Methods for measuring respiratory activity can detect adverse effects on heterotrophic microorganisms. These methods are useful tools for assessing the impact of chemicals on biological wastewater treatment processes. They are also well suited for evaluating the treatability potential of individual wastes. However, varying results are oRen reported when using municipal or industrial activated sludge substrate in toxicity assessments. The lack of reproducibility of these tests has also greatly limited efforts to measure the effectiveness of treatment plants in removing toxic contaminants. The toxicity of wastewaters and chemicals to biological treatment systems can be determined in 30 min with the new Polytox@ toxicity procedure. The Polytox@ kit utilizes a specialized blend of bacterial cultures. The objective of this paper is to evaluate the relative sensitivity of the new PolytoxQ toxicity procedure with two accepted microbial assay procedures; namely, the MicrotoxQ bioluminescence assay and the Organization for Economic Cooperation and Development's Activated Sludge Respiration Inhibition test. This paper compares toxicity values for selected inorganic and organic chemicals as determined in the three microbial assay systems. The sensitivity and reliability of the new PolytoxQ toxicity procedure is discussed.

Static acute and renewal chronic tests were conducted with Daphnia magna, Daphnia pulex and Ceriodaphnia reticulata to determine their relative sensitivities to selected organic and inorganic chemicals: 2-chloroethanol, 2,4-pentanedione, pentachlorophenol, hexachloroethane, 2,2,2-trichloroethanol, 2-methyl-l-propanol, 2-methyl-2,4-pentadiol, Endrin@, silver, lead, chromium, cadmium, copper, arsenic and mercury. The three species tested yielded comparable acute EC50 values for most chemicals tested. The acute EC50 values for D. magna, D . pulex and C. reticulata varied twofold for hexachloroethane, Endrin, cadmium, arsenic and mercury. Chronic EC5O values for the three species were within one order of magnitude for 2-chloroethanol, 2,4-pentanedione, cadmium, chromium and silver. Differences in the sensitivities of these three popular cladoceran test species were within one order of magnitude. Reproductive impairment in all three test species appeared to be a more sensitive indicator of chronic toxicity than survival. This study suggests that the 7-d Ceriodaphnia chronic test may be used as an alternative short-term method for the screening of chemical toxicities.

Static acute and renewal chronic tests were conducted with Daphnia magna, Daphnia pulex and Ceriodaphnia reticulata to determine their relative sensitivities to selected organic and inorganic chemicals: 2‐chloroethanol, 2,4‐pentanedione, pentachlorophenol, hexachloroethane, 2,2,2‐trichloroethanol, 2‐methyl‐1‐propanol, 2‐methyl‐2,4‐pentadiol, Endrin®, silver, lead, chromium, cadmium, copper, arsenic and mercury. The three species tested yielded comparable acute EC50 values for most chemicals tested. The acute EC50 values for D. magna, D. pulex and C. reticulata varied twofold for hexachloroethane, Endrin, cadmium, arsenic and mercury. Chronic EC50 values for the three species were within one order of magnitude for 2‐chloroethanol, 2,4‐pentanedione, cadmium, chromium and silver. Differences in the sensitivities of these three popular cladoceran test species were within one order of magnitude. Reproductive impairment in all three test species appeared to be a more sensitive indicator of chronic toxicity than survival. This study suggests that the 7‐d Ceriodaphnia chronic test may be used as an alternative short‐term method for the screening of chemical toxicities.

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