Water treatment and reuse
The Australian Government is encouraging and supporting businesses to identify options for waste water
reuse under the Water Efficiency Opportunities program.
The commercial and industrial sector consumes about 20 per cent of urban water in Australia. Water reuse is
one option to improve water efficiency.
The business opportunity
Many Australian businesses use water treatment technologies for cost effective water reuse. These
technologies can be combined with other water efficiency measures to reduce ongoing water and wastewater
costs. For instance:
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Inghams Enterprises have reduced mains water usage by 70 per cent in their poultry processing
business, achieving savings of 545 megalires (ML) a year, using an integrated approach to water
treatment and reuse.
At their Cartonboard Mill in Petrie, Amcor Australia has achieved annual savings of more than 1000
ML by using treated and recycled water in the manufacturing process, reducing drinking water use
by 90 per cent.
Diageo Australia Limited, an international beverage manufacturer, has achieved a 43 per cent water
saving at its Huntingwood site in Sydney. This annual saving of 55.5 ML has been made possible
through a combination of improved management practices and implementing a reverse osmosis
water treatment and recovery process, which accounts for 50 per cent of the savings.
The Rossdale Golf Club has achieved an annual reduction of mains water usage of 35 ML, a
reduction of 56 per cent, through water treatment and reuse from a combination of stormwater
harvesting, aquifer storage, and a recovery and reuse facility.
Water can be treated and reused from a wide variety of sources including rainwater, stormwater, greywater,
groundwater and industrial water. To reuse this water, appropriate water quality standards need to be met for
specific purposes such as irrigation, garden watering or toilet flushing. These standards are set out in
national and state guidelines.
Water treatment options
The treatment method chosen for a system must deliver water quality appropriate for the end uses. It is
important to analyse the characteristics of your source water and compare it to your proposed end uses to
identify the water quality risks your treatment system needs to address.
There are three main methods of treating wastewater to improve water quality – physical, biological and
chemical. Within these three areas, six different types of water or wastewater treatments are commonly used.
Physical
Flotation and basic filtration: flotation effectively removes grease, oil and suspended solids. The most
common flotation process is dissolved air flotation (DAF); air is dissolved under pressure in wastewater then
released into a flotation tank at atmospheric pressure. Suspended matter adheres to the air bubbles, floats to
the surface, and is collected via skimming. DAF is relatively cheap and easy to use. It is commonly used in
commercial kitchens to remove oil and grease; in meat processing to treat effluent; and in treating the
industrial wastewater effluents from oil refineries, petrochemical and chemical plants, natural gas processing
plants, paper mills, general water treatment and similar industrial facilities.
Membrane filtration: this involves forcing pressurised water or wastewater through a semi-permeable
membrane to remove solids and dissolved salts. Membrane technology has made some major advances in
recent years and now has broad application. The four main types are: microfiltration, ultrafiltration, reverse
osmosis and nanofiltration. The latter two are particularly effective at removing salts, dissolved solids,
enhanced organics and pathogens. Whilst membranes are effective water treatment technologies, they can
become fouled from suspended solids or covered in scale and salts if not properly operated. This risk can be
reduced by selecting the appropriate membrane, maintaining proper operating conditions, cleaning
membranes regularly and pre-treating wastewater. Examples of membrane treatment are listed in Table 1.
Table 1: Filtration method and a selection of their applications (adapted from Sydney Water)
Filtration method
Business sector application
Reverse osmosis
Salt removal from brackish or saline solutions
Aquariums use reverse osmosis systems to enable
water reuse and the maintenance of their artificial
mixture of seawater
Ultrafiltration
Oily waste water treatment
Pulp and paper water recovery
Ultrafiltration/nanofiltration/reverse osmosis Colour removal in the textile industry
Laundry effluent treatment
Ultrafiltration/reverse osmosis
Boiler feed water treatment
Dairy industry for dewatering of milk to create milk
powder and dairy products enabling water reuse.
Physical and biological
Membrane bioreactors: membrane bioreactors (MBR) combine biological processes and membrane
technology to treat wastewater. Within one process unit, a high standard of treatment is achieved. A key
advantage of this technology is the ease of upgrading or retro-fitting existing treatment plants. MBRs have
application for both domestic wastewater, and municipal and industrial waste treatment. When applied to the
former, MBR output is of sufficient quality to be released to surface, brackish or coastal waterways or used
in urban irrigation.
Biological
Biological treatment: biological treatment processes use micro-organisms to treat wastewater using similar
naturally occurring processes, but under more controlled conditions. There are three types of biological
treatment approaches: anaerobic, aerobic and mixed anaerobic/aerobic systems.
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Anaerobic: breaks down the biodegradable component of the waste to produce biogas and soil
improver. Biogas can be used to generate electricity and heat, and reduces greenhouse gas emissions.
Aerobic treatment: air is pumped through the wastewater in biological reactors. Aerobic biological
systems are mostly used for treating low concentration waste (typically where the biochemical
oxygen demand is less than 1000mg/L). In these systems, about 50 per cent of biodegradable organic
matter is converted to sludge, which must be disposed of. The rest is converted to water and air.
Aerobic systems are used in the food manufacturing industry and to treat municipal wastewater.
Chemical
Ion exchange: ion exchange consists of a specially made resin which removes unwanted ions dissolved in
wastewater and replaces them with desirable ions that are held in the resin. Ion exchange resins can be used
to remove or recover water hardness (calcium and magnesium ions), alkalinity, metals, nitrates, sulphates,
and even ammonia. Ion exchangers remove trace contaminants in water for high-water quality applications
such ultra pure water for the pharmaceutical and semi-conductor industries.
When water to be treated passes through the ion exchange unit, ions in the water are attracted by either a
positive or a negative charge to the ions in the resin bed. Since the ions from the water are held more tightly
by the resins than they were held in the water, they are removed from the water in the exchange process.
The effectiveness of ion exchange resins reduces over time and need to be regenerated or replaced
periodically. Pre-treating water with membrane filtration will greatly reduce the frequency of regeneration.
The waste accumulated in the resins from this process needs to be disposed of appropriately.
Disinfection: this includes processes such as chlorination and the use of ozone and ultra violet light, and is
effective at killing pathogens such as viruses, bacteria and protozoa. It is usually applied as a secondary
treatment in situations where there is a risk that treated water will come into contact with the human
population. If water is turbid (cloudy with suspended solids) or if contact times are too low, disinfection will
be less effective. Contaminants such as ammonia can also make chlorine ineffective. Chlorination can result
in disinfection by-products, hence the use of chlorination needs to follow recommended guidelines,
especially if being reused for drinking quality water. Ultra-violet lamps and ozone generators need
maintenance to provide consistent performance.
More information
For more information about Water Efficiency Opportunities call 1800 218 478 or visit
www.environment.gov.au/water/policy-programs/weo/index.
For more information about Water for the Future visit
www.environment.gov.au/water
Published by the Department of Sustainability, Environment, Water, Population and Communities,
November 2010.