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4ª REUNIÓN PROGRAMA CONSOLIDER TRAGUA – 17, 18 y 19 de junio de 2009, Alicante
Tratamiento y Reutilización de Aguas Residuales para una Gestión Sostenible
Removal of emerging pollutants in urban
wastewater through biological treatment followed
by ozonation (1)
AUTORES:Roberto Rosal, Antonio Rodríguez, Pedro Letón, María José Gómez, José Antonio Perdigón, Alice Petre, Karina Boltes, Eloy García, Ana Agüera y Amadeo R. Fernández-AlbaGRUPOS . T1 y TC 10 - UAH y UAL INTRODUCTION
The objective of this research was to verify the occurrence and fate of different anthropogenic emerging pollutants traced during wastewater treatment in a conventional urban STP and to identify the impact of ozone exposure on individual pollutants encountered in the secondary effluent. Wastewater samples were taken every month over a one year period from the input and output of the secondary clarifier of a STP located in Alcalá de Henares (Madrid). The pollutants quantification in the ng/L range was performed by Liquid Chromatography-QTRAP-Mass Spectrometry and Gas Chromatography coupled to Mass Spectrometry. The ozonation runs were carried out in a 5-L glass jacketed reactor operating in semi-batch mode at 25 ºC and pH ~ 8.5. The gas containing about 9.7 g/Nm3 ozone was bubbled by means of a porous glass disk with a gas flow of 0.36 Nm3/h. The mass transfer coefficient was determined in transient runs with pure water with a value of kLa = 0.010 ± 0.005 s-1.
The detailed data for the concentrations of the individual pollutants are shown in Table 1. It includes the pKa and octanol-water distribution coefficient, Kow, and the maximum and minimum values of those compounds encountered over their quantification limit in at least 4 samples in the influent of the biological treatment. a Muñoz et al., 2008. bUnless otherwise indicated, values obtained from the experimental database LOGKOW Databank Sangster Research Laboratories, monréal, Canada. cValues estimatedwith thE KOWWIN program included in EPI Suit (Meyland and Howard, 1995). dTixier et al., 2003. eKameda et al., 2002. f Zhu, et al., 2002 REMOVAL IN STP
The removal efficiency for every individual compound was determined from average concentrations calculated excluding samples whose concentrations fell below LOQ. During wastewater treatment in STP, PPCP as well as their metabolites partition into the solid phase or remain dissolved depending on their hydrophobic condition. This can be expressed by the pH-dependent or apparent octanol-water distribution coefficient, Dow, that considers both the dissociation constant of acidic solutes, pKa, and the current pH of wastewater (eq .1). The removal efficiency obtained for the compounds indicated in Table 1 has been related to Dow in Fig. 1. For a significant group of compounds ranging from ketorolac (D = 5.90), the removal efficiency during biological treatment increased with hydrophobicity. Código de referencia del Programa: CSD2006-00044
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4ª REUNIÓN PROGRAMA CONSOLIDER TRAGUA – 17, 18 y 19 de junio de 2009, Alicante
Tratamiento y Reutilización de Aguas Residuales para una Gestión Sostenible
Removal of emerging pollutants in urban
wastewater through biological treatment followed
by ozonation (2)
AUTORES:Roberto Rosal, Antonio Rodríguez, Pedro Letón, Alice Petre, Karina Boltes, José Antonio Perdigón, Eloy García, María José Gómez, Ana Agüera y Amadeo R. Fernández-AlbaGRUPOS . T1 y TC 10 - UAH y UAL They are all important pharmaceuticals prescribed and delivered to sewage in high amounts. These are the beta-blockers atenolol, metoprolol andpropanolol; the lipid regulator bezafibrate, fenofibric acid; the antibiotics erythromycin, sulfamethoxazole and trimethoprim; the antiinflammatoriesdiclofenac, indomethacin, ketoprofen and mefenamic acid; the antiepileptic carbamazepine and the antiacid omeprazole. Fig. 1. Removal efficiency during conventional activated sludge treatment: (1) paraxanthine, (2) caffeine, (3) acetaminophen, (4) nicotine, (5)
ibuprofen, (6) ketorolac, (7) clofibric acid, (8) furosemide, (9) ciprofloxacin, (10) fluoxethine, (11) ofloxacin, (12) naproxen, (13) hydrochlorothiazide,
(14) 4-amino-antipyrine, (15) metronidazole, (16) N-acetyl-4-amino-antipiryne, (17) codeine, (18) N-formyl-4-amino-antipiryne, (19) 4-
methylaminoantipyrine, (20) ranitidine, (21) antipyrine, (22) gemfibrozil, (23) benzophenone-3, (24) triclosan, (25) tonalide, (26) galaxolide, (27)
atenolol, (28) sulfamethoxazole, (29) fenofibric acid, (30) metoprolol, (31) bezafibrate, (32) ketoprofen, (33) trimethoprim, (34) Diclofenac, (35)
indomethacine, (36) propanolol, (37) mefenamic acid, (38) omeprazole, (39) carbamazepine, (40) erythromycin.
REMOVAL BY OZONATION
The efficiency of ozonation for the removal of the main micropollutants whose concentration in biologically treated wastewater was > 10 ng/L is
indicated in Table 2. The table shows the evolution of the concentration for samples taken during ozonation up to a reaction time of 15 min and the
amount of ozone required for a given degree of removal. The amount of ozone transferred to the liquid at a certain reaction time, TOD, was
determined, from the integration of the ozone absorption rate equation (eq. 2)
The last right column of Table 1 shows the dose of ozone required for the complete removal (no detection) of a given compound or to achieve a certain removal efficiency in cases where ozonation was unable to get complete oxidation in less than 15 min corresponding to a dose of ozone of 0.34 mmol/L of wastewater. OZONATION KINETIC
As raw wastewater contains a number of compounds whose second order direct reaction constants ( et al., 2003) mass transfer is likely to limit the ozonation rate during the first reaction minutes. Once ozone appears in solution, the following inequality holds: Código de referencia del Programa: CSD2006-00044
Web:
4ª REUNIÓN PROGRAMA CONSOLIDER TRAGUA – 17, 18 y 19 de junio de 2009, Alicante
Tratamiento y Reutilización de Aguas Residuales para una Gestión Sostenible
Removal of emerging pollutants in urban
wastewater through biological treatment followed
by ozonation (3)
AUTORES:Roberto Rosal, Antonio Rodríguez, Pedro Letón, Karina Boltes, José Antonio Perdigón, Alice Petre, Eloy García, María José Gómez, Ana Agüera y Amadeo R. Fernández-AlbaGRUPOS . T1 y TC 10 - UAH y UAL Therefore an upper limit can be obtained for Ha as follows: 3 113 73 85 56 14 3 Still detected at 340 μM 4 81 12 10 13 10 14 Still detected at 340 μM 52 246 55 72 79 70 53 Still detected at 340 μM * LOQ calculated in ozonated samples. Cconcentration expressed as ng/L where is the diffusivity of ozone in water (1.77 x 10-9 m2 s-1). The equilibrium concentration of ozone was calculated from Henry’s law using the correlation of Rischbieter et al. (2000). The value of the mass transfer coefficient, kL = 5.5 x 10-5 m s-1, was calculated by using the correlation of Calderbank and Moo-Young (1961). At the beginning of the run, there was no ozone in solution and Ha is supposed to reach high values. After about three minutes, the concentration of ozone that increased during runs approaching equilibrium was over 2 x 10-3 mM. Código de referencia del Programa: CSD2006-00044
Web:
4ª REUNIÓN PROGRAMA CONSOLIDER TRAGUA – 17, 18 y 19 de junio de 2009, Alicante
Tratamiento y Reutilización de Aguas Residuales para una Gestión Sostenible
Removal of emerging pollutants in urban
wastewater through biological treatment followed
by ozonation (4)
AUTORES:Roberto Rosal, Antonio Rodríguez, Pedro Letón, José Antonio Perdigón, Karina Boltes, Alice Petre, Eloy García, María José Gómez, Ana Agüera y Amadeo R. Fernández-AlbaGRUPOS . T1 y TC 10 - UAH y UAL nsures Ha < 0.3 and, therefore, the kinetic regime was slow for the sample taken at 4 min and those taken A mass balance to a given compound in solution yields the following expression Based on the observation that Rct (Elovitz and von Gunten, 1999) can be considered constant at least though certain periods of the ozonation runs, the concentration of the two main oxidants involved in ozonation reactions can be related so that eq.5 can be solved without Second order kinetic constants could be obtained as indicated before for bezafibrate, cotinine, diuron, ketoprofen and metronidazole. The logarithmic concentration decay is represented against the integral ozone dose in Fig. 2 in which, the experimental points represent data from samples taken at 4, 6, 10 and 15 min. Fig. 2. Logarithmic decay of the concentration of diuron (○), metronidazole (●), ketoprofen (Δ) bezafibrate (□)
and cotinine (■) as a function of the integral ozone exposure. (Two y-axes have been used for clarity.)
No ozonation constants have been found in the literature to compare results except for the lipid regulator bezafibrate. The ozonation of bezafibratewas previously studied Dantas et al. (2007) who reported k = 4.24 x 103 ± 0.66 x 103 M-1s-1 for pH 7 and k = 1.0 x 104 ± 1.07 x 103 M-1s-1 for pH 8. In this work, at pH 8.5, we obtained a value of 3.19 x 103 ± 9.4 x 102 M-1s-1, that represents about one order of magnitude lower. It is to be noted that the matrix was a real wastewater that contained a number of radical scavengers like carbonate and bicarbonate ions. The comparison of results suggests that the transformation of ozone-resistant micropollutants may take place primarily via indirect radical oxidation as it is inhibited by the wastewater matrix. CONCLUSION
This work reports the results of a one-year monitoring programme that followed the occurrence of pharmaceuticals, personal care compounds, agrochemicals and certain metabolites in the wastewater treated in a conventional STP treating urban wastewater. The research showed the regular presence of over seventy anthropogenic individual pollutants, some of which are encountered in relatively high amounts. In raw sewage, 25 compounds were detected in the μg/L range, 15 of which exceeded this level in yearly averages. The efficiency of removal of PPCPs in STP was roughly dependent on its hydrophobic condition expressed as apparent octanol-water distribution coefficient. An ozonation treatment performed at pH 8.5 yielded high removal efficiencies of most individual pollutants detected in treated wastewater. The kinetic analysis of the part of the run that takes place in the slow kinetic regime, allowed the determination of second order kinetic constants for the ozonation in wastewater matrix Código de referencia del Programa: CSD2006-00044
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