Characterization of Miscellaneous Effluent Discharges from a Mobile Offshore Drilling Unit to the Marine Environment

Abstract

A study was performed to evaluate the potential biological impacts from 8 different miscellaneous discharges from an oil and gas mobile offshore drilling unit (MODU) including deck drainage, desalination unit waste, boiler blowdown, fire control system test water, noncontact cooling water, and bilge water. Samples were evaluated for toxicity using a rapid (<1 h) initial screening test (echinoderm [Dendraster excentricus] fertilization test), and if toxicity was found, further testing was conducted using 3 chronic whole‐effluent toxicity tests. This additional testing included the embryo larval development 72‐h echinoderm (D. excentricus); 7‐d mysid (Americamysis bahia) survival, growth, and fecundity invertebrate test; and 7‐d topsmelt (Atherinops affinis) survival and growth fish test. Toxicity identification evaluations were performed on 3 discharges that consistently elicited a toxic response during whole‐effluent toxicity testing. To place the results of the toxicity testing into the context of environmental risk, the spatial extent of potential biological effects was investigated using the CORMIX mixing zone model. The output of the modeling indicated that discharge of selected effluents did not result in concentrations, or duration of exposure, that would elicit toxic effects to organisms living in the surrounding environment. The present study provides a comprehensive data set that was used to characterize potential toxicity and environmental risk of MODU “miscellaneous discharges” which could help inform future risk assessments of these discharges. Environ Toxicol Chem 2019;38:2811–2823. © 2019 SETAC

Are Vertebrates Still Needed in Routine Whole Effluent Toxicity Testing for Oil and Gas Discharges?

“…Alongside the desire to optimize WET testing performance, there is an increasing societal awareness of animal ethics, with regulatory mandates recently put in place to reduce vertebrate animal testing (e.g., Wheeler 2019). Because fish are almost always included in WET testing, this further warrants the exploration of trophic sensitivities within effluent WET test data and a search for opportunities either to use fish testing in a tiered approach or to remove it altogether (e.g., Hughes et al 2019).…”

“…For example, removing vertebrate testing from the facilities investigated in the present study could have reduced the number of vertebrates used in 2018 alone by approximately 26 000. The reduction in numbers of fish, or the replacement of fish with invertebrates, also offers other opportunities to fulfill permit compliance needs in logistically more challenging sampling environments where fish testing is not available and/or sample volume requirements for a fish test make sample transport difficult or impossible (Hughes et al 2019). There are significant opportunities to leverage all the WET information gained from effluent discharges in one region to new areas where there are similar operations with no historical effluent data.…”

“…Recent estimates indicate that >5 million vertebrates are used annually in effluent assessments worldwide (Norberg‐King et al 2018). In addition, effluent testing in very remote locations poses considerable logistical challenges to the traditional multispecies WET assessment design incorporating fish, due to the need to transport large volumes of water by helicopter within holding time limits (e.g., Hughes et al 2019). Altogether these questions and concerns motivate a comprehensive evaluation of current WET testing requirements to determine whether the use of vertebrates is still necessary, and whether current practices are environmentally protective.…”

Exploring Alternatives for Marine Toxicity Testing: Initial Evaluation of Fish Embryo and Mysid Tests

“…In this test, juvenile mysid shrimp ( Americamysis bahia ; formerly Mysidopsis bahia ) are exposed to a potentially toxic effluent and their mortality is monitored. The use of A. bahia as a model organism has proved effective for laboratory testing of potentially toxic effluents and chemicals (Boardman et al, 2004; Cleveland et al, 2000; Hughes et al, 2019). Because this test utilizes mysid shrimp rather than fish, an animal higher on the phylogenetic scale, it is considered a relative replacement in terms of the 3Rs (Institute for Laboratory Animal Research, 2011).…”