Removal of pharmaceutically active compounds from water systems using freeze concentration / by Yuanyuan Shao.
SubjectWater purification by freezing process
Drugs - Environmental aspects
Drug residue in wastewater
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In the last few years, there has been a growing concern in the occurrence of pharmaceutically active compounds in the aquatic environment. Just in Europe, more than 3000 prescription and non-prescription drugs are used by human and animals and more than 80 drugs have been detected in municipal wastewater treatment plant effluent, surface water, groundwater, and in a few isolated cases, in drinking water, some at alarmingly high concentrations. Although no known human health effects have been associated with exposure to drinking water containing trace concentrations of drug residues, there is concrete evidence that these drug residues could cause numerous adverse health effects on aquatic life, even at very low concentrations. Municipal wastewater treatment plant effluents have been identified as the major source of drug residues in surface waters. Conventional wastewater treatment systems cannot effectively remove pharmaceutically active compounds. The suitability of distinct wastewater treatment processes for the elimination of drug residues has not been studied. Freezing has been used successfully to treat various wastewaters. Application of freezing technology to purify water is based on the principle that when water freezes, ice crystals grow of pure water and impurities are rejected from the ice structure and become concentrated in the unfrozen liquid. Without addition of any chemicals, contaminants in a large volume of dilute wastewater can be effectively removed by freeze concentration. Objectives of this study are: 1) literature review of occurrence of pharmaceutically active compounds, treatment technologies and analytical methods; and 2) experimental study: evaluate the potential of the freeze concentration process for the removal of selected pharmaceutically active compounds, the effect of initial concentration of drug residues, freezing temperature and degree of freezing on the removal efficiency of pharmaceutically active compounds. Five drugs aspirin, ibuprofen, gemfibrozil, metoprolol and sulfamethoxazole were selected to investigate the removal efficiency of freeze concentration. Gas chromatograph-mass spectrometry and total organic carbon were used to quantify the drug concentrations in water samples. After first freezing cycle, ibuprofen and gemfibrozil were concentrated 2-3 times compared to the feed water and the concentration factors reached 12 after second freezing cycle. The total removal efficiency of the selected pharmaceutically active compounds was about 80% after one stage freeze concentration. Results indicated that aspirin degraded during the treatment; therefore, the concentration of aspirin was difficult to measure. Analysis of sample total organic carbon concentration indicated that about 84% and 92% removal efficiency was achieved for ibuprofen and gemfibrozil one stage freeze concentration. Approximately 99% impurity removal efficiency and around 60% volume reduction was observed in refrozen ice obtained from the first freezing. This research results indicated freeze concentration was effective and not sensitive to the natural of target pharmaceutically active compounds in the feed water. In addition, the analytical methodology for the determination of drug residues in complex environmental matrices is still evolving and it may takes years before the universally accepted methods are developed. The gas chromatograph-mass spectrometry method used by many researchers requires complex sample preparation, which could influence the accuracy of the analysis.