Water treatment

There has therefore once again been a strong incentive for the development of a wide variety of innovative, low-cost treatment processes adapted to specific local water quality problems. Of the capital cities, Brisbane found it necessary to treat its water 80 years ago, long before any other. Most of the other capitals enjoyed for many years the privilege of protected uninhabited catchments, and consequently there was no incentive for water treatment.

In the 1920s an Australian company, Filtration and Water Softening Ltd, invented an enclosed sand filter of cellular construction, with an associated clarifier. These were simple and effective with adequate maintenance, and were widely used in the 1920s and 1930s. Many are still operating. During the same period, several Candy Filter Company plants were installed in rural areas. These were essentially adaptations of overseas technology to suit local conditions.

In recent years, the number of water treatment plants in Australia has increased dramatically, reflecting a growing awareness of health problems in some areas and a general desire for improved water quality. Adelaide, Melbourne, Perth and Hobart all treat some or all of their water, but Sydney has as yet (1986) no major treatment plant. Significant local development has occurred in the design of water clarifiers, including solids-contact clarifiers, tube settlers and pulsating clarifiers. Dissolved air flotation, using European technology, has been widely used for the removal of algae, which develop to nuisance proportions in several Australian reservoirs and in slow moving rivers such as the Murray.

Standard American designs for rectangular sedimentation basins have been substantially modified after local research, resulting in considerable cost-saving without loss of efficiency. Direct filtration is possible with some water qualities, making it possible to do away with the sedimentation stage, and achieve significant cost reductions of 20 to 30 per cent. Once again, European technology has been successfully adapted for local conditions. Typical is a plant of 70 ML/d capacity at Albury, commissioned in 1981, which has coped successfully with sudden increases in algae and with unexpectedly high temperatures.

Small treatment plants have been evolved for small towns and mine supplies, using various proprietary processes with some adaptations. One successful local development was a product of the Public Works Department of Western Australia in 1978. This combined the three elements of flocculation, sedimentation and filtration into one unit, with a capacity of 1.2 ML/day. These are used in multiples for small town supplies and are manufactured in Perth at a cost of $50,000 per unit.

Australian Academy of Technological Sciences and Engineering