Taronga Zoo

Sydney Harbour has copped a fair battering from human activities throughout the last two centuries. Recent revelations about the extent of dioxin contamination are a sad reflection of the careless way in which we have used and abused the harbour as a dump for disposal of a wide range of wastewaters. Contaminated sources have included considerable industrial discharges, municipal wastewaters and urban stormwater.

A decade ago, the cocktail discharged to Sydney Harbour included one more unusual source of contaminants. Elephants, tigers, camels and giraffes contributed to wastewater discharged from Taronga Zoo on Bradley's Head.

Between 1989 and 1992, Mosman Council’s water quality monitoring showed high faecal coliform counts at beaches adjacent to the zoo. At that time, water from the animal enclosure wash downs and all stormwater was being discharged directly into the harbour causing concerns for public health, beach closures and complaints from local residents.

But the situation was dramatically improved in 1996 with the implementation of a modern water recycling scheme. At a cost of $2.2 million, the scheme was developed with the assistance of Sydney Water, The NSW Department of Health and Clean Up Australia. It now treats between 100 and 650 kilolitres of water onsite each day.


Wastewater at Taronga Zoo consists primarily of stormwater, hose washings from animal enclosures and moat fillings. The first flush runoff and wastewater from enclosure wash downs and moats are now directed through the water recycling plant.

At the plant, the water flows through a screen and grit removal chamber for the removal of large solids. Next it undergoes a biological aeration treatment process to degrade dissolved organic chemicals. Biological treatment is succeeded with a hollow-fibre microfiltration membrane process. In addition to suspended particulates, the microfiltration process is effective for the removal of many bacteria and viruses. Ultraviolet disinfection is then used to inactivate remaining pathogens.

The recycled water is redistributed around the zoo via a separate reticulation system comprising two and a half kilometres of PVC pipe. The water is then reused for lawn and garden irrigation, animal exhibit hose down, moat filling as well as toilet and urinal flushing within the zoo.

A decade on, the water recycling scheme has proved its worth in achieving its original aim of reducing and improving discharged water quality into Sydney Harbour. An additional benefit has been a considerable reduction of use of Sydney’s dwindling fresh potable water supplies. This reduction has led to water bill savings for the zoo of around $70,000 per year.

Taronga Zoo’s water recycling scheme is a relatively simple, but highly effective innovation, providing a great precedent for zoos and other animal-housing operations throughout the world. I'd be keen to hear of any similar good opportunities that you can think of.

Lessons from Toowoomba

It is now more than a fortnight since the City of Toowoomba voted ‘no’ to an indirect potable water recycling proposal. The outcome of the poll will have been cause for concern for other towns and cities currently considering similar proposals.

However, having watched the Toowoomba debate closely (if from a distance) and communicated with a number of prominent ‘yes’ and ‘no’ campaigners, I have arrived very firmly at one conclusion: Overwhelmingly, the people of Toowoomba did not reject the concept of potable water recycling, they rejected the process being used to introduce it. The concept may have been workable, but the process deeply flawed.

Accordingly, I present some lessons from Toowoomba, which community leaders in Australia may like to closely consider.

1. Involve the community early

If potable water recycling is subject to serious consideration, now is the time to say so. Planning first and informing later is a doomed strategy. Planning that is perceived to have been undertaken in secret breeds suspicion and contempt. Preparing an application to fund a potable recycling scheme prior to properly involving the community is offensive and sets the scene for confrontation. It sends the message that decisions have been made and that the role of the community is to accept them.

Communities have a valuable role to play in planning, and public officials should recognise and capitalise on this. Your community is home to a diverse collection of combined experience, technical knowledge and skills. Not only are they capable of constructively contributing to debate and decision-making, they have a right to do so.

2. Keep outside interests at bay

The purpose of a local water management strategy is to address local problems and it requires local decisions. The community that is most directly affected has the most to gain or lose by any strategy. Perceptions of outside influences driving the agenda will naturally lead to resentment.

The suggestion that a local plan may provide a case study, a demonstration, or worse –a pioneering experiment for the benefit of other communities is inappropriate and unconstructive. If you must be a pioneer of something, make it community involvement in decision-making.

The water industry has an essential contribution to make in water management. However, conflicts of interest (real or perceived) are too easily created. A private company or organisation with a financial interest in the outcome of a consultation process is probably a poor choice for facilitator. Accepting offers from out-of-town environmental groups to come in and tell people how to vote is a similarly crummy decision.

3. Give serious consideration to all options

Real choice is not about ‘yes’ or ‘no’. Real choice involves putting all options on the table for fair consideration. Potable water recycling has many attributes to recommend it, but it makes little sense when considered in isolation. Therefore, it is essential for potable recycling proposals to be judged by detailed comparison to alternative strategies.

Other strategies requiring equal consideration include water conservation, increased utilisation of natural resources, dam construction, non-potable recycling strategies, water trading, ‘do nothing’, and applying limits to population growth. A triple-bottom-line evaluation process will allow transparent consideration of environmental, social and economic costs and benefits. If potable water recycling can not stand up against these alternatives, it is simply not the optimum strategy.

4. Inform, don’t coerce

Potable recycling is an issue that most communities have not had reason to seriously consider until very recently. Therefore, reliable information is required for them to make an informed decision. It is the responsibility of community leaders to provide this information and there are many effective means of doing so. It is essential for this information to be balanced and to stick closely to the facts. It should avoid making unreasonable predictions about how dire things may become if a strategy is not adopted.

If you are convinced that you have identified the best solution, then say so. Be enthusiastic about it. But do not allow yourself to give the impression that any sensible person should use the same information to arrive at the same conclusions as you. Attempts to coerce polarise communities. It offends those who disagree and will only harden their resolve.

5. Explain relative risk

Risk is a difficult and complex topic, and one which is commonly misunderstood. Effective risk communication is notoriously difficult and blundered attempts can cause unnecessary alarm. No human activity is without risk, including the use of any water supply. Accordingly, demands that risks be proven to be ‘zero’ can never be satisfied.

A more effective communication approach is to explain the relativeness of the risks that we take and accept in everyday life. Compared to risks such as eating in restaurants, crossing roads, or driving a car, health risks associated with consuming well treated recycled water are negligible. Millions of people consume the product of ‘unplanned potable recycling’ in developed countries everyday. Yet, there is no (reliable) observed evidence of negative health impacts (excluding those exposed to poorly treated sewage in developing countries). Advanced water treatment can only be expected to reduce the risks even further. An improved community understanding of these facts will encourage acceptance.

6. Accept dissent

When people are given choice, some make different decisions. It is their right to do so, and community leaders should respect that right. There is no justification for belittling, ridiculing, demonising or ostracising dissenters. There is a sometimes fine line between ‘engaging in constructive debate’ and arguing stubbornly. If you find yourself telling people that ‘if they don’t like it then they can drink bottled water’ or that you ‘would be prepared to go to war on this issue’, then you have probably missed that line. A better approach is to acknowledge that the community as a whole will need to make a decision and that it is inevitable that not every individual will agree with the outcome.

7. Understand and accept the ‘yuck factor’

The ‘yuck factor’ is real, perfectly normal, and has an essential human purpose. It guards us from dangerous exposure to contaminated and unhygienic substances. It is pointless (and incorrect) to suggest that the ‘yuck factor’ is irrational or the result of a lack of intelligence.

Getting over the ‘yuck factor’ for potable recycling is tough for many of us (myself included!). But the important point to make is that advanced-treated water has no relationship to sewage other than its recent history. Water is water and the safety of water is determined entirely by the contaminants that it may contain. Advanced-treated recycled water is unique in terms of its purity and quality control. Understanding this will allow people to logically disassociate clean water from dirty water.

8. Express costs in meaningful terms

Water management is an expensive business. However, most of us are not accustomed to dealing with multimillion dollar costs. Comparing potential water strategies in these terms can seem meaningless, especially when costs are to be shared over large population. Numerous comments left on this blog are along the lines of ‘why do you mention costs? Cost doesn’t matter!’ The fact is that all responsible government decisions will take costs into account and costs will play an important role in defining viability. A strategy that will bankrupt a local government or require rates to rise excessively is unlikely to be viable. A better communication approach is to define costs in terms of those that will need to be met by individual rate-payers. A strategy that is explained to require a small rate-rise will be seen as a legitimate advantage over one that requires a very large rate-rise.

9. Don’t oversell technology

Misrepresenting the capabilities and limitations of proposed technology is a shortcut to undermining your own credibility. However, I suspect that many such misrepresentations are not the result of deviancy, but more of naivety.

Water treatment is a highly competitive business internationally. Like any competitive industry, the private companies involved are not always enthusiastic about promoting the limitations of the technologies that they supply. Nonetheless, it is the responsibility of decision makers to demand accurate information and to make this available to citizens. Lazy simplifications like ‘reverse osmosis removes all molecules except water’ will only get you into trouble. A quick Google-search will show up the inaccuracy of such simplifications and provide the community with a reason to question both your credibility and motives.

10. Always remember the goal

Remember, the goal is not to introduce a planned potable water recycling scheme to your community. The goal is to identify and implement the optimum sustainable water management strategy, whatever it may be.


Any feedback, further lessons or criticism would be appreciated…

Environmental Estrogens

Queensland opposition leader, Lawrence Springborg, raised the issue of ‘environmental estrogens’ this week. Predictably, various newspapers and blogs were jammed with arguments about whether chemicals in sewage can change the sex of fish and whether they could turn a male human into a female. Seriously, they were. So let’s get a few facts straight.

A one-paragraph biology lesson: Human sexuality is determined by DNA chromosomes. Most of us have two chromosomes, either XX or XY (yes, I know there are other possibilities, but lets keep this simple). You got one of these from your father (an X or a Y) and one from your mother (an X). If you scored XX, you are genetically female. If you scored XY, you are genetically male. No amount of exposure to chemicals (such as hormones) in the environment can change this. You can not change a man to a woman or a woman to a man. Yes, I accept that people may identify as “male” or “female” regardless of chromosomes...I don’t mean to offend anyone...I simply want to deal with this complex topic in a single paragraph…woah…a can of worms that I really didn’t mean to open...Move on!

But fish and reptiles are different to mammals. Changing sex is natural for many species and it is common to do this in response to chemical signals.

Researchers have found that if they paint a turtle's egg with estrogen, the turtle inside can change from male to female. Strangely enough, the same thing can be achieved using industrial chemicals called polychlorinated biphenyls (PCBs). These (artificial) PCBs have some chemical similarities to (natural) estrogen, which causes them to interact with the estrogen-receptors. In other words, the PCBs ‘mimic’ the action of estrogen.

Male frogs’ eggs or embryos exposed in the lab to the widely used pesticide, atrazine, develop ovaries and are infertile. In fact, not only do the males (which normally only have testes) develop ovaries, they develop multiple ovaries, sometimes six or seven. Unlike the PCBs, atrazine does not mimic estrogen. Instead, it enhances the conversion of testosterone to estrogen.

Even mammals can be affected by these chemical ‘endocrine disruptions’ (although they don’t change sex). For example, sheep that graze on clover ingest natural plant estrogens (phytoestrogens) which can make them infertile.

Recently, researchers at the Cincinnati Zoo were trying to work out why some cheetahs were not breeding. It turned out that phytoestrogens in soy-based materials included in their diet was acting as a contraceptive. When the cheetahs were given a diet without soy several quickly gave birth to kittens.

There are lots of compounds that can act like estrogen. From the above examples, we know that they include natural estrogens, industrial compounds, pesticides and natural phytoestrogens (plant estrogens). Many of these compounds can wind up in sewage, so it is no surprise that poorly treated sewage can also have these sorts of effects.

For example, there are reports of fish in the Potomac River (USA) being “feminised” by water-borne pollutants. This was identified by an increase in the production of the protein that is involved in egg-production, by male fish. This protein, called ‘vitellogenin’ is not usually made by male fish unless they are treated with estrogen. It turns out that some detergents in the water are likely to be responsible for tricking male fish into producing vitellogenin. These detergents can be major constituents of municipal sewage. Human estrogens (excreted in urine) and synthetic steroids such as the contraceptive pill can have the same effect.

So what does all of this have to do with recycled water? Well that depends on how we define ‘recycled water’. If we are talking about advanced water treatment (processes such as reverse osmosis, granular activated carbon, advanced oxidation), then the answer is 'absolutely nothing'.

The concentrations of estrogenic substances in advanced treated recycled water are miniscule (or unmeasurable). We know this both by chemical analysis (measuring the concentrations of chemicals) and by estrogenic activity (running assays to measure the effect of any estrogens or estrogen mimics that may be present).

However, if we are talking about conventionally-treated (or poorly-treated) sewage, then yes, discharging poorly-treated sewage into creeks and rivers can be expected to disrupt the sexuality of some species including fish. All the more reason why we should pay better attention to treating water to a higher level than what we generally get away with today.

If you've come this far, leave a comment...tell me what you reckon.