Effluent toxicity testing using nitrifiers and Microtox™

In an effort to develop a less expensive method of assessing wastewater toxicity, two bacterial alternatives to Ceriodaphnia were tested: the commercially available Microtox™ procedure (using Photobacterium phosphoreum ) and a nitrifier respiration procedure. Forty‐four biologically treated municipal wastewaters were evaluated. Neither the Microtox nor the nitrifier test is sufficiently sensitive to detect acute Ceriodaphnia toxicity when testing biologically treated municipal wastewaters. The 7‐day chronic Ceriodaphnia procedure is more sensitive than the 48‐hour acute Ceriodaphnia test, with 14 of the 16 wastewaters tested for chronic toxicity exhibiting toxicity using 100% wastewater.