Seasonal Variation in the Occurrence and Removal of

ARTICLE pubs.acs.org/est

Seasonal Variation in the Occurrence and Removal of Pharmaceuticals and Personal Care Products in Different Biological Wastewater Treatment Processes Qian Sui, Jun Huang, Shubo Deng, Weiwei Chen, and Gang Yu* School of Environment, THU VEOLIA Joint Research Center for Advanced Environmental Technology, Tsinghua University, Beijing 100084, China

bS Supporting Information ABSTRACT: The occurrence of 12 pharmaceuticals and personal care products (PPCPs) in two wastewater treatment plants in Beijing was studied monthly over the course of one year. The removal of PPCPs by three biological treatment processes including conventional activated sludge (CAS), biological nutrient removal (BNR), and membrane bioreactor (MBR) was compared during different seasons. Seasonal variations of PPCPs in the wastewater influent were discrepant, while in the wastewater effluent, most PPCPs had lower concentrations in the summer than in the winter. For the easily biodegradable PPCPs, the performance of MBR was demonstrated to be more stable than CAS or BNR especially during winter months. Diclofenac, trimethoprim, metoprolol, and gemfibrozil could be moderately removed by MBR, while their removal by CAS and BNR was much lower or even negligible. Nevertheless, no removal was achieved regardless of the season or the treatment processes for the recalcitrant PPCPs. Studies on the contribution of each tank of the MBR process to the total removal of four biodegradable PPCPs indicated the oxic tank was the most important unit, whereas membrane filtration made a negligible contribution to their elimination.

’ INTRODUCTION Pharmaceuticals and personal care products (PPCPs) have received growing global attentions as emerging contaminants threatening drinking water safety and aquatic organisms.13 Considering the pathways by which PPCPs enter into the water environment, effluent from wastewater treatment plants (WWTPs) has been identified as an important source.4 A great deal of work has been done to monitor the concentration in both influent and effluent of WWTPs in many countries, and to evaluate the removal efficiency of wastewater treatment processes.59 These studies have provided necessary fundamental data helpful to the process improvement for higher removal efficiency in terms of PPCPs. However, most reported studies have been based on very short monitoring periods with only one or two sampling campaigns, which made it difficult to describe the occurrence of PPCPs over an extended period of time. The most comprehensive study was done by Loraine and Pettigrove, who sampled four drinking water treatment plants and a wastewater reclamation plant in San Diego during a period of ten months. The results revealed that the seasonal variations of some PPCPs were considerable.4 Therefore it is necessary to study the seasonal variations of both occurrence and removal of PPCPs in various processes of WWTPs. Compared to the conventional activated sludge (CAS) process most widely adopted, the emerging membrane bioreactor r 2011 American Chemical Society

(MBR) process has shown its advantage in removing bulk organic matter.10 Evaluations of MBR’s potential for PPCPs removal from municipal wastewaters have been conducted.1113 In some reports, more complete elimination of PPCPs was observed by MBR than CAS;1214 while in other studies, MBR and CAS were comparable in PPCPs removal.11,15 Most of these results were based on studies conducted over a short period or several discontinuous periods of time, and the incomprehensive evaluations might be the reason for the conflict. The only exception is a 2-year continuous investigation done by Zuehlke, which confirmed that removal efficiencies of some PPCPs fluctuated and were temperature-dependent.16 However, this study focused on limited types of PPCPs, such as phenazone-type pharmaceuticals and estrogenic steroids. In addition, in most investigations, only the influent and effluent were sampled in the MBR based processes,13,16 which prevented the assessment of individual tanks’ contributions in PPCP removal by the MBR process. Therefore, the major objective of the present study was to gain an insight into the seasonal variations in the occurrence and Received: January 20, 2011 Accepted: March 9, 2011 Revised: March 2, 2011 Published: March 23, 2011 3341

dx.doi.org/10.1021/es200248d | Environ. Sci. Technol. 2011, 45, 3341–3348

Environmental Science & Technology

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removal of PPCPs in two municipal WWTPs in Beijing. Special emphasis was placed on the comparison of three biological treatment processes, including a CAS and an MBR process in parallel and a biological nutrient removal (BNR) process, over the course of one year. A secondary objective was to understand PPCPs removal contributions of each tank in the MBR-based biological treatment process.

a cooler, and transported to the laboratory. Immediately after delivery to the laboratory, all influent and effluent samples were filtered through prebaked (400 °C, >4 h) glass microfiber filters (GF/F, Whatman). The mixed liquor samples were centrifuged at 3000 rpm for 3 min first, and then the supernatant was collected and filtered as described above. The PPCPs were extracted and analyzed by the method reported before,8,17 and briefly described in Supporting Information 4. Quality Assurance and Quality Control (QA/QC). Strict QA/ QC was implemented to ensure the identification and accurate quantification of the target PPCPs, as described previously.8,17 Median instrument, laboratory, and field blanks were all below limit of quantification (LOQ), and only concentrations detected three times above them were reported.18 As duplicate samples were collected and analyzed, mean concentrations were adopted, and the deviations of duplicate samples were less than 20%. For the statistical analysis, the concentrations below LOQ were replaced by 50% of the LOQ.19,20

’ EXPERIMENTAL SECTION

’ RESULTS AND DISCUSSION

Chemicals. Standards of 12 PPCPs, sulpiride (SP), N,Ndiethyl-meta-toluamide (DEET), caffeine (CF), chloramphenicol (CP), trimethoprim (TP), diclofenac (DF), propranolol (PPN), metoprolol (MTP), carbamazepine (CBZ), clofibric acid (CA), bezafibrate (BF), gemfibrozil (GF) (Figure S1 in the Supporting Information), as well as the internal standard (IS) 13 C-phenacetin and 3D-mecoprop, were purchased from Sigma-Aldrich (Steinheim, Germany) and Dr. Ehrenstorfer (Augsburg, Germany). These PPCPs were frequently detected in the wastewaters of many countries,57 consumed in China, and included in our previous studies regarding the analytical method and preliminary survey.8,17 Methanol and formic acid (Dikma, USA) were HPLC grade, and ultrapure water was produced by a Milli-Q unit (Millipore, USA). Stock solutions of individual compounds were prepared in methanol, and a mixture standard solution was prepared by diluting the stock solutions before each analytical run. All the solutions were stored at 4 °C in the dark. Sampling and Analysis. Two WWTPs in Beijing were selected for investigation. WWTP A employs an MBR process and a CAS process in parallel, which are fed with the same raw wastewater. WWTP B employs a BNR process, with a configuration similar to the MBR in WWTP A: both utilize anaerobic, anoxic, and oxic (A/A/O) tanks. All three processes operated efficiently during our sampling. Schematic diagrams and detailed information of these treatment processes are shown in Table 1 and Supporting Information 2. Grab samples of wastewater influent and secondary effluent were collected monthly for a whole year (Feb 2009Jan 2010) at fixed times (MBR effluent sample was not collected in March 2009 due to the maintenance of MBR). Although this sampling strategy was limited by the lack of autosamplers, it was still deemed acceptable, as the relative standard deviations (RSDs) of the concentrations of most PPCPs in the grab and 2 h-composition samples did not exceed 30% in the influent and 15% in the effluent (Supporting Information 3). In Nov 2009 and Jan 2010, additional samples of the mixed liquor from the anaerobic tank, anoxic tank, and oxic tank of MBR process were collected. All samples were collected in duplicate (500 mL for influents and 1000 mL for the others) in prewashed amber glass bottles, kept in

Occurrence in Overall. The concentrations and the detection frequencies of PPCPs in all the wastewater influent and effluent samples are present in Table 2. All the investigated PPCPs except CA, CP, and PPN were found in every influent sample. CF showed the highest contamination level, with a median concentration of 5650 ng/L. DEET, DF, TP, SP, and MTP followed, of which median concentrations were above 100 ng/L. For the wastewater effluent samples, DF and TP were identified as the predominant PPCPs, with concentrations of 35.3463 ng/L and 6.6772 ng/L, respectively; while BF, CA, CF, CP, GF, and PPN had concentrations lower than 50 ng/L and low detection frequencies (99% during the whole year. The removal efficiencies of BF were 70100% by MBR, 55100% by CAS, and 1376% by BNR process (Figure 2), which is consistent with ref 13. The removal of BF by MBR was very stable, while a minor fluctuation in removal by CAS was observed (Figure 3). The performance of BNR was temperature-dependent, as the BF removal efficiencies decreased from >60% to 60% during May to September to 90%. During CAS treatment, the same high removal was achieved in July and August (9699%). However, it decreased dramatically with the decrease of temperature. In summary, the higher biomass and the longer SRT could be the reason for the better performances of MBR over CAS and

BNR. Higher biomass in MBR led to a lower food to microorganisms (F/M) ratio. Under these conditions, the relative shortage of biodegradable organic matter may force microorganisms to metabolize more recalcitrant compounds.29,30 Longer SRT would allow the enrichment of slow-growing bacteria and the establishment of a more diverse bacterial population.12,31 The nature of microbial population has been shown to have a significant impact on the biodegradation of some PPCPs.31 Removal Contribution of MBR Tanks. To further study the performance of MBR, concentrations of four biodegradable PPCPs (BF, CF, DEET, and TP) in different tanks of MBR 3344

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Figure 2. Comparison of the overall removal efficiencies by CAS, BNR, and MBR processes.

Figure 3. Seasonal variation in the removal efficiencies of PPCPs during the whole year: comparison among MBR and other two biological treatment processes.

processes were analyzed twice to determine their removal contributions. As a portion of the wastewater was recycled from the anoxic to the anaerobic tank and from the oxic to the anoxic

tank (Figure S2), to exclude the concentration reduction due to dilution, the load based on the amount, rather than the concentration, of PPCP was used to calculate the removal efficiency in 3345



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Figure 4. Removal efficiencies of PPCPs in each tank of A/A/O-MBR process: (a) BF, (b) CF, (c) DEET, (d) TP. *** means that the removal efficiency of aerobic tank and membrane filtration could not be calculated because the CF concentrations were 72% and 98%, respectively. In the first trial, 54% of TP was removed in the oxic tank, while in the second trial the removal was negligible. For DEET, lower but still notable reduction (2124%) was observed. The oxic tank was also considered to be crucial for the biodegradation of some PPCPs in previous studies.32 The first-order biodegradation rate constant k1 of CF was found to be 0.38 h1 under aerobic conditions, much higher than those under anaerobic (0.05 h1) and anoxic conditions (0.08 h1).32 The anaerobic tank showed different performances for each PPCP. High removal efficiencies (5778%) were observed for CF. TP and DEET were moderately reduced (1439%), while less than 20% reduction of BF was achieved in the anaerobic tank. The reduction after the anaerobic tank may be ascribed to the rapid sludge-adsorption rate, which was confirmed by batch experiments.32 The adsorption of PPCPs might occur despite the redox conditions. When a full-scale anoxicanaerobicoxic process was investigated, a significant decrease of sulfonamide antibiotics was also found in the first tank.33 Biodegradation by microorganisms might be another influence on this phenomenon. Some inorganic ions, such as Fe3þ, and various organic oxidative compounds may have acted as electron acceptors.34 In addition,

some microorganisms, for instance the phosphate accumulating organisms, might use PPCPs as carbon sources during the phosphorus release process, converting them into polyhydroxyalkanoates, and then storing them in the cells in the anaerobic tank.32 The anoxic tank showed negative removal for all the 4 PPCPs. The increased load in the anoxic tank might be explained by the presence of PPCP conjugates. PPCPs can be excreted as unchanged parent compounds or as conjugates of glucuronic and sulphuric acid,33 so deconjugation during contact with activated sludge may occur, leading to an increased PPCP load. Meanwhile, as most PPCPs are mainly excreted with bile and feces, they could be enclosed in feces particles and released during biological treatment,29 therefore leading to apparent concentration increases.14 It should be noted that because the concentrations of PPCPs in the sludge were not determined, the contribution of sludge adsorption could not be distinguished, and may lead to some uncertainty when calculating aqueous phase removal. Differences between the two trials in the removal of PPCPs achieved by membrane filtration were observed. As the concentrations of the biodegradable PPCPs were very low in the oxic tank, a reasonable analytical error may lead to false apparent removal efficiency by comparing the load before and after membrane filtration. In fact, the contribution of membrane filtration was very small compared to the total removal (Figure S4).

’ ASSOCIATED CONTENT

bS

Supporting Information. This material is available free of charge via the Internet at http://pubs.acs.org.

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’ AUTHOR INFORMATION Corresponding Author

*Tel.: þ86 10 6278 7137; fax: þ86 10 62794006; e-mail: [email protected].

’ ACKNOWLEDGMENT This work was financially supported by the National Science Fund for Distinguished Young Scholars (50625823). The assistance provided by the operators of investigated WWTPs is also appreciated. ’ REFERENCES (1) Daughton, C. G.; Ternes, T. A. Pharmaceuticals and personal care products in the environment: Agents of subtle change?. Environ. Health Perspect. 1999, 107, 907–938. (2) Snyder, S. A.; Westerhoff, P.; Yoon, Y.; Sedlak, D. L. Pharmaceuticals, personal care products, and endocrine disruptors in water: Implications for the water industry. Environ. Eng. Sci. 2003, 20, 449–469. (3) Fent, K.; Weston, A. A.; Caminada, D. Ecotoxicology of human pharmaceuticals. Aquat. Toxicol. 2006, 76, 122–159. (4) Loraine, G. A.; Pettigrove, M. E. Seasonal variations in concentrations of pharmaceuticals and personal care products in drinking water and reclaimed wastewater in southern California. Environ. Sci. Technol. 2006, 40, 687–695. (5) Ternes, T. A. Occurrence of drugs in German sewage treatment plants and rivers. Water Res. 1998, 32, 3245–3260. (6) Nakada, N.; Tanishima, T.; Shinohara, H.; Kiri, K.; Takada, H. Pharmaceutical chemicals and endocrine disrupters in municipal wastewater in Tokyo and their removal during activated sludge treatment. Water Res. 2006, 40, 3297–3303. (7) Kim, S. D.; Cho, J.; Kim, I. S.; Vanderford, B. J.; Snyder, S. A. Occurrence and removal of pharmaceuticals and endocrine disruptors in South Korean surface, drinking, and waste waters. Water Res. 2007, 41, 1013–1021. (8) Sui, Q.; Huang, J.; Deng, S. B.; Yu, G.; Fan, Q. Occurrence and removal of pharmaceuticals, caffeine and DEET in wastewater treatment plants of Beijing, China. Water Res. 2010, 44, 417–426. (9) Schultz, M. M.; Furlong, E. T.; Kolpin, D. W.; Werner, S. L.; Schoenfuss, H. L.; Barber, L. B.; Blazer, V. S.; Norri, D. O.; Vajda, A. M. Antidepressant pharmaceuticals in two US effluent-impacted streams: Occurrence and fate in water and sediment, and selective uptake in fish neural tissue. Environ. Sci. Technol. 2010, 44, 1918–1925. (10) Melin, T.; Jefferson, B.; Bixio, D.; Thoeye, C.; De Wilde, W.; De Koning, J.; van der Graaf, J.; Wintgens, T. Membrane bioreactor technology for wastewater treatment and reuse. Desalination 2006, 187, 271–282. (11) Clara, M.; Strenn, B.; Ausserleitner, M.; Kreuzinger, N. Comparison of the behavior of selected micropollutants in a membrane bioreactor and a conventional wastewater treatment plant. Water Sci. Technol. 2004, 50, 29–36. (12) Kimura, K.; Hara, H.; Watanabe, Y. Elimination of selected acidic pharmaceuticals from municipal wastewater by an activated sludge system and membrane bioreactors. Environ. Sci. Technol. 2007, 41, 3708–3714. (13) Radjenovic, J.; Petrovic, M.; Barcelo, D. Fate and distribution of pharmaceuticals in wastewater and sewage sludge of the conventional activated sludge (CAS) and advanced membrane bioreactor (MBR) treatment. Water Res. 2009, 43, 831–841. (14) Gobel, A.; McArdell, C. S.; Joss, A.; Siegrist, H.; Giger, W. Fate of sulfonamides, macrolides, and trimethoprim in different wastewater treatment technologies. Sci. Total Environ. 2007, 372, 361–371. (15) Smook, T. M.; Zho, H.; Zytner, R. G. Removal of ibuprofen from wastewater: Comparing biodegradation in conventional,

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Seasonal Variation in the Occurrence and Removal of

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