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Monday, December 27, 2010

Let it snow, let it flow? Road salt and water quality

Scarves and shovels and salt are all common responses to the snows of winter. But how does the rock salt protecting us on the roadways affect the quality of the water flowing to the Cuyahoga River and Lake Erie?

While no risk to humans, rock salt can affect water flowing into our sewers and the environment and, in large amounts, can be toxic for aquatic organisms. Fertilizer and other chemicals can have similar impacts, which is why water quality is a concern all year round.

Studies can help uncover these potential sources of pollution and identify remedies to keep our waterways safer, whatever the season may bring.

Tests tell the tale

One way to measure the impacts on water quality is known as whole effluent toxicity (WET) testing. WET tests compare the activity of aquatic organisms in a controlled environment with the activity of organisms in an environment containing outside influences—in this case, whatever remains in wastewater after it’s treated.

Wastewater treatment plants—such as those operated by the Northeast Ohio Regional Sewer District—use this form of testing to evaluate the treated wastewater’s effect on aquatic life. Ideally, organisms tested in the treated wastewater should show no effects differing from the control group.

Facing the factors

Many factors affecting WET testing results can be found in runoff, or the water which flows over hard surfaces such as parking lots and streets. Substances or chemicals on these hard surfaces are carried to a street sewer, and eventually to the wastewater treatment plant.

From lawn fertilizers in the spring, to oil deposits in the summer and fall, to rock salt in the winter, these chemicals affect the flow coming to a wastewater treatment plant. WET testing helps us study these factors and our processes to improve water quality.

Ongoing improvements

Most treatment plants can make adjustments within their processes to account for seasonal or other fluctuations in pollution levels, and testing is an ongoing means of tracking performance in protecting the water quality of our streams and lake.

Reposted from Northeast Ohio Regional Sewer District's environotes column January 2008


  1. what organisms are used in the WET tests?

  2. @anonymous: We use fathead minnows and water fleas in our whole effluent toxicity (WET) tests because they are sensitive to pollution and are easily cultured in a laboratory environment.


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