Designed, built and operated by Worth Recycling, the filtration plant treats about 660,000 litres of underground low-level saline water for use onsite and at nearby mines.

The plant has been so successful it contributed to mine operator BHP Billiton Illawarra Coal winning the Largest Volume Reduction Award at Sydney Water's Every Drop Counts business awards.

Illawarra Coal president Colin Bloomfield said the plant has not only enabled the mine to reduce its demand on Sydney's water supply, but also reduce the volume and salinity of mine discharge water.

Worth Recycling director John Vincent said the filtration plant was a credit to his company and Appin.

"We worked in partnership with BHP Billiton to design and build this plant, to tailor it to their exact needs," Vincent said.

"The immediate success of the plant is a testament to our engineering ingenuity and expertise, which places us as the country's foremost provider of innovative technical solutions to industry's sustainable development requirements."