Environ. Sci. Technol. 2002, 36, 1102-1106
Removal of Sulfur-Organic Polar Micropollutants in a Membrane Bioreactor Treating Industrial Wastewater THORSTEN REEMTSMA,* BRITTA ZYWICKI, MARKUS STUEBER, ACHIM KLOEPFER, AND MARTIN JEKEL Department of Water Quality Control, Technical University of Berlin, Sekr. KF 4, Strasse des 17 Juni 135, 10623 Berlin, Germany
While membrane bioreactors (MBR) have proven their large potential to remove bulk organic matter from municipal as well as industrial wastewater, their suitability to remove poorly degradable polar wastewater contaminants is yet unknown. However, this is an important aspect for the achievable effluent quality and in terms of wastewater reuse. We have analyzed two classes of polar sulfurorganic compounds, naphthalene sulfonates and benzothiazoles, by liquid chromatography-electrospray ionizationtandem mass spectrometry (LC-ESI-MS) over a period of 3 weeks in the influent and effluent of a full-scale MBR with external ultrafiltration that treats tannery wastewater. While naphthalene monosulfonates were completely removed, total naphthalene disulfonate removal was limited to about 40%, and total benzothiazoles concentration decreased for 87%. Quantitative as well as qualitative data did not indicate an adaptation to or a more complete removal of these polar aromatic compounds by the MBR as compared to literature data on conventional activated sludge treatment. While quality improvements in receiving waters for bulk organic matter are documented and the same can be anticipated for apolar particle-associated contaminants, these data provide no indication that MBR will improve the removal of polar poorly biodegradable organic pollutants.
Introduction Membrane bioreactors (MBR) that combine a biological wastewater treatment with membrane separation to retain particles attract increasing attention. Municipal as well as industrial wastewaters may be treated in this kind of reactor (1, 2), and its main advantages as compared to conventional activated sludge (CAS) treatment are less sludge production, smaller footprint size, and unsurpassed effluent quality in terms of turbidity, bacteria and viruses, and, occasionally, dissolved organics. The main application of MBR reported in industry are heavily loaded wastewaters such as those discharged from tanneries (3) and from the textile industry (4) or oily wastewaters (5, 6). Besides improving the discharge quality, the use of membrane processes in wastewater treatment (e.g., reversed osmosis, nanofiltration) may enable the reuse of * Corresponding author phone: +49-30-31426429; fax: +49-3031423850; e-mail:
[email protected]. 1102
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 36, NO. 5, 2002
industrial wastewater as process water and may allow the indirect potable reuse of municipal wastewaters. A wider application of membrane processes is thus expected to reduce freshwater consumption. Operational influences on the performance of MBR have been investigated in numerous studies, but the microbiology and physiology of MBR are far from being understood (7). Several factors may contribute to the lower organic carbon content of MBR effluents as compared to CAS processes: (i) more complete mineralization of degradable raw water organics due to a lower feed to biomass ratio because of the higher biomass concentration; (ii) more effective removal of less degradable high molecular weight compounds due to higher lysis activity in the reactor induced by elevated concentrations of these high molecular weight compounds, which were rejected by the ultrafiltration membrane (8, 9); (iii) adaptation of microorganisms to less degradable compounds enabled by the enhanced sludge retention time (SRT); (iv) lower concentrations of soluble microbial products (SMP) in the effluent, as cell decay occurs in the bioreactor and SMP released by this process are hydrolyzed and used as feed therein (10). Although the potential of MBR to remove dissolved organic compounds is well documented in terms of the dissolved organic carbon content (DOC) or the chemical oxygen demand (COD), it is still unknown whether MBR are able to mineralize polar low molecular weight contaminants that are presently not removed by CAS treatment. Knowledge about this aspect appears important to truly evaluate the potential of the MBR technology and its applicability in terms of water reuse and to assess whether MBR treatment provides a solution to environmental concern related to the use of certain polar persistent pollutants. We report here on the removal of two classes of polar sulfur-containing aromatic industrial chemicals, naphthalene sulfonates and benzothiazoles, in a membrane bioreactor treating industrial wastewater. We use these compound classes as model substances to study the removal capacity of MBR toward hardly degradable organic compounds in comparison to that of CAS. These compound classes were selected for several reasons: (a) both are used frequently in various industrial processes and are thus relevant for numerous industrial effluents (11-14). they are also found in municipal wastewaters (11, 15, 16). (b) Both compound classes consist of members that are known to be well degradable in CAS and of others that were shown to persist. Their removal in MBR can thus be well compared to that in CAS in terms of quality and quantity. (c) Both are polar compound classes of low molecular weight and are neither removed by sorption nor rejected by the membrane itself. We have previously developed highly selective methods for the detection of naphthalene sulfonates (12) and benzothiazoles (17) from industrial wastewater by means of LCMS/MS that are now utilized in this study.
Materials and Methods Treatment Facility. The full-scale biological treatment of the tannery consisted of a pressurized bioreactor that was coupled to a ultrafiltration unit (see figure in Supporting Information) and that treated an average of 430 m3 d-1 wastewater; the system was in operation for several years prior to this investigation (3). Several treatment steps precede the biological treatment: sulfide of the beamhouse waste10.1021/es010185p CCC: $22.00
2002 American Chemical Society Published on Web 01/23/2002
water is oxized with oxygen and Mn2+, while chromium in the tanning stream is removed by precipitation at pH 10. Four pressurized bioreactors (1.5-2 bar) were coupled in series giving a total volume of 680 m3. The first reactor was operated under denitrifying conditions with an average recycle flux of 100 m3 h-1 from the membrane unit (see below), but complete nitrification and denitrification were not obtained; the average N-removal was about 86%. All reactors were operated at a temperature of 35-40 °C and with a mean liquor suspended solids (MLSS) contents of 10-20 g L-1. The average solids retention time (SRT) was 56 d, and the hydraulic retention time (HRT) was around 1.5 d. The average reactor feed (F/M ratio) of the system was 0.14 kg of COD (kg of MLSS)-1 d-1. The reactor effluent was coupled to a tubular cross-flow ultrafiltration consisting of six units that can be operated in parallel and that are equipped with membranes of a nominal cutoff value of 100 000 U comprising a total membrane surface area of 288 m2. An average membrane flux of 130 L m-2 h-1 with a feed flow of 610 m3 h-1 and a mean crossmembrane flux of 5.6 m s-1 was obtained. The average recycle flux of about 500 m3 h-1 was directed to the reactor influent (15%) and effluent (85%). Sampling, Storage, and Handling. The 24-h composite samples were taken from the reactor influent and effluent during 4 weeks (November and December 1999; April and December 2000). The samples of each week were stored at 4 °C and transported to the laboratory in a cooled container. After the arrival of the containers, pH and conductivity were measured directly, and the samples were filtered over 0.45µm membrane filters and stored in a refrigerator. DOC, UV absorbance, COD, and anion concentrations were determined within the next day. Influent samples were diluted 1/200 for DOC and COD measurements, while effluents were diluted 1/10. For benzothiazole analyses, 5-mL aliquots were stored frozen until the day of analysis, and naphthalene sulfonates were determined from the filtered (0.45 µm) and cooled (4 °C) samples within 1 week. Analytical Procedures. Bulk Parameters. DOC was determined from membrane-filtered samples by a LiquiToc analyzer (Elementar, Hanau, Germany). The UV absorbance was measured with a spectrophotometer (Lambda 12; PerkinElmer, U ¨ berlingen, Germany), and the COD was photometrically detected from filtered samples after dichromate oxidation with the HACH rapid test (Lange, Du ¨ sseldorf, Germany) after appropriate dilution. Anions were detected by suppressor ion chromatography after 1/10 dilution (nitrite, nitrate, phosphate) or 1/200 dilution (chloride, sulfate) with an AS 50 system (Dionex, Idstein, Germany). Microcontaminants.. The samples from three of the four weeks were analyzed for the microcontaminants. The analysis of naphthalene sulfonates was performed by reversed-phase high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The sulfonates were detected in the negative ionization mode by multiple reaction monitoring (MRM) as described elsewhere (12). After the filtered wastewater samples were diluted 1/10, a 10-µL sample volume was directly injected into the chromatographic system. Quantitation was performed by standard addition of the concentration levels of 1, 5, 10, 20, 50, and 100 µg L-1 for the influent samples and 0.5, 1, 5, 10, 20, and 50 µg L-1 for the reactor effluents (18). Benzothiazoles were also analyzed by HPLC-ESI-MS/ MS. For this chemically more heterogeneous class of compounds, a set of two methods were employed with MRM detection in the positive and the negative ionization modes (17). The analytes were quantified via an internal standard by external calibration. Sample volumes of 100 µL were used for analysis in the positive mode, while a 15-µL sample aliquot was injected in the negative mode.
TABLE 1. Average Bulk Parameters of the Four 1-Week Investigation Periods influent
effluent
parameter
na
mean S(x) mean S(x)
pH CODb (mg L-1) DOC (mg L-1) Abs254 (cm-1) Cl (mg L-1) SO4 (mg L-1) PO4-P (mg L-1) NO3-N (mg L-1)
23 14 23 23 23 23 20 23
9.2 2990 1200 5.6 2680 2250 720 18
a
No. of measurements.
b
1.1 770 340 2.4 710 380 430 21
7.7 180 64 0.9 2960 3390 10 33
0.4 40 15 0.2 600 260 13 27
diff -2810 -1130 -4.7 280 1140 -710 15
diff (%) -94 -95 -84 10 51 -99 86
Of the filtered (0.45-µm) sample.
Results and Discussion General Quality Parameters. The quality parameters for the influent and the effluent of the MBR averaged over the four weeks of investigation are summarized in Table 1. The removal of COD and DOC was about 95%; removal rates exceeding 90% are characteristic for MBR treatments of industrial wastewaters using ultrafiltration membranes (e.g., refs 6 and 19). It should be noted that the filtered COD was determined in this study, while typically the COD is determined from the homogenized sample including its particles. Since MBRs completely retain particulate material, the removal rate of this reactor if related to the homogenized COD would be even higher. The removal of aromatic compounds as determined by the UV absorbance (Abs254) in the MBR was lower (84%) than the DOC removal; this is a feature common to any biological wastewater treatment, as the aromatic compounds are generally less amenable to biodegradation than aliphatic ones and become relatively enriched. This decrease in dissolved organics as a whole and its aromatic fraction illustrates the unsurpassed removal efficacy of the MBR technology toward bulk organic matter: in a two-step anaerobic and aerobic laboratory treatment of a tannery wastewater of slightly lower average load (900 mg L-1 of DOC and 4.0 m-1 of Abs254), total removals were significantly lower with 85% and 50% for DOC and UV absorbance, respectively (20). However, those results were already the best reported for a pure biological treatment of tannery wastewater. Although the lower growth rate of biomass in a MBR reduces its nutrient requirements as compared to CAS systems (19), phosphate was added to the raw wastewater prior to the treatment as this improved the DOC removal; indeed all phosphate (99%) was utilized by the microorganisms (Table 1). However, phosphorus addition must be performed carefully, as an excess phosphorus supply may decrease the efficacy of MBRs; a COD:P ratio of 10:0.6 was reported to be a typical value (21). The sulfate concentration increased drastically during the treatment due to the oxidation of residual sulfide from the beamhouse wastewater. Nitrate-N concentrations did also increase to a final 33 mg L-1 in the effluent (Table 1). Tannery wastewater is a complex mixture of biogenic compounds of the skins and synthetic chemicals that are used in the production process (20). Aromatic sulfonated compounds (22) and benzothiazoles (14) are well-known constituents of many tannery wastewaters. Naphthalene Sulfonates. Naphthalene monosulfonates (NSA) and disulfonates (NDSA) are widely used in and discharged from aqueous production processes (12). Their major use is as dispersants, and they are intermediates in the production of sulfonated naphthalene formaldehyde condensates that are used as concrete plasticizers and VOL. 36, NO. 5, 2002 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
1103
TABLE 2. Average Removal Efficacies (% of Influent Concentrations) for Naphthalene Monosulfonates (NSA) and Disulfonates (NDSA) in a Sewage Treatment Plant with CAS Treatment (1 week; 28) and the MBR Treating Tannery Wastewater (3 weeks) NSA
CASa MBRb MBR 25d MBR 75d
NDSA
1-
2-
2,6-
1,6-
1,7-
2,7-
1,5-
100 >99 94.7 99.7
100 >99 98.5 100
95 97 31 98.5
96 87 39 99.5
5 44 0 86
78 c 0 40
4 c 0 41
a Data from ref 28. b Based on the median values. c No statistically significant difference (two-tailed T test). d 25 and 75 percentile values of the concentration difference between influent and effluent.
FIGURE 1. LC-MS/MS chromatograms of naphthalenesulfonates in (a) the influent and (b) the effluent of the MBR: (1) 2,6-, (2) 1,5-, (3) 2,7-, (4) 1,6-, (5) unknown NDSA, (6) 1,7-NDSA, (7) 1-, and (8) 2-NSA.
FIGURE 2. Influent and effluent concentrations of naphthalene sulfonates in daily composite samples of 3 weeks (n ) 17). Note that the concentration axis has two different scales; the boxes represent the 25-75% percentile; the whiskers extend to the extremes. synthetic tanning agents (23). A typical chromatogram of the naphthalene sulfonates that were detected in the influent and the effluent of the MBR by LC-MS/MS with MRM detection is given in Figure 1. The concentration data for all of the detected naphthalene sulfonates are depicted in Figure 2. The high variability of the influent quality is indicative of the discontinuous production processes in the tannery. From the total concentration of 8.8 µmol L-1 of naphthalene sulfonates in the influent, 93% were removed in the MBR process, resulting in an average total effluent concentration of 0.64 µmol L-1. The extent of removal of naphthalene sulfonates thus corresponds to that found for bulk organic matter (see above). However, the removal efficacy strongly depends on the molecular structure of the naphthalene sulfonates (Figure 2). The removal of the monosulfonates accounted for 94% of the total decrease of naphthalenesulfonate concentration as 1-NSA and 2-NSA were degraded to more than 99%. However, the total concentration of disulfonates was reduced for 40% only. Of the various isomers, only the 2,6- and the 1,6-NDSA are effectively removed. The 1,7-isomer exhibits a moderate removal efficacy (44%), while no significant 1104
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 36, NO. 5, 2002
decrease in 1,5- and 2,7-NDSA is visible from our data (Figure 2). This variable and partly limited biological removal of NDSA corresponds to findings from natural environments. The biological removal of 1,6- and 2,6-NDSA is known from bank filtration (24) and laboratory tests (25). Results from bank filtration show incomplete removal for the 2,7-isomer (26, 27) and 1,7-NDSA (26). 1,5-NDSA appeared to be the most stable isomer in all studies. The most comprehensive data on the removal of naphthalene sulfonates by CAS of municipal wastewater originate from Altenbach and coworkers (11, 28). They investigated removal of naphthalene sulfonates at concentrations of 2-60 µg L-1 from a wastewater with a significant contribution (15-25%) from textile industry and with sludge ages of up to 20 d (28). In comparison to their data, the potential of MBR to remove naphthalene sulfonate isomers from wastewater appears to be very similar to that of the CAS treatment, although differences concerning 1,7- and 2,7-NDSA are visible (Table 2). In light of the specific operational conditions of a MBR, one could have expected that this kind of treatment shows improved removal of some NDSA, as the low substrate supply and a high sludge age (adaptation) should favor the complete degradation of certain isomers such as 1,7- and 2,7-NDSA. This is, however, not visible from the data we obtained. Despite the variability in the wastewater composition, the various NDSA isomers were supplied to the reactor all the time; thus, the variability of wastewater composition is not expected to have hampered adaptation to these substrates. It is noteworthy that no indication from literature could be found that the longer SRT in MBR leads to the expected adaptation and enhanced removal of polar contaminants. Benzothiazoles. Derivatives of 2-mercaptobenzothiazole (MBT) such as 2-thiocyanomethylthiobenzothiazole (TCMTB) are used as fungicides in the tanning process (14). The main use of MBT and its derivatives is as vulcanization accelerators in rubber production, but there are many other applications that make these compounds frequent constituents of many industrial wastewaters (13, 14) and municipal effluents (15, 16). Contrary to the naphthalene sulfonates mentioned above, the benzothiazoles investigated here are not all active ingredients of production processes but are chemical and microbial transformation products (Figure 3). For example, MBT is a major hydrolysis product of TCMTB, whereas methylthiobenzothiazole (MTBT) was shown to originate from the microbial methylation of MBT (14). Only recently, 2-hydroxybenzothiazole (OHBT) was shown to be an intermediate in the mineralization of benzothiazole (BT) by pure bacterial cultures (29) (Figure 3). The concentrations of the various benzothiazoles in the reactor influent and effluent over the 3-week period are displayed in Figure 4. The median total concentration in the
FIGURE 3. Benzothiazole transformation scheme as derived from laboratory experiments with mixed (14, 30-32) and pure cultures (29). and 72% were obtained for two different tannery wastewaters with the two-step treatment. In that study, MBT, BT, and MTBT were the most important constituents of the aerobically treated wastewater. Considering the total concentrations, the elimination potential for benzothiazoles in the MBR is comparable to but not significantly better than that previously reported for a CAS system.
FIGURE 4. Influent and effluent concentrations of benzothiazoles in daily composite samples of 3 weeks (n ) 12-20). Note that the concentration axis has two different scales; refer to Figure 2 for explanation of the boxplot. influent adds up to 3.7 µmol L-1; with an average of 87% of this being removed in the MBR treatment the effluent concentration amounts to 0.5 µmol/L. The concentrations as well as the extent of removal strongly differ for the various members. MBT is the dominant compound in the raw wastewater (95 % of total concentration), and it is almost completely (99.9 %) removed in the MBR treatment. However, a part of this “removal” appears to be due to oxidation to the corresponding benzothiazole-2-sulfonic acid (BTSA), as its concentration significantly increases from a median concentration of 29 µg L-1 in the raw wastewater to 85 µg L-1 in the reactor effluent (Figure 4). There, BTSA accounts for 80% of the total concentration of benzothiazoles. BT is removed by 37% only, while no significant alteration in the concentrations was detected for 2-aminobenzothiazole (ABT), OHBT, and MTBT. The occurrence of BTSA and BT in the reactor effluent is astonishing as BT is easily degradable and OHBT was found as an intermediate in this degradation (29). Even BTSA has been reported to be degradable by mixed cultures (30, 31). Literature data that would allow a comparison with CAS treatment of benzothiazoles are scarce. The only data available originate from a two-step bench-scale anaerobicaerobic treatment of tannery wastewater (14). Starting with average total raw wastewater concentrations that are comparable to this study (8 and 3.4 µmol L-1), removals of 80%
Implications for Surface Water Quality. Despite the unsurpassed potential of the MBR to remove bulk organic matter of the industrial wastewater, the data obtained for naphthalene sulfonates and benzothiazoles do not indicate an improved degradation of polar organic pollutants of “borderline biodegradability” as compared to CAS. Neither were adaptation phenomena observed that would have led to the degradation of analytes that were not removed in CAS systems, nor was any positive effect of the lower feed discernible in that a compound was more completely removed than by CAS treatment. However, the data available for this comparison do not originate from a parallel CAS treatment. Rather literature data of either a municipal wastewater treatment (sulfonates; 11, 28) or a lab-scale treatment (benzothiazoles; 14) had to be used. On this basis, no indication was obtained that the use of MBR for the treatment of watewaters will cease the discharge of poorly degradable polar pollutants into receiving water and their distribution in the aquatic system. This clearly contrasts the behavior of apolar contaminants that are associated with particulate material and, thus, rejected by the ultrafiltration. Rather, it may be questioned whether the fraction of bulk organic matter that is more effectively removed by MBR as with CAS treatment would also be amenable to the self-purification potential of the receiving surface waters. In this case, MBR can help to further reduce oxygen consumption in a receiving water and thus to improve surface water quality on a local scale. But MBR would then not be able to contribute to a global improvement of water quality by avoiding the discharge of polar pollutants. Additional investigations are needed to fully elucidate these aspects, namely, with immersed membrane systems that are used increasingly and that avoid shear stress toward the biomass.
Acknowledgments We thank the tannery and the responsible wastewater treatment engineers (ITG, Gomaringen, Germany) for kind cooperation. Financial support by the German Research Council (DFG, Bonn) through SFB 193 (TP A14) and by the European Union through Grant ERB IC18*CT98-0286 in the INCO/DC framework is gratefully acknowledged. VOL. 36, NO. 5, 2002 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
1105
Supporting Information Available Scheme of the biological treatment of tannery wastewater. This material is available free of charge via the Internet at http://pubs.acs.org.
Literature Cited (1) van Dijk, L.; Roncken, G. C. G. Water Sci. Technol. 1997, 35 (18), 35-41. (2) Visvanathan, C.; Ben Ami, R.; Parameshwaran, K. Crit. Rev. Environ. Sci. Technol. 2000, 30, 1-48. (3) Krauth, K. Water Sci. Technol. 1996, 34 (3-4), 389-394. (4) Rozzi, A.; Malpei, F.; Bianchi, R.; Mattioli, D. Water Sci. Technol. 2000, 41 (10-11), 189-195. (5) Zaloum, R.; Lessard, S.; Mourato, D.; Carriere, J. Water Sci. Technol. 1994, 30 (9), 21-27. (6) Knoblock, M. D.; Sutton, P. M.; Mishra, P. N.; Gupta, K.; Janson, A. Water Environ. Res. 1994, 66, 133-139. (7) Rosenberger, S.; Witzig, R.; Manz, W.; Szewzyk, U.; Kraume, M. Water Sci. Technol. 2000, 41 (10-11), 269-277. (8) Confer, D. R.; Logan, B. E. Water Res. 1997, 31, 2137-2145. (9) Cicek, N.; Franco, J. P.; Suidan, M. T.; Urbain, V.; Manem, J. Water Environ. Res. 1999, 71, 64-70. (10) Confer, D. R.; Logan, B. E. Water Res. 1997, 31, 2127-2136. (11) Altenbach, B.; Giger, W. Anal. Chem. 1995, 67, 2325-2333. (12) Storm, T.; Reemtsma, T.; Jekel, M. J. Chromatogr. A 1999, 854, 175-185. (13) Jungclaus, G. A.; Games, L. M.; Hites, R. A. Anal. Chem. 1976, 48, 1894-1896. (14) Reemtsma, T.; Fiehn, O.; Kalnowski, G.; Jekel, M. Environ. Sci. Technol. 1995, 29, 478-485. (15) Clark, L. B.; Rosen, R. T.; Hatman, T. G.; Alaimo, L. H.; Louis, J. B.; Hertz, C.; Ho, C.-T.; Rosen, J. D. Res. J. Water Pollut. Control Fed. 1991, 63, 104. (16) Paxeus, N. Water Res. 1996, 30, 1115-1122. (17) Reemtsma, T. Rapid Commun. Mass Spectrom. 2000, 14, 16121618.
1106
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 36, NO. 5, 2002
(18) Stu ¨ ber, M.; Reemtsma, T. In Anwendung der LC-MS in der Wasseranalytik; Kornmu ¨ ller, A., Reemtsma, T., Eds.; Technical University of Berlin: Berlin, 2001; pp 157-171. (19) Scholz, W.; Fuchs, W. Water Res. 2000, 34, 3621-3629. (20) Reemtsma, T.; Jekel, M. Water Res. 1997, 31, 1035-1046. (21) Cicek, N.; Franco, J. P.; Suidan, M. T.; Urbain, V. J. Environ. Eng. ASCE 1999, 125, 738-746. (22) Reemtsma, T.; Jekel, M. J. Chromatogr. 1994, 660, 199-204. (23) Wolf, C.; Storm, T.; Lange, F. T.; Reemtsma, T.; Brauch, H.-J.; Eberle, S. H.; Jekel, M. Anal. Chem. 2000, 72, 5466-5472. (24) Lange, F. T.; Wenz, M.; Brauch, H.-J. J. High Resolut. Chromatogr. 1995, 18, 243-252. (25) Da Canalis, C.; Krull, R.; Hempel, D. C. GWF, Wasser/Abwasser 1992, 133, 226-230. (26) Lange, F. T.; Redin, C.; Brauch, H.-J.; Eberle, S. H. Vom Wasser 1998, 90, 121-134. (27) Neitzel, P. L.; Abel, A.; Grischek, T.; Nestler, W.; Walther, W. Vom Wasser 1998, 90, 245-271. (28) Altenbach, B. Determination of substituted benzene- and naphthalenesulfonates in wastewater and their behaviour in sewage treatment. Ph.D. Thesis, EAWAG/ETH, Zu ¨ rich, Switzerland, 1996. (29) Besse, P.; Combourieu, B.; Boyse, G.; Sancelme, M.; de Wever, H.; Delort, A.-M. Appl. Environ. Microbiol. 2001, 67, 1412-1417. (30) Mainprize, J.; Knapp, J. S.; Callely, A. G. J. Appl. Bacteriol. 1976, 40, 285-291. (31) De Wever, H.; Verachtert, H. Appl. Microbiol. Biotechnol. 1994, 42, 623-630. (32) De Vos, D.; De Wever, H.; Verachtert, H. Appl. Microbiol. Biotechnol. 1993, 39, 622-626.
Received for review July 10, 2001. Revised manuscript received October 30, 2001. Accepted November 9, 2001. ES010185P
