What is recycled water?
Water recycling is the process of taking effluent (wastewater and sewage) and treating it so that it can be reused. For potable (drinkable) use, the recycled water has to be treated to a sufficiently high level that it's suitable for human consumption.
Do we drink recycled water in Australia?
Depending on where you live, or where you've travelled, there's a chance you've already drunk recycled water.
- NSW – in the Goulburn Valley, wastewater is recycled and returned to the Goulburn River where it can eventually be harvested and processed per usual for drinking.
- Queensland – the Western Corridor Recycled Water Scheme is the largest in Australia; the water is currently used for industrial purposes such as power plants but can be used for agriculture and to supplement drinking water supplies in the event of drought.
- Western Australia – the Groundwater Replenishment Scheme has been successfully trialled and full-scale development is proceeding. It returns recycled water to natural groundwater storage (aquifers) for later extraction as drinking water.
Water recycling happens in other regions of Australia but the water is generally directed exclusively for irrigation or industrial use.
Recycled water overseas
- Orange County, California - managed aquifer recharge since 1976.
- Scottsdale, Arizona - managed aquifer recharge since early 1990s.
- North Virginia - reservoir augmentation since 1978.
- Windhoek, Namibia - direct reuse since 1968 and upgraded in 2002.
- Veurne-Ambacht, Belgium - managed aquifer recharge since 2002 (also prevents saltwater intrusion into ground drinking water).
- Singapore - reservoir augmentation since 2003.
- London, UK - upstream wastewater treatment plants discharge into the Thames, so part of the city's water supplies come indirectly from recycled water.
The recycling process
There's no standard 'off the shelf' process for recycling water — each method is specific to local requirements and environments, with different technologies and very diverse natural water catchment characteristics — but, generally speaking, indirect potable reuse involves the following steps:
- Effluent gets treated at existing wastewater treatment plants before it reaches the recycling plant. The recycled water is then mixed with the natural water supply.
- After going through micro filters, the water undergoes a reverse osmosis process, which involves forcing the water molecules across a dense plastic film. Water can pass through the film, but other molecules (even tiny salt molecules) and microbes (including viruses and bacteria) can't.
- As an added precaution the water undergoes oxidation and disinfection, using hydrogen peroxide and very strong ultraviolet light.
- The recycled water is then added to a reservoir or groundwater aquifer, where it can be stored and blended with the regular water supply.
- Before being put into the drinking water system, the blended recycled and regular water also undergoes the normal drinking water treatment process.
There's a difference between this kind of planned reuse — with advanced water treatment and risk management — and incidental reuse. In some river systems, towns upstream discharge their treated sewage into the river and towns further downstream draw water from the same river.
With national guidelines on recycling water for drinking established in 2008, and with increasing demand on our water supply, recycling is going to become more common. The aim of the guidelines is to make sure recycling is done safely, without being sidetracked by the debate over whether recycling is a good or bad idea. The guidelines are aimed at decision makers and project managers, and explain what the risks are and how to manage them.
Any problems with recycled water are really not about the science or the engineering feasibility – these have already been proven. The sticking point is community acceptance and trust in authorities.
Setting national guidelines for recycled water for drinking was an important step. There also needs to be the flexibility to update and strengthen water management requirements as more is learnt.
Recycled water through indirect potable reuse can be an important addition to the water supply. It's unlikely to end water restrictions in times of drought, but on the bright side it should help stop restrictions getting worse.
Myths and facts about water recycling
There's a lot of conflicting information about the pros and cons of recycling water for drinking. Here, we sort fact from fiction.
"Adding recycled water to the environment improves it."
Namibia is the only country that pumps its recycled water directly into drinking water pipes. Most schemes add recycled water to a river, underground aquifer or reservoir (in Queensland's case, the Wivenhoe dam). This step' has been dubbed 'the miracle mile' or 'shandying' — but it works and it's how indirect potable reuse will happen in Australia.
It might simply be because of the obvious dilution, but Australians are much more comfortable with recycling if the process includes a natural environmental stage combined with the thorough treatment.
There's a less obvious reason too. Authorities tweak water treatment operations for our existing water supply, depending on the particular qualities of the water coming downstream. So putting the recycled water into the main water supply adds another safety buffer, because it provides time to identify and respond to blips in water quality.
"It's not clean: you'd be drinking sewage."
The yuck factor is a key reason people oppose recycling wastewater for drinking. However, experts say the perception simply doesn't match reality. By the time recycled water has passed through all the treatment processes it's in fact cleaner than regular drinking water and has less 'taste', because it has fewer impurities. In fact, it's of such a high standard that, theoretically, it could be used in hospitals for kidney dialysis.
Schemes under consideration in Australia would treat the wastewater at regular sewage treatment plants before it arrives at the recycling plant, so treated domestic and industrial wastewater going into the recycling plants would already be more than 99% water.
Some experts have raised legitimate concerns about the fact that wastewater also contains contaminants of organic material (poo), viruses and bacteria, detergents, grease and oil, salts, nutrients, organic chemicals, metals and other inorganic chemicals. It's obviously important that these health risks are managed well and that recycling processes are designed to remove these contaminants.
The multi-barrier approach used in producing recycled drinking water means that sewage contamination of the end product is unlikely. The idea is that even if there's a fault at one stage, the next will be there to remove the contaminants.
For example, if there's a fault with one of the membranes in the reverse osmosis process and unwanted molecules slip through, many will be removed or destroyed by the hydrogen peroxide and ultraviolet light used in the next stage of the process. The likelihood of contamination is further reduced by having a series of membranes, conducting frequent maintenance, and a set of extra barriers when the water reaches the regular drinking water treatment plant (for example, lime is often added to reduce trace amounts of metals).
"It turns men into women."
Micro pollutants are a legitimate concern, because we're putting an increasing mix of chemicals into our water systems. These include nasties such as detergents, personal care products, antibiotics, hormones, insecticides and chemicals that make plastic soft (plasticisers).
The Toowoomba and southeast Queensland campaigns against the introduction of recycled water argued that it had the ability to change the sex of fish. But experts say that evidence of harm to human health – let alone sex change – isn't supported by strong scientific evidence. The fear of feminisation comes from studies of fish swimming in sewage that hadn't been completely treated, and can't be simply translated to humans and highly treated recycled water. Experts say there's no evidence that recycled water contains dangerous levels of hormones.
Conventional sewage treatment processes in Australia remove 95-99% of hormones. The potable recycling process, particularly the reverse osmosis stage, can then remove the remainder of trace hormones to below the limit of detection.
"It's cheaper so it must be poor quality."
A lot of Singapore's recycled water gets used for electronic chip manufacturing that demands higher-quality water than drinking water. It's true that when recycled water is provided for non-drinking purposes it's sometimes offered at a discount, but quality isn't the reason.
The price was set lower when these schemes were introduced, to encourage people to use recycled water. But as with any water, recycled supplies can't be regarded as an unlimited resource; they need demand management too. It costs money to produce recycled water, so in future its price is likely to more closely reflect this cost.
"It uses a lot of energy."
This is no myth. It does take a lot of energy to make each litre of recycled water, and to add it to a reservoir — for example pumping it from the coast to a dam that's inland and uphill. It will also take a lot of energy to build new infrastructure for the recycled water schemes.
However, other strategies for increasing water supply – such as desalination, which involves treating seawater by reverse osmosis to make it suitable for drinking – can use even more energy and could be even more costly.
That said, Australia needs a number of strategies working together to overcome water shortages – for example, water conservation measures, evaporation control, rainwater tanks, groundwater recharge and water-efficient appliances.
Water intended for human consumption – suitable on the basis of both health and aesthetic considerations for drinking or culinary purposes.
Indirect potable reuse
Putting recycled water into surface water or groundwater (called managed aquifer recharge) to supplement drinking water supply, rather than going directly from the treatment plant to your tap.
Water that's been reclaimed from sewage, greywater or stormwater systems and treated to a standard that's appropriate for its intended use.
An advanced method of wastewater treatment that works by forcing water molecules across a semi-permeable membrane to separate it from impurities.
Material from internal household and other building drains. It includes faecal waste and urine from toilets; shower and bath water; laundry water and kitchen water (sewerage is the network of pipes and infrastructure that transport the sewage).
Fit for purpose
Residents in some newer housing developments have two sets of water pipes — one for drinking water and a purple one for recycled water, used for things like washing the car, watering the garden and toilet flushing.
In two homes in Newington, Sydney, these pipes were cross-connected, meaning the residents were inadvertently drinking recycled water. It was up to four years before the mistake was discovered, following a complaint about the taste of the water.
The recycled water in purple pipes isn't intended for drinking – it tastes salty because it's recycled to a significantly lower standard than water produced by indirect potable reuse. Even so, no health problems were reported. All 1500 houses in Newington had their connections inspected.
New homes now have an inspection by a licensed plumber. New residents in old homes are advised to check the official inspection tag on their recycled water meter.
Some years ago a newspaper reported that an Australian government agency's 'recycled' drinking water supply was contaminated with lead and other metals.
The system was disconnected and thankfully the staff checked out OK. But while the report described the water as recycled, in fact the agency used a rainwater tank. And it wasn't that tank water in general is unsafe, but that lead, copper and zinc were present in that particular water collection area.
This case goes to show that careful installation and maintenance of any water supply system is crucial – as is accurate reporting.
A matter of trust
Sydneysider Chris lived and worked in Singapore for nearly 10 years, during the time recycled water for drinking was introduced there. He travelled a lot in the region for work and Singapore was one of the few Asian countries where he could drink water straight from the tap.
He recalls the Singaporean government having a publicity campaign about NEWater. Just like in Australia, there was community concern that it would mean 'drinking toilet water'. In the end, in Singapore, they didn't wait to win over the public — they just did it.
The treated water from the plant is perfectly drinkable — even the Prime Minister drank it for the cameras. But for everyday use a small proportion of the recycled water is pumped into the reservoirs and mixed with regular water, before being sent to people's taps. The remainder used for industrial purposes. Chris couldn't taste a difference.
The issue, Chris reckons, is how much people trust governments to make sure their drinking water is safe. He says he's comfortable with the idea of drinking recycled water in Australia. He thinks people need to understand where water comes from now, and all the things that already get filtered out — like kangaroo poo from around Sydney's Warragamba dam. It all gets taken out, which is what water treatment is all about.