Recycled drinking water

Recycling waste water for drinking could help with water shortages but is it safe?
 
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  • Updated:27 Jan 2008
 

01 .The recycling scene

Water

In brief

  • Recycling waste water for drinking is going ahead in south-east Queensland, being trialled in Perth, and being considered by Goulburn.
  • If managed carefully, recycling water for drinking could significantly reduce water shortages.

There's very high support for using recycled water on parks and gardens, but strong debate over whether it's safe to drink. By some it’s viewed as a last resort, at best.

With so much conflicting information on the pros and cons of recycling water for drinking, it's hard to know the truth. In this report we sort the myths from facts. 

Please note: this information was current as of January 2008 but is still a useful guide to today's market.


The recycling scene in Australia

Toowoomba residents voted down a proposal to recycle waste water for drinking in 2006, with 62% opposed. Taking this message on board, Goulburn in NSW is undertaking lengthy community consultation on all its available water management options. A recycling option being considered there could contribute up to half the area’s water needs, but so far 41% of people surveyed considered the proposal undesirable.

Recycling isn’t going ahead in Toowoomba itself, but the Queensland government did come to regard it as the only choice for securing the water supply in neighbouring southeast Queensland and Toowoomba may yet be connected to that bigger scheme. The Queensland scheme, which includes Brisbane, is one of the largest of its type in the world.

Canberra has, for now, stopped short of recycling water to supplement the drinking water supply, even though it was identified as an option during recent community consultations.

Instead, last October the ACT government approved the design of a water recycling demonstration project. Wastewater will be recycled to drinking quality, but used for research and monitoring purposes – and the recycled water won’t be added to drinking water supplies.

The wider scene

It’s far from an exhaustive list, but here are some examples of recycled water initiatives worldwide.

  • 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.
  • Perth - trialling managed aquifer recharge (2005–2008).
  • Southeast Queensland - reservoir augmentation (in construction, ready late 2008).
  • Goulburn NSW - considering reservoir augmentation via wetlands.

Choice verdict

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.

The national guidelines for recycled water for drinking will be an important step. There also needs to be the flexibility to update and strengthen water management requirements as more is learnt.

Recycled water is coming to Queensland and there are likely to be more projects on the way. Since the decision to go ahead with indirect potable reuse, a Water Commission survey has shown 74% of south-east Queenslanders are supportive of the scheme. On the other hand, a survey conducted by opponents showed 90% were against it – although only 1.5% of people invited to respond to that survey did so.

Recycled water through indirect potable reuse can be an important addition to the water supply. Don’t get too excited — it’s unlikely to eliminate water restrictions — but on the bright side it should help stop them getting worse.

 
 

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02.The recycling process

 

What exactly is recycled water?

Water recycling is the process of taking effluent (wastewater and sewage) and treating it to a level that’s appropriate for its intended use. For potable (drinkable) use, the recycled water has to be treated to a sufficiently high level that it’s suitable for human consumption.

The indirect potable reuse process being implemented in southeast Queensland, trialled in Perth and under discussion in Goulburn adds another step: highly treated recycled water is mixed with other water supplies above or below ground before it arrives at your tap (see Jargon buster).

There’s no standard 'off the shelf' project — each one is unique, with different specific technologies and very diverse natural water catchment characteristics — but generally speaking indirect potable reuse involves a number of steps.

  • After going through micro filters, the water undergoes a reverse osmosis process, which involves forcing the water molecules across a dense plastic film. The water can pass through the film, but other molecules, including viruses, bacteria and even tiny salt molecules, 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.

The process

DiagramCAPTION: 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 and undergoes existing drinking water treatment before arriving again at your tap.

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. For example, people living in towns that draw water from the Murrumbidgee below Canberra, and then down the Murray to Adelaide, are already partly using reuse water.

Even the city of London is located downstream from a number of wastewater treatment plants that discharge into the Thames, so part of its water supplies also reuse water. And Sydney’s water supply receives some treated sewage from Goulburn and Lithgow. This water goes through the regular water treatment system and is considered perfectly fit to drink.

With national guidelines on recycling water for drinking likely to be finalised in April, greater expansion of water recycling is anticipated over the longer term. The aim of the guidelines is to make sure recycling is done safely, without being sidetracked by whether recycling is a good or bad idea. The guidelines will explain what the risks are, and how to manage them. Decision makers and project managers should use the guidelines when assessing and carrying out projects.

Jargon buster

  • Potable water: Water intended for human consumption — suitable on the basis of both health and aesthetic considerations for drinking or culinary purposes.
  • Indirect potable reuse: The discharge of 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.
  • Recycled water: Water that’s been reclaimed from sewage, greywater or stormwater systems and treated to a standard that’s appropriate for its intended use.
  • Reverse osmosis: An advanced method of wastewater treatment that works by forcing water molecules across a semi-permeable membrane to separate it from impurities.
  • Sewage: 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.)
  • Water recycling: A generic term for water reclamation and reuse.

03.Are the myths true?

 

There's a lot of conflicting information circulating about the pros and cons of recycling water for drinking. Here, we sort the myths from the facts.

"Adding it to the environment improves it."

Overseas, Namibia is unique in directly reusing its recycled water — meaning that the recycled water is put directly into the drinking water pipes. Most schemes add recycled water to a river, underground aquifer or reservoir (in Queensland’s case the Wivenhoe dam). This step’s been dubbed 'the miracle mile' and 'shandying' — but it works and it’s how indirect potable reuse will occur in Australia.

It might simply be because of the obvious dilution it receives, but Australians are much more comfortable with recycling if the process includes a natural environmental stage combined with the thorough treatment given to the rest of the water supply.

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 (see diagram of the recycling process). 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.

Where we do recycle our wastewater, it’s clearly important that these health risks are managed well. The recycled water guidelines are being developed with this front-of-mind, so 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 and the potable recycling process, particularly the reverse osmosis stage, can then remove the remainder of trace hormones to below the limit of detection.

All this emphasises the importance of caution: multiple barriers in the treatment process, water quality testing, monitoring and research. The draft recycled water guidelines include quality criteria for pharmaceuticals and other chemicals of concern.

"It’s cheaper so it must be poor quality."

In fact, 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 chief 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 and could therefore be 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 efficient appliances.

In southeast Queensland, desalination and recycled water are expected to eventually contribute over half the total water supply. But, of course, for inland centres desalination of seawater isn’t a viable solution.

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 purposes — 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 just check the official inspection tag on their recycled water meter.

Taking precautions

Two years ago a newspaper reported that an Australian government agency had lead and other metals contaminating its recycled drinking water supply.

The system was disconnected and thankfully the staff checked out OK. But the report had described the water as 'recycled', when 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 was 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 ultimately 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.