Water futures

Despite what people may think, I don’t have any political ambition. I left private enterprise because it looked as if they needed a bit of common sense in Council. Similarly, I’m not a brave leader pushing ahead with a contentious plan to recycle water. I am someone who has been convinced by science that water can be purified to an acceptable standard, and I see the Water Futures - Toowoomba water recycling project as being a sensible step forward for this city.

There is no new water on earth. Through the water cycle, the same finite quantity of water has been circulating the earth for approximately three billion years. Unfortunately for humans, the water is not always in the places where we need it the most, and water supplies for cities and towns throughout Australia are experiencing a strain on this resource previously unknown to most of us.

Although a greater harvest of rainwater is possible for most places, this alone will not drought-proof a heavily populated and growing region, particularly if rainfall is unreliable. Obtaining a new water source for a community invariably means taking it from the potential sources of another district.

An additional factor influencing my enthusiasm for recycling is the need to take greater responsibility for the way in which, until now, we have used water once and then dumped it without a thought for the consequences.

In November 1991, Australia embarrassed itself internationally with the largest river toxic algal bloom in history. National media identified Toowoomba as the biggest contributor of nutrients to the river systems in Queensland and one of the sources responsible for the blue-green algae outbreak.

Toowoomba’s three water supply dams are now at historically low levels. Further bores are being drilled and, with Queensland Government approval, we plan to tap into the artesian basin as an emergency water source. The Toowoomba City Council is encouraging the installation of rainwater tanks in homes to lighten the burden on current water sources. We are also conducting a public education program aimed at changing people’s attitudes towards our most precious resource and to foster a “water-valuing” culture.

The legacy I wish to leave is one of taking responsibility. That is why I am advocating Toowoomba build an Advanced Water Treatment plant (AWT) to recycle our water for indirect potable reuse. I’ve seen this science at work, in Singapore and Orange County in the US, but the defining place for me was the facility I inspected at Upper Occoquan, Fairfax County in the US. There they have been recycling wastewater since 1978. At times, up to 90 per cent of the drinking water for 1.5 million people has been recycled and there has not been one negative medical side effect reported. Indeed, theirs is a community that is thriving and prospering because they have a reliable water source.

The technology available to Toowoomba for our AWT is far superior to that which has been used by Fairfax County for the past 28 years. Water purification processes and testing of water sources will continue to improve. It has been said that, due to improved screening methods, Giardia and Cryptosporidium seem more prevalent today than they were in former times, however, it is likely these parasites have always been around and that our immune systems cope very well in their presence.

The key to the Water Futures - Toowoomba project is in the use of multiple barriers. A multi-barrier process works on the principle of providing more that one means of removing any particular contaminant. It means we do not rely on just one treatment process to do the job and a failure of one component will not compromise water quality.

Experts agree that a multiple barrier system employing appropriate treatment technologies is capable of reducing the concentrations of contaminants to such a low level that any risk becomes negligible. This approach is supported by highly credible agencies such as the US Environmental Protection Authority and World Health Organization (pdf file 1.08MB) in their guideline documents.

Toowoomba’s treated wastewater, from the Wetalla Water Reclamation Plant, will be purified through the use of a multi-barrier treatment process incorporating:

• ultrafiltration;
• reverse osmosis;
• ultraviolet disinfection & advanced oxidation;
• surface water mixing at Cooby Dam; and
• extraction from Cooby Dam then conventional water treatment at Mt Kynoch Water Treatment Plant.

It will also integrate a HACCP risk management and quality assurance system for the whole water cycle (HACCP is recognised and used all over the world as a system for ensuring the quality and safety of food products). Toowoomba City Council already has an independently certified and audited HACCP system to ensure drinking water quality.

The seven barriers of Water Futures - Toowoomba

Barrier 1 - Wetalla Water Reclamation Plant

First, the wastewater goes through the Wetalla Water Reclamation Plant. Here the wastewater treatment plant combines several different processes to purify water. The physical process of screening removes all large particles and material that will not dissolve. A biological process follows, where a population of small organisms such as protozoa and bacteria feed on the dissolved organic material in the water. Oxygen is supplied at controlled rates to create zones ranging from high oxygen to none at all, to encourage specific types of organisms to grow.

The water then flows through large settling tanks where the organisms and their feed (organic matter) are separated out and returned to water at the beginning of this process to do their job all over again. The solid by-product of this process, called biosolids, has excellent nutrient value and is used as a soil additive in agriculture. To ensure that there are no dangerous bacteria or viruses remaining, the water to be discharged down Gowrie Creek is disinfected using chlorine or UV light. The water to be purified for potable reuse then continues to the next barrier.

Barrier 2 - Ultrafiltration

The next stop for the water is at the Advanced Water Treatment Plant where it will undergo ultrafiltration. This involves the use of polymer or ceramic membrane filters, with a pore size of 0.01 micron, to remove very fine colloidal (very small suspended) particles from water.

At this stage in the process parasites such as Giardia, Cryptosporidia and bacteria such as E coli (Escherichia coli), and any other disease-causing microbes that might have been present in the water are removed.

Barrier 3 - Reverse osmosis

Our third barrier is the use of reverse osmosis (RO). During the RO process, pressure is applied to squeeze the water across an extremely fine membrane filter. The pore size of the RO membrane is so small (0.0001 micron) that bacteria, viruses and chemicals cannot pass through.

The membrane traps small pollutants such as salts, drugs (for example, chemotherapy drugs, anti-inflamatories, antibiotics and other pharmaceuticals), chemicals (such as personal care products), hormones, and importantly, viruses, while allowing the water molecules to pass through.

Very small amounts of some organic chemicals may pass through a RO membrane, but these are safely destroyed at one of the next two stages in the process.

It is important to note that, to begin with, not many hormones enter our water system. Hormones are large organic molecules (more than ten times the size of water molecules). This makes them relatively easy to remove through membrane filtration. Current Australian research shows more than 90 per cent of the hormones in raw sewage will be destroyed in the water reclamation stage (barrier 1).

Barriers 4 and 5 - Ultraviolet light disinfection and advanced oxidation

By this stage the water is already more than pure enough to drink, but ultraviolet (UV) light disinfection and advanced oxidation will provide additional layers of protection by passing the water through intense light, similar to the cleansing rays of the sun but hundreds of times stronger.

UV disinfection irradiates drinking water killing pathogens such as bacteria and viruses, and inactivating Cryptosporidium and Giardia. Advanced oxidation will break down and destroy any remaining organic chemicals or contaminants.

Barrier 6 - Cooby Dam

The recycled water is then blended with Lake Cooby’s surface water.

The water from Cooby Dam is naturally hard and contains dissolved organic matter. In the days before Toowoomba found other water supplies hardness was a major water quality issue for Toowoomba. Hardness destroys soap and leaves a calcium carbonate buildup around tap fittings. Bore water and dam water both pick up minerals through the ground. Water that has been processed through RO is soft And so the water that will come through the Advanced Water Treatment plant will improve the quality of Cooby Dam’s water.

Barrier 7 - Mount Kynoch Water Treatment Plant

At the Mt Kynoch Water Treatment Plant, where our current drinking water is already processed, Toowoomba's water is treated to meet the health and aesthetic requirements of the National Health and Medical Research Council’s Australian Drinking Water Guidelines. This process does not change with the advent of Water Futures - Toowoomba: it is something we have always done.

Turbidity is taken out of the water in a large settling tank and multi-media filters (crushed coal, sand and gravel) remove the remainder of the turbidity. To settle and filter small particles, a specialised treatment chemical (coagulant) is added that makes the particles larger (flocculate). The larger particles (flocs) containing the dirt settle and become sludge that is removed. The smaller flocs are trapped in the filters.

Under conditions where the raw dam water is relatively clean, the settling stage is not needed, and the plant can be operated in what is called “contact filtration”.

Nuisance minerals such as iron and manganese are removed through adding chlorine prior to filtration. Chlorine oxidises these metals, bringing them from solution into suspension so that they may then be filtered out. Adding chlorine in the treated water also destroys microorganisms, not trapped by the filters, and a sufficient quantity of chlorine is added to ensure some is present at the consumer tap, to prevent bacteriological re-growth in the pipes.

The science advocated through the Water Futures - Toowoomba recycling project is not new it is, however, a first for Australia. Our city has a unique opportunity to lead this country in responsible water conservation with the adoption of a technique of water purification I believe will soon be commonplace throughout the world. It is time Australians took responsibility for the environment we leave to future generations and had the courage and commitment to make it a world of which we can be to be proud.