Brackish water, a mix of fresh water and saltwater, can be found in coastal regions and aquifers across the world. While its high salinity makes it unsuitable for drinking or crop irrigation, it is a largely undeveloped resource that could relieve the water scarcity crisis.
Brackish water contains higher concentrations of dissolved salts than fresh water but lower concentrations than seawater. Its desalination, powered by reverse osmosis, offers a promising and efficient solution for water shortages as a sustainable alternative supply of fresh water to communities.
Understanding Brackish Water
The salinity level of brackish water ranges from 1,000 to 10,000 parts per million (ppm). Fresh water has salinity levels lower than 1,000 ppm, and saltwater has higher than 10,000 ppm. Seawater typically has dissolved salt levels exceeding 35,000 ppm.
In coastal regions, brackish water may be found in estuaries, mangrove thickets, wetlands, and salt marshes, where fresh water from rivers mixes with seawater. Brackish water can also be found in coastal and inland aquifers in many regions of the world, including the United States.
In Texas, which has an estimated 2.7 billion acre-feet of brackish groundwater stored in aquifers, this undeveloped reserve could build resilience to drought. Innovation in desalination technology is making it more feasible to tap into this resource.
The Role of Reverse Osmosis
Reverse osmosis (RO) is a membrane-based desalination technology that is used to remove salts, minerals, and other impurities from water. During this process, saline or brackish water is forced under pressure through a semipermeable membrane. Water molecules move through tiny pores, about 0.0001 to 0.001 microns, that trap and reject dissolved salts and minerals. The result is purified water and a concentrated brine containing the rejected salts and minerals.
Reverse osmosis offers several advantages over other desalination methods. RO is more energy efficient than thermal desalination because it uses pressure rather than heat to remove salt. This significantly reduces energy consumption and its costs, making it less expensive and more environmentally friendly, especially when powered by renewable energy. RO is extremely versatile and can be used to remove impurities from seawater, brackish water, and even wastewater. Because brackish water contains less salt than seawater, the desalination process is more efficient and less costly than seawater desalination.
RO membranes are effective at removing not only salts but also bacteria, viruses, heavy metals, and organic contaminants, including emerging contaminants. It produces high-quality drinking water that often exceeds regulatory standards. Membrane-based desalination systems also can be easily scaled. This flexibility makes them suitable for all sizes of desalination projects and offers an attractive and reliable option for regions with water quality challenges.
Technological Advancements
Recent upgrades in RO desalination technology have significantly improved its performance, making brackish water desalination more energy-efficient, cost-effective, and viable as an alternative water supply. These innovations in RO membranes and pretreatment techniques reduce membrane fouling, and using energy-efficient pumps and energy recovery systems have driven these improvements.
Like many areas in Texas, the city of Alice struggled to meet a growing demand for water because its surface water supply was becoming increasingly unreliable due to ongoing drought. Brackish water aquifers offered a viable alternative supply. The city turned to Seven Seas Water Group, a global water treatment provider known for its water treatment as a service approach, to create a self-sufficient and drought-proof solution for their water security.
The initial phase of the project involved the completion of source wells and pipelines, which were financed with government funding. The city entered into a public-private partnership with Seven Seas for the construction of a brackish water RO desalination plant with an initial capacity of 3 million gallons per day, with the option to expand should demand increase. Seven Seas operates the plant on the city's behalf for the 15-year term of the contract, after which ownership will be transferred to the city.
A Powerful, Sustainable Solution
While brackish water reverse osmosis desalination has challenges such as fouling, brine disposal, energy use, and environmental concerns, advanced technologies, energy-efficient systems, and sustainable practices mitigate these challenges, enabling cost-effective and environmentally responsible options.
With abundant sources of brackish water available worldwide, reverse osmosis technology and advances in membranes, pretreatment methods, and energy efficiency offer an economically viable and environmentally sustainable way to meet the growing demand for clean water. As we continue to refine and enhance these technologies, brackish water desalination can play a pivotal role in providing a reliable, scalable solution to one of the most pressing challenges of our time.
