Recruiting Tiny Organisms to Detect Water Pollution

by | 2.8.2011 at 3:41pm
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In September, World Water Week director Jens Bergren warned that climate change, with the extreme weather conditions scientists say it can produce, has huge implications for water pollution. “If there is too much water, it flushes out much more in the way of pollutants, spreading them around…but if there is a drought, there is less water in rivers and lakes to dilute the pollutants there, and they do more harm,” said Bergren. Water pollution decreases the amount of water available for human consumption, agriculture and industry, so with increasing climate change effects and the concern that many regions on the planet are approaching peak water, timely water pollution detection is critical.

Most traditional water quality testing involves manual sampling, lab analysis, the need to test for specific pollutants, and a waiting period sometimes as long as 72 hours before results are available.  It’s a time-consuming and expensive process.  But some scientists are putting tiny organisms to work testing water quality in ways that are quicker, cheaper, more accurate and have tremendous potential for use in water stressed countries around the world.

In Israel, Dr. Yulia Pinchasov and Zvy Dubinsky, an aquatic biologist at Bar Ilan University, discovered a way to use algae to test water quality by measuring their rate of photosynthesis. Most of the Earth’s oxygen is produced by algae through photosynthesis, and algae are sensitive to water quality.

Algae - photo credit: Daveness_98

Dubinsky’s prototype tester (about one meter square) shoots a laser beam at algae in water samples to stimulate photosynthesis. Some of the laser’s heat is not used in the photosynthesis and is returned to the water where it creates sound waves that can be measured with special underwater equipment. The health of the algae and the surrounding water can be determined by the strength and quality of the sound waves.

Pinchasov said, “Algae suffering from lead poisoning, like waste discharged from battery and paint manufacturing plants, will produce a different sound than those suffering from lack of iron or exposure to other toxins.” The technology has the potential to be used to monitor water quality in drinking water reservoirs, wastewater treatment lagoons, lakes, rivers and in the open seas.

Scott Gallager, a biologist from The Woods Hole Oceanographic Institution, and former colleague Wade McGillis who’s now at Columbia University’s Lamont-Doherty Earth Observatory, developed Swimming Behavioral Spectrophotometer (SBS). SBS detects water pollution through monitoring the movements of one-celled protozoa, genus Tetrahymena, in water, and was selected as a 2010 “Better World” technology by the Association of University Technology Managers.

Tetrahymena - photo credit: The JCB

Protozoa in water samples are placed in the chambers of a container about the size of a dorm refrigerator.  Their swimming movements (produced by tiny hair-like cilia) are compared to those of control samples with a digital camera and a special software program that tracks 50 characteristics of protozoan movement in two and three dimensions. “Toxins like heavy metals inhibit calcium transport and affect cilia motion,” said Gallager. “Sometimes the cells just stop.  Sometimes they begin spinning around…if the front cilia move into a toxin and slow down while the back cilia don’t, the cell is likely to start tumbling.”  Any irregularities in the protozoa’s movements are a sign that the water is compromised: a green light indicates that the water is safe to drink, a yellow means a retest is needed, and a red light signals “deadly.”

SBS can detect an array of chemical and biological contaminants  including industrial chemicals, pesticides, pharmaceuticals, biological warfare agents, nerve agents and rodentificides. It can be programmed to test as often as every 10 seconds or once a day and results are virtually immediate.  Though you won’t necessarily know what the exact pollutant is, you’ll know you have a problem and can begin to take action on it.

In 2009, Gallager and his team created Petrel Biosensors, a company  whose mission is to create a portable commercial product employing SBS that can be easily transported to a water supply to provide and communicate the results of continuous water quality monitoring. The company  is working on making the units smaller so that eventually devices the size of a laptop can be stationed at many rivers and streams. SBS could be used to test public drinking water supplies, industrial waste discharge, water resources for military units in battle, and sites where hydraulic fracturing (or fracking), the controversial drilling technique used to access natural gas in shale, is occurring. SBS’s instant results cost $1 to $2 per test as compared to traditional water quality testing that can run $50 to $250. Gallager envisions a worldwide, 24/7 monitoring network where “Somebody at a central location could be monitoring all drinking water world wide.”

Dr. Paula Mouser, a Research Assistant Professor at the University of Maine, is working with microorganisms to test the quality of groundwater around landfills. Leachate, the contaminated liquid that seeps out of unlined landfills, can infiltrate and pollute local drinking water supplies. The 30-acre Schuyler Falls Sanitary Landfill in New York State was closed in 1996, but leachate leaking from the unlined site prompted the setup of 22 monitoring wells around the dump to test for contaminants. Monitoring wells commonly test for two to four dozen pollutants, but because leachate can contain so many chemicals, it’s difficult to know which ones to look for.  Moreover, traditional monitoring is usually incapable of detecting the leading edge or fringe of the contaminated plume which can pollute the groundwater.

Mouser sampled microbes from the groundwater in monitoring wells that were both clean and contaminated, identifying each well’s microbes by its 16S rRNA gene. Since each type of bacteria has a slightly different nucleic acid sequence, she could identify it by its “fingerprint.” Through analyzing the fingerprints, and comparing the bacteria present in the clean and contaminated areas, she determined that the bacteria present along plume fringes corresponded to the bacteria sampled from the leachate-contaminated wells. “The patterning of the communities of bacteria itself was indicative of leachate—the patterns corresponding to the clean areas vs. the leachate areas were very clear,” said Mouser. The microbes react to the low-level leachate at the fringe before traditional water quality tests can detect its presence. “And the plume fringe is most important to detect because it’s the leading edge of contamination so if we know about it sooner, we can clean it up sooner and be more protective of human health,” Mouser noted.

While the microbes don’t indicate which specific pollutants are present, Mouser explained that they could figure it out by using information about what types of bacteria thrive in which contaminants. The technology could also be used to detect contaminants that only certain species of microbes like to eat, or if there’s already pollution, it could monitor microbial communities to see how effective the cleanup is. Mouser’s current research focuses on figuring out if the microbes found in the leachate are moving with the contamination or if they are already present in the soil and move towards the leachate as it approaches. If it turns out they move with the leachate, they could help anticipate where a contaminated plume is heading.

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