Use of toxicity identification evaluation methods to characterize, identify, and confirm hexavalent chromium toxicity in an industrial effluent

A toxicity identification evaluation (TIE) was conducted on effluent from a major industrial discharger. Although initial monitoring typically showed only slight, intermittent, chronic toxicity to Ceriodaphnia dubia. a later sample showed substantial acute toxicity to C. dubia (48-h lc(50) = 9%). Ac ute phase I toxicity characterization tests were conducted on this acutely toxic sample; none of the phase I manipulations reduced sample toxicity. Th e toxic effluent sample was then treated with activated carbon, and cation, anion, and mixed-bed ion exchange. Acute toxicity was not reduced by treat ment with activated carbon or cation exchange, but was completely removed b y anion and mixed-bed ion exchange. Based on these data, we concluded that the causative toxicant(s) was likely an inorganic anion(s); chemical analys is detected hexavalent chromium Cr[VI] at concentrations sufficient to acco unt for the observed acute toxicity. Although Cr[VI] could clearly explain the presence of acute toxicity, subsequent confirmation testing was designe d to determine whether Cr[IV] was responsible for the low-level chronic tox icity more typical of the effluent. Concurrent chronic tests conducted on u naltered and anion-exchanged effluent showed that the presence of chronic t oxicity was associated with chronically toxic concentrations of Cr[VI]. The source of Cr[VI] in the effluent was traced to a malfunctioning heat excha nger. after this malfunction was corrected, neither chronic toxicity nor ap preciable Cr[VI] was observed in the effluent again. Published by Elsevier Science Ltd.