Use of bench-top biological reactors for determining non-toxic disposal rates of wastes

During a recent turn-around in a high conversion refinery, a number of untreated waste streams were demonstrated to be toxic to rainbow trout in pre-release screening studies. The potential for these wastes to be detrimental to biomass in th facility`s biological oxidation unit (BIOX) and/or cause BIOX effluent to be toxic to the facility`s biomonitoring species was unknown. Consequently, bench-top biological reactors were used to investigate the potential effects of certain combinations of wastes on BIOX performance and final effluent toxicity. Physico-chemical parameters monitored in two control bench-top biological reactors, receiving the same input as the Refinery`s BIOX units, demonstrated that the bench-top reactors were representative surrogates for the facility`s BIOX treatment. Toxicity reductions, resulting from treatment of various waste streams using the bench scale reactors, were determined. Information from these studies was used to establish non-toxic discharge rates of the waste streams to the refinery`s BIOX. The authors will present an overview of the toxicity screening and bench scale biological reactor studies, as well as discuss the use of bench scale bioreactors in toxicity identification and prevention studies.