Copper Bioavailability and Toxicity in the Houston Ship Channel

Test solutions used in copper WER studies are prepared by carefully spiking copper into synthetic laboratory water and site waters.

National ambient water quality criteria (AWQC) set threshold concentrations for a variety of environmental contaminants. These criteria are stringent enough to protect the most sensitive species potentially exposed to a contaminant in a water body.  However, because water quality characteristics and the sensitivities of resident species are highly variable among water bodies, the AWQC may prove over- or under-protective in some aquatic systems.  To account for this, EPA guidelines provide several methods for adjusting AWQCs considering site-specific factors.

One such method, derivation of a water-effect ratio (WER) applicable to a particular site, has proved especially useful. In the WER method, median lethal concentrations (LC50) are derived using experimental data from parallel acute toxicity tests in which the metal of concern is added to a clean laboratory water and site water. The LC50 from the site water test is divided by the LC50 from the laboratory water test to obtain the WER. The applicable water quality standard is then multiplied by the WER to establish a site-specific standard for the water body of concern.

The Houston-Galveston Area Council, the regional oversight agency for the Texas Clean Rivers Program, selected PBS&J as part of a team to study copper bioavailability and toxicity in the Houston Ship Channel and associated tidal tributaries and bays. The PBS&J team employed the WER procedure to establish a regional copper water quality standard that could be used by all dischargers to the relevant water bodies.

As a result of this project, and similar studies conducted for several industrial facilities along the Gulf coast, millions of dollars of additional wastewater treatment required to reach very low effluent discharge limits have been avoided.