Environ. Sci. Technol. 1991, 25, 150-155
Application of the Master Analytical Scheme to the Determination of Volatile Organics in Wastewater Influents and Effluents Larry C. Michael," Edo D. Pellizzari, and Daniel L. Norwood+ Research Triangle Institute, P.O. Box 12194, Research Triangle Park, North Carolina 27709
Volatile organic compounds were isolated, identified, and quantitiated in wastewater influents and effluents by using the EPA Master Analytical Scheme. These analyses were performed as part of a US.EPA assessment of water quality in the Great Lakes basin. In addition to 50 target compounds, up to 55 nontarget (unknown) compounds were identified and quantitated in 20 samples obtained from public-owned treatment works (POTWs). This analytical approach showed clear reductions between influents and effluents, in the number of compounds identified, the total concentration of halogenated and nonhalogenated compounds, and the concentration of the largest component. Reductions in the number of target compounds detected in influents vs effluents were relatively small in proportion to reductions in the total amounts of halogenated and nonhalogenated compounds. Overall, reductions in nontarget compounds, before and after treatment, were comparable to reductions in target compounds in terms of both number and total concentration.
Table I. POTW Samples Analyzed for Volatile Organics by Using the Master Analytical Scheme Protocol
Introduction Effluents from municipal wastewater treatment plants are commonly discharged into rivers, either directly or into smaller streams, which subsequently feed into rivers. The chemical composition of these effluents may be affected by many factors, including the industrial/municipal composition of the influent and the nature and performance of the treatment facility. Wastewater effluents contain a variety of pollutants that may ultimately affect the quality of the receiving surface water. Of these diverse pollutants some are present a t very low concentrations (pg/L) but nevertheless pose a significant threat to water quality. In addition to their direct adverse influence on river water quality, low-level pollutants associated with municipal and industrial wastewaters may also deteriorate treatment efficiency through intrinsic toxicity to treatment plant biota. Overall, the influence of these micropollutants will be most acute during periods of low river volume, when the plant discharge(s) may represent a significant portion of the overall river composition. A program was conducted by EPA's region V on the Great Lakes basin to acquire data needed to model the water quality impacts of specific organic pollutants. Chemical analysis of influent and effluent water samples from municipal wastewater treatment plants for specific organic pollutants was performed as part of this program. The organic analyses employed the Master Analytical Scheme (MAS) (I), a set of protocols developed to determine a broad spectrum of organic pollutants from a wide variety of chemical classes. The MAS volatile organics (VO) protocol is designed to measure purgeable organic compounds in wastewaters, as well as other types of water. The development and validation of the MAS protocol for volatile organics in water has been previously described (2, 3 ) . The purpose of this study was to determine the
Experimental Procedures The MAS VO protocol prescribed all aspects of sample handling and analysis, including sample collection, sample handling, analyte extraction and subsequent isolation of organics, and analysis of volatile organics by gas chromatography/mass spectrometry ( I , 2). Sample Collection and Handling. Volatile organic (VO) compounds were sampled according to the MAS protocols ( I ) . Briefly, water samples were collected without headspace in 250-mL septum-sealed bottles containing National Institute of Science & Technology (NIST) deuterated internal standards (in crushable microcapsules) and magnetic stir bars. Sampling containers were supplied by Research Triangle Institute (RTI) to EPA's region V personnel, who collected the samples and returned them to RTI. Table I lists the samples collected and their origin. Upon receipt of each sample in the laboratory, chlorine was determined and stoichiometrically reduced with sodium thiosultate. The microcapsules containing the NIST internal standards were crushed by rapid magnetic stirring. The samples were stored at 4 OC in the dark. Blanks (reagent water), controls (reagent water spiked with selected target analytes), and duplicate samples were also dosed with the internal standards and were maintained for quality control purposes. Isolation of Volatile Components and Analysis. Prior to analysis of samples, system performance solutions (SPS) were analyzed on a Finnigan 4500 GC/MS/COMP to ensure that acceptable instrumental performance was maintained. The system performance solution comprised selected compounds listed in Table 11. These compounds were introduced into the chromatographic system as a gas mixture to approximate the conditions encountered by sample components. Subsequently, relative molar response (RMR) factors were determined according to the VO MAS protocol (I) for the target analytes available in the RTI inventory vs deuterated internal standards and external standards. The external standards, 1-bromo-4-fluoro-
Present address: Glaxo, Inc., 5 Moore Dr., Research Triangle Park, NC 27709. 150
Environ. Sci. Technol., Vol. 25, No. 1, 1991
sample code wastewater treatment influenta effluentb plant collection location JI1-I JI2-I JIB-I JI4-I A1-I A2-I G1-I G2-I W1-I W2-I
JI1-E JIBE JI3-E JI4-E A1-E A-2E G1-E G2-E W1-E W2-E
Jones Island' Jones Island Jones Island Jones Island Akron, OH Akron, OH Gary, IN Gary, IN Wyandotted Wyandotte
I, nonchlorinated influent. CMilwaukee,WI. dDetroit, MI.
date collected 08/19,20/85 08/19,20/85 08/19,20/85 08/19,20/85 07/23,24.85 07123,24185 10/21,22/85 10/21,22/85 12/15,16/85 12115,16185
E, chlorinated effluent.
relative levels of organic chemicals in influents and effluents a t public-owned wastewater treatment works (POTWs) by using the MAS volatile organics protocol.
0013-936X/91/0925-0150$02.50/0
0 1990 American Chemical Society
Table 11. System Performance Solution" test/function limit of detection (S/N)* peak asymmetry ( PAF)c acidity/ basicityd separation number (SN)' chromatographic resolution (R)f capillary capacityg NIST internal standards
external standards
components (9)
acceptance criteria
1,3,5-trimethylbenzene 1-octanol 5-nonanone acetophenone acetophenone (A) 2,6-dimethylphenol (DMP) 2,6-dimethylaniline (DMA) n-octane n-decane ethylbenzene p-xylene n-nonane bromoethane-d, chlorobenzene-d, anisole-2,4,6-d3 naphthalene-& 1-bromo-4-fluorobenzene perfluorotoluene
S/N ( m / z 51) >4:1 PAF ( m / z 70 or 84) 40
observed range
loo->
120
>40
N/A
" A comprehensive presentation of the application of the system performance solution is given in ref 1. Signal-to-noise ratio for 10 ng of the specific component. 70 peak asymmetry factor = B / F X 100, where B is the width of the back half of the chromatographic peak and F is the width of the front half of the chromatographic peak-both a t 10 above baseline. dCalculated as peak area ratio. eSeparation number = D / ( W , t W,) -- 1, where D is the distance between the apices; W1, W , are the peak widths a t half-height. fcalculated as valley = valley/peak height, where valley is the height of the interpeak valley above baseline; peak height is the height of the first peak of the doublet. g Calculated equivalent to peak asymmetry factor. Not significant for nonpolar, volatile compounds. benzene (BFB) and perfluorotoluene (PFT),were used to assess recovery of the internal standards and were used for quantitiation only if recovery of all of the latter fell below 40%. Volatile organic compounds were isolated from the water samples and analyzed as prescribed by the MAS protocol. Briefly, 200 mL of sample was transferred from the sample container into the purge flask, containing 60 g of anhydrous sodium sulfate, by means of a helium-pressurized sample delivery system. After the salt was dissolved, the sample was purged with helium for 20 min at 25 mL/min. During the purging, volatile organic sample components were partitioned into the gas stream and subsequently collected on a Tenax GC (Enka Research Institute, Arhem, The Netherlands) trap. After residual water vapor was removed from the trap with a 5-min "dry purge", the trapped compounds were desorbed from the Tenax trap for 8 min (15 mL/min He) at 200 "C, cryofocused in a liquid nitrogen cooled trap, and subsequently flash evaporated at 200 "C onto the capillary chromatography column. All samples, blanks, and controls were processed by this procedure. Identification. The procedure for identifying chemicals is not delineated in the Master Analytical Scheme protocol. Compounds were divided into two groups: targets and unknowns. Targets were those compounds for which a relative molar response (RMR) factor had been previously determined. Unknowns were all other volatile organic compounds. Targets were identified by spectral matching of components eluting in specific retention time windows to INCOS (Finnagin MAT) mass spectral library spectra or to published spectra. These retention windows were determined from the elution of target compounds in the calibration mixtures used previously to determine RMRs. Mass spectra for unknowns, detected above a predetermined threshold, were also compared with INCOS library or published spectra. Accuracy of identification of unknowns was reported as the FIT (i.e., the agreement of the intensity of an ion in the unknown with the intensity of the same ion in the library spectrum, integrated across all spectral ions). Quantitation. Compounds isolated from water samples were quantified by using a spreadsheet program based on SYMPHONY (Lotus Development Corp.). This program
directly incorporated raw data files from the GC/MS data system into a master spreadsheet and calculated chemical concentrations by using the previously determined RMR factors. Fifty compounds were targeted for measurement in each sample. Prior to sample analysis, a set of initial RMR values was compiled by repetitive analysis of a calibration mixture of target compounds and internal standards at known relative concentrations. Calculated RMR factors were then input directly to the spreadsheet for use in subsequent calculations. RMR factors were also calculated for the internal standard compounds vs the external standard, PFT, from daily analysis of the system performance solution. These "daily" RMRs were regressed with the initial RMRs (for internal standards vs PFT) to yield a daily RMR correction factor. This correction factor consisted of a slope and y intercept which, when multiplied by the initial RMR database, resulted in an RMR factor that compensated for differences in instrument performance between the date the initial RMR database was created and the specific date of sample analysis (I). Blank samples were processed by using historical analyte recoveries (2). Mean background values (ng) were computed for all analytes detected above 1 wg/L in the blank samples. Control samples were processed by using this blank datum and assumed quantitative recoveries. Ultimately, target compounds identified in each sample were quantitated with the appropriate RMR, the RMR correction factor, the mean background value, the mean recovery and, finally, the sample volume to yield the concentration of that component in micrograms per liter. This mathematical process can be described by the equations
%(A) =
(area,) (MWd (pg(1.S.)) ( a r e a d (MW1.s.)(RMRA/l.s.)(RMR corr. factor) (1)
( d A ) - wg(b1ank)) concn (ppb) = recovery(A,x sample volume (L) (2) where areaA is the integrated peak area for analyte, A; areaI.s,is the integrated peak area for the internal standard; Environ. Sci. Technol., Vol. 25, No. 1, 1991
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Table 111. Concentrations (ppb) of Target Compounds Quantitated in POTW Influent and Effluent Samplesa
compoundc 1,2,4-trimethylbenzene 4-methylisopropylbenzene p-diethylbenzene p-diethylbenzene sec-butylbenzene naphthalene toluene ethylbenzene p-xylene 1,3,5-trimethylbenzene 1,4-dichlorobenzene
POTW SITEbte$f 53 54 A1 A2 G1 G2 W1 w2 - -___ - - __ I E I E I E I E I E I E I E I E P E
-
52 mean _J1 _ r e c d I E 94 100 81 81 113 74 125 96 98 181
7 6 4 4
