Real-Time Whole Effluent Toxicity Monitoring


How Can We Possibly Justify Building a 3000 Gallon Aquarium?

Zach Margolis, Mike Bittner, Jim McLaughlin P.E.

As currently practiced, Whole Effluent Toxicity (WET) testing has minimal value as an operations tool because it only provides a "snapshot" of treatment plant effluent quality and the picture isn't developed until long after the snapshot was taken. The results, reported as viability and reproduction of fathead minnows and water fleas, aren't particularly fascinating to either Town Councils or participants in wastewater treatment facility tours. Construction and operation of a wastewater treatment facility is one of the biggest capital expenditures a community faces, yet the image the facility projects to it's rate payers doesn't always reflect the effectiveness of the treatment plant, magnitude of the plant investment, or the professionalism of the operators.

The Blue River Treatment Plant engineer and staff decided to construct an aquarium at the facility that would be fed by plant effluent and dilution water to approximate the concentration of plant effluent in the receiving stream. Our Goal was to enhance our image and improve the educational opportunities at the Blue River Treatment Plant by making a clearly recognizable connection between wastewater treatment and the environment we are protecting, and also to provide real-time monitoring of effluent quality, both for appearance and toxicity indications.


Our solution was to incorporate a 3000 gallon aquarium in a new entryway. The design includes piping for well water, plant effluent, and aeration. There are three four-foot square windows and an underwater light. The aquarium was stocked with Rainbow (Oncorhynchus mykiss) and Brown Trout (Salmo trutta) both of which are found in the Blue River. We had no trouble locating volunteers for the translocation of the biological specimens. After 12 months of operating the Aquarium we have had no water quality related failures, though we have seen mortality due to low dissolved oxygen (due to operator error) and predation. The aquarium is now the high point and the focus of plant tours. The public perception and understanding of the importance of water quality, and the effectiveness of their investment in the treatment planthave been greatly enhanced. Operators now have an immediate indication of a serious toxic effluent event, as well as a new tool for observing effluent quality. For more information go to