An Evaluation of a Point Source Brine Discharge into a Riverine System and Implications for TDS Limitations

The North Fork Holston River (NFHR) below Saltville, Virginia, has been the subject of many studies due to years of contamination from a closed chloroalkali plant. In addition, a point source brine discharge high in total dissolved solids (TDS) may also be adversely affecting aquatic biota. This study assessed the toxicity of the brine discharge to selected test organisms, including two freshwater mussel species and also discusses implications for development of a TDS limit based on brine toxicity. Ceriodaphnia dubia was the most sensitive organism in acute and chronic brine toxicity tests. Bivariate analysis of the brine conductivity and C. dubia LC50 values showed no relationship (p=.1756); however, LC50 values were strongly related (r(2)=0.8818) to sodium concentrations in the brine discharge. A comparison of the results from acute tests with the brine effluent and the reference toxicant sodium chloride (NaCl) demonstrated that organisms were more sensitive to NaCl. Brine discharge toxicity to C. dubia was variable during the study duration with toxicity determined to be dependent on specific TDS constituents rather than conductivity or TDS. These results suggest the need for site-specific development of TDS criteria that are based on the specific constituents in a discharge.