The world is running out of water. It is estimated that by 2025 two-thirds of the world's population could be living under water stressed conditions [1]. Not only is the supply of freshwater dwindling, but the cost of transporting clean water into parched areas is rising.
However, a potential water source may be flowing out of the largest consuming sector. Today, the majority of freshwater is expended on agricultural operations to feed the growing population. In the United States, irrigation accounts for approximately 42% of all freshwater withdrawals (118 billion gallons per day). It is estimated that 45 billion gallons of excess irrigation water drain off agricultural
fields every day in the U.S.[2]. That same water, however, does not have to go to waste. When cleaned, it can serve as a supplementary source for irrigation, closing the loop and eliminating waste. My current research, under the mentorship of Dr. Dionysiou of the UC Environmental Engineering department, is developing this possibility into reality. The project is federally funded by the Department of Energy and is part of the National Alliance for Water Innovation. Since my first semester at UC, I have been studying the use of constructed wetlands for treating saline and selenium-contaminated agricultural drainage water.
After irrigation and use in agricultural operations, the water that runs off from fields is considered nonpoint source pollution. Agricultural drainage water often contains nitrates, phosphates, salts, and other soluble chemicals and have been associated with surface water eutrophication and increased salinity in surface and groundwater. Particularly in the 17 U.S. western states, the elevated levels of salts and toxic constituents (i.e., selenium and boron) present in agricultural drainage water have restricted its direct reuse for irrigation and require treatment.
Constructed wetlands have been shown to offer an alternative method to remove contaminants from agricultural drainage water. Constructed wetlands apply the concept of passive biological filtration on a large scale. Often established on the edge of fields, constructed wetlands intercept the flow of polluted water from agricultural operations. This natural treatment uses a combination of adsorption, bio assimilation, and microbial methods to remove constituents from agricultural drainage water. The versatility of constructed wetlands is endless, as there are many potential combinations of vegetation, soil, and organisms. This unique feature allows for customization to the land type and pollutant content of the water to be treated. Aside from their direct functionality, wetlands also harbor habitats for wildlife and increase aesthetic value.
To optimize this technology for the removal of salts and selenium, different plants, hydraulic effects, and microorganism interactions have been studied. My role is to synthesize existing literature on effective constructed wetlands. By critically reviewing previous studies, I identify the key design and operational considerations as well as future research needs for the optimization of constructed wetlands for treatment of saline and selenium-laden agricultural drainage water. In the next stage, I will begin laboratory experiments on the topics of highest priority, advancing knowledge on this cutting-edge technology. My future plan is to receive a PhD after I graduate, so I am currently building the skills needed for my career.
As an environmental engineer, it is my job to ensure a future for the global society. And, through my research project I get to do so, one drop of agricultural wastewater at a time.
[1]https://www.un.org/waterforlifedecade/scarcity.shtml#:~:text=Did%20you%20know%3F,living%20under%20water%20stressed%20conditions.
[2] https://pubs.er.usgs.gov/publication/cir1441
(Answering the Year-In-Review prompt: What complex problem or social issue have you worked on this year? Why did you pursue this specific topic? What did you do? What are your goals and next steps?)