How simple chemistry provides a necessity for millions each day
The privilege of clean drinking water is readily available to American society; each day, we all open the tap multiple times for washing hands, doing the dishes, and even, filling up our water bottles. National water treatment systems continue to evolve to best support the circumstances individual communities face, such as climate change.
Currently, in the United States, a common series of five steps occur after water is procured from various places, such as springs, before it is distributed to communities across the nation (1). The first step of coagulation is when chemicals with positive charges are added to the water. With this process, the positively charged chemicals bind with negatively charged dirt and other impurities in the water to form larger, more visible particles (2). Next, flocculation occurs; the water is mixed with an instrument similar to a wooden paddle to encourage the contamination to form larger particles, called flocs (2). After the formation of flocs, sedimentation is the subsequent step where solids are separated from the water because of varying densities. Flocs sink to the bottom of the water tank since they have a higher density compared to water (2). The last two tasks of filtration and disinfection respectively remove unwanted particles by passing the water through a filter and killing extraneous bacteria with added chemicals such as chlorine (2).
While water treatment systems in America are often standardized, out-of-the-box thinking is required when the typical water sources are depleted due to climate change. As the majority of the American West Coast is grappling with a harrowing drought, San Diego County has revolutionized a water treatment system that is not dependent on lakes, streams, and rainfall. The Carlsbad Desalination Plant, a one-billion-dollar facility, was inaugurated in 2015 and continues to create 50 million gallons of fresh drinking water every day (3). Leaders at the Carlsbad Desalination Plant stated how “the ocean is a rare drought-proof water source,” and the company takes advantage of the Pacific Ocean (3). At first, seawater is pumped into filters that contain sand and anthracite, a brittle coal (4). Before reaching the primary water treatment step of reverse osmosis, the seawater undergoes a secondary pretreatment, where microfilters are present to remove small impurities (4). Next, salt and minerals are separated through reverse osmosis, a separation technique where pressure is applied to a solution. Reverse osmosis is the exercise of separating solvents (liquids in which other substances dissolve) and solutes (substances dissolved in solvent) with the help of motor pressure and semi-permeable membranes (5). Typically, when osmosis occurs, solvents move from high to low concentration, but the act of forcing the solvent to move in the opposite direction causes a pseudo-biological separation and filtration system (5). With reverse osmosis, the pure water is isolated from salts, minerals, and unwanted particles. After the four main steps, minerals, such as magnesium are added back to the water, and the desalinated seawater is moved to tanks that mix with the public water supply (4). The initiation of the Carlsbad Desalination Plant allows 400,000 people to sustainably have access to clean drinking water each day, regardless of increasing water concerns in California and the West Coast.
With technological advances, local water treatment plants in the United States have been restructuring treatment systems to best support provincial communities. In our country, it is common for manufacturers to derive water from natural bodies of water which are replenished by rain and snowfall. Despite the ever-growing challenges concerning climate change and drought, San Diego County and the Carlsbad Desalination Plant continue to demonstrate the power ingenuity and simple chemistry hold when it comes to accessibility of necessities, like clean drinking water. As millions worldwide struggle to find clean water each day, the creativity at the Carlsbad Desalination Plant can ultimately become a model for modernizing the world in a sustainable manner.
A diagram of the semi-permeable membranes utilized for reverse osmosis. (6)
A common progression of an American Water Treatment system (2) https://www.cdc.gov/healthywater/drinking/public/water_treatment.html#:~:text=These%20filters%20remove%20dissolved%20particles,or%20instead%20of%20traditional%20filtration.
- Water Sources. (2022). Retrieved from https://www.cdc.gov/healthywater/drinking/public/water_sources.html#:~:text=Most%20U.S.%20tap%20water%20comes,water%20supplies%20and%20private%20wells.
- Water Treatment. (2022). Retrieved from https://www.cdc.gov/healthywater/drinking/public/water_treatment.html#:~:text=These%20filters%20remove%20dissolved%20particles,or%20instead%20of%20traditional%20filtration.
- How San Diego Gets Drinking Water From the Ocean. (2022). The New York Times. Retrieved from https://www.nytimes.com/2021/10/29/us/san-diego-drinking-water.html
- Carlsbad Desal Plant. (2015). Carlsbad Desal Plant. Retrieved from https://www.carlsbaddesal.com/
- reverse osmosis | Definition, Process, Uses, Applications, & Facts | Britannica. (2022). In Encyclopædia Britannica. Retrieved from https://www.britannica.com/science/reverse-osmosis
- Reverse osmosis membranes construction. (2022). Lenntech.com. Retrieved from https://www.lenntech.com/processes/reverse-osmosis-membranes-construction.htm#:~:text=Most%20commonly%20used%20RO%20membranes,layer%20on%20the%20top%20surface.