Creating a Sustainable Future for Desalination
Reverse osmosis (RO) has gained prominence as a means to meet the region’s power and water needs with the added advantage of being both less energy intensive and costly. Yet just as with energy, diversification of technologies will play an important role in the sustainable transition of the water industry
It is no secret that we live in a water scarce region. Confronted by limited freshwater resources and growing demand – increasing more than 60 percent by 2025, desalination ensures access to clean water across the Gulf.
Governments and companies are prioritizing water sustainability and overall efficiency to meet this rapidly increasing demand. As a result, seawater desalination capacity of GCC countries is expected to grow by at least 37% in the next five years with investments of up to as much as $100 billion by 2020, according to MENA Desalination Market.
Thermal techniques such as multi-stage flash (MSF) and multiple effect distillation (MED), both of which distill seawater using heat, have been the primary method for producing desalinated water in the region since the 1960s and have maintained their competitive edge for decades. However, reverse osmosis (RO) – a process that forces seawater through semi-permeable membranes to remove salt – has overtaken these methods to become the most cost-effective and energy-efficient solution for producing water in the Gulf.
Today, producing 1 million imperial gallons per day (MIGD) of water by RO requires approximately 0.95 kWh of electricity or approximately 1.2 to 1.5 kWh of electricity for a greenfield MSF project. That means RO plants use nearly half the amount of electricity as MSF plants.
Although RO technology is maturing, there are three areas to explore as the region moves towards its wholesale adoption:
- Water quality
- Knowledge transfer
Water quality as a measure of success
Traditional thermal distillation methods such as MSF and MED yield the highest water quality among available desalination techniques. MSF and MED conductivity are around 5 to 40 micro Siemens per centimeter (μS/cm), within the range of good quality drinking water. Water from RO plants can reach more than 100 μS/cm, which means thermal methods of distillation produce higher quality output.
Thermal techniques like MSF can help bridge these gaps as the region pursues greater investment in RO technologies. Blending MSF-produced water with RO-produced water would reduce the conductivity of the water to make it higher quality. Similarly, blending reduces cost by introducing more energy-efficient – and less costly – water production from RO and equalizing the quality by blending it with high-quality water from MSF.
Investing in training and knowledge transfer
The introduction of MSF to the Gulf presented an invaluable opportunity to operators at desalination plants to gain experience from experts on the thermal process. As a result, engineers developed expertise without relying on the original equipment manufacturer (OEM). Today, we have reached a point where expertise on thermal processes is both broad and deep – engineers and others understand the system, are able to modify, challenge and ultimately make it more efficient.
Unlike MSF, RO desalination processes require limited maintenance and are highly automated, requiring minimal operator attention or intervention. In addition, contractual obligations typical of RO plants require development and operation to stay with the OEM. However, one potential area of knowledge development is pretreatment requirements. By more accurately characterizing seawater for pretreatment, engineers can eliminate or minimize fouling of RO membranes. Fouling can occur when salt or other compounds deposit on the membrane surface, restricting water flow and ultimately damaging the filters. In addition, research on pretreatment technologies could also achieve energy savings.
Offering capacity-building opportunities would not only contribute to developing indigenous technical capabilities but would also create an environment to test new ideas.
Ensuring sustainable growth
Large-scale RO projects currently in development across the region illustrate just how committed Gulf countries are towards increasing capacity while transforming and modernizing their water industries.
Most recently, Saudi Arabia’s Shuqaiq 3 and the UAE’s Taweelah RO independent water project are both touted to become two of the largest RO plants globally with capacities of 228 MIGD and 200 MIGD, respectively.
Ensuring sustainable scalability without compromising quality and efficiency requires significant investment, particularly in membrane technology.
The largest cost component of desalination is the cost of construction, which makes up more than 75%, for thermal plants and about 60% for RO plants. The costs are even higher when pursuing full decommissioning of thermal plants and replacing them with new RO projects.
MSF can provide a sizeable cost-saving opportunity on infrastructure spending, particularly as Gulf countries transition from conventional plants. Developers can re-purpose infrastructure from older MSF plants, including seawater pumps, brine discharge and water intake all the way down to breakers, switchgears, gates and offices.
Providing water to water-scare communities is energy intensive – desalination accounts for 10 to 25% of the energy consumption in the GCC. Decoupling power generation from water production is a solution that can address energy and cost concerns. RO plants allow for a decoupling, which means reducing dependence on burning gas to produce water, especially in the winter months. The future seems headed in that direction. However, RO will not replace traditional thermal techniques overnight. The transformation will be gradual, and during that time, MSF, in terms of high-quality water output and common infrastructure, can ensure the transition to an RO-dominated landscape is successful.
Mohammed Karam is Head of Projects and Operations, Abu Dhabi National Energy Company (TAQA)