltration is a key process of RO pre-treatment to remove the pathogens, colloidal and particles, according to Zhang.

“The UF performance is closely monitored, and optimisation is carried out to delivery better filtration recovery, production and better membrane performance,” he said.

“After ultrafiltration, there is a cartridge filter as a final barrier before RO to remove big particles and biological regrowth. We set up a quantified method to benchmark different filter products in terms of performance and operation cost. This helped us select the best product suited to our plant.

“The membranes performance is well managed and satisfactory for us,” Zhang said.

The plant has been operating at full capacity every day since July 2015 and supplies recycled water for industrial customers and irrigation customers in the area.

“Our industrial customer takes consistent 5.5ML per day all year round, and local golf courses and parks irrigation customers take 2 to 3ML per day during irrigation season,” Zhang said.

Register for Ozwater’18 to hear more from Shanli Zhang about the innovative pre-treatment process applied at Altona Salt Reduction Plant.