Turning up the pressure on reuse
Water reuse and protection of water supplies are currently hot topics of discussion. Here, Malcolm Hallsworth of WWT outlines some reuse strategies of Veolia Water's Bruce Durham
Bruce Durham, alternative water resource project manager at Veolia Water, believes that planned reuse of treated wastewater represents an important and necessary element of any strategy to protect water supplies. In an interview with WWT he discussed why he believes reuse is as relevant for the UK as for those regions more usually associated with difficulties in meeting their demands for water. As well as detailing those factors he believes will influence the need for reuse, Durham also outlined the way he believes a cohesive reuse strategy can be arrived at and why he is optimistic things are moving in the right direction.
The discussion began by addressing the factors Durham believes mean planned reuse is already a requirement in the UK, and those which will make it even more vital in the short to medium term. Central to his argument is the fact "the UK can no longer take water for granted". The last two summers have provided an illustration of how climate change is already creating problems in the management of water resources. During 2003 average temperature and quantity of sunshine reached record highs, while rainfall was at a record low. In contrast, summer 2004 was characterised by heavy rainfall events, unusual in their frequency and scale, leading to flash flooding. For a country that relies in many of the most densely populated areas on groundwater for the bulk of its water supplies, both have serious implications. Under drought conditions water availability is restricted because groundwater supplies are not recharged. During periods of flood, contamination of groundwater by surface water can also threaten supply. The unpredictability of future weather patterns represents a largely unquantifiable problem. Diffuse pollution of groundwaters, most notably with nitrates and pesticides from agricultural sources, is also causing increasing difficulties for water companies.
Environmental legislation is another pressure on water supplies. The Urban Waste Water Treatment Directive (UWWTD) requirements are included in the Water Framework Directive (WFD), which states "treated wastewater should be reused whenever appropriate" but there are no quality, best practice or legal definitions of what is appropriate. The WFD prioritises the environment, ecology and biodiversity above the abstraction of drinking water, which has led a number of water companies to suggest a percentage of their groundwater abstraction licences are at risk as a result of the need to protect dry-weather river flows.
Durham speculated the figure could be in the region of 15-20%, which in a country that depends on groundwater for its high-quality water resources, "could have a dramatic impact on water availability". The traditional practice of exporting wastewater away from the city to prevent contamination of potable water supplies does not help the ecological water cycle. The centralised wastewater treatment strategy has resulted in wastewater being piped downhill many miles from major towns to very large WwTWs close to the bottom of the catchment.
This process bypasses the rivers between the town and the WwTW and reduces the water available for the river ecology and groundwater recharge. There is a need for decentralised modern WwTWs that discharge high-quality treated water into local tributary rivers. This could overcome many low flow issues and may even allow for additional groundwater abstraction, in part using re-infiltrated water from these larger river flows. This could be more cost-effective than pumping the treated wastewater back uphill to the city to maintain river ecology, especially if measured by environmental, economic and social benefits as well as the impact of the anthropogenic water cycle. Perhaps compact, quiet and odourless decentralised reuse schemes would be a more attractive solution to the stakeholders, compared to building new regional storage reservoirs in the south-east?AUSTRALIAN PROJECT
Durham illustrates the point about environmental legislation affecting abstraction with reference to a river basin water management strategy implemented in New South Wales, Australia. The project was similar to the WFD in that it sought to maintain the quantity and quality of surface and groundwater bodies, in doing so it reduced the availability of water for abstraction by 20%. "Is that going to happen in Europe? I don't know, but several water companies have said this is a risk", he concludes.
Water utilities in the UK have already observed a reduction of available water as a result of the Habitats Directive.
Urbanisation represents a major challenge to water resource management, in the UK its effects are being most dramatically felt in the south-east. The World's Water Crisis, a UNESCO report, demonstrates that 80% of water stress is a result of population density and 20% is due to global warming. The south-east, the driest part of the country, is already the most densely populated. The region is also experiencing the highest levels of population growth and is forecast to do so for the foreseeable future. Broadly speaking Durham sees water reuse as tackling supply problems in two ways:
Industries that use a lot of steam - power generation for example - do not require a potable water quality for boiler feed, but seek instead very low levels of salts such as sodium and silica. Secondary sewage, treated further by microfiltration and reverse osmosis to achieve a low total dissolved solids (TDS) value, offers a highly suitable alternative supply. Such a system is operated at Anglian Water's Flag Fen WwTW, where sewage is passed through a series of membrane steps before being pumped to Peterborough power station as boiler feed. There are around ten similar power projects worldwide, along with hundreds of potable substitution projects for industry.
Internationally, irrigation is the biggest growth area for planned water reuse, and the WHO is producing guideline quality standards for irrigation applications. This area highlights one of several anomalies, which Durham believes need to be overcome before water reuse becomes more common. Wastewater used for irrigation will have to undergo tertiary treatment despite the fact secondary sewage often has lower bacterial counts than some river waters that are acceptable for irrigation. The problem is largely a matter of perception: "If you ask someone 'do you want to take your water from a river or a sewage works?' they will always go for the river." The key municipal use for water reuse is aquifer recharge. In both Belgium and Spain highly treated wastewater is already used to manage groundwater recharge and later abstracted for indirect potable use. In effect, reusing wastewater to recharge water bodies takes place already, as Durham points out: "The UK is totally dependant on treating wastewater to a high quality for river recharge."
Almost every catchment has an element of wastewater feeding into it eventually, dry-weather flows in some rivers can have a treated wastewater component of up to 80%. This form of reuse has an important sustainability benefit, especially if treated wastewater is restored to the quality at the point of abstraction. Statistics from the United States Environment Protection Agency (USEPA) estimated between 5-8M people receive potable water where the majority of the source is treated wastewater. This is common practice and several large cities in Europe depend on appropriately treated wastewater to supplement 70% of the freshwater through surface water or groundwater, which are then carefully treated for potable use. The mass balance of water in/water out of any major city will show a significant percentage of water "going round in circles". That this happens, but awareness and acknowledgement of the process is limited, Durham sees as a stumbling block to the successful implementation of large-scale indirect reuse of treated wastewater. He believes people need to be familiar with the 'real' water cycle, and its complexities, as opposed to the more commonly accepted natural water cycle - which fails to take account of human intervention through abstraction and wastewater discharge. More open acknowledgement of the real water cycle will help mitigate against the public resistance problems some reuse projects have come up against, Durham believes: "Water reuse is a very sensitive issue, it has to be understood." Another essential step in promoting water reuse is making people aware of what it is and the need for it. Water reuse is one of the fastest growing water applications internationally.
There is a vast amount of experience in regions around the world that have recognized the real benefits of reuse. The growth in the volume of water reuse internationally ranges from 25-60%/pa in the countries that understand the benefits. This average growth per annum has been maintained for periods between four and 11 years. This proves reuse is competitive with traditional options. These solutions are also more robust than water efficiency measures that try to persuade customers to reduce their demand. In the UK this means fostering a greater understanding of the pressures on the security of supply - climate change, environmental legislation, pollution of water sources and increased urbanisation. The other side of this coin is also promoting the benefits of reuse - securing water supplies, protecting the size and quality of water bodies and facilitating social and economic progress.
The compartmentalisation of regulators and institutions provides a further obstacle along the road to reuse, it leads to a lack of joined-up thinking with almost nobody looking at the water cycle as a whole. Durham illustrates the point with reference to the fact most governments, regulators and water companies place a divide between their potable and wastewater activities. This means reuse, which straddles both fields, does not readily fit in - making it a very difficult item to get on to the agenda.
Elaborating on the 'blindspot' into which reuse can end up, he stated: "The problem is it fits everywhere and fits nowhere. Because it's not drinking water or wastewater, it's difficult to manage. If you are selling reuse technology, who do you get to the meeting? Turning wastewater into drinking water means you need people from both departments. Unless there is a designated reuse department, it is very difficult to get the people together." Promotion of the real water cycle, explaining the requirement for and benefits of reuse, the need for inter-disciplinary dialogue and a requirement to discuss the options for tackling water scarcity all feed into the central plank of Durham's strategy for promoting water reuse - all encompassing stakeholder dialogue.
There is no point, he suggests, in saying a reuse scheme is needed, building a plant then telling people what you have done - it will not work. You have to get all the people who have an interest or will be affected involved from the start. The approach taken in the state of Western Australia exemplifies the type of approach he has in mind.
The state is around ten times the size of the UK, is home to 1.5M people, had been suffering drought for eight years and experienced a 3% increase in population. To tackle the problem the state government:
Based on the Western Australian experience Durham advocates the formation of a stakeholder group of "respected, knowledgeable individuals", which embraces all areas of interest. This group should be able, he hopes, to divine the most appropriate solution to the UK's water scarcity problems and promote it to the public and government.
Despite the challenges, a number of factors make Bruce Durham optimistic about the future of planned wastewater reuse in the UK. Discussions are already under way about the formation of the type of stakeholder group he is advocating, funding is being sought. One stakeholder group that is being discussed is a Water Saving Trust.
UKWIR is completing a study to define a protocol for developing reuse criteria, the work is currently being reviewed by the project steering group and publication is likely before Christmas. The work should provide a framework for reuse. Another steering group, on behalf of Defra and the Inland Revenue, is investigating the wisdom of tax incentives to encourage industry to reuse wastewater.
Critically, in Durham's view, reuse has made its way onto the agenda of EU policy makers, thanks in some degree to work by Eureau, the umbrella group representing Europe's water and wastewater industry. The Eureau reuse group, Durham is its technical secretary, has been advised to convince the EU's water directors - state-level water policy representatives - of their argument. At recent meetings the EU executives have responded positively and water reuse has been included as one of the alternative solutions in combating the effects of European droughts and flooding.
There has been a request to clarify the meaning of reuse and the status of water reuse in Europe. This is an opportunity to clarify the meaning in the UWWTD statement "treated wastewater should be reused whenever appropriate" through agreed definition of applications, quality guidelines, best practice examples and by removing the institutional barriers that stop worthwhile solutions being implemented.reuse in CHINA
The Chinese are taking reuse very seriously. A presentation in September at the IWA Global Water Conference showed that northern China is the most water stressed region with water availability of 990m3/inh.yr. (this compares with 265m3/inh.yr in London).
The Chinese government has reviewed and adopted best practice on water reuse from international experience with the following results: