Pharmaceuticals in drinking water: Occurrence, toxicity, and removal by ozone treatment

The presence of pharmaceuticals and personal care products (PPCPs) and endocrine disrupting chemicals (EDCs) in source water is considered an emerging issue in the environmental field. These chemicals find their way into water from sewage and industrial effluents and nonpoint sources of water pollution such as agricultural runoff. The aim of this research was to investigate the occurrence of EDCs and PPCPs in the Detroit River watershed, to study the efficiency of their removal by ozone treatment, and to determine their potential toxicity to human and ecosystem health. The experimental results show that a number of PPCPs and EDCs enter surface waters mainly from sewage discharges. Although they are diluted as they travel downstream Detroit River, they persist in surface water and eventually enter the drinking water treatment plant, where they are not completely removed by conventional treatment with or without ozonation.;Experiments show that ozonation is an effective technique in removing these contaminants. However, removal by ozone is affected by several factors like dissolved organic matter (DOC) load, ozone dosage and contact time, and pH plays an important role as well. Bench-top ozonation that was designed to simulate full scale treatment proved to be much more effective in eliminating most PPCPs/EDCs than the actual large-scale treatment process. As a result of the increased efficiency of the small (bench) scale treatment, an effort to identify reactive intermediates of the oxidation process from ozonation, was unsuccessful except that for carbamazepine, one byproduct was identified. Once the PPCPs begin to be oxidized, complete mineralization occurs rapidly for most chemicals tested.;Whole drinking water samples were tested for toxicity to developing fish. Fish embryos reared in whole drinking water samples that were dechlorinated before exposure had mortality rates from 50 to 75% after 14 days compared to controls of zero mortality. Hatching success of fish eggs and heart rate in juvenile fish were only minimally impacted by exposure to whole water samples. The results did not correlate with the concentrations of target compounds, thus there are likely other chemicals present in the water samples that were not evaluated that contributed to the overall toxicity.;Extracts of water were tested by microarray scans of human keratinocytes. The toxicological results are cause for concern; many chemicals in the water at ng/L concentrations can illicit toxicity. Although the microarray scan tests were designed for sensitivity, the results for the water samples were surprising; all cells exposed to the drinking water extracts failed to proliferate. Dose-response curves were generated for each target PPCP/EDC; the total toxicity to water extracts exceeded the predicted toxicity based upon the dose-response of the standard target compounds. Like the fish development assay, the conclusion is that there are more chemicals contributing to the overall toxicity of the drinking water than just the target chemicals that were analyzed.;There are fewer than 100 chemicals regulated in drinking water. This study shows that there are PPCPs/EDCs present in drinking water that are not presently being regulated. There are over 100,000 chemicals in use in the USA per year, thus there are potentially many chemicals present in drinking water that are currently not being evaluated on a regular basis. This study suggests that surface waters and drinking water should be evaluated for the occurrence of emerging chemicals, and that the regulatory standards are insufficient in protecting human and ecosystem health.