Water: Essential and Problematic

Water depletion and pollution are the major causes of biodiversity loss and ecosystem degradation, which, in turn, reduce ecosystem resilience, making societies more vulnerable to climate and non-climate risks

United Nations
Water around the world

Earth’s water is finite. It is essential. Water is also problematic when it is contaminated with chemicals from industry, agriculture, or natural sources.

With an increase in global population, the call for more clean drinking water becomes of higher importance. Saltwater makes up about 96.5% of water while only 3.5% is freshwater. Of that 3%, only about a third is found in beautiful rivers, lakes, and streams like the one shown above. 1

So how will the world deal with this water shortage? One answer is by desalination.

Saltwater processing technologies

Desalination is, as the name implies, a process for removing salt (sal in Spanish) from water. Let’s review the existing technologies.

  • Temperature-driven systems (flash distillation, solar distillation, humidification)
  • Pressure-driven systems (reverse osmosis, electro-dialysis, nanofiltration)
  • Chemically driven systems (ion-exchange, extractions)
  • Adsorption (like absorption but only on the surface) technologies.

A 2014 study showed that adsorption technologies were promising due to their ability to handle water with high amounts of salt, produce water with low amounts of salt, minimize environmental impact, and reduce costs.2 It will be exciting to see what continues to develop!

Quantity and quality are both issues faced with water today and will become an obstacle in the future. Because these systems are not 100% efficient, they will inevitably produce waste brine water or highly concentrated saltwater with more than 35,000 parts per million (ppm) salt. For comparison, freshwater has only 500 ppm salt.3

Quantity and quality are both issues faced with water today

Environmental impacts of brine water 4

Contaminated water is problematic. Large amounts of brine are produced from these processes: desalination of seawater, mining of salt domes for oil and natural gas storage,  oil and potash (potassium compounds) mining, and ponds used to produce salt by evaporation (salt ponds). When the industries mentioned above are close to the coast, the brine waste is disposed into the sea which causes environmental degradation and endangers marine life.

  1.  Cell disruption: The increase in salt can disrupt balances within cells that that causes dehydration and potentially death  
  2. Temperature increase: increased toxicity of chemicals, less oxygen dissolved, fatal over long term
  3. Toxicity: lead, zinc, copper, arsenic, and naphthalene (extremely dangerous to marine life at low concentrations)

What can pollution do to marine life? One effect is coral bleaching. When under higher temperatures and pollution, the corals turn white and are more vulnerable to death. Check out this kid’s activity from NASA that shows how temperature and pollution affect coral reefs! Click on the picture to the left.5

So the only source of pollution is from desalination right? No. Chemical industries (i.e. hydraulic fracturing), agricultural runoff, wastewater all produce pollution that require research to implement solutions. Desalination research is discussed below.

Desalination Research

Dr. Will Tarpeh, a researcher and chemical engineering professor at Stanford University, is currently working towards solutions for brine water waste. Tarpeh and  Linchao Mu, a postdoctoral researcher in Tarpeh’s group, are taking the approach of valorizing the waste by recovering the chemicals through an electrochemical process designed to select and separate specific chemicals from the water. Basically, concentrated salt water enters, a voltage is applied, the salt is split into ions to produce commodity chemicals like sodium hydroxide and hydrochloric acid.6 This process is called electrochemical water-salt splitting (makes sense). I look forward to keeping an eye on further developments of this research!

              Another approach for handling brine discharge is to use it to make “blue energy”, or energy sourced from seawater and freshwater. Semih Cetindag, a Ph.D. researcher at Rutgers University, has developed an electrochemical setup that uses the ionic charges from salts to generate electricity. Although this is in the research phase, it will be worthwhile to watch the progress as it is applied on a larger scale.7

Summary

To wrap it all up, the United Nations world water development report 2020 on water and climate change states, “Water depletion and pollution are the major causes of biodiversity loss and ecosystem degradation, which, in turn, reduce ecosystem resilience, making societies more vulnerable to climate and non-climate risks”.8 With that in mind, it is important to become aware of industry waste and its impact on surrounding ecosystems. Creating environmental regulations to prevent harm is beneficial and developing sustainable technologies from research adds another level of prevention. We need water, and we also need to preserve it.

References
  1. How Much Water Is on Earth? (2020, March 26). https://spaceplace.nasa.gov/water/en/
  2. Youssef, P. G., Al-Dadah, R. K., & Mahmoud, S. M. (2014). Comparative analysis of desalination technologies. Energy Procedia61, 2604-2607.
  3. Team, F. (2020, March 02). Brackish Water as a Resource: What is Brackish Water? https://www.fluencecorp.com/what-is-brackish-water/
  4. Ahmad, N., & Baddour, R. E. (2014). A review of sources, effects, disposal methods, and regulations of brine into marine environments. Ocean & coastal management87, 1-7.
  5. Coral Bleaching. (n.d.). https://climatekids.nasa.gov/coral-bleaching/
  6. Mu, L., Wang, Y., & Tarpeh, W. A. (2020). Validation and mechanism of a low-cost graphite carbon electrode for electrochemical brine valorization. ACS Sustainable Chemistry & Engineering.
  7. Robert F. Service. (2019, December 06). Rivers could generate thousands of nuclear power plants worth of energy, thanks to a new ‘blue’ membrane.
  8. World Water Development Report 2020: UN-Water. (2020) https://www.unwater.org/publications/world-water-development-report-2020/