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Volatile organic components of municipal primary sewage effluent after chlorination and dechlorination

University of British Columbia

The extraction, separation and identification of volatile organic components of primary effluent before and after chlorination was undertaken to ascertain whether the chlorination of treatment plant effluents results in the formation of new volatile chlorinated organics. Extraction efficiencies of 70 to 90 percent of an aqueous solution of phenols were obtained by both continuous solvent extraction and sorption on a column of a macroreticular resin. Tests with primary effluent showed that the macroreticular resin recovered a slightly larger number of compounds than the solvent extractor which also suffered from emulsion problems.' Since the resin was also expedient in handling replicate samples it was adopted and further studies indicated that it had a capacity of 1.7 mg TOC/cc of resin and recoveries of the phenols were unaffected by pH or detergents. Preliminary separation of the. .components on the basis of acidity with .05'M^NaOH and diethyl ether and by thin layer chromatography on silica gel with pet ether and methanol proved to be useful. Gas chromatographic (GC) studies with various silicone liquid phases demonstrated that OV-101, 0V-17, and 0V-225 all provide good separation after optimization of temperature programs. Primary effluent samples taken from Lion's Gate Treatment Plant in North Vancouver on Monday mornings proved to be remarkably consistent in their GC 63 traces as monitored by Ni electron capture (EG) and flame ionization (FID) detectors. A series of spectacular new peaks was consistently observed by EC as a result of chlorination, but the FID showed only minor changes. Dosage levels of up to 120 mg/1 Cl₂ (NaOCl) produced similar chromatograms while a dosage of 200 mg/1 produced a new set of changes not found at the dosage levels used in treatment plants. Gas chromatographic studies with a micro- electrolytic conductivity detector showed that 10 or 11 new halogenated peaks in the neutral and basic fraction and 6 or 7 new halogenated peaks in the acidic fraction result from chlorination. These compounds all of which are in μg/l concentrations account for only 0.01 percent of the applied chlorine dosage but make up about 40 percent of the more volatile organically bound halogen present in chlorinated primary effluent. After a series of partially successful attempts by retention time, GC-MS and GC effluent trapping, a number of components were positively identified by a computerized GC-MS. TRirty-one compounds were positively identified by mass spectra and GC retention times, another 24 were tentatively identified by mass spectra and an additional seven were very tentatively identified by GC retention times. Only three of the compounds resulting from chlorination were positively identified. All compounds identified by mass spectra are present in concentrations in primary effluent. The implications of this study and suggestions for further investigations are also discussed.

Text

2010-02-08

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http://hdl.handle.net/2429/19798

Civil Engineering

University of British Columbia

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