By Ken Ross
The bad news for Cherokee is that some water fleas died in a state lab and the good news is that the fathead guppies survived.
Such creatures are exposed to water coming out wastewater treatment plants on a quarterly basis as a test to determine whether the water has been appropriately processed for discharged.
If an unacceptably high number of the creatures die after being exposed to the water for a specified period, the wastewater treatment plant fails the test. If the plant fails the test two consecutive times, as the industrial wastewater treatment plant in Cherokee did last year, the city is required to conduct a TRE (toxic reduction evaluation).
The industrial wastewater treatment plant is separate from the city's main plant. The industrial plant processes only wastewater from the Tyson Foods meat processing plant, which is outside of city limits but contracts with the city for the wastewater treatment. The city bills Tyson for operation and for repairs to the plant.
The water samples last year that killed fleas did not kill guppies, Ron Strickland, city administrator, noted. He added that water taken the same day from the discharge passed flea tests at labs in Omaha and Pennsylvania.
Strickland said the lengthy process of conducting a TRE is in its latter stages. He is not overly concerned, saying that the city will just do what the DNR tells the city to do to take care of the problem, possibly as simple as changing the chemicals used by Tyson in cleaning its floors.
The first step at the industrial wastewater treatment plant involves an anaerobic digestion pond where bacteria that live in the absence of oxygen break down the solids that settle out. The next step is an aeration tank in which forced air is used to keep aerobic bacteria active. Those are bacteria that require oxygen.
The next step is a clarifier and then the water is discharged.
There have already been recent changes in the operation, including dredging the anaerobic pond and making new holes in piping for more even distribution of solids in the aerobic tank. Work on the clarifier has been approved.
Strickland said the problem is first evident in the anaerobic pond where the bacteria are not surviving. The pond is almost sterile.
Since there is only one source for the wastewater, determining the source for any chemical problem that might be present would be less difficult than for a plant that processed wastewater from multiple sources.