By Brigitte Rodriguez, Associate Researcher & Writer for Save The Water | June 25, 2022

Eutrophication is the excess of nutrients in water. As a form of nutrient pollution, it can have negative impacts leading to harmful algal blooms and hypoxia (lack of oxygen) in aquatic ecosystems. Luckily, there are some technologies that can be used to control eutrophication.    

What is Eutrophication?

Eutrophication occurs when excess nutrients enter a body of water, such as a lake or reservoir. This is usually the result of  anthropogenic, or human-caused, nutrient loading which consists of higher than normal amounts  of natural elements such as phosphorus (P) and nitrogen (N). As a consequence, the growth of algae is accelerated, which creates an imbalance in aquatic ecosystems that can ultimately affect water quality.

What are the main sources of eutrophication?

Though not always clear, the many sources of nutrient pollution often stem from anthropogenic activities across various sectors and industrial processes. These include agriculture, aquaculture, industry (food and meat processing, paper mills) and sewage disposal. The nutrient byproducts of these processes then make their way into nearby water bodies as surface run-off.

While difficult to pinpoint, some of the main sources of excess nutrients are:

• Commercial fertilizers and animal manure
• Domestic and industrial sewage 
• Waste water

What are the symptoms of eutrophication in water bodies?

The most significant effects of excess nutrients in the water are harmful algal blooms (HABs) and hypoxia:

• Harmful Algal Blooms: produced by different types of algae. The most frequent and severe blooms are caused by cyanobacteria (cyanHAB), which are the only known freshwater algae with toxins potent enough to harm human health. In addition, cyanoHABs can threaten aquatic ecosystem health.
• Hypoxia: this refers to low levels of oxygen in water leading to dead zones. The lack of oxygen threatens the survival of most aquatic species.

     Additionally, it is important to mention that studies by the World Resources Institute states have found that the effect of hypoxia for eutrophication has escalated dramatically over the last 50 years. There were 10 documented cases in 1960, which has since then increased to 169 in 2007.  

     In the case of the Yangtze River (China), nutrient pollution is intensifying due to food production and increasing urbanization. As a consequence, the urban run-off is elevating nutrient concentrations in the river, resulting in coastal eutrophication. Two of the main administrative solutions aim to reduce the levels of nitrogen and phosphorus in fertilizers as well as recycle the manure so it can be re-used as organic fertilizer for farmland and soil. In this way, researchers predict that coastal eutrophication can be significantly reduced by 2050. However, this must be accompanied by better opportunities for scientists, students and farmers to share their ideas and knowledge.

     In another case study, the Pañe Reservoir in Peru demonstrates evidence of algal blooms such as cyanobaceria, which has been a key indicator of eutrophication for more than 5 years. The sources of increased nutrient levels in the water  are related to the aquaculture and livestock sectors in the area. In order to mitigate eutrophication and maintain water quality standards, a team of researchers suggest a total annual aquaculture production of 36,000 kilograms. In addition, sediment monitoring must continue in certain areas of the reservoir in order to ensure the long-term sustainability of aquaculture and water quality.

Which water treatment technologies are available to reduce eutrophication?

Currently, there are several innovative technologies available to reduce the excess of nutrients in water. These include the following:

• BioPhree: This technology captures dissolved phosphorus in water. It can be used in surface water and wastewater. The advantage of using this tech is its ability to produce fertilizer for agricultural use, making it both effective and sustainable.

• TerraNova® Ultra: is an innovative sewage sludge technology that extracts phosphorus and nitrogen and allows for the recovery of  nutrients.

What You Can Do To Help

There are a few ways you can reduce the effects of eutrophication in bodies of water:

• If you own or manage farmland, it is important to limit nutrient pollution sources by reducing the use of fertilizers and implementing proper soil management practices.
• Volunteer for  local public awareness campaigns to draw attention to eutrophication
• If you live in a country or region with water bodies at risk of eutrophication, urge your government to better manage cleaning of sewage and wastewater.
• Use soap and detergents with less phosphate.

It is challenging to find a reality where phosphorus is not an integral part of our society. It is found in chemistry classrooms, the human body, and the Earth’s atmosphere, but it is most notably found as one of the three core components of the standard NPK fertilizer. What society doesn’t always associate the chemical with, however, is water pollution. According to Associate Professor Kasper Reitzel, Department of Biology, University of Southern Denmark, the water quality in 40% of Europe’s lakes does not meet the demands of EU’s [European Union’s] Water Framework Directive, mainly due to phosphorus pollution” (ScienceDaily, 2016).

Phosphorus pollution may seem like a foreign concept to many. Unlike arsenic and mercury, phosphorus isn’t normally an element notorious for its toxicity. Many would be surprised, then, to know that “phosphorus from industrial and municipal wastewater facilitates eutrophication” (Stoddard, 2016) which is caused by an excess of nutrients in the water. This leads to a large growth of algae, which depletes the water of oxygen (National Oceanic and Atmospheric Administration, 2008).

Concentrations of the chemical in lakes and streams worldwide has been increasing. “The percentage of lakes with TP [total phosphorus content] of ≤10 μg/L decreased from 24.9 to 6.7 between 2007 and 2012” (Stoddard, 2016). Additionally, its concentrations seem to be rising even when other nutrients, like nitrogen are not. Phosphorus tends to enter aquatic environments through runoff, when soil particles containing said chemical (as well as nitrogen, potassium, and other chemicals) erode and are carried by precipitation to the ecosystem. However, phosphorus could also be entering aquatic environments through condensation in the atmosphere, exacerbating the problem. Moreover, phosphorus exposure is hard to mitigate through conventional methods once in the water, since it can be stored in the lake’s bed sediments and later released and recycled back into the water.

So how do we solve the dilemma of phosphorus pollution? Solutions vary, ranging from advanced technology to chemical methods. In Vermont, authorities plan to clean up the local Lake Champlain by introducing various regulations, such as custom manure application training, the inspection of large, medium, and small farms, and other advanced technology and training (Aragon, 2016). In a study evaluating the impact of aluminum salts on internal phosphorus loading, scientists found that the “threshold criteria for treatment longevity indicated the importance of Al [Aluminum] dose, watershed to lake area ratio, and lake morphology as important factors for treatment success” (Huser, 2016).

If there is anything we know for sure, it is that phosphorus pollution is a major concern. According to a study found in the journal Environmental Science and Technology, “eutrophication costs an estimated $2.2 billion per year in the U.S. alone and is the leading cause of drinking water problems in most developing countries” (Schindler, 2016). A special issue of Water Research stated that “phosphorus is the biggest cause of water quality degradation worldwide, causing “dead zones,” toxic algal blooms, loss of biodiversity and increased health risks for the plants, animals and humans that come in contact with polluted waters” (ScienceDaily, 2016). Further, the issue, noted that humans are still pumping almost 10 million tons of extra phosphorus in freshwater sources every year, namely in the form of runoff. Thus, phosphorus pollution has been and remains a critical problem we have to address.

References

Aragon, R. (2016, August 29). VT Drafts Lake Champlain Clean Up Plan. Retrieved September 30, 2016, from http://www.mychamplainvalley.com/news/vt-drafts-lake-champlain-clean-up-plan

Huser, B. J., Egemose, S., Harper, H., Hupfer, M., Jensen, H., Pilgrim, K. M., . . . Futter, M. (2016, June). Longevity and effectiveness of aluminum addition to reduce sediment phosphorus release and restore lake water quality. Water Research, 97, 122-132. doi:10.1016/j.watres.2015.06.051

National Oceanic and Atmospheric Administration. (2008, March 25). NOAA’s National Ocean Service Education: Estuaries. Retrieved September 30, 2016, from http://oceanservice.noaa.gov/education/kits/estuaries/media/supp_estuar09b_eutro.html

Schindler, D. W. (2016, August 18). Cut phosphorus to reduce algae blooms, say scientists. Retrieved September 30, 2016, from http://phys.org/news/2016-08-phosphorus-algae-blooms-scientists.html

Stoddard, J. L., Sickle, J. V., Herlihy, A. T., Brahney, J., Paulsen, S., Peck, D. V., . . . Pollard,
A. I. (2016, February 25). Continental-Scale Increase in Lake and Stream Phosphorus: Are Oligotrophic Systems Disappearing in the United States? Environmental Science & Technology Environ. Sci. Technol., 50(7), 3409-3415. doi:10.1021/acs.est.5b05950

University of Southern Denmark. (2016, July 8). After decades of clean up attempts, world’s lakes still suffer from phosphorus pollution. Retrieved September 30, 2016, from https://www.sciencedaily.com/releases/2016/07/160708105428.htm