ABSTRACT
Esso Resources Canada Limited, Research Department, 339-50th Avenue S.E., Calgary, Alberta T2G 2B3 Canada
MERL L. KORCHINSKI, DONALD C. ROBERTS, IRENE B. ZABORSKI, and J. ROGER CREASEY
Energy Resources Conservation Board, Chemical Research Laboratory, 3512-33rd Street N.W., Calgary, Alberta T2L 2A6 Canada
ABSTRACT A two-phase Esso Resources Canada Limited (ERCL)/Energy Resources Conservation Board (ERCB) research project that examined nine fresh water-based drilling sump fluids failed to produce a meaningful correlation between Microtox and trout toxicity data. For example, the coefficient of correlation between multiple dilution trout and Microtox toxicity data for the sump fluid samples from Phase II of this study was in the range 0.14-0.44. Notwithstanding, a Western Canada Microtox Users Committee (WCMUC) Microtox round robin study involving these same samples and twelve participating laboratories demonstrated that the Microtox toxicity test possesses very good precision for the toxicity evaluation of drilling sump fluids (RSD for EC( 50) = 22-25%; RSD for EC( 20 ) = 37-40% (data quoted are after rejection of outliers)). Sample turbidity and colour were found to be more detrimental to the Microtox test than to fish toxicity tests, and the Microtox test was observed to be more sensitive than the fish tests for the toxicity evaluation of liquid drilling wastes. Sample age and handling were found to be important factors with respect to the toxicity data produced by the Microtox test, and the response of the Microtox reagent bacteria was not significantly affected by sample pH as long as it was in the range 6%5-9.0. Finally, routine sample analyses are not deemed to be reliable for the identification of potential toxicants in a sump fluid sample.
