Parched City (29 page)

The supply’s next treatment stage is storage, utilising the precious time factor that Dr Houston advocated so vociferously a century ago. Principles governing storage in water treatment have little altered since Dr Houston’s days, according to Colbourne: ‘It’s a completely natural process and it uses sunlight and temperature and about ninety per cent of all purification of water supply happens just standing it in those reservoirs.’ This is certainly a revelation. Steve White adds sagely that ‘storage is about providing time’. Whilst potentially pathogenic bacteria are starved of sustenance, particles of organic and inorganic solids also drift to the bottom of the reservoir. Most of them, obligingly, stay there. Storage’s power of bactericide also explains why groundwater requires less treatment, given its natural incubation period (groundwater can also become more intensely polluted because of the difficulty of diluting it).

Because Thames Water inherited most of Greater London’s storage infrastructure accrued during the nineteenth and twentieth centuries with privatisation, the natural water treatment benefits of this method can be employed on a London
scale. Though reservoir capacity is critical to water quality, it is equally critical to managing the quantity of water that London consumes. Professor Colbourne believes that the land purchased by private water companies during the industry’s expansion in the late eighteenth and early nineteenth centuries has played a vital role in preventing London from a water crisis: ‘They actually bought sufficient land in the area where most of the abstraction takes place from the upper Thames, you know around Hampton, Heathrow Airport and also to some extent up on the River Lee. They bought enough land to be able to build works with, what some people might say in this modern day was over capacity, as a result of which…London has survived.’ Some of the land that used to house water treatment infrastructure has become redundant, as technologies have been streamlined. This provides a lucrative bonus for Thames Water shareholders in residential property development (such as the New River Village). But the vast reservoirs remain in situ. For instance, Queen Mary reservoir in west London has a capacity of 30,360 million litres. It seems extraordinary to consider the waste of any of this water, post-purification, being flushed down the toilet.

A cycle around the exterior of one of Thames Water’s main water treatment works, in East London, helps to visualise the scale of a reservoir. Water held in the Walthamstow Reservoirs (which looks more like a lake) awaits transfer to Coppermills Advanced Water Treatment Works. The reservoirs are something of a suburban wildlife paradise. Anglers and birdwatchers can revel in these bio-diverse sanctuaries for an affordable daily or annual fee: impressive fishing catches from the reservoirs can be seen on angling websites.
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On the road bisecting the reservoirs from the treatment works entrance, one side borders a wilderness-like scene behind a high metal fence. Birds set off on flights from an island in the centre of the reservoir and water gently lapping against its edge provides a soothing counterpoint to ambient urban noises. Across the road, behind another high fence, a more rational industrial scene unfolds.
The Coppermills Advanced Water Treatment Works is not the kind of place you would stumble across, though some residents on Coppermill Lane have good views over the slow-sand filter beds with Canary Wharf’s skyscrapers looming in the background. In a recent book entitled
Edgelands
, its authors are preoccupied with the significance of the land morphed between the city and the countryside, where places such as sewage treatments works are located: ‘…they toil anonymously in the edgelands, never to be looked at, hidden away from business and residential areas, unvisited.’
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Certainly, sewage works have good reason to be more distant, from an olfactory perspective at least, than drinking water treatment works, but there is no denying that Coppermills is obscured from the daily views of most East Londoners who rely on its product to survive.

Coppermills Advanced Water Treatment Works, Walthamstow, London, 2012. Author’s own photograph.

A slightly unnerving statutory health and safety sign posted
on the fence warns locals what to do in the event of a major chemical accident involving chlorine, sulphur dioxide, ammonia, liquid oxygen or fuel oil: ‘Go indoors, stay indoors and seal all external ventilation until emergency services announcements are relayed on the radio.’
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This gives more of an idea why the water industry might want to keep a low profile.

Behind the sign, the next stage of water’s journey towards wholesome is on display. Vast field-like rectangular filter beds are filled with ‘crops’ of water. The development of slow-sand filtration during the nineteenth-century radically improved the quality of drinking water, however those innovators were not aware of the full extent of the microbiological good they were performing in the process (until the Franklands research proved it, as we learned in chapter four). During slow-sand filtration, water percolates through a layer of fine sand, which is supported by a layer of gravel. Sand filtration is highly effective for ridding water of any unwanted fragments of iron, rust or manganese; however, as a biologist by training, Steve White is also enthused by the removal of organic material such as algae, bacteria and parasites. As he puts it, the slow-sand filter ‘reduces substances that are amenable to biological degradation’. Not so amenable, are some synthetic chemicals.

Chemical Challenges

When Steve White started working at the newborn Thames Water in 1989, the toxic chemical controversy was at its height. The problem had to be tackled by the corporation in order to comply with the law that adopted the European Drinking Water Directive as part of the terms of the industry’s privatisation. In terms of nitrates, the distance of London’s abstraction of river water from farmland relieved its levels of fertiliser by-products (in comparison to East Anglia for instance), but the slower process of nitrate seepage into groundwater sources was a slower-burning problem. Local to London, the large-scale
spraying of the chemicals Atrazine and Simazine to suppress weeds on the edges of roads and railway lines in and around the city introduced a toxic substance into the aquatic environment. Addressing these chemical presences caused slow-sand filtration technology to be ‘tweaked around’, to use Steve White’s modest description of what was, in reality, many years of engineering and scientific research in the early-to-mid 1990s. The case is a reminder of how there is no quick fix to complex water pollution problems, which is why pollution needs to be prevented by industry and the Environment Agency and why the ‘polluter pays’ maxim should be strictly enforced.

During those years what is now known in the industry as ‘advanced water treatment’ evolved. This involves a modular system of processes and technologies that can be targeted at specific water pollution culprits. For instance, if required, ozone dosing can take place before water enters the slow-sand filters. Steve White explains how this ‘highly reactive form of oxygen gas breaks organic molecules down into material that’s more readily digestible by microorganisms’ and therefore builds up a ‘biological community that adds to the natural cleaning process’ within the filter. Filtration’s other change is more materially solid. It employs a substance known as granular activated carbon (GAC), lodged between sand and gravel. Steve White describes it as ‘a slow-sand, or a GAC, sandwich’ and he clearly enjoys sharing the industry slang. GAC’s principle function is the removal of pesticides but the treatment process is also capable of conquering other chemicals. ‘It’s a good thing for water treatment’, White emphatically states about GAC. Londoners have benefitted from advanced water treatment since trials were completed in the late 90s. This technological evolution shows how polluters and pollutants have demanded costly new technologies and research programmes to be mounted in order to meet European drinking water standards, now U.K. law. Steve White was also personally active in the campaign that successfully
banned the herbicides, or weed-killers, Atrazine and Simazine.

Chemical Concerns

Negotiating strategies for the prevention of toxins entering water catchments is still a facet of Steve White’s work, in partnership with the Environment Agency (the rebranded National Rivers Agency) in its capacity as an environmental police force. He claims that he is ‘less reactionary’ than he was earlier in his career, meaning that he now considers the perspective of farmers more sympathetically in the agrichemicals-versus-water-pollution equation. It is important to note here that there is a distinction between synthetic and natural chemicals in pesticides. Choosing the latter is one of the bedrocks of the modern organic farming movement, but some scientists argue that any chemical, naturally occurring or not, can be toxic in high concentrations and that synthetic pesticides in safe quantities are no more carcinogenic than their naturally occurring counterparts.
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No doubt that debate about synthetic chemicals and an evidence base will continue to grow throughout the twenty-first century.

Under current legislation, the permitted concentration of an individual pesticide in a sample of tap water is 0.1 microgrammes per litre, or one part in ten billion.
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Some people would understandably have concerns about any trace of
any
pesticide entering their bodies, on the basis of fears that the cumulative effects of gradually absorbing multiple toxins in our environment can eventually cause cancers to develop (known as ’environmental toxicology’ in academia). Proving this is, of course, very difficult given our exposure to so many substances involuntarily and as lifestyle choices, not to mention the lottery of genetic predisposition and the rise of epigenetics. The World Health Organisation’s 2001
Guidelines for Drinking-Water Quality
confronts this valid public health concern. In fact, the topic appears prominently on page one of the current 564-page edition
of the publication, suggesting the perceived importance of this issue: ‘Safe drinking water, as defined by the Guidelines, does not represent any significant risk to health over a lifetime of consumption, including different sensitivities that may occur between life stages.’
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Its authors’ certainty is reassuring. The same definition of safety is enshrined in the 1998 EU Drinking Water Directive on which the U.K.’s current drinking water quality law is based. It states that the combined total of pesticide residues in a sample of water must not exceed 0.50 microgrammes per litre, but this measurement only applies from 25
^th
December 2013.
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Reassuringly, Thames Water’s website states that this is already the Maximum Admissible Concentration (MAC) of combined pesticide concentration that it observes.
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Of course, a substance can only be ruled out if it is on the industry’s search radar in the first instance. Pesticide compounds should all be detectable as their use in the European Union has to be licensed but there are measures in place to search for known illegal, or unknown, chemicals too.

In 2007 Steve White thought his days of worrying about pesticides were over. Another water company detected traces of a chemical compound called Metaldehyde.
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The ingredient contained in some slug pellets was previously not thought to be capable of entering water sources. Metaldehyde’s ‘discovery’ precipitated the creation of a national Metaldehyde Stewardship Group.
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This group set up a ‘Get Pelletwise!’ information website to encourage and educate farmers about protecting water when using the product.
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Thames Water recorded eight failures for the pesticide in 2009, out of more than forty thousand tests.
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These breaches were minor and of no immediate concern for human health, but they had to be resolved because they transgressed the permitted MAC for a single pesticide. Thames Water recorded no Metaldehyde failures, from water produced in its own works, in 2010 or in 2011. The current emphasis on tackling the latest pesticide challenge is preventative, as the synthetic
chemical compound stubbornly eludes all treatment processes apart from reverse osmosis.

Since 2001, the Voluntary Initiative — a national coalition of agricultural organisations — has been working to encourage pesticide education and offers technical advice on how to reduce the negative impact from pesticides on the environment, as an alternative to the introduction of a pesticide tax. The Voluntary Initiative’s foci are protecting biodiversity and water, whilst continuing to permit agricultural professionals to use approved pesticide products. Its metaldehyde leaflet offers guidelines on the quantity of metaldehyde to use per hectare of land, along with instructions not to apply the substance within ‘6 metres of a watercourse’ or when ‘heavy rain is forecast’.
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For the environ-mentally-conscious farmers this might work well, but what about when they are under pressure to protect their crops from a slug invasion? It would be extremely difficult, if not impossible, for metaldehyde detected in a water catchment to be traced to a specific farm or farm worker. The Royal Society for the Protection of Birds, which is represented on the Voluntary Initiative’s steering group, and its supporters advocate education for pesticide users but argue that regulations to enforce the reduction of the most harmful pesticides are still needed.
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