Blue-green and sometimes unseen: How moving beyond visual detection of algae can help inform the treatment of cyanotoxins in drinking water
A WaterLeadership Snapshot
WaterLeadership Snapshots feature articles written by graduate students participating in the Water Institute’s WaterLeadership training program, which focuses on skills development in knowledge mobilization, leadership, and research communication. Here, students describe the value of their research and its potential for ‘real world’ impact.
By Taylor Virgin
Are algae growing in your utility’s source water?
You might be envisioning a green surface scum or a reservoir that looks like pea soup, but algae can be found in amounts that are invisible to the human eye. And not visible does not mean non-toxic.
Cyanobacteria, or blue-green algae, are a type of bacteria that thrive in warm, slow-moving environments like reservoirs. They feed on nutrients including phosphorus and nitrogen and, like plants, use energy from the sun to grow. The rapid growth of cyanobacteria, known as a bloom, can make treating water more difficult. Larger chemical doses might be required to remove algae from water, and cells might clog granular media filters.
Taylor Virgin, Master of Applied Science student, Department of Civil Engineering.
Some cyanobacteria pose additional risks to drinking water supplies by producing cyanotoxins. These chemicals are released when the bacteria die, either at the end of their life cycle or when treatment causes cells to burst open. Cyanotoxins can damage the nervous system or liver, if ingested, or irritate skin exposed to them. Many cyanotoxins are treated using conventional drinking water treatment methods, but there have been cases where they have been found in finished water. For example, a “do not drink” advisory was issued in Toledo, Ohio for nearly three days in 2014 when microcystin, the most prevalent cyanotoxin, was detected after treatment.
High amounts of cyanobacteria increase the risk of cyanotoxin occurrence, but it is complicated to predict when toxins will actually be produced. Cyanobacterial cells may look identical under a microscope but differ in their ability to produce cyanotoxins. Additionally, low numbers of cyanobacteria can release toxins, even when there is no visible bloom.
Given these challenges, how can water utilities stay informed about the risk of cyanotoxins? Working under Drs. Monica Emelko and Kirsten Müller, Master’s student Taylor Virgin is investigating how monitoring source waters using molecular biology methods can help.
Molecular biology involves studying the building blocks of cells to understand how living things operate. Both bacterial and human cells contain DNA, a molecule that acts as a blueprint specifying what structures the cell should build and when.
Taylor is sequencing the DNA of a cyanobacterium growing at a treatment plant to determine whether it has the capacity to make toxins. The building blocks of DNA, called bases, can be represented by the letters A, T, C, and G. During sequencing, DNA is separated from other cell components and the order of the bases is determined. The DNA sequence of the cyanobacterium can then be compared to known cyanotoxin synthesis sequences to look for matches. The presence of a sequence within the DNA does not always mean cyanotoxins are being produced, but these results can help determine if cyanotoxins represent a potential threat to the production of safe drinking water.
With warmer temperatures and increases in nutrient concentrations affecting many North American water bodies, it may be a question of when algae will grow in your reservoir. Using molecular methods to better understand the cyanobacteria in source water can help inform whether additional treatment steps for cyanotoxins should be implemented before cyanobacteria are even visible in the system.
This research is supported by NSERC, the forWater Network, and the Regional Municipality of Wood Buffalo.