Incessant pressure on the Gulf Cooperation Council (GCC) region's water resources means reuse is likely to grow. Black & Veatch's John Abi-Hanna considers five steps central to a safe reuse programme.
Despite the water supply challenges facing many arid and sometimes not so arid regions, use of recycled water, or water reuse, remains low. Wastewater reuse stands at only 2.41% of all water withdrawals globally according to the Merrill Lynch and Bank of America 2012 report A Blue Revolution. Data from the Abu Dhabi Environment Agency indicates Gulf states follow this trend: 72% of water used in the UAE comes from groundwater, 21% comes from desalination and only seven per cent is reused water(1).
A series of workshops addressing barriers to reuse - for which Black & Veatch won Environmental Business Journal's 2010 Industry Leadership Award - found reasons for low levels of water reuse are complex. Chief among them, however, is reused water's association with wastewater, i.e. sewage and health issues associated with sewage.
This view is supported by other sources. In the New York Times Carol Nemeroff, Professor of Social and Behavioural Sciences at the University of Southern Maine, USA, observed that the notion of treated sewage "hooks into the intuitive concept of contagion." To overcome this, a city must '"unhook the current water from its history." said Nemeroff (2).
Despite the challenges, some cities and regions are successfully 'unhooking water from its history,' and integrating water reuse into balanced supply portfolios. Among our clients we have seen that the successful strategies have often been those which combine messages about reused water with messages promoting the overall value of water; in Western Australia and Singapore for example.
Water demand in the Gulf states is high and rising, putting increased pressure on limited resources. On a per capita basis, for example, Saudi Arabia and the UAE consume 91% and 83% more water than the global average; and about six times more water than the UK(3). This is driven in part by some of the highest domestic consumption in the world. Abu Dhabi consumes 550 litres of water per person per day, two to three times the world average of 180-200 litres(4). Industrial use is also significant, the World Energy Council estimates an average of 40 barrels of water are needed for the production of one barrel of oil. Agriculture is the region's largest user.
Against this backdrop the significance of water reuse in meeting the region's demand/supply balance is likely to grow. While approaches to reuse can be quite different - depending on factors such as the end-uses and regulatory regime - there are some common steps which can help ensure the safety and acceptance of a reuse programme.
STEP 1: Understand the programme
This may seem obvious, but developing a full understanding, from the outset, of the application(s) for which the reused water will be used is central to ensuring the programme's long-term success. The options include direct and indirect potable use, dual domestic use (greywater) and industrial use. Each of these will require very different approaches in terms of treatment - industrial applications run from washwater through to high-purity process water for example - supply network and system management. The successful outcome of the subsequent steps all stem from achieving clarity of purpose for the programme.
STEP 2: Understand the source water
Different wastewater sources will require different levels of treatment. The type of treatment required depends upon how the treated water will be used. If the source is domestic wastewater it will be necessary to understand the type and nature of pharmaceutical contaminants, for instance. This is in addition to investigating pathogens and viruses.
If the source wastewater has an industrial component it is vital to know the types of industries discharging into the wastewater stream. This will help inform more detailed investigations into the actual nature of the wastewater.
These are required because common metrics alone - such as chemical oxygen demand (COD), solids and volume - provide insufficient information about the make-up of the wastewater stream to ensure safe reuse. COD does not identify contaminants.
Similarly it is important to understand if the sewerage system carrying the wastewater stream is dual usage, and therefore likely to carry surface runoff which can include hydrocarbons for instance. Although traditional wastewater treatment practices and processes are good at removing solids, a multi-barrier approach may be required to remove the type of contaminants outlined above.
STEP 3: Understand what treatment is required
The type of treatment will be governed by the standard the water needs to reach to ensure reuse is safe. Standards differ around the world. For example, while Australia and the USA-grade treatment standards for different types of use, the UK does not have a standard for nonpotable use.
Given the sensitivities around reuse, however, consideration may also be given to additional treatment steps which go beyond the technical requirements.
Such steps may be helpful in building the public health consensus vital to a successful reuse programme. Such multi-barrier approaches may include membrane bioreactors or reverse osmosis with advanced oxidation.
When considering safety and suitability of treatment options it is essential to take into account the training and capabilities of the treatment plant's operators. Multi-barrier systems are advanced chemical and biological processes and their safe operation is dependent upon the availability of suitably qualified and trained staff.
Also significant is having the right policies and procedures to ensure the plant's safe operation in the long-term. These procedures are vital in giving the public confidence that the appropriate safeguards are in place. The operations staff need to have sufficient technical ability to recognise when there is a problem, they also need to be prepared and capable to fully implement the necessary remedial strategies.
STEP 4: Understand how to distribute the treated water
The application for which the water will be used has the greatest influence upon the distribution network requirements. As a result distribution needs to be viewed as an integral phase of reuse programme planning. If the reused water is for potable applications, connection to an existing network is possible. In this instance compatibility with the existing supply needs to be addressed. This means considering things such as water hardness and residual disinfection within the network. If a non-chloraminated supply is mixing with other water, for example, the risk of trihalomethanes forming needs to be assessed and managed.
When the reused water is destined for non-potable applications a separate distribution network is necessary. The cost implications of this can make treating to non-potable standards unattractive even if the water will be used for non-potable applications. To provide safe operation and maintenance it is very important that a new non-potable network is readily distinguishable from existing or future potable networks. Making the nonpotable network identifiable requires not just a physically distinguishable system but also good, easy-to-access records. To deliver long-term safety, the records need to be accompanied by policies and procedures that support network integrity.
In essence, the non-potable system means a new asset class is being introduced into the asset base and, as a result, procedures need to be in place to ensure it is properly managed. For instance, if the non-potable network is physically different from existing networks these procedures need to ensure that those responsible for maintenance have the correct type and quantities of replacement fittings.
STEP 5: Understand how the water will be used
This final step is in some ways very close to the first, but also subtly different. Understanding the programme means knowing what application the reused water is for. Understanding how the water will be used refers to preparing in detail for what will happen to the water when it reaches the point of use. This is often the point at which the reuse supply ceases to be under the control of the water utility.
Where the supply has been treated to non-potable standards, safety dictates that taps and other end-user fittings are clearly labelled to indicate the water is not for consumption. As well as not for drinking it needs to be clear that the supply is unsuitable for food preparation and other uses which may lead to ingestion. For example people often touch water features and fountains, and children may play in them.
Policies, procedures and documentation also need to be prepared to ensure a non-potable system remains safe if the building in which it operates changes ownership. New owners, unfamiliar with a non-potable water supply need to understand properly how to safely use the water and how to safely maintain the system.
Where a non-potable system is in operation, re-plumbing and building work can represent a management control exercise. For industrial and commercial premises this is less of an issue because facilities managers can be trained in a non-potable system's use. In a domestic setting the risk is greater because the knowledge transfer is not likely to be as comprehensive.
Water reuse has a viable role in an integrated water resource portfolio.
The above steps represent a high-level, and not exhaustive, outline of some key considerations which will help ensure reused supplies are safe and, importantly, engender public confidence.
(The author is Black & Veatch Water's Business Development Director for the Gulf Co-operation Council (GCC) region)
References
1. The Water Challenge in the UAE, Dubai School of Government, 2011
2. New York Times, 9 February, 2012
3. Booz & Company, 2011
4. Mohamed Daoud, UAE Environment Agency, (Cited Reuters 21 June, 2010).
© Power & Water Middle East 2013
