ECOTOXICOLOGICAL ASSESSMENT OF PRODUCED WATERS IN INDONESIA

An ecotoxicological study aimed at deriving practical methods for assessing the impact of complex discharges from offshore facilities has been conducted. The study focused on large volume discharges in the West Java Sea, Indonesia, which exhibit limited mixing in the receiving waters and can form “ponds” of elevated concentration as a result of variable hydrodynamic flows. A number of experiments and analyses have been conducted aimed at characterizing the effluent during the process of degradation. This information has been used to determine likely body residues in test organisms used in 96-h exposure toxicity tests. The data from the toxicity tests have been correlated with the predicted body residues to provide an approach [whole effluent toxicity (WET)] to evaluate likely mortality arising from a complex mixed effluent. This semiempirical approach has been used in an integrated physicochemical transport model where time-varying exposure concentrations can be simulated and the resulting uptake into biota modelled. This permits direct assessment of the risk posed by discharges. The toxicity test results show that, at concentrations of effluent commonly found in the receiving waters, some mortality may be encountered albeit at low levels, probably not exceeding 5%. These results are confirmed by the modelled mortality using the WET approach. The groups of compounds most likely to be contributing to the toxicity include the PAHs and phenols. Contributions from each group vary between different characterized effluents from different facilities. © 1998 John Wiley & Sons, Inc. Environ Toxicol Water Qual 13: 323–336, 1998