ISSN: 1579-4377 REMOVAL OF PHARMACEUTICALS AND PERSONAL CARE PRODUCTS (PPCPS) FROM MUNICIPAL WASTEWATERS BY PHYSICO-CHEMICAL PROCESSES M. Carballa, F. Omil and J.M. Lema University of Santiago de Compostela, Spain -
[email protected]
KEYWORDS PPCPs, wastewaters, coagulation-flocculation, flotation, adsorption ABSTRACT Two physico-chemical processes such as coagulation-flocculation and flotation have been used to study the removal of Pharmaceuticals and Personal Care Products (PPCPs) from municipal wastewaters. Seven PPCPs have been selected for this study, which belong to four different therapeutic classes: antiphlogistics (ibuprofen, naproxen and diclofenac), antiepileptic (carbamazepine), tranquiliser (diazepam) and two musks (galaxolide and tonalide). It was found that coagulation-flocculation processes are only effective for the two fragrances and diclofenac, with removal efficiencies between 50-75% independently of the dose of coagulant and temperature. On the other hand, all PPCPs were partially removed by flotation, with efficiencies between 20-75%, depending on the temperature and the initial content of fat. INTRODUCTION Municipal wastewater contains a number of persistent organic compounds derived from domestic application such as active ingredients in pharmaceuticals and personal care products, which are used in large quantities throughout the world. Here both groups will be collectively referred to as “Pharmaceuticals & Personal Care Product ingredients” (PPCPs) (Daughton et al., 1999). PPCPs constitute a diverse group of chemicals which comprise all drugs, diagnostic agents, “nutraceuticals”, fragrances, sun-screen agents, etc., and they have received very little attention as potential environmental pollutants. Many PPCPs are highly bioactive, most are polar, optically active, and all are present in the environment at extremely low concentrations. Many human and veterinary pharmaceuticals are incompletely metabolized and excreted unchanged via urine and feces. These excreted wastes are subjected to further metabolism by microorganisms in sewage treatment plants. However, there are fractions of these compounds which are recalcitrant to biological treatment, and they remain in the liquid streams being finally discharged into the environment. Moreover, in other cases PPCPs remain adhered to the solids (sludge), which are finally disposed in various ways on land. PPCPs passing wastewater treatment systems are continuously infused to the environment via Waste Water Treatment Plants (WWTP) discharges and are present in the feeding water (groundwater, bank filtrates, surface water) of waterworks. In some cases even drinking water is contaminated with PPCPs. Although little is known about potential adverse effects on non-target species, these substances can be endocrine disruptors that mimic, enhance or inhibit the action of hormones (Fawell et al., 2001; EU, 1999). While PPCPs in the environment (or drinking water) are not regulated, and even though their
Electron. J. Environ. Agric. Food Chem. ISSN 1579-4377
309
Carballa et al. EJEAFChe, 2 (2), 2003. [309-313]
concentrations are extremely low (ng/L-μg/L), the consequences of exposure over multiple generations to multitudes of compounds with similar modes of action are unknown. In this way, the main characteristics, which determine the fate of such contaminants in the water cycle, is their ability to interact with particulates. These particulates can be naturally occurring (clays, sediments, colloids coated with natural organics, microorganisms) or added during treatment (activated sludge, powdered activated carbon, ion exchange resin, coagulants). The transition of trace contaminants to the solid phase will greatly enhance their chances of removal. In contrast, the interaction of trace contaminants with dissolved organics can increase their mobility in the environment and through the treatment plant (Ohlenbusch et al., 2000). Coagulation-flocculation processes facilitate the removal of suspended solids and colloids. The addition of mineral salts or organic compounds causes the agglomeration of these particles, allowing their elimination by settling or filtration (Alaert et al., 1981; Li et al., 1991). Adsorption onto the flocculated aggregates might provide removal mechanisms to some of the trace compounds which are present in municipal wastewaters, mainly dissolved in the aqueous phase, and could imply potential difficulties to the biological treatment process. On the other hand, Dissolved Air Flotation (DAF) is an increasingly applied technology for particle removal in water and wastewater treatment. In these units, tiny air bubbles attach to the particles, which float to the surface, forming flocs which can be periodically discharged to a sludge channel. Joined to solids separation, other pollutants like PPCPs can be removed from the wastewaters based on sorption onto aggregates, which can be efficiently removed by dissolved air flotation (Galil et al., 2000). The aims of this study were to evaluate the removal efficiencies of PPCPs in coagulationflocculation and flotation units, influenced by several operation parameters, such as type and dose of coagulant, the initial content of fats and the temperature. The mechanism could be explained by the hydrophobic characteristics of some of these substances, which could bind to the solid surfaces. MATERIAL AND METHODS Wastewaters The waste waters used in this work were collected from an urban WWTP located in Galicia (NW of Spain). Table 1 shows the main characteristics of these wastewaters. Table 1 – Initial characteristics of wastewaters used in physico-chemical assays (mg/L)
CoagulationFlocculation 500-900 300-500 100-350 100-250 300-700 100-500
TS VS TSS VSS CODt CODs
Flotation 500-900 200-500 100-400 100-300 200-800 100-500
Coagulation-Flocculation assays Coagulation-Flocculation assays were carried out in a Jar-Test device (Figure 1) in vessels of 1 L of liquid volume. The influence of the type and dose of coagulant and the temperature was studied. Agitación Temperatura Coagulante Floculante
Figure 1 – Jar-Test device
Electron. J. Environ. Agric. Food Chem. ISSN 1579-4377
310
Carballa et al. EJEAFChe, 2 (2), 2003. [309-313]
Three additives were used: ferric chloride (FeCl3, 50 g/L), aluminium sulphate (Al2(SO4)3, 50 g/L) and aluminium polichloride (PAX-18, 17,5% w/w) and the assays were carried out at two temperatures, 12ºC and 25ºC, simulating winter and summer conditions respectively. The test included a first 3 minutes period of rapid stirring (150 rpm), while the coagulant and neutralisation with lime have been added, followed by 5 minutes of slow mixing (50 rpm) for emulsion breaking and floc formation, and 1 hour without mixing, for floc separation. Table 2 shows the initial conditions for each experiment. The concentration of PPCPs in the supernatant was monitored during each experiment (Table 3). Table 2 – Initial concentrations (μg/L) of PPCPs in Coagulation-Floccultion assays
12ºC 3,70 3,03 13,42 12,00 14,50 17,50 14,00
Galaxolide Tonalide Diazepam Carbamazepine Ibuprofen Naproxen Diclofenac
25ºC 2,10 1,50 10,00 10,20 12,60 16,60 18,00
Table 3 – Concentration (μg/L) of PPCPs in the supernatant after coagulation-flocculation assays
No additive FeCl3 (12ºC) Al2(SO4)3 (12ºC) PAX-18 (12ºC) FeCl3 (25ºC) Al2(SO4)3 (25ºC) PAX-18 (25ºC)
GLX 3,44
TON 2,71
DZP 15,10
CBZ 12,30
0,44 0,93 1,10 0,79
0,44 0,72 0,70 0,44
11,06 7,43 8,07 9,60
13,00 10,50 10,70 10,40
IBU 15,0 15,0 15,0 15,5 11,7 12,5 13,2
NPX 18,5 19,0 17,8 20,0 11,7 12,5 13,2
DCL 13,9 14,0 13,9 16,5 5,5 6,0 9,5
Flotation assays Flotation assays were carried out in a flotation unit (Figure 2). The experimental device is formed by a pressurised cell of 2 L and a flotation cell of 1 L. The pressurised cell has two inlets, for air and for water, and one outlet, for the pressurised liquid. Also, a manometer is set up in the air line to check the pressure. The flotation cell comprises a test tube with two channels: the inlet of pressurised liquid and the outlet of the supernatant. The influence of the initial content of fats and the temperature has been studied. Assays were carried out in duplicate (Experiment 1 and 2). Table 4 shows the initial conditions for each experiment. The final concentrations of PPCPs in the supernatant were monitored (Table 5).
Manómetro Entrada aire(1) Despresurización (2) Entrada agua (3)
Entrada líquido presurizado Salida líquido presurizado (4)
Salida líquido flotado
Dispositivo medida grado de saturación
Celda flotación
Figure 2 – Flotation unit
Electron. J. Environ. Agric. Food Chem. ISSN 1579-4377
311
Carballa et al. EJEAFChe, 2 (2), 2003. [309-313]
Table 4 – Inicial concentrations (μg/L) of PPCPs in Flotation assays
Experiment 1 BSF1i BS1i 4,13 2,40 3,25 1,80 15,66 12,13 12,60 10,90 9,60 12,50 13,10 17,50 17,50 23,00
Galaxolide Tonalide Diazepam Carbamazepine Ibuprofen Naproxen Diclofenac
Experiment 2 BS2i BSF2i 3,04 0,82 2,36 0,64 10,18 6,78 11,06 8,35 13,13 12,26 9,27 9,45 10,08 11,48
Table 5 – Concentration (μg/L) of PPCPs in the supernatant after Flotation assays
Galaxolide Tonalide Diazepam Carbamazepine Ibuprofen Naproxen Diclofenac
Experiment 1 12ºC 25ºC BSF1f BS1f BSF1f BS1f 1,71 1,96 2,16 2,25 1,59 1,51 1,61 1,90 8,55 7,65 8,72 8,94 9,80 8,90 10,20 8,50 7,80 10,00 7,30 8,00 10,10 13,00 9,20 11,70 13,80 16,50 12,40 14,50
Experiment 2 12ºC 25ºC BS2f BSF2f BS2f BSF2f 2,53 0,90 1,77 0,81 1,92 0,70 1,31 0,62 6,85 4,75 5,92 4,53 8,85 6,58 8,94 6,85 11,46 10,25 10,02 9,95 8,59 7,16 6,46 5,68 6,67 5,34 3,58
Analytical techniques TS, VS, TSS, VSS, COD and the content of fats were analysed according to Standard Methods (APHA, 1992). A Solid Phase Micro Extraction (SPME) method using PDMS/DVB fiber allows the determination of galaxolide and tonalide. A SPE (Solid Phase Extraction) method using OASIS cartridges and elution with ethylacetate allows the determination of ibuprofen, naproxen and diclofenac (after silylation) and carbamazepine and diazepam (after concentration). In all cases, GC/MS technique was used for the separation and analysis of the PPCPs. pH and temperature were determined by selective electrodes. RESULTS AND DISCUSSION Coagulation-Flocculation assays The best dose-range for each coagulant was determined previously, based on removal efficiencies of suspended solids and organic matter. In a first experiment the effect of the dose of coagulant was studied. The coagulant selected was FeCl3, at four concentrations (200, 250, 350 and 400 mg/L) and two temperatures (12ºC, 25ºC). The removal efficiencies ranged from 60% for galaxolide at 25ºC to 70% for tonalide at 25ºC, and this removal was independent of the dose of coagulant used. The influence of the temperature was opposite for both substances. Whereas for galaxolide the elimination was higher at 12ºC, for tonalide was higher removed at 25ºC. In a second experiment the effect of the type of coagulant was studied. One dose of three additives (FeCl3, Al2(SO4)3 and PAX) has been used. The behaviour of PPCPs during coagulation-flocculation processes was different for neutral (galaxolide, tonalide, carbamazepine, diazepam) and acidic (ibuprofen, naproxen, diclofenac) compounds. Concerning neutral compounds, Table 3 shows an important removal of galaxolide (50-65%) and tonalide (55-70%), with lower values for diazepam (10-25%) and no effect on carbamazepine. At both temperatures, the PAX is the coagulant that causes the higher removal of the musks; however, in the case of diazepam, ferric chloride carried out the best removal. The three compounds were better eliminated at 12ºC.
Electron. J. Environ. Agric. Food Chem. ISSN 1579-4377
312
Carballa et al. EJEAFChe, 2 (2), 2003. [309-313]
Among acidic compounds, Table 3 shows that only diclofenac was affected by this process at 25ºC (50-70%). In this case, the coagulants that caused the higher removal were ferric chloride and aluminium sulphate. Apart from these assays, an experiment without additive was performed to study the possible removal of PPCPs merely related to solids settling, although no elimination was obtained for any substance. Flotation assays Preliminary assays have been carried out to determine the pressurised liquid airflow necessary to produce the fat separation in the flotation cell. This value was fixed in 200 mL. Afterwards, two parameters have been studied: the initial content of fat and the temperature. Two initial concentrations of fat have been used: the content of the raw wastewater (BS) and one concentration higher (150 mg/L) obtained after adding a small amount of fat (BSF) The temperatures selected were the same as in coagulation-flocculation assays: 12ºC and 25ºC. The results shown in Table 4 indicate that the simple addition of fat reduces considerably the initial concentration of galaxolide and tonalide, and in less extent, carbamazepine and diazepam. This reduction was higher in experiment 2. However, acidic compounds were not affected. The removal efficiencies of neutral compounds were between 20% for carbamazepine and 60% for galaxolide; while for acidic compounds the range obtained was between 20-40%. The influence of the temperature differs for both types of substances. While for acidic compounds, the removal is higher at 25ºC in both experiments, in the case of neutral compounds, the effect is not clear, since during the first experiment the elimination was better at 12ºC and, during the second experiment, it occurred at 25ºC. In both cases, for all compounds, the influence of the temperature is independent of the initial content of fat. Concerning the initial content of fat, both types of compounds were better removed when higher concentrations of fat are used, independently of temperature. CONCLUSIONS A blank assay carried out using the Jar-test procedure but without any coagulant addition showed no significant removal of PPCPs. When coagulants were used, only galaxolide, tonalide and diclofenac were significantly removed, around 50-75%. These removal efficiencies were not dependent on the dose of coagulant and the temperature. PAX-18 was the most effective for neutral compounds (galaxolide and tonalide), whereas FeCl3 gave better results for diclofenac. However, the results obtained in flotation assays showed that all compounds are affected by this process. When a high fat concentration wastewater was used, PPCPs removal (20-75%) proceeded very efficiently in all cases. While for the neutral substances, the elimination was independent of the working temperature; acidic compounds were better removed at 25ºC. However, when the content of fat was low, a high temperature increases always the efficiency of the flotation unit. REFERENCES Alaert, G., Van Haute, A. (1981). Coagulation and flocculation mechanism in diverse colloidal suspensions. Proceedings fo Joint Seminar of S. V. Ward S.E.D.E., 45-74 APHA-AWWA-WPCF. (1992). Metodos normalizados para el análisis de aguas Daughton, C.G. and Ternes, T.A. “Pharmaceuticals and Personal Care Products in the environment: Agents of subtle change?” Environ. Health Perspect. 1999, 107 (suppl. 6), 907-938. EU (1999), p96 Report of the Working Group on Endocrine Disruptors of the Scientific Committee on Toxicity, Ecotoxicity and Environment (CSTEE) of Directorate General XXIV, Consumer Policy and Consumer Health Protection. Fawell, J.K., Sheahan, D., James, H.A., Hurst, M., Scott, S. (2001) Oestrogens and oestrogenic activity in raw and treated water in severn trent water. Water Research, 35 1240-1244. Galil, N. I., Wolf, D. (2000) Removal of hydrocarbons from petrochemical wastewater by dissolved air flotation, The 4th International Conference. Flotation in Water and Wastewater Treatment. IAWQ. Finlandia. Li, G., Gregory, J. (1991). Flocculation and sedimentation of high turbidity waters. Water Res. 25, 1137-43. Ohlenbusch, G., Kumke, M.U., Frimmel, F.H. (2000) Sorption of phenols to dissolved organic matter investigated by solid phase microextraction, The Science of the Total Environment 253 63-74. Electron. J. Environ. Agric. Food Chem. ISSN 1579-4377
313
