Australia State of the Environment Report 2001 (Theme Report)
Lead Author: Professor Peter W. Newton, CSIRO Building, Construction and Engineering, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06747 7
Liveability: environmental quality (continued)
At a national scale, 93% of the population has access to reticulated water supply (ABS 2000f) and nearly 90% are connected to reticulated sewerage (AWWA 2000a). The 21 major water authorities (businesses that have 50 000 or more water service connections) supply 68% of the population with water and collect 65% of the population's wastewater (WSAA 1999). Another 55 non-major water authorities (businesses that have between 10 000 and 50 000 water service connections) supply water to 16% of the population and collect wastewater from 14% of the population nationally (AWWA 2000c).
During the period of rapid urban growth after World War II, all cities lost the battle to match the rate of water supply provision with mains sewerage services (Smith 1998). However, by the 1960s and 1970s the sewerage backlog was addressed in all capital cities, with the exception of Perth. As recently as 1997, only 60% of urban, commercial and industrial developments in Perth and the south-west region of Western Australia had treatment and disposal services (Thomas et al. 1997). Most unsewered areas use septic tanks that come under the control of the Western Australian Health Department. Currently these areas are undergoing a large sewerage connection program.
The proportion of properties in a non-major water authority region that do not have a sewerage connection varies from 0% through to 53% in Geraldton and 78% in outer Adelaide (AWWA 2000c). Some utilities have customers awaiting reticulated sewerage services, but other authorities have employed on-site alternatives to relieve the need for a connection (AWWA 2000c). In unsewered areas of Australia there is a trend towards small-scale, single-household sewage treatment plants (Thomas et al. 1997).
Figure 72 illustrates the level of wastewater treatment provided by each state and territory in 1994. Throughout Australia, 17.8% of all wastewater was treated to tertiary standard, 54.6% to secondary standard, 27.2% to primary standard, and 0.5% received no treatment. The level of treatment received in each state and territory varies significantly: the ACT treats all wastewater to tertiary level, while in Western Australia two-thirds is treated to secondary level and the remainder receives primary treatment only.
Figure 72: Proportion of wastewater treated to different levels, 1994.A [HS Indicator 2.6]
APrimary treatment involves separation of suspended solids from wastewater by screening and sedimentation; secondary treatment involves additional treatment, usually by biological processes, to remove organic matter and residual suspended material followed by disinfection; tertiary treatment produces higher quality effluent through the further removal of contaminants such as nitrogen, phosphorus, heavy metals, residual suspended and dissolved solids, and synthetic organic chemicals. Tertiary treatment can involve processes such as carbon adsorption, reverse osmosis, microfiltration, and biological nitrogen and phosphorus removal.
Source: Thomas et al. (1997).
Figure 73 presents data on the level of wastewater treatment provided by WSAA members in 1995-1996 and 1998-2000 respectively. It can be seen that treatment practices vary between major urban water authorities. ACTEW and Yarra Valley Water are two authorities that treat all wastewater to tertiary standard, with both discharging effluent to inland waterways.
Figure 73: Levels of wastewater treatment for major urban water authorities, 1995-96 and 1999-2000.
Note: WSAA membership is drawn from businesses that have 50 000 or more water service connections.
Sources: WSAA (1997, 2000).
Comparison of the level of wastewater treatment provided by the major urban water authorities in 1995-96 and 1999-2000 exhibits a general trend towards higher levels of treatment. Barwon Water dramatically increased the level of treatment its wastewater received, with 100% receiving secondary treatment in 1999-2000 compared to 96% receiving primary level treatment in 1995-96. The Power and Water Authority of Northern Territory treated all wastewater from Darwin in 1999-2000, whereas 8% of wastewater received no treatment in 1995-1996. As a result, all wastewater in Australia received by the major urban water authorities was treated in 1999-2000.
Only three major urban water authorities employed primary treatment for a component of the wastewater in 1999-2000, being Power and Water Authority, Sydney Water Corporation and Water Corporation (WA), a reduction from four authorities in 1995-96. All three major urban water authorities employing primary treatment in 1999-2000 are located on the coast and discharge a large portion of the effluent via ocean outfall.
Figure 74 presents data on the level of wastewater treatment provided by non-major urban water authorities in 1998-99. These authorities collected 307 GL of wastewater in comparison to 1451 GL that the major authorities collected. It can be seen that treatment practices vary between non-major urban water authorities. The majority treat all wastewater to either secondary or tertiary standard, with only five treating a portion to primary standard only. Eleven of the 53 non-major authorities treat all wastewater to tertiary standard in comparison to only two major authorities.
Figure 74: Level of wastewater treatment for non-major urban water authorities in 1998-99. [HS Indicator 2.6]
Note: Non-major urban water authority membership is drawn from businesses that have between 10 000 and 50 000 water service connections.
Source: AWWA (2000c).