Learning to cope with change
Tackling water-borne substances which can affect hormonal balanceSome researchers believe inactive oestrogen in human waste is 'reactivated' by bacteria during sewage treatment, writes Chris Webb. Research has shown, however, the impacts of such chemicals can be mitigated by adding new levels of treatment at WTWs or changes in the way sewage systems are managed.
In 1995 Friends of the Earth (FoE) called on the government to ban chemicals implicated, inter alia, in rising infertility and testicular cancer among men and breast cancer among women. The 1995 report Environmental Oestrogens: Consequences to Human Health and Wildlife confirmed it was "plausible" oestrogens or oestrogenic disrupters were responsible for the cancers. The report followed damning research by the US and Danish environmental protection agencies. long division
Experts remain divided on whether such hormones are being effectively removed from drinking water supplies. It could take years to conclusively prove or disprove a risk, yet it seems certain the presence of oestrogens in water being discharged from WwTWs is a real and growing problem. Seven years after the FoE report, in March 2002, the Environment Agency (EA) called for moves to implement a risk management strategy for oestrogens in sewage following a five-year research project which concluded traces of the female hormone oestrogen in English lowland rivers were affecting the reproductive ability of male fish. Research showed compelling evidence, the EA said. The agency added the problem is likely to force changes in sewage treatment practices and the development of new technology for some WwTWs.
Water UK responded by pledging to put forward proposals for a collaborative programme to look further into the impacts, to identify WwTWs likely to discharge oestrogens at worrying levels and to evaluate treatment options. Water UK also pointed to research by the Drinking Water Inspectorate (DWI) which showed no oestrogens had been found in raw water reservoirs or river intakes, no oestrogenic steroids had been detected in treated waters and water treatment processes such as chlorination, ozonation, powdered activated carbon and aeration had been shown to remove more than 95% of any oestrogenic steroids that might enter a water source.
In October 2001, Water UK said: 'At the present time and on the current best scientific evidence, European water suppliers believe that it is neither necessary nor practical to set any formal statutory standards for endocrine disrupters.' There are those, however, who believe we are only now beginning to discover how to measure and evaluate the potential toxicity of the organic pollutants being introduced to aquatic ecosystems. At least that is the view of Dr Damia Barcelo, one of Europe's leading experts in the field of monitoring and evaluating the quality of underground, river and maritime waters.
In the first half of the 1990s experts started to express concerns about the effects of substances collectively known as endocrine disrupters. Endocrine disrupters are defined as chemicals which mimic or inhibit the effects of hormones. They fall into two categories: those that behave like female hormones (oestrogenic) and those that antagonise male hormones (anti-androgenic). There is evidence of falling sperm counts in humans, an increase in the incidence of testicular cancer and an increase in the incidence of boys being born with abnormalities to their reproductive systems. It has been speculated that these phenomena may have been caused by endocrine disrupters. In 1998 detailed research from the former Ministry of Agriculture, Fisheries & Food (MAFF) Centre for Environment, Fisheries and Aquaculture Science (CEFAS) demonstrated that a number of flounders in some heavily polluted estuaries were being 'feminised' through contact with pollution. The effects of the substances, oestrogenic hormones and their mimics, included egg cell growth in the testes of male fish and egg yolk production in male and juvenile female fish.
This sexual dysfunction in living organisms seems to be linked with the increasing use of new industrial, chemical and pharmaceutical products from which certain organic compounds are entering the water cycle. The only creatures for which there is a strong body of evidence that endocrine disrupters are playing a major role in gender modification is fish. A number of independent scientific studies carried out in different European rivers and fish farms have shown with absolute certainty that the high concentration of products which behave like oestrogens leads to an abnormal feminisation of resident species of fish. There has been a clear fall in the number of male fish being born.
The effects are strongly associated with oestrogenic chemicals discharged via effluents into rivers, particularly natural and synthetic hormones (steroid oestrogens) that arise from humans and alkylphenols (APs) that breakdown from alkylphenol ethoxylate (APE) surfactants.Risk assessed
This year the EA is due to confirm which WwTWs should be considered at risk. The agency is also continuing research into setting relevant targets (chemical standards and biological effects) to protect the environment. The EA also believes the water industry should start to investigate treatment technologies for the removal of priority oestrogens.
Currently the agency is calling for an initial study on the feasibility of risk management options in 2003-4, followed by detailed studies on the implementation of these at priority sites in 2005-7. The programmes will focus on a number of high-risk sites and will establish how effluents can be managed to reduce the risk to acceptable levels.
While the effects of endocrine disrupters have been implicated in falling sperm counts in men, almost nothing is known about their effect on female mammals because mammal eggs are few in number and can only be examined by invasive surgery. However, a recent Natural Environment Research Council (NERC) report describes work by scientists at the University of Sheffield who have pioneered a way to monitor the effects of endocrine disrupters on female fertility using zebrafish. These small tropical fish release several hundred eggs a day into the water and have transparent embryos that are easily studied. The researchers found both natural and synthetic oestrogen had a dramatic effect on the production of eggs, the structure of the sex organs and the mortality and sex ratio of the embryos.
A team from Oxford University and the Natural Environment Council's Centre for Ecology and Hydrology have modelled the kinetic/equilibrium performance of bioreactors and put forward recommendations for modifications at WTWs. Richard Darton, a professor of engineering science at Oxford, and Andrew Johnson from the NERC, suggest using biofilters located at the front of aeration tanks at treatment works. "The job of the carrier media is to encourage biofilm growth," says Darton, "yet at the same time it must not restrict through-flow. As far as possible the design must guarantee contact with passing micro-organic contaminants. It would be attractive to use mobile carrier particles at a packing density that would permit their movement in the water and air-flow (a fluidised bed approach), and so minimise the clogging danger. However, a low packing density may lead to more contaminants by-passing the biofilms altogether. Excess biofilm growth leading to clogging will need to be managed by recirculating the biofilters within the tank."
In this arrangement, Darton says, the oestrogens are removed and degraded within the aeration tank, and do not escape in the water phase or accumulate in the secondary sludge - a feature not offered by end-of-pipe technologies, Darton believes.
There is ongoing research, too, at the University of Ulster. Scientists there have been looking both at developing sensors to detect very small amounts of oestrogen in water supplies and at ways of removing them using photocatalysis. Most of Ireland's drinking water is taken from reservoirs filled with rainwater, which should not contain pollutants such as oestrogens. But many EU countries, including Britain, abstract most drinking water from groundwater sources. A former Ulster researcher, who now works at Queen's University, Belfast, believes photocatalysis is the answer to the problem. Dr Heather Coleman used the photocatalysis system using titanium oxide and ultraviolet light, which appeared to prove itself ten times more effective at removing all oestrogenic pollutants from water than UV alone.
According to Coleman: "Water treatment is the key. It would be easy to integrate photocatalysis as the very last stage in water treatment. It would remove, not just oestrogen, but a wide range of pollutants." The problem, she says, is one of getting people interested: "The government agencies are very complacent. They said they didn't know anything about the problem, so therefore we don't have it."