Human Settlements Theme Report

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

Waste, recycling and reuse (continued)

Wastewater (continued)

Utilising wastewater as a resource

There is a growing momentum favouring reuse of natural resources. In fact, there is strong resistance to current disposal methods that have been seen as both environmentally damaging and a waste of a potentially valuable resource (Thomas et al. 1997). Prolonged drought conditions have forced water authorities, consumers and local councils to consider wastewater reuse as a supplementary supply source (Thomas et al. 1997). The increasing utilisation of wastewater is supported by the COAG Water Reform Agenda, which recommended the use of treated wastewater within municipal and industrial systems (Thomas et al. 1997). Table 66 presents a national picture of the amount of wastewater reused and the economic sectors involved.

Table 66: National wastewater reuse volumes and percentage by water sector. [HS Indicator 2.10]
Year Volume reused (ML) (percentage of total wastewater) Water sector
Domestic Industrial Commercial Rural
1993-94 93 902 (4.7) 0 36 30 34
1994-95 101 292 (5.3) 0 35 26 39
1995-96 109 238 (5.4) 0 37 25 38
1996-97 134 427 (6.5) 0 43 26 31

Source: ABS (2000f).

On a national basis, the industrial, commercial and rural sectors each accounted for roughly one-third of the volume reused in 1993-94. But by 1996-97 the relative proportions had altered, with the industrial sector increasing its portion to 43% and the commercial sector decreasing its portion to 26%. Note that reuse may be greater within the manufacturing sector than was quantified by ABS, due to on-site reuse activities not being fully accounted for (ABS 2000f). There is no domestic wastewater reuse recorded in the ABS Water Account (ABS 2000f) for the years 1993-94 to 1996-97. Domestic wastewater reuse is still in its infancy in Australia, although it is increasingly being considered. Several examples of recent domestic wastewater reuse schemes are given in Table 67.

Table 67: Some examples of domestic wastewater reuse schemes.
Scheme Description
Wagga Wagga, New South Wales (C. Earnshaw, pers. comm. 2000) The city of Wagga Wagga in regional New South Wales operates a demonstration domestic wastewater reuse system which supplies 100 house blocks with treated wastewater for yard watering through a dual reticulation system. Currently, households are not charged for the second source of water, but there are plans to charge up to two-thirds of the price of potable water in the future.
Rouse Hill Recycled Water Scheme (E. Engelbrecht, pers. comm. 2000) The Rouse Hill Recycled Water Scheme is a domestic non-potable reuse scheme that has been constructed as part of the Rouse Hill residential development in the Hawkesbury-Nepean region, north-west of Sydney. The scheme comprises a dual water supply system, with the recycled wastewater used for toilet flushing, car washing and garden watering. It is expected to be operating by late 2000.
Sydney's Sustainable House (Mobbs 1998) A smaller-scale example of a domestic wastewater reuse scheme is 'Sydney's Sustainable House' in inner-city Sydney. All wastewater generated by the household is treated by a wet compost system in the backyard of the house. Wastewater is recycled for toilet flushing, clothes washing and garden watering. A rainwater tank supplies water to the kitchen, bathroom and laundry.

Agricultural reuse of wastewater has been in operation in Australia for the past 100 years (Hunter et al. 1993). In 1997, 70 country Victorian towns reused all of their wastewater for agricultural purposes, while another 38 reused a portion of their wastewater, and more towns plan to begin reusing their wastewater in future (Thomas et al. 1997). The Western Treatment Plant in Werribee, which serves the city of Melbourne, is the most notable example of agricultural reuse in Victoria, accounting for much of the volume reused each year. Recently there has been significant progress in promoting wastewater reuse, particularly for agriculture, through the Clean Seas Program, a component of the Natural Heritage Trust.

Data on wastewater reuse volumes by major urban water authorities reported by WSAA (1999) indicates that, for the year 1996-97, some 81 627 ML of wastewater was reused by these authorities, 4.9% of their total wastewater output. This figure is 61% of the volume stated as being reused nationally, by all economic sectors, in 1996-97 by ABS (2000f). In 1999-2000 the proportion reused by these authorities had risen to 8.8% of total wastewater output, with a significant increase in reuse by Melbourne Water Corporation (rising from 8.8% in 1996-97 to 21% in 1999-2000; WSAA 2000). Notably, the rate of reuse by Gold Coast Water went against the trend during this period, dropping from 16% in 1996-97 to 8.5% in 1999-2000 (WSAA 2000).

In 1998-99, 40 of the 57 non-major urban water authorities utilised wastewater effluent, with a median reuse rate of 10%, although Albury City Council, Bathurst City Council and Lower Murray Water (in Victoria) all reused 100% (AWWA 2000b).

Current minimum projections for 2001-2008 are that 328 GL/year of wastewater from water utility treatment plants will be reused, which is about 19% of the total projected wastewater output from water utility wastewater treatment plants in Australia (Dillon 2000). The highest rate of reuse is projected for Queensland (30%), with the lowest rate for the ACT (3%). According to Anderson (1996b), the level of reuse in Australia is substantial by world standards although the contribution to total urban water needs in Australia is small.

Internationally, most large-scale wastewater reuse schemes are in arid or dry climates (e.g. Israel, South Africa, and arid areas of the USA) where alternative sources of water are limited. The high cost for additional water supplies is a problem in remote towns of arid Australia which exist to service the mineral and processing industries (Thomas et al. 1997). More intensive use and recycling of locally available water could mitigate this cost. Limited scope for storage has encouraged wastewater reuse in Florida, which is generally not a dry area, with annual rainfall of 1400 mm/year, but suffers water shortages in dry spells (Thomas et al. 1997, Williams 1998).

Israel utilises around 80% of its wastewater for large-scale agricultural reuse and groundwater recharge (Anderson 1996b). In the USA, interest in water reclamation has increased considerably (Jacangelo et al. 1996). In Los Angeles, 30% of wastewater is reused for a combination of agricultural purposes, landscape irrigation and groundwater recharge (Anderson 1996b). In Namibia, the City of Windhoek uses treated wastewater to supply 12% of its potable water (Anderson 1996b). This facility is the best-known instance of direct potable and non-potable wastewater reuse (Williams 1998).

The extent of wastewater reuse varies throughout Europe, influenced by the price of water and the effective application of standards (Ben Aim 1996). The industrial sector is more significantly involved in reuse than the municipal sector, because of constraints on the disposal of industrial wastewater and because new regulations concerning standards are stimulating new investments in treatment facilities (Ben Aim 1996).

As in the case of stormwater use, the benefits and costs of wastewater utilisation should be assessed alongside all other options for providing water services in order that the least-cost approach that best meets the requirements is found.

Implications

The increase in wastewater reuse in the second half of the 1990s was significantly greater than that projected in the early 1990s. There has also been an increase in the level of wastewater treatment and a movement away from discharge to inland waterways. Increased concern about the impact of wastewater disposal on the environment has contributed to all of these changes, and the identified trends are expected to continue into the near future.

Cities must alter the way in which water services are provided in order to be more sustainable. A list of technologies and management processes that could be used to effect have been identified by Newman and Mouritz (1996) and Varis and Somlyody (1997), viz.:

  • small-scale high-quality sewage treatment,
  • water-sensitive design processes,
  • localised stormwater treatment and reuse,
  • total water cycle planning; water harvesting for localised supply purposes,
  • urban integrated catchment management,
  • water-efficient appliances, fittings and technologies, and
  • localised community processes in water management.

The increasing acceptance of these approaches can be seen in the stormwater and wastewater reuse schemes outlined earlier, and the water management system of Charles Sturt University's Thurgoona campus.