Something is killing the Harrison wastewater treatment plant’s water fleas and it could cost tens of thousands if not hundreds of thousands of dollars to find out what it is.
The water fleas, Ceriodaphnia, are metazoan crustaceans used in biological toxicity testing. Water fleas in the treated wastewater are an indication that it is very clean and not harmful to the environment because the fleas are very sensitive to a wide variety of toxic agents.
Wade Phillips, Harrison’s chief operations officer, said water fleas and fat head minnows are used at the plant to make sure the discharge into Crooked Creek is clean, according to government standards, for various species. A sub-lethal failure was indicated for the water fleas last July, and last September both lethal and sub-lethal failures were documented.
Those reports are prompting the city wastewater plant to proceed with a Toxicity Reduction Evaluation (TRE). The US Environmental Protection Agency defines a TRE as “a site specific study conducted in a stepwise process designed to identify the causative agents of effluent toxicity, isolate the sources of toxicity, evaluate the effectiveness of the toxicity control options, and then confirm the reductions in effluent toxicity.”
Nothing at the plant has changed over the past five years, so the source of the toxicity isn’t at the plant itself, Phillips believes.
The TRE process is about the worst-case scenario for a medium sized wastewater plant, Phillips told council members. The city has to have its action plan submitted to ADEQ by Jan. 3 and begin implementing it by Feb. 3.
An environmental firm that the city has worked with in the past has been contacted to help develop the plan and identify the costs, Phillips said. He said he has not had any experience concerning TRE in his career. He said he did not know what the cost would be, but understands it could reach $300,000 to $400,000. He would have more information by the next regular council meeting. The water department’s 2021 budget will have to be adjusted to meet those costs.
While there are no definite answers at this time, Phillips did throw out a theory that the cause of the toxicity at the plant might be tied to the COVID-19 pandemic.
Phillips said Harrison’s wastewater plant isn’t the only one of its size having biological monitoring issues for the first time, ever. He said the laboratory used by Harrison said at least four other similar sized plants are having the same problem. None have large industrial customers that could be causing the pollution.
Discussions lead Phillips and others to think that the increase use of sanitizing chemicals over the past six months could be the source. Medical facilities such as hospitals, nursing homes and manufacturing facilities are using more sanitizing products. He noted the city is using more of those products as well. There is a lab in Memphis, Tennessee, that is already studying disinfectants as the cause of some of these biological monitoring issues.
Phillips said the government might offer some relief if this is the case. He did not know if the full TRE process would have to be carried out. It could take as long as 2.5 years. One of the most frustrating things, Phillips said, is that a majority of the time the toxicity goes away and the cause is never determined.