Surveys for the first sewerage system began in 1910, and the treatment plant was completed in 1915. The original treatment plant consisted of huge underground septic tanks. Liquid overflow (effluent) passed through rubble filters and into the Macquarie River.
Between 1928 and 1930 the septic tank plant was converted to a more complex system, which used the existing tanks in combination with a "trickling filter" and some experimental process units known as "Imhoff tanks". These additions ensured that the sewerage was more thoroughly treated.
The updated plant also included facilities for drying the solid waste (sludge) and for chlorinating the effluent before discharge to the river. In 1965, a major upgrading of the sewerage system was completed. It included the construction of a conventional "trickling filter" treatment plant, and abandonment of the old septic tank plant completely.
The first experimental intermittently decanted extended aeration (IDEA) tank was built in 1976, with a further four being added in 1982. At that time a new inlet works, sludge lagoons and effluent ponds were also constructed. Further experiments were carried out between 1990 and 1993 to further develop IDEA technology to biologically remove phosphorus. In 1998 two 17,500 IDEA Bio-P tanks were completed and successfully commissioned. This was a significant technological milestone as the new treatment plant produces effluent within EPA standards. Alum dosing was commenced in 2002 to further reduce nutrient loads and improve the final effluent quality.