Biomonitors: An Emerging Technology for Detecting Contaminants in Water

Before miners entered a mine, they would lower a canary in a cage into the mine to determine whether deadly gases were present. This is an early example of a biomonitor of the environment. Biomonitors are a class of monitors that rely upon the responses of living organisms to detect the presence of a contaminant in the environment.

A Daphnia Toximeter

Biomonitors for detecting water pollutants use a range of organisms including fish, mussels, daphnia, algae, and bacteria to detect contamination. In each case, the organisms are observed in order to detect irregular behavior indicating that the organisms either sense the presence of contaminants or are being stressed by the contaminants. The monitors cannot determine what is causing this behavior but can serve as an early warning that there is a pollutant present in the water.

Early biomonitors for water were simply aquariums filled with the water to be tested and contained fish. The behavior of the fish were then routinely observed. Modern fish biomonitors use the concept of avoidance and employ sophisticated instrumentation to monitor the behavior of the fish. Typically, the fish remain near the inlet to the tank where they are continually fed. If they sense a toxic pollutant entering the tank then they swim to other parts of the tank and this behavior is detected through use of cameras and automated counters.

One of the most sophisticated biomonitors today employs daphnia, water fleas the size of a head of a pin. In the commercial unit shown in the picture, sample water continuously flows through a chamber containing 8 to 10 daphnia. The behavior of the daphnia is observed by a camera that takes 25 pictures per second, which are analyzed by an online computer. The movement of each organism is evaluated in terms of several factors including speed, height in the chamber, distance from other daphnia, etc. A statistically significant deviation from a norm results in an alarm.

This monitor has been used throughout the world and was part of an early warning system for source water contamination at the 2002 Winter Olympics in Salt Lake City.

Though the use of biomonitors for water contamination dates back about a quarter of a century, it continues to be an emerging technology whose full potential has yet to be felt in the water quality field.

This article is the first in a regular series of reports on emerging and innovative technologies relevant to the area of the environment and water resources. It is a product of EWRI’s Emerging and Innovative Technologies Council (EITC). EITC’s mission is to advance the development, knowledge, and application of emerging and innovative technologies for the planning and management of water resources and the protection and enhancement of the environment. If you are interested in contributing an article or becoming a member of this Council, please contact Richard Palmer, incoming Chair of EITC, at palmer@u.washington.edu.