What is Desalination?: Solving for Municipal Water Scarcity
Fresh water is becoming increasingly scarce around the globe. The U.S. population has doubled over the past 50 years, with at least 40 states anticipating water shortages by 2024. In North America, moderate to exceptional drought affects 26.3 percent of the area and 34 percent of the population, according to the National Oceanic and Atmospheric Administration (NOAA).
According to the United Nations-Water, water use has been growing globally at more than twice the rate of population increases in the last century. Moreover, an increasing number of regions are reaching the limit at which water can be delivered sustainably.
Given these dire circumstances, state and municipal governments are increasingly considering sea desalination to alleviate freshwater scarcity. Desalination is best done in tandem with other measures, such as conservation, rainwater capture and stormwater management. However, desalination—particularly using a technology known as reverse osmosis (more about that below)—can be part of the solution and is, in fact, an increasingly popular choice.
SUEZ builds, equips and operates made-to-measure desalination facilities. The 255 desalination plants that we have built and commissioned all over the world produce more than 4.2 million cubic meters of fresh water per day, supplying 10 million inhabitants in Australia, Spain, Saudi Arabia and elsewhere.
Education: Too many people in industrialized countries don’t realize how much water they use, the true cost of having access to that water, and how much treated water is wasted. Education is needed not only to improve individual behavior but to have an informed citizenry that can influence public policy.
Improved water infrastructure: Most water leaks are hard to spot—unless you know where and how to look. Undetected residential leaks are responsible for the loss of more than 1 trillion gallons of treated drinking water each year, according to the U.S. Environmental Protection Agency (EPA).
That’s why SUEZ has been a leader in the development and application of Advanced Metering Infrastructure (AMI) for more than 25 years and has the largest deployment of AMI meters—more than 255,000 in the country. Using AMI, SUEZ has saved cities in New York, New Jersey, Pennsylvania, Idaho, Michigan and Connecticut, hundreds of millions of gallons of water. AMI allows meters to be read electronically and in real-time. But AMI also serves as an aggressive leak detection tool that allows leaks to be detected in homes or businesses quickly and helps to protect budgets.
Water reuse: SUEZ has been helping communities on both U.S. coasts recycle wastewater for non-potable uses, including irrigation, industrial, and other uses. In doing so, we’ve helped conserve the drinking water supplies needed by those communities. On the West Coast, SUEZ operates and manages the Edward C. Little Water Recycling Facility in Los Angeles County. The facility recycles some 40 million gallons of water per day. On the East Coast, SUEZ partnered with Nassau County, NY, to build a water recycling system that saves up to 300 million gallons of groundwater annually. The recycling system at the Cedar Creek Water Pollution Control Plant reuses treated wastewater for plant operations such as cooling generators and washing tanks and equipment.
Conservation: Water conservation is the single most important step anyone can take. There are many ways to conserve water, as outlined in the EPA’s WaterSense program. Through the end of 2020, WaterSense has helped Americans save a cumulative 5.3 trillion gallons of water and more than $108 billion in water and energy bills.
Desalination: In some areas of the world, including the U.S. Southeast, conservation, water reuse, and improved water infrastructure are simply not enough. Desalination—performed through energy efficient means—is another part of the solution.
In some regions, conservation and water reuse—while essential—are not enough. That’s when some municipalities turn to seawater desalination, as well. In Barcelona, for example, SUEZ was entrusted with the design and the construction of Barcelona’s reverse osmosis desalination plant, the largest in Europe. We were therefore able to manage the water supply for urban areas while also:
- reducing withdrawals from drinking water supplies
- limiting the use of surface water
- respecting biodiversity and the marine ecosystem
SUEZ is renowned for its leading-edge skills in seawater and brackish water desalination technologies and in the reuse of treated wastewater.
In Melbourne, Australia, a SUEZ-built plant can produce and supply 450,000 cubic meters (expandable to 600,000 cubic meters) of drinking water to the city of Melbourne per day. The Victorian Desalination Plant was announced as a project during the Millennium Drought when water storage levels were critically low (16.5 percent in the city’s largest reservoir) and can now deliver up to 150 billion liters of high-quality drinking water a year. But because it can only meet part of Melbourne’s annual water demand, it needs to be used early and often to build a buffer in the city’s storages, by regularly topping up its reservoirs, and taking pressure off its reservoirs during drier periods and droughts.
SUEZ employs reverse osmosis in producing desalinate water. In general, three key steps are used in the process: pre-treatment, the desalination process itself and post-treatment. Details of these steps vary from plant to plant, depending on the salinity of the source water, presence of organic material and pollutants, and the desired use for the water (e.g., industrial use, aquifer recharging, or drinking). SUEZ solutions for this first step include Seadaf ™, a compact clarification solution adapted to water subject to occasional peaks of suspended solids and algal bloom; Seaclean™, a pretreatment technology that uses dual-media filtration (anthracite and sand) to improve the performance of the reverse osmosis; and Ultramarine™ Smartrack™, a universal rack for interchangeable ultrafiltration modules.
The second key step is the reverse osmosis. Reverse Osmosis (RO) is a desalination process that uses membrane technology. Filtered seawater passes through two stages of reverse osmosis, where it is pushed through membranes under high pressure to separate salt and water molecules. In the end, pure water is left on one side, and seawater concentrate (brine) on the other. SUEZ offers a wide array of media, including ultrafiltration (UF) and nanofiltration (NF).
During the post-treatment, water is treated depending on its intended use. If it is to be used for drinking water, the process often includes a remineralization step, with the injection of CO2 and water lime, and fluorination. The water is then given a final disinfection, using using sodium hypochlorite.
Different regions require different solutions; SUEZ can accommodate them all.
Shallow Surface Seawater
Most desalination projects use seawater just off the coast and in relatively shallow waters, but at least 30 feet below the surface. These projects may have a lower initial capital cost but may require more maintenance because of effects on the intake pipe and filter by tidal currents, wind, pollution and seasonal changes.
Deep water intakes at 600 feet or more below the surface provide cooler water and more stability. But they can also incur larger start-up costs.
Brackish River Water
The salinity recorded in the various oceans and seas throughout the world is the product of an equilibrium achieved between evaporation, rainfall and the input from rivers (low salinity) on the one hand, and water exchanges with the other seas or oceans with which these different seas or oceans are connected on the other hand. Therefore, this salinity is extremely variable. Desalination processes must account for this shift in salinity, particularly in brackish river water, where the salinity—as well as the organic matter and turbidity, or cloudiness—changes often.
Beach Well Seawater
This method involves withdrawing seawater from below the level of the seabed. The seabed acts as a slow sand filter and blocks the intrusion of marine creatures. However, local geography where beach intake sites can be established is often limited by competing uses for the land.
Understanding their stakes, anticipating their needs, innovating and controlling costs, SUEZ offers treatment solutions which match their objectives and address the challenges that water represents for them.
Working with local authorities, SUEZ can provide the population with desalinated drinking water of guaranteed hygienic quality, in accordance with local health, safety and environmental standards. For example, in Al Dur, Bahrain, SUEZ built the largest desalination plant in the Persian Gulf, capable of producing 218,000 cubic meters of drinking water per day. In order to maintain a low clogging index and preserve the reverse osmosis membranes, the pre-treatment process has been designed to manage the high concentration of organic matter and significant build-up of algae in the waters of the Persian Gulf.
The use of desalinated water for irrigation is relatively novel, though it has been used with success in Spain, in the Middle East, and in Australia. Water reuse, or the recycling of wastewater, is often a more obvious choice for municipal water systems.
Industry can increase their competitiveness thanks to reliable process water and effective purification of their effluent, while reducing environmental impact and continuously complying with increasingly stringent standards. For example, the reverse osmosis seawater desalination plant at Minera Escondida (Chile’s second biggest copper producer/exporter) produces 45,000 cubic meters a day of process water for its mine in the Antofagasta region at an altitude of 2,800 meters. Desalination enables the mine’s production capacity to be increased to meet the sector’s future development and at the same time saves using surface water in this desert area. Pre-treatment is carried out in various stages integrating the Seadaf TM rapid flotation process which can deal with the chronic “red tide” phenomenon (proliferation of red microalgae).
Desalination is one of several solutions to water scarcity-- it is not a silver bullet, and it’s not always the right solution for every region and every community. However, it’s a good solution that should be included the mix for many regions as climate change worsens and demand for water, particularly drinking water increases.
Contact a representative to learn more about water desalination solutions SUEZ North America can provide your municipality.