| Federal regulations such as the Clean Water Act (P.L. 92-500), and its amendments, direct the Environment Protection Agency (EPA) to implement programs to control the releases of conventional pollutants and toxics into the waterways of the United States. The EPA began requiring treatment plants to conduct toxicity tests (biomonitoring) of their effluent discharges. To control toxicity caused by chlorination of wastewater discharges, the EPA also began requiring some treatment facilities to dechlorinate their wastewater before discharging.;The study evaluated the impact of chlorination prior to dechlorination, which served as a baseline. Responses determined during dechlorination were compared to the baseline data. An overall improvement in species richness and diversity was seen at those river stations which had previously been adversely impacted by chlorine.;Aquatic toxicity tests, such as those required to be used by dischargers, were conducted during this study. Periodic toxicity was observed with these tests in the effluent and river samples after dechlorination was initiated. Those tests, along with in situ toxicity assays, proved to be good predictors of biological community responses.;This research was funded by the EPA to document the changes that occurred in the Trinity River from the dechlorination of the effluent from Ft. Worth's Village Creek municipal wastewater treatment plant. The study occurred over a two year period beginning in August 1990. A wide variety of biological field assessments and toxicological assays were used to measure various responses. Seven river stations, covering approximately twenty river miles, and the treatment plant effluent were assessed. Two of the river stations were upstream from the treatment plant and used as reference sites. The remaining five river stations were downstream from the treatment plant, spread out over seventeen river miles. |
