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Cosmetic wastewater treatment by coagulation and advanced oxidation processes a
a
a
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Jeremi Naumczyk , Jan Bogacki , Piotr Marcinowski & Paweł Kowalik a
Faculty of Environmental Engineering, Warsaw University of Technology, Nowowiejska 20, 00-653 Warsaw, Poland Accepted author version posted online: 29 May 2013.Published online: 25 Jun 2013.
To cite this article: Jeremi Naumczyk, Jan Bogacki, Piotr Marcinowski & Paweł Kowalik (2014) Cosmetic wastewater treatment by coagulation and advanced oxidation processes, Environmental Technology, 35:5, 541-548, DOI: 10.1080/09593330.2013.808245 To link to this article: http://dx.doi.org/10.1080/09593330.2013.808245
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Environmental Technology, 2014 Vol. 35, No. 5, 541–548, http://dx.doi.org/10.1080/09593330.2013.808245
Cosmetic wastewater treatment by coagulation and advanced oxidation processes Jeremi Naumczyk∗ , Jan Bogacki, Piotr Marcinowski and Paweł Kowalik Faculty of Environmental Engineering, Warsaw University of Technology, Nowowiejska 20, 00-653 Warsaw, Poland
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(Received 23 January 2013; final version received 20 May 2013 ) In this study, the treatment process of three cosmetic wastewater types has been investigated. Coagulation allowed to achieve chemical oxygen demand (COD) removal of 74.6%, 37.7% and 74.0% for samples A (Al2 (SO4 )3 ), B (Brentafloc F3) and C (PAX 16), respectively. The Fenton process proved to be effective as well – COD removal was equal to 75.1%, 44.7% and 68.1%, respectively. Coagulation with FeCl3 and the subsequent photo-Fenton process resulted in the best values of final COD removal equal to 92.4%, 62.8% and 90.2%. In case of the Fenton process, after coagulation these values were equal to 74.9%, 50.1% and 84.8%, while in case of the H2 O2 /UV process, the obtained COD removal was 83.8%, 36.2% and 80.9%. High value of COD removal in the Fenton process carried out for A and C wastewater samples was caused by a significant contribution of the final neutralization/coagulation. Very small effect of the oxidation reaction in the Fenton process in case of sample A resulting from the presence of antioxidants, ‘OH radical scavengers’ in the wastewater. Keywords: chemical treatment; coagulation; cosmetic wastewaters; Fenton/photo-Fenton process; H2 O2 /UV process
1. Introduction Cosmetic wastewater is characterized by a significant changeability of its composition and the concentration of pollutants, which is caused by the changeable production profile. Independent of the aforementioned variability, some substances are always present in cosmetic wastewater. They include synthetic musks, mainly polycyclic musks, as well as ketone and xylene musks. Among them, galaxolide and tonalide are used in the largest amount. These compounds are not easily biochemically degradable and are partially removed in a municipal wastewater treatment plant mainly due to adsorption on activated sludge.[1] Other important and not easily biodegradable compounds present in cosmetic wastewater include UV filters. These are the components of creams and their main responsibility is to absorb UV radiation. UV filters include among others: benzophenone derivatives, p-aminobenzoic acid, benzoic acid esters, ethylhexyl salicylate and heptan-2-one derivatives. These compounds are called emerging pollutants and pose a real threat to the water environment due to their toxicity.[2,3] Literature concerning the application of chemical methods in cosmetic wastewater treatment is scarce. El-Gohary et al. compared the effect achieved by means of the coagulation combined with sedimentation and pressure flotation.[4] The coagulants used in this study included Al2 (SO4 )3 , polymerized aluminium chloride, FeSO4 and FeCl3 . All coagulants gave comparable results and their efficiency depended on the type of investigated wastewater. The efficiency of chemical oxygen demand (COD) removal was ∗ Corresponding
author. Email: [email protected]
© 2013 Taylor & Francis
equal to approximately 75%. The application of coagulation combined with flotation did not improve the effect of COD removal, compared with the effect of coagulation with sedimentation. However, the sludge volume decreased. The effect of flotation process was improving with the increasing contents of oils and fats. The results obtained for the electrocoagulation and electro-Fenton processes, which were carried out in parallel, gave slightly better results compared with the results obtained for coagulation alone.[5] In both cases, the COD removal was close to 80%. The Fenton process for sewage pretreated by coagulation, with COD 4730 and 2660 mg/L and biochemical oxygen demand (BOD)5 /COD ratio of 0.123 and 0.161, was also investigated by Bautista et al. [6] At optimal pH value 3, Fe(II) dose was 300–500 mg/L, while H2 O2 /COD ratio was 2.12, COD removal was equal to approximately 55%. Cosmetic wastewater also underwent electrocoagulation process and subsequent photocatalytic oxidation with TiO2 , which allowed for COD removal of 78–82%.[7] Bautista et al.[8] also employed the catalytic oxidation process by means of the H2 O2 and Fe/γ Al2 O3 catalyst. At 85◦ C, the COD removal in the first cycle of the catalyst operation was equal to 80%, while in the third cycle, it was 60%. In this process, the improvement of organics biodegradability was observed.[8] Martins et al. applied catalytic ozonation and Fenton-like processes to treat wastewater from the detergent industry, which also contains many substances present in cosmetic wastewater.[9] The best treatment results and improvement of BOD5 /COD ratio
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from 0.32 to 0.80 was achieved by applying the classic Fenton process and ozonation catalysed by the mixture of Ce and Mn oxides. The removal of synthetic musks has also been studied. Carballa et al. employed the coagulation and pressure flotation in order to remove tonalide and galaxolide from municipal wastewater.[10] The best effect of tonalide (71%) and galaxolide (63%) removal was achieved using PAX as a coagulant. Slightly worse results were obtained when FeCl3 and Al2 (SO4 )3 were used. The presence of fats improved the effect of flotation. Similar studies have been carried out by Suarez et al. [11] As a result of coagulation employing FeCl3 , the obtained removal of tonalide, galaxolide and celestoide was equal to 83.4%, 79.2% and 77.7%, respectively. In case of the coagulation/flotation process with Al2 (SO4 )3, the effect was slightly worse – 75.8%, 64.8% and 72.1%, respectively. Felis et al. removed polycyclic musks from wastewater by means of the UV photolysis and UV/H2 O2 processes, achieving the decrease in their content by 93% and 99%, respectively.[12] Rosal et al. employed ozonation to remove musks and UV filters from municipal wastewater.[13] Galaxolide was removed in 72%, while ketone musks only in 38%. Xylene musks and UV filters – 3-(4-benzylidene) camphor, octyl methoxycinnamate and benzophenone-3 – turned out to be completely resistant to ozonation. Triclosane was removed in 78%, while octocrylene in 20%. High efficiency of ozonation of tonalide and galaxolide has been also confirmed by Ternes et al. [14] Li et al. investigated the removal of four UV filters – benzophenone-3, 4,4-methylbenzylidene camphor, octyl methoxycinnamate and octocrylene – in the municipal wastewater plant by means of subsequently applied processes: coagulation with polyaluminium chloride, microfiltration and ozonation.[15] The removal of the investigated substances in the three above-mentioned processes was equal to 7.6–21%, 3.6–8.2% and 16–28%, respectively. Many studies focused on the elimination of surfactants from wastewater. Kaleta and Elektorowicz revealed that coagulation with Al2 (SO4 )3 and FeCl3 yields poor effect of anionic surfactant removal (24%).[16] Significantly better effect of surfactants removal was achieved by means of the Fenton process and H2 O2 /UV process – almost 100% removal of six alcohol ethoxylates and four alkylphenol ethoxylates.[17] The aim of this study was to provide further information and deepen the knowledge concerning cosmetic wastewater treatment by means of coagulation and oxidation processes for wastewater with different pollutants composition and concentration. In the investigation of coagulation, the range of coagulants employed has been significantly extended. The results of coagulation have been compared with the results of the Fenton process. The effect of wastewater treatment in combined processes: coagulation + advanced oxidation processes (AOPs) – has also been investigated. Preliminary results of raw wastewater treatment by means of H2 O2 /UV and the photo-Fenton
processes were unsatisfactory due to high wastewater turbidity. Therefore, these methods have been used only for the treatment of wastewater which was preliminarily coagulated. 2. Materials and methods Wastewater samples were collected from the big cosmetic factory in Poland, between October 2011 and February 2012. In this facility, a wide range of cosmetics, including lipsticks, shampoo, serum, liquid soap and creams, was manufactured. As main compounds galaxolide, tonalide (synthetic musks), ethylhexyl salicylate (UV filter) and D5 (cosmetic base) were used. In raw wastewater, the following parameters were determined according to EN or ISO Standards: COD, CODdis (for sample filtered with 0.45 μm filter) (ISO 6060), BOD5 (EN 1899), total suspended solids (TSSs) (EN 872), pH (EN ISO 10523), turbidity (EN ISO 7027), specific conductivity (EN 27888), alkalinity (ISO 740), chlorides (ISO 9297), phosphates (EN 1189), ammonia (ISO 5664), nitrates (V) (EN ISO 13395) and anionic surfactants (EN 903). Petroleum ether extractable organics (PEEOs) were gravimetrically determined by the extraction of 500 mL sample with petroleum ether (50 + 50 mL). COD of wastewater treated with AOP’s was determined without the removal of unreacted H2 O2 . It was impossible to remove residual H2 O2 by means of catalase, due to the inhibiting effect of some pollutants present in the samples. Therefore, H2 O2 was determined by means of the iodometric method and the value of COD was corrected according to Kang’s equation.[18] In the studies of the coagulation of raw wastewater, the following solutions have been used: FeCl3 and Al2 (SO4 )3 with the concentration of 100 mg/mL Fe3+ and 50 mg/mL Al3+ , Brenntag Al: 1019, 3010, 3030, 3035 prehydrolysed coagulants containing aluminium salts, FeCl3 -based Brentafloc F3 and Kemipol PAX16 and PAX19 coagulants containing aluminium salts. The correction of the pH value after the addition of coagulant was done by means of NaOH or H2 SO4 solutions. 5 min fast and 10 min slow stirring times were employed. During 60 min of sedimentation after coagulation, the changes in the sludge volume were investigated. Wastewater after coagulation with FeCl3 at pH 6.0 was treated using Fenton, photo-Fenton and H2 O2 /UV processes. The application of the Fe salt was a result of the application of Fe salt in the Fenton and photo-Fenton processes. Consequently, it was necessary to assess the contribution of the final coagulation in these processes. The assumed value of pH 6.0 (not 9.0) resulted from the necessity to reduce the amount of H2 SO4 used to decrease the pH value in order to perform these processes. Also the amount of NaOH solution needed for the adjustment to pH 9.0 is significantly higher than the pH 6.0. The Fenton process was carried out in a 2 L cylindrical reactor with a magnetic stirrer, at pH 3.0, by adding appropriate amounts of
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Environmental Technology Table 1.
The doses of reagents (mg/L) for AOP’s.
Sample
Fenton process for raw wastewater H2 O2 /Fe2+
A B C
1200–1700/150–250 600–800/80–100 1900–2300/200–360
Fenton process H2 O2 /Fe2+ 400–500/50–80 500–700/60–80 550–700/80–120
acidic FeSO4 solution with the concentration of 50 mg/mL Fe2+ and 30% H2 O2 solution. After a specified time of 5, 15, 30 and 60 min, the process was stopped by increasing the pH value to 9.0 and the reactor was left for 240 min in order to allow for the sedimentation of the resulting sludge. The Photo-Fenton process was carried out in a glass cylindrical 1 L Heraeus Nobelight photoreactor with a water cooling blanket and TQ (150 W) medium pressure mercury lamp. The lamp radiation includes the range from 200 to 580 nm with several sharp emission peaks at 365 (the strongest peak), 545, 580, 430, 320, 250, 265 and 300 nm. The conditions of the process were the same as in the case of the Fenton process with the only difference being that Fe2+ /H2 O2 weight ratios were lower. The process duration time and the operation after finishing the process were the same as in case of the Fenton process. The H2 O2 /UV process was carried out in a glass cylindrical 1 L Heraeus Nobelight photoreactor equipped with a low-pressure mercury lamp (15 W). The lamp emits a sharp radiation of the wavelength of approximately 254 nm. Since, during the process, the pH value slightly decreased, its initial value was increased to 8.0. The process duration time was the same
Table 2.
Photo-Fenton process H2 O2 /Fe2+
H2 O2 /UV process H2 O2
400–500/40–55 500–700/50–70 600–750/55–70
1000–1500 1500–2000 1500–2000
as in the Fenton process. The doses of reagents applied for all AOPs and all samples are listed in Table 1. 3. Results 3.1. Wastewater characteristics The characteristic of the investigated wastewater is presented in Table 2. The investigated samples were diversified as far as both quality and pollutant concentration is concerned. The highest COD value was observed for sample C (2124 mg/L), while the lowest value was obtained for sample B (758 mg/L). The majority of the pollutants having contributed to the COD value was dissolved (CODdis ). Wastewater was not susceptible to biological treatment, which is proved by the BOD5 /COD ratio – 0.06–0.10. Oil content was not at a high level and the highest contribution of oils to the total organics (PEEO/COD) was detected in sample B. Sample A was characterized by the highest TSS content, but at the same time, the highest value of CODdis /COD ratio (0.78) implies that there is a significant contribution of mineral TSS. The lowest level of TSS in relation to content of organic substances was detected in
Characteristics of raw wastewaters.
Parameter (unit)
pH (−)
Conductivity (μS/cm)
COD (mg/L)
Sample A Sample B Sample C
7.9 9.1 7.4
1265 1042 2640
1507 758 2124
Parameter (unit)
Turbidity (NTU)
Chlorides (mg/L)
Sample A Sample B Sample C
150 70 800
122 82 742
Table 3.
543
CODdis (mg/L) 1179 527 1402 Ammonia (mg/L) 12.5 2 2.5
BOD5 (mg/L)
BOD5 / COD (−)
150 48 168 Nitrates (mg/L)
0.1 0.06 0.08 Phosphates (mg/L)
2.5 2 3
PEEO (mg/L) 58 137 258
811 129 584
Alkalinity (mval/L)
2 4 5
TSS (mg/L)
7.6 5.3 3.2
Surfactants (mg/L) 20 15 20
Coagulation results for wastewater A.
Coagulant pH COD (mg/L) Optimal dose (mg/L or mL/L) Sludge volume (mL/L)
FeCl3 6.0 435 100 150
FeCl3 9.0 392 100 95
F3 6.0 400 1.5 230
Al2 (SO4 )3 7.0 383 125 230
3010 7.0 409 1.0 280
1019 7.0 383 1.0 430
3030 7.0 387 1.0 450
3035 7.0 418 0.5 320
PAX16 7.0 400 1.25 200
PAX19 7.0 400 0.75 170
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sample C. Very high turbidity of wastewater C implies that the suspension was very fine. Content of anionic surfactants was low for all samples.
3.2. Wastewater treatment 3.2.1. Wastewater A Table 3 shows the results of the studies of the coagulation process for wastewater A. The differences between COD removal values obtained using different coagulants are small – the values ranged from 71% (FeCl3 at pH 6.0) to 74.6% (Al2 (SO4 )3 and Brenntag Al 1019). FeCl3 at pH 9.0 was regarded as the best Fe-based coagulant. The obtained value of COD removal (74.0%) corresponded to the smallest volume and hydration of the resulting sludge – 95 ml/L after 60 min of sedimentation. The Fenton process proved to be efficient as well (Figure 1). For optimal doses of H2 O2 /Fe(II) equal to 1500/190 mg/L and after 60 min of the process, the obtained COD removal was 75.1% (down to 375 mg/L). The process was very fast during the first 5 min (36.6% COD removal) and after 30 min slowed down significantly (74.6% COD removal). The Fenton process using the doses of H2 O2 /Fe(II) of 435/55 mg/L carried out after coagulation with FeCl3 at pH 6.0 and dose of 100 mg/L (Figure 2(a)), resulted in COD removal of only 12.9% (from 435 to 379 mg/L) – in total 74.9%. Significantly better results of the treatment of the same sample were achieved by means of the H2 O2 /UV process (Figure 2(a)) – after 60 min of the process and with the H2 O2 dose of 1300 mg/L, the COD removal value was equal to 43.9%, while the total result for COD removal: coagulation and H2 O2 process was equal to 83.8% (down to 244 mg/L). The best effect of wastewater treatment for sample A after coagulation was achieved by means of the photo-Fenton process with H2 O2 /Fe(II) doses of 435/45 mg/L. After 60 min (Figure 2(a)), the obtained COD removal was equal to 73.1% (down to 117 mg/L) and the total effect was equal to 92.4%.
Figure 1. COD vs. reaction time: Fenton process for raw wastewater.
Figure 2. COD vs. reaction time: AOP’s for samples after coagulation: sample A (a), sample B (b) and sample C (c).
3.2.2. Wastewater B The effect of coagulation (Table 4) achieved for sample B was significantly lower than in the case of sample A (Table 3). The highest effect of COD removal (37.7%) was obtained by means of F3 at pH 6.0 and also by means of FeCl3 at pH 9.0–32.2%. Additionally, in the latter case, the lowest sludge volume (45 mL/L) was obtained, in contrary to the coagulation with F3, when the volume was 80 mL/L. The lowest efficiency in COD removal was observed for the coagulation with FeCl3 at pH 6.0 (20.1%), but the sludge volume was one of the lowest (80 mL/L). The Fenton process after 60 min proved to be more effective compared with coagulation (Figure 1 vs. Table 4). The value of COD removal at the optimal H2 O2 /Fe(II) dose of 760/90 mg/L and after 60 min of the process was 44.7% (down to 419 mg/L). The instant drop in the COD value in the initial stage of the process has not been observed. The Fenton process of wastewater B after coagulation and
Environmental Technology Table 4.
Coagulation results for wastewater B.
Coagulant pH COD (mg/L) Optimal dose (mg/L or mL/L) Sludge volume (mL/L) Table 5.
FeCl3 6.0 606 75 80
FeCl3 9.0 514 75 45
F3 6.0 472 0.75 80
Al2 (SO4 )3 7.0 589 100 110
3010 7.0 573 0.5 130
1019 7.0 589 0.5 150
3030 7.0 589 0.75 170
3035 7.0 573 0.5 90
PAX16 7.0 539 1.0 130
PAX19 7.0 570 1.0 130
F3 6.0 595 1.0 80
Al2 (SO4 )3 7.0 680 125 200
3010 7.0 595 0.5 120
1019 7.0 595 0.5 120
3030 7.0 658 0.75 120
3035 7.0 595 0.75 110
PAX16 7.0 552 1.25 180
PAX19 7.0 595 1.0 120
Coagulation results for wastewater C.
Coagulant pH COD (mg/L) Optimal dose (mg/L or mL/L) Sludge volume (mL/L)
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FeCl3 6.0 637 100 65
FeCl3 9.0 680 100 55
at the optimal doses of reagents equal to 600/75 mg/L (Figure 2(b)) allowed for 37.6% COD removal (down to 378 mg/L) and total COD removal at the level of 50.1%. The H2 O2 /UV process (Figure 2(b)) was less effective – after 60 min of the process at the H2 O2 dose of 1800 mg/L, 20.1% of COD removal (down to 484 mg/L) was achieved, while the total effect was equal to 36.2%. The photo-Fenton process proved to be the most effective of all processes investigated (Figure 2(b)). At the optimal H2 O2 /Fe(II) dose of 600/60 mg/L, the values of COD removal and total COD removal after 60 min of the process were 53.5% (down to 282 mg/L) and 62.8%, respectively.
3.2.3. Wastewater C The best effect of COD removal (Table 5) was achieved for PAX 16–74.0% of COD removal. However, the sludge volume was one of the highest – 180 mL/L. The effect obtained by means of the F3 coagulant can be regarded as optimal – 72.0% COD removal and sludge volume of 80 mL/L. The worst effect was achieved using FeCl3 at pH 9.0–68.0% COD removal but the sludge volume was the lowest (55 mL/L). The process was carried out using FeCl3 at pH 6.0 that produced the COD removal at the 70.0% level (down to 637 mg/L) and the sludge volume of 65 mL/L. The Fenton process on raw wastewater (Figure 1) resulted in 68.1% COD removal (down to 680 mg/L) when using optimal H2 O2 /Fe(II) doses of 2125/265 mg/L. A relatively high value of COD removal (39.3%) was already obtained after 5 min of the process. In the case of wastewater after coagulation with FeCl3 at pH 6.0, the Fenton process produced 52.4% COD removal (down to 324 mg/L) when using optimal H2 O2 /Fe(II) doses of 640/105 mg/L (Figure 2(c)) and a total COD removal of 84.8%. In case of this type of wastewater, the relatively high value of COD removal was also observed after 5 min (33.8%). The H2 O2 /UV process (Figure 2(c)) turned out to be less effective, since COD removal after 60 min of the process and with the H2 O2 dose of 1900 mg/L was only 36.4% (down to
405 mg/L). The total COD removal was 80.9%. The photoFenton process proved to be the most effective (Figure 2(c)). With the H2 O2 /Fe(II) dose of 640/65 mg/L, the COD removal value, achieved after 60 min of the process, was equal to 67.5%. Total COD removal value was 90.2%. Similarly, the raw wastewater and in the case of the Fenton process, a relatively high decrease in COD (54.0%) was observed within the first 5 min.
4. Discussion Diversity of the chemical composition and the total organic content in three investigated samples of wastewater induce the differences in their susceptibility to chemical treatment. Samples A and C exhibit a high susceptibility to coagulation for all coagulation tests. The obtained high value of COD removal (>70%) is suspected, since both the samples of wastewater are characterized by a high content of suspended solids. In the case of sample C, its contribution to COD [(COD – CODdis )/COD] was equal to 34%, while in the case of sample A its contribution was much lower and high efficiency of the process might have been affected by the presence of fine, easily coagulating mineral SS, acting as a load for organic suspension. The presence of a high amount of synthetic musks might have been another reason for high efficiency of coagulation of sample A. Polycyclic musks are characterized by high lipophilicity, especially galaxolide and tonalide (log Kow 5–6), which are used in large amounts.[14,19] Musk xylene and musk ketone are only slightly less lipophilic. Studies on the coagulation of those types of musks in hospital wastewater revealed that they are removed in 70–84%, and the effect achieved by means of FeCl3 is better than the ones obtained using Al2 (SO4 )3 .[11] These compounds are removed mostly as a result of their adsorption on the resulting sludge. The best effect for wastewater A achieved using FeCl3 at pH 9 means that in the case of dissolved organic removal, the sorption process plays a crucial role. At pH 9, the Fe(OH)3 species are present in the solution, while at lower pH Fe(OH)+ 2,
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Fe(OH)2+ and Fe3+ ions are detected.[4] A poor coagulation effect is observed for sample B that resulted from a relatively lower TSS content and from a relatively high content of substances much more polar than synthetic musks, which have nonionic composition and can be extracted from petroleum ether. Those substances mostly include UV filters (produced in the periods preceding sample collection), which according to the results of studies carried out by Li et al. were removed in 7.1–21% by means of coagulation with polyaluminium chloride.[15] The best results of COD removal by means of F3 at pH 6 proves that in cases of these types of wastewater, the mechanism of pollutant removal was mixed. In the case of sample C, high values of COD removal achieved for all coagulants studied proves the mixed mechanism of pollutant removal. The best results obtained using (prehydrolized) PAX 16 coagulant and good results obtained using other prehydrolized polyaluminium salts are consistent with the results reported by Carballa et al. [10] The polymeric structure leads to the agglomeration properties of these coagulants and stronger destabilization of negative colloids. The results of the studies on the efficiency of the Fenton process for wastewater A proved the dominant contribution of the final neutralization/coagulation to the final value of COD removal. This contribution is characterized by a high value of COD removal in the first stage of the process (5 min).[20] In the Fenton process carried out after the coagulation of wastewater A, general COD removal was only 3.8% higher than the one obtained by means of coagulation alone, which proves the conclusions presented above. Substances remaining in the wastewater after coagulation are characterized by relatively low susceptibility to oxidation by HO radicals, which is confirmed by the value of COD removal equal to only 12.9%. Those substances mostly included the ketone and xylene musk. As it was shown by Rosal et al. [13] and Li et al. [15], they are poorly (that is to significantly lower extent than polycyclic musks) removed not only in the coagulation process, but also in the ozonation process. Poorly removable UV filters were present in the wastewater at low concentration. A much better effect in the H2 O2 /UV process was achieved for the wastewater after coagulation and even better results were obtained by the photo-Fenton process, which may be explained by the excitation of UV filters and other compound molecules by means of UV radiation. In the case of the photo-Fenton process, the emission spectrum was broader and this phenomenon was much stronger. The reason for low efficiency of the Fenton process after coagulation for sample A and a small contribution of the oxidation reaction in the Fenton process for raw wastewater might have been the presence of antioxidants (i.e. hyaluronic acid), which are HO radical scavengers.[21] Those substances were used in the production of cosmetics just before sample A collection. Those substances undergo photolysis, which explains the good results of H2 O2 /UV and photo-Fenton processes.[21] Similarly to sample A, in the Fenton process carried out
for sample C, the final neutralization/coagulation plays a significant role. However, a high value of COD removal achieved after 5 min of the process may result from the presence of a certain amount of substances quickly reacting with HO radicals. This is confirmed by high value of COD removal after 5 min in cases of all AOPs carried out for wastewater after coagulation, which is most evident in the case of the photo-Fenton process. Lower values of COD removal in H2 O2 /UV process compared with the value of COD removal in the Fenton process results probably from a significant contribution from coagulation in the Fenton process, which is absent in the H2 O2 /UV process. In the case of sample B, the effect of neutralization/coagulation in the total effect of the Fenton process is significantly lower. It results from the weak effect of coagulation itself. However, this effect exists and most probably consists in the adsorption of pollutants. It is confirmed by the fact that the Fenton process carried out after coagulation in conditions producing the worst effect (FeCl3 , pH 6) gave better results of COD removal than the effect of H2 O2 /UV process. Definitely the best, but worse than in the case of sample A, the effect of the photo-Fenton process may be explained by the contribution of neutralization/coagulation, by the stronger excitation of molecules of UV filters by the UV lamp irradiation and by Fe2+ ions reproduction according to reaction (1).[20] Fe(OH)2+ + hν → Fe2+ + HO• .
(1)
In all Fenton and photo-Fenton processes, the optimal dose of H2 O2 was similar to the COD value, while Fe(II) dose was eight times smaller. Increasing the doses did not improve the effect of the process. In order to estimate the efficiency of the Fenton process, a parameter referred to as ‘efficiency of hydrogen peroxide’ was recommended by Kang and Hwang.[22] η(%) =
COD × 100 , 0.476[H2 O2 ]
(2)
where COD, COD removed (mg/L); [H2 O2 ], dose of H2 O2 (mg/L); 0.476, factor COD theoretically removed (mg) by 1 mg of H2 O2 . The value of this parameter for the Fenton process and sample A was high – 160.0. Such high values of H2 O2 efficiency are caused not only by the oxidation process, but also by the final coagulation. This is proved by a very low value (27.4%) of this parameter for the same wastewater sample, but after the coagulation process. For wastewater B, for which the effect of the Fenton process is smaller, the value of η parameter is also lower, namely 94.7%. The contribution of the final coagulation to this parameter is less significant. For wastewater B after coagulation, this value is slightly lower (80.7%). In the case of wastewater C, for which the effect of the Fenton process is intermediate (closer to the effect for wastewater A), the value of η parameter (144.7%) is close to the value obtained for wastewater A. The contribution of the final coagulation to this parameter
Environmental Technology Table 6.
H2 O2 efficiency (%) in AOP’s for samples A, B and C and process time 60 min. Coagulation + Fenton process
Fenton process for raw wastewater A
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160.0
Coagulation+H2 O2 /UV process
C
A
B
C
A
B
C
A
B
C
94.7
144.7
27.4
80.7
112.3
155.3
114.8
142.8
31.3
14.4
26.0
HO• + RH → R • + H2 O, R + O2 →
RO•2 .
Cosmetic wastewater is generally characterized by high but diversified (37.7–74.6% COD removal) susceptibility to coagulation, which depends on the wastewater composition. The effect of the Fenton process is slightly higher than the coagulation effect (44.7–75.1% COD removal). Contribution of the final neutralization/coagulation to the final effect is significant. Antioxidants present in wastewater lead to the decrease in the effect of the Fenton process. In the case of wastewater after coagulation, the photoFenton process proved to be the most effective of all oxidation processes investigated. In case of wastewater A, the total effect of COD removal was equal to 92.4%.
(3) (4)
Very low values of η parameter for the H2 O2 /UV process for wastewater after coagulation, which are equal to 31.3%, 14.4% and 26.0%, respectively, result not only from the low efficiency of this process. It was achieved using relatively a high (optimal) H2 O2 /COD ratio. Presented results of the studies may be compared only with the results of the studies published by El-Gohary et al. [4] The results obtained by those authors were slightly higher (up to 77.5% COD removal) and similar to the studies presented in this paper, the differences between the coagulants were small. The investigated samples of wastewater were characterized by COD values similar to the value for sample C. However, they contained much more biodegradable substances – i.e. vitamins and sorbitol. The results of the studies on the Fenton process may be compared with the results presented by Bautista et al. [6] The authors treated the pre-coagulated wastewater with a COD value of 2720 mg/L and with a higher susceptibility to biological treatment. The obtained results of COD removal were slightly lower than those reported in the present study. Additionally, they were achieved using almost twofold higher values of H2 O2 /COD ratio. 5.
Coagulation + photoFenton process
B
is low, which is proved by the value of η parameter for the wastewater after coagulation (112.3%). This value is only slightly lower than without the coagulation process. The value of η parameter for the photo-Fenton process and wastewater after coagulation is high for all investigated wastewater samples and is equal to 155.3%, 114.8% and 142.8%, respectively. The values of η for all processes and wastewater, and 60 min reaction time, are presented in Table 6. Since the contribution of the final coagulation to the value of η parameter cannot be significant, the high value of the parameter is caused by the presence of oxygen in the aerated sample and the presence of organic radicals formed in the reactions mentioned below.[23] •
547
Conclusions
Composition and concentration of pollutants in cosmetic wastewater generated by a big cosmetic factory significantly changes in time and according to the changes in the production profile. This type of wastewater is resistant to biological treatment and the pollutant concentration is usually high.
Acknowledgements The authors gratefully acknowledged the financial support provided by the National Science Centre (grant no. 7385/B/ T02/2011/40 ‘Chemical pretreatment of effluents from cosmetic industry’).
References [1] Carballa M, Omil F, Lema JM, Llompard M, Garcia-Jares C, Rodriguez I, Gomez M, Ternes T. Behavior of pharmaceuticals, cosmetics and hormones in a sewage treatment plant. Water Res. 2004;38:2918–2926. [2] Dhanirama D, Gronow J, Voulvoulis N. Cosmetics as a potential source of environmental contamination in the UK. Environ Technol. 2012;33:1597–1608. [3] Tamura I, Kimura K, Kameda Y, Nakada N, Yamamoto H. Ecological risk assessment of urban creek sediments contaminated by untreated domestic wastewater: potential contribution of antimicrobials and a musk fragrance. Environ Technol. 2013. doi:10.1080/09593330.2012.758667 [4] El-Gohary F, Tawfik A, Mahmoud U. Comparative study between chemical coagulation/precipitation (C/P) versus coagulation/dissolved air flotation (C/DAF) for pretreatment of personal care products (PCPs) wastewater. Desalination. 2010;252:106–112. [5] Aloui F, Kchaou S, Sayadi S. Physicochemical treatments of anionic surfactants wastewater: effect on aerobic biodegradability. J Hazard Mater. 2009;164:353–359. [6] Bautista P, Mohedano AF, Gilarranz MA, Casas J, Rodriguez J. Application of Fenton oxidation to cosmetic wastewaters treatment. J Hazard Mater. 2007;143:128–134. [7] Boroski M, Rodrigues AC, Garcia JC, Sampaio LC, Nozaki J, Hioka N. Combined electrocoagulation and TiO2 photoassisted treatment applied to wastewater effluents from pharmaceutical and cosmetic industries. J Hazard Mater. 2009;162:448–454.
Downloaded by [The University of British Columbia] at 04:12 24 November 2014
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J. Naumczyk et al.
[8] Bautista P, Mohedano A, Menendez N, Casas J, Rodriguez JJ. Catalytic wet peroxide oxidation of cosmetic wastewaters with Fe-bearing catalysts. Catal Today. 2010;151:148–152. [9] Martins RC, Silva AMT, Castro-Silva S, Garção-Nunes P, Quinta-Ferreira RM. Advanced oxidation processes for treatment of effluents from a detergent industry. Environ Technol. 2011;32:1031–1041. [10] Carballa M, Omil F, Lema JM. Removal of cosmetic ingredients and pharmaceuticals in sewage primary treatment. Water Res. 2005;39:4790–4796. [11] Suarez S, Lema JM, Omil F. Pre-treatment of hospital wastewater by coagulation–flocculation and flotation. Biores Technol. 2009;100:2138–2146. [12] Felis E, Alder A, Surmacz-Górska J, Miksch K. Advanced oxidation of the polycyclic musk fragrances with using UV and UV/H2 O2 processes. Arch Environ Prot. 2008;34: 13–23. [13] Rosal R, Rodriguez A, Perdigon-Melon JA, Petre A, GarciaCalvo E, Gomez MJ, Aguera A, Fernandez-Alba R. Occurrence of emerging pollutants in urban wastewater and their removal through biological treatment followed by ozonation. Water Res. 2009;44:578–588. [14] Ternes TA, Stuber J, Herrmann N, McDowell D, Ried A, Kampman M, Teiser B. Ozonation: a tool for removal of pharmaceuticals, contrast media and musk fragrances from wastewater. Water Res. 2003;37:1976–1982. [15] Li W, Ma Y, Guo C, Hu W, Liu K, Wang Y, Zhu T. Occurrence and behavior of the most used sunscreen UV filters in
[16] [17] [18] [19]
[20] [21] [22] [23]
a wastewater reclamation plant. Water Res. 2007;41:3506– 3512. Kaleta J, Elektorowicz M. The removal of anionic surfactants from water in coagulation. Environ Technol. 2013;34:999– 1005. Pagano M, Lopez A, Volpe A, Mascolo G, Ciannarella R. Oxidation of nonionic surfactants by Fenton and H2 O2 /UV processes. Environ Technol. 2008;29:423–433. Kang YW, Cho M-J, Hwang K-Y. Correction of hydrogen peroxide interference on standard chemical oxygen demand test. Water Res. 1999;33:1247–1251. Carballa M, Fink G, Omil F, Lema JM, Ternes T. Determination of the solid-water distribution coefficient (Kd ) for pharmaceuticals, estrogens and musk fragrances in digested sludge. Water Res. 2008;42:287–295. Krzysztoszek A, Naumczyk J. Landfill leachate treatment by Fenton, photo-Fenton processes and their modifications. J Adv Oxid Technol. 2012;15:53–63. Caillet S, Yu H, Lessard S, Lamoureux G, Ajdukovic D, Lacroix M. Fenton reaction applied for screening natural antioxidants. Food Chem. 2007;100:542–552. Kang YW, Hwang K-Y. Effect of re action conditions on the oxidation efficiency in the Fenton process. Water Res. 2000;34:2786–2790. Naumczyk J, Prokurat I, Marcinowski P. Landfill leachates treatment by H2 O2 /UV, O3 /H2 O2 , modified Fenton, and modified photo-Fenton methods. Int J Photoenergy. 2012, Article ID 909157, 9 pages, doi:10.1155/2012/909157
Environmental Technology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tent20
Cosmetic wastewater treatment by coagulation and advanced oxidation processes a
a
a
a
Jeremi Naumczyk , Jan Bogacki , Piotr Marcinowski & Paweł Kowalik a
Faculty of Environmental Engineering, Warsaw University of Technology, Nowowiejska 20, 00-653 Warsaw, Poland Accepted author version posted online: 29 May 2013.Published online: 25 Jun 2013.
To cite this article: Jeremi Naumczyk, Jan Bogacki, Piotr Marcinowski & Paweł Kowalik (2014) Cosmetic wastewater treatment by coagulation and advanced oxidation processes, Environmental Technology, 35:5, 541-548, DOI: 10.1080/09593330.2013.808245 To link to this article: http://dx.doi.org/10.1080/09593330.2013.808245
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Environmental Technology, 2014 Vol. 35, No. 5, 541–548, http://dx.doi.org/10.1080/09593330.2013.808245
Cosmetic wastewater treatment by coagulation and advanced oxidation processes Jeremi Naumczyk∗ , Jan Bogacki, Piotr Marcinowski and Paweł Kowalik Faculty of Environmental Engineering, Warsaw University of Technology, Nowowiejska 20, 00-653 Warsaw, Poland
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(Received 23 January 2013; final version received 20 May 2013 ) In this study, the treatment process of three cosmetic wastewater types has been investigated. Coagulation allowed to achieve chemical oxygen demand (COD) removal of 74.6%, 37.7% and 74.0% for samples A (Al2 (SO4 )3 ), B (Brentafloc F3) and C (PAX 16), respectively. The Fenton process proved to be effective as well – COD removal was equal to 75.1%, 44.7% and 68.1%, respectively. Coagulation with FeCl3 and the subsequent photo-Fenton process resulted in the best values of final COD removal equal to 92.4%, 62.8% and 90.2%. In case of the Fenton process, after coagulation these values were equal to 74.9%, 50.1% and 84.8%, while in case of the H2 O2 /UV process, the obtained COD removal was 83.8%, 36.2% and 80.9%. High value of COD removal in the Fenton process carried out for A and C wastewater samples was caused by a significant contribution of the final neutralization/coagulation. Very small effect of the oxidation reaction in the Fenton process in case of sample A resulting from the presence of antioxidants, ‘OH radical scavengers’ in the wastewater. Keywords: chemical treatment; coagulation; cosmetic wastewaters; Fenton/photo-Fenton process; H2 O2 /UV process
1. Introduction Cosmetic wastewater is characterized by a significant changeability of its composition and the concentration of pollutants, which is caused by the changeable production profile. Independent of the aforementioned variability, some substances are always present in cosmetic wastewater. They include synthetic musks, mainly polycyclic musks, as well as ketone and xylene musks. Among them, galaxolide and tonalide are used in the largest amount. These compounds are not easily biochemically degradable and are partially removed in a municipal wastewater treatment plant mainly due to adsorption on activated sludge.[1] Other important and not easily biodegradable compounds present in cosmetic wastewater include UV filters. These are the components of creams and their main responsibility is to absorb UV radiation. UV filters include among others: benzophenone derivatives, p-aminobenzoic acid, benzoic acid esters, ethylhexyl salicylate and heptan-2-one derivatives. These compounds are called emerging pollutants and pose a real threat to the water environment due to their toxicity.[2,3] Literature concerning the application of chemical methods in cosmetic wastewater treatment is scarce. El-Gohary et al. compared the effect achieved by means of the coagulation combined with sedimentation and pressure flotation.[4] The coagulants used in this study included Al2 (SO4 )3 , polymerized aluminium chloride, FeSO4 and FeCl3 . All coagulants gave comparable results and their efficiency depended on the type of investigated wastewater. The efficiency of chemical oxygen demand (COD) removal was ∗ Corresponding
author. Email: [email protected]
© 2013 Taylor & Francis
equal to approximately 75%. The application of coagulation combined with flotation did not improve the effect of COD removal, compared with the effect of coagulation with sedimentation. However, the sludge volume decreased. The effect of flotation process was improving with the increasing contents of oils and fats. The results obtained for the electrocoagulation and electro-Fenton processes, which were carried out in parallel, gave slightly better results compared with the results obtained for coagulation alone.[5] In both cases, the COD removal was close to 80%. The Fenton process for sewage pretreated by coagulation, with COD 4730 and 2660 mg/L and biochemical oxygen demand (BOD)5 /COD ratio of 0.123 and 0.161, was also investigated by Bautista et al. [6] At optimal pH value 3, Fe(II) dose was 300–500 mg/L, while H2 O2 /COD ratio was 2.12, COD removal was equal to approximately 55%. Cosmetic wastewater also underwent electrocoagulation process and subsequent photocatalytic oxidation with TiO2 , which allowed for COD removal of 78–82%.[7] Bautista et al.[8] also employed the catalytic oxidation process by means of the H2 O2 and Fe/γ Al2 O3 catalyst. At 85◦ C, the COD removal in the first cycle of the catalyst operation was equal to 80%, while in the third cycle, it was 60%. In this process, the improvement of organics biodegradability was observed.[8] Martins et al. applied catalytic ozonation and Fenton-like processes to treat wastewater from the detergent industry, which also contains many substances present in cosmetic wastewater.[9] The best treatment results and improvement of BOD5 /COD ratio
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from 0.32 to 0.80 was achieved by applying the classic Fenton process and ozonation catalysed by the mixture of Ce and Mn oxides. The removal of synthetic musks has also been studied. Carballa et al. employed the coagulation and pressure flotation in order to remove tonalide and galaxolide from municipal wastewater.[10] The best effect of tonalide (71%) and galaxolide (63%) removal was achieved using PAX as a coagulant. Slightly worse results were obtained when FeCl3 and Al2 (SO4 )3 were used. The presence of fats improved the effect of flotation. Similar studies have been carried out by Suarez et al. [11] As a result of coagulation employing FeCl3 , the obtained removal of tonalide, galaxolide and celestoide was equal to 83.4%, 79.2% and 77.7%, respectively. In case of the coagulation/flotation process with Al2 (SO4 )3, the effect was slightly worse – 75.8%, 64.8% and 72.1%, respectively. Felis et al. removed polycyclic musks from wastewater by means of the UV photolysis and UV/H2 O2 processes, achieving the decrease in their content by 93% and 99%, respectively.[12] Rosal et al. employed ozonation to remove musks and UV filters from municipal wastewater.[13] Galaxolide was removed in 72%, while ketone musks only in 38%. Xylene musks and UV filters – 3-(4-benzylidene) camphor, octyl methoxycinnamate and benzophenone-3 – turned out to be completely resistant to ozonation. Triclosane was removed in 78%, while octocrylene in 20%. High efficiency of ozonation of tonalide and galaxolide has been also confirmed by Ternes et al. [14] Li et al. investigated the removal of four UV filters – benzophenone-3, 4,4-methylbenzylidene camphor, octyl methoxycinnamate and octocrylene – in the municipal wastewater plant by means of subsequently applied processes: coagulation with polyaluminium chloride, microfiltration and ozonation.[15] The removal of the investigated substances in the three above-mentioned processes was equal to 7.6–21%, 3.6–8.2% and 16–28%, respectively. Many studies focused on the elimination of surfactants from wastewater. Kaleta and Elektorowicz revealed that coagulation with Al2 (SO4 )3 and FeCl3 yields poor effect of anionic surfactant removal (24%).[16] Significantly better effect of surfactants removal was achieved by means of the Fenton process and H2 O2 /UV process – almost 100% removal of six alcohol ethoxylates and four alkylphenol ethoxylates.[17] The aim of this study was to provide further information and deepen the knowledge concerning cosmetic wastewater treatment by means of coagulation and oxidation processes for wastewater with different pollutants composition and concentration. In the investigation of coagulation, the range of coagulants employed has been significantly extended. The results of coagulation have been compared with the results of the Fenton process. The effect of wastewater treatment in combined processes: coagulation + advanced oxidation processes (AOPs) – has also been investigated. Preliminary results of raw wastewater treatment by means of H2 O2 /UV and the photo-Fenton
processes were unsatisfactory due to high wastewater turbidity. Therefore, these methods have been used only for the treatment of wastewater which was preliminarily coagulated. 2. Materials and methods Wastewater samples were collected from the big cosmetic factory in Poland, between October 2011 and February 2012. In this facility, a wide range of cosmetics, including lipsticks, shampoo, serum, liquid soap and creams, was manufactured. As main compounds galaxolide, tonalide (synthetic musks), ethylhexyl salicylate (UV filter) and D5 (cosmetic base) were used. In raw wastewater, the following parameters were determined according to EN or ISO Standards: COD, CODdis (for sample filtered with 0.45 μm filter) (ISO 6060), BOD5 (EN 1899), total suspended solids (TSSs) (EN 872), pH (EN ISO 10523), turbidity (EN ISO 7027), specific conductivity (EN 27888), alkalinity (ISO 740), chlorides (ISO 9297), phosphates (EN 1189), ammonia (ISO 5664), nitrates (V) (EN ISO 13395) and anionic surfactants (EN 903). Petroleum ether extractable organics (PEEOs) were gravimetrically determined by the extraction of 500 mL sample with petroleum ether (50 + 50 mL). COD of wastewater treated with AOP’s was determined without the removal of unreacted H2 O2 . It was impossible to remove residual H2 O2 by means of catalase, due to the inhibiting effect of some pollutants present in the samples. Therefore, H2 O2 was determined by means of the iodometric method and the value of COD was corrected according to Kang’s equation.[18] In the studies of the coagulation of raw wastewater, the following solutions have been used: FeCl3 and Al2 (SO4 )3 with the concentration of 100 mg/mL Fe3+ and 50 mg/mL Al3+ , Brenntag Al: 1019, 3010, 3030, 3035 prehydrolysed coagulants containing aluminium salts, FeCl3 -based Brentafloc F3 and Kemipol PAX16 and PAX19 coagulants containing aluminium salts. The correction of the pH value after the addition of coagulant was done by means of NaOH or H2 SO4 solutions. 5 min fast and 10 min slow stirring times were employed. During 60 min of sedimentation after coagulation, the changes in the sludge volume were investigated. Wastewater after coagulation with FeCl3 at pH 6.0 was treated using Fenton, photo-Fenton and H2 O2 /UV processes. The application of the Fe salt was a result of the application of Fe salt in the Fenton and photo-Fenton processes. Consequently, it was necessary to assess the contribution of the final coagulation in these processes. The assumed value of pH 6.0 (not 9.0) resulted from the necessity to reduce the amount of H2 SO4 used to decrease the pH value in order to perform these processes. Also the amount of NaOH solution needed for the adjustment to pH 9.0 is significantly higher than the pH 6.0. The Fenton process was carried out in a 2 L cylindrical reactor with a magnetic stirrer, at pH 3.0, by adding appropriate amounts of
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Environmental Technology Table 1.
The doses of reagents (mg/L) for AOP’s.
Sample
Fenton process for raw wastewater H2 O2 /Fe2+
A B C
1200–1700/150–250 600–800/80–100 1900–2300/200–360
Fenton process H2 O2 /Fe2+ 400–500/50–80 500–700/60–80 550–700/80–120
acidic FeSO4 solution with the concentration of 50 mg/mL Fe2+ and 30% H2 O2 solution. After a specified time of 5, 15, 30 and 60 min, the process was stopped by increasing the pH value to 9.0 and the reactor was left for 240 min in order to allow for the sedimentation of the resulting sludge. The Photo-Fenton process was carried out in a glass cylindrical 1 L Heraeus Nobelight photoreactor with a water cooling blanket and TQ (150 W) medium pressure mercury lamp. The lamp radiation includes the range from 200 to 580 nm with several sharp emission peaks at 365 (the strongest peak), 545, 580, 430, 320, 250, 265 and 300 nm. The conditions of the process were the same as in the case of the Fenton process with the only difference being that Fe2+ /H2 O2 weight ratios were lower. The process duration time and the operation after finishing the process were the same as in case of the Fenton process. The H2 O2 /UV process was carried out in a glass cylindrical 1 L Heraeus Nobelight photoreactor equipped with a low-pressure mercury lamp (15 W). The lamp emits a sharp radiation of the wavelength of approximately 254 nm. Since, during the process, the pH value slightly decreased, its initial value was increased to 8.0. The process duration time was the same
Table 2.
Photo-Fenton process H2 O2 /Fe2+
H2 O2 /UV process H2 O2
400–500/40–55 500–700/50–70 600–750/55–70
1000–1500 1500–2000 1500–2000
as in the Fenton process. The doses of reagents applied for all AOPs and all samples are listed in Table 1. 3. Results 3.1. Wastewater characteristics The characteristic of the investigated wastewater is presented in Table 2. The investigated samples were diversified as far as both quality and pollutant concentration is concerned. The highest COD value was observed for sample C (2124 mg/L), while the lowest value was obtained for sample B (758 mg/L). The majority of the pollutants having contributed to the COD value was dissolved (CODdis ). Wastewater was not susceptible to biological treatment, which is proved by the BOD5 /COD ratio – 0.06–0.10. Oil content was not at a high level and the highest contribution of oils to the total organics (PEEO/COD) was detected in sample B. Sample A was characterized by the highest TSS content, but at the same time, the highest value of CODdis /COD ratio (0.78) implies that there is a significant contribution of mineral TSS. The lowest level of TSS in relation to content of organic substances was detected in
Characteristics of raw wastewaters.
Parameter (unit)
pH (−)
Conductivity (μS/cm)
COD (mg/L)
Sample A Sample B Sample C
7.9 9.1 7.4
1265 1042 2640
1507 758 2124
Parameter (unit)
Turbidity (NTU)
Chlorides (mg/L)
Sample A Sample B Sample C
150 70 800
122 82 742
Table 3.
543
CODdis (mg/L) 1179 527 1402 Ammonia (mg/L) 12.5 2 2.5
BOD5 (mg/L)
BOD5 / COD (−)
150 48 168 Nitrates (mg/L)
0.1 0.06 0.08 Phosphates (mg/L)
2.5 2 3
PEEO (mg/L) 58 137 258
811 129 584
Alkalinity (mval/L)
2 4 5
TSS (mg/L)
7.6 5.3 3.2
Surfactants (mg/L) 20 15 20
Coagulation results for wastewater A.
Coagulant pH COD (mg/L) Optimal dose (mg/L or mL/L) Sludge volume (mL/L)
FeCl3 6.0 435 100 150
FeCl3 9.0 392 100 95
F3 6.0 400 1.5 230
Al2 (SO4 )3 7.0 383 125 230
3010 7.0 409 1.0 280
1019 7.0 383 1.0 430
3030 7.0 387 1.0 450
3035 7.0 418 0.5 320
PAX16 7.0 400 1.25 200
PAX19 7.0 400 0.75 170
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sample C. Very high turbidity of wastewater C implies that the suspension was very fine. Content of anionic surfactants was low for all samples.
3.2. Wastewater treatment 3.2.1. Wastewater A Table 3 shows the results of the studies of the coagulation process for wastewater A. The differences between COD removal values obtained using different coagulants are small – the values ranged from 71% (FeCl3 at pH 6.0) to 74.6% (Al2 (SO4 )3 and Brenntag Al 1019). FeCl3 at pH 9.0 was regarded as the best Fe-based coagulant. The obtained value of COD removal (74.0%) corresponded to the smallest volume and hydration of the resulting sludge – 95 ml/L after 60 min of sedimentation. The Fenton process proved to be efficient as well (Figure 1). For optimal doses of H2 O2 /Fe(II) equal to 1500/190 mg/L and after 60 min of the process, the obtained COD removal was 75.1% (down to 375 mg/L). The process was very fast during the first 5 min (36.6% COD removal) and after 30 min slowed down significantly (74.6% COD removal). The Fenton process using the doses of H2 O2 /Fe(II) of 435/55 mg/L carried out after coagulation with FeCl3 at pH 6.0 and dose of 100 mg/L (Figure 2(a)), resulted in COD removal of only 12.9% (from 435 to 379 mg/L) – in total 74.9%. Significantly better results of the treatment of the same sample were achieved by means of the H2 O2 /UV process (Figure 2(a)) – after 60 min of the process and with the H2 O2 dose of 1300 mg/L, the COD removal value was equal to 43.9%, while the total result for COD removal: coagulation and H2 O2 process was equal to 83.8% (down to 244 mg/L). The best effect of wastewater treatment for sample A after coagulation was achieved by means of the photo-Fenton process with H2 O2 /Fe(II) doses of 435/45 mg/L. After 60 min (Figure 2(a)), the obtained COD removal was equal to 73.1% (down to 117 mg/L) and the total effect was equal to 92.4%.
Figure 1. COD vs. reaction time: Fenton process for raw wastewater.
Figure 2. COD vs. reaction time: AOP’s for samples after coagulation: sample A (a), sample B (b) and sample C (c).
3.2.2. Wastewater B The effect of coagulation (Table 4) achieved for sample B was significantly lower than in the case of sample A (Table 3). The highest effect of COD removal (37.7%) was obtained by means of F3 at pH 6.0 and also by means of FeCl3 at pH 9.0–32.2%. Additionally, in the latter case, the lowest sludge volume (45 mL/L) was obtained, in contrary to the coagulation with F3, when the volume was 80 mL/L. The lowest efficiency in COD removal was observed for the coagulation with FeCl3 at pH 6.0 (20.1%), but the sludge volume was one of the lowest (80 mL/L). The Fenton process after 60 min proved to be more effective compared with coagulation (Figure 1 vs. Table 4). The value of COD removal at the optimal H2 O2 /Fe(II) dose of 760/90 mg/L and after 60 min of the process was 44.7% (down to 419 mg/L). The instant drop in the COD value in the initial stage of the process has not been observed. The Fenton process of wastewater B after coagulation and
Environmental Technology Table 4.
Coagulation results for wastewater B.
Coagulant pH COD (mg/L) Optimal dose (mg/L or mL/L) Sludge volume (mL/L) Table 5.
FeCl3 6.0 606 75 80
FeCl3 9.0 514 75 45
F3 6.0 472 0.75 80
Al2 (SO4 )3 7.0 589 100 110
3010 7.0 573 0.5 130
1019 7.0 589 0.5 150
3030 7.0 589 0.75 170
3035 7.0 573 0.5 90
PAX16 7.0 539 1.0 130
PAX19 7.0 570 1.0 130
F3 6.0 595 1.0 80
Al2 (SO4 )3 7.0 680 125 200
3010 7.0 595 0.5 120
1019 7.0 595 0.5 120
3030 7.0 658 0.75 120
3035 7.0 595 0.75 110
PAX16 7.0 552 1.25 180
PAX19 7.0 595 1.0 120
Coagulation results for wastewater C.
Coagulant pH COD (mg/L) Optimal dose (mg/L or mL/L) Sludge volume (mL/L)
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FeCl3 6.0 637 100 65
FeCl3 9.0 680 100 55
at the optimal doses of reagents equal to 600/75 mg/L (Figure 2(b)) allowed for 37.6% COD removal (down to 378 mg/L) and total COD removal at the level of 50.1%. The H2 O2 /UV process (Figure 2(b)) was less effective – after 60 min of the process at the H2 O2 dose of 1800 mg/L, 20.1% of COD removal (down to 484 mg/L) was achieved, while the total effect was equal to 36.2%. The photo-Fenton process proved to be the most effective of all processes investigated (Figure 2(b)). At the optimal H2 O2 /Fe(II) dose of 600/60 mg/L, the values of COD removal and total COD removal after 60 min of the process were 53.5% (down to 282 mg/L) and 62.8%, respectively.
3.2.3. Wastewater C The best effect of COD removal (Table 5) was achieved for PAX 16–74.0% of COD removal. However, the sludge volume was one of the highest – 180 mL/L. The effect obtained by means of the F3 coagulant can be regarded as optimal – 72.0% COD removal and sludge volume of 80 mL/L. The worst effect was achieved using FeCl3 at pH 9.0–68.0% COD removal but the sludge volume was the lowest (55 mL/L). The process was carried out using FeCl3 at pH 6.0 that produced the COD removal at the 70.0% level (down to 637 mg/L) and the sludge volume of 65 mL/L. The Fenton process on raw wastewater (Figure 1) resulted in 68.1% COD removal (down to 680 mg/L) when using optimal H2 O2 /Fe(II) doses of 2125/265 mg/L. A relatively high value of COD removal (39.3%) was already obtained after 5 min of the process. In the case of wastewater after coagulation with FeCl3 at pH 6.0, the Fenton process produced 52.4% COD removal (down to 324 mg/L) when using optimal H2 O2 /Fe(II) doses of 640/105 mg/L (Figure 2(c)) and a total COD removal of 84.8%. In case of this type of wastewater, the relatively high value of COD removal was also observed after 5 min (33.8%). The H2 O2 /UV process (Figure 2(c)) turned out to be less effective, since COD removal after 60 min of the process and with the H2 O2 dose of 1900 mg/L was only 36.4% (down to
405 mg/L). The total COD removal was 80.9%. The photoFenton process proved to be the most effective (Figure 2(c)). With the H2 O2 /Fe(II) dose of 640/65 mg/L, the COD removal value, achieved after 60 min of the process, was equal to 67.5%. Total COD removal value was 90.2%. Similarly, the raw wastewater and in the case of the Fenton process, a relatively high decrease in COD (54.0%) was observed within the first 5 min.
4. Discussion Diversity of the chemical composition and the total organic content in three investigated samples of wastewater induce the differences in their susceptibility to chemical treatment. Samples A and C exhibit a high susceptibility to coagulation for all coagulation tests. The obtained high value of COD removal (>70%) is suspected, since both the samples of wastewater are characterized by a high content of suspended solids. In the case of sample C, its contribution to COD [(COD – CODdis )/COD] was equal to 34%, while in the case of sample A its contribution was much lower and high efficiency of the process might have been affected by the presence of fine, easily coagulating mineral SS, acting as a load for organic suspension. The presence of a high amount of synthetic musks might have been another reason for high efficiency of coagulation of sample A. Polycyclic musks are characterized by high lipophilicity, especially galaxolide and tonalide (log Kow 5–6), which are used in large amounts.[14,19] Musk xylene and musk ketone are only slightly less lipophilic. Studies on the coagulation of those types of musks in hospital wastewater revealed that they are removed in 70–84%, and the effect achieved by means of FeCl3 is better than the ones obtained using Al2 (SO4 )3 .[11] These compounds are removed mostly as a result of their adsorption on the resulting sludge. The best effect for wastewater A achieved using FeCl3 at pH 9 means that in the case of dissolved organic removal, the sorption process plays a crucial role. At pH 9, the Fe(OH)3 species are present in the solution, while at lower pH Fe(OH)+ 2,
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Fe(OH)2+ and Fe3+ ions are detected.[4] A poor coagulation effect is observed for sample B that resulted from a relatively lower TSS content and from a relatively high content of substances much more polar than synthetic musks, which have nonionic composition and can be extracted from petroleum ether. Those substances mostly include UV filters (produced in the periods preceding sample collection), which according to the results of studies carried out by Li et al. were removed in 7.1–21% by means of coagulation with polyaluminium chloride.[15] The best results of COD removal by means of F3 at pH 6 proves that in cases of these types of wastewater, the mechanism of pollutant removal was mixed. In the case of sample C, high values of COD removal achieved for all coagulants studied proves the mixed mechanism of pollutant removal. The best results obtained using (prehydrolized) PAX 16 coagulant and good results obtained using other prehydrolized polyaluminium salts are consistent with the results reported by Carballa et al. [10] The polymeric structure leads to the agglomeration properties of these coagulants and stronger destabilization of negative colloids. The results of the studies on the efficiency of the Fenton process for wastewater A proved the dominant contribution of the final neutralization/coagulation to the final value of COD removal. This contribution is characterized by a high value of COD removal in the first stage of the process (5 min).[20] In the Fenton process carried out after the coagulation of wastewater A, general COD removal was only 3.8% higher than the one obtained by means of coagulation alone, which proves the conclusions presented above. Substances remaining in the wastewater after coagulation are characterized by relatively low susceptibility to oxidation by HO radicals, which is confirmed by the value of COD removal equal to only 12.9%. Those substances mostly included the ketone and xylene musk. As it was shown by Rosal et al. [13] and Li et al. [15], they are poorly (that is to significantly lower extent than polycyclic musks) removed not only in the coagulation process, but also in the ozonation process. Poorly removable UV filters were present in the wastewater at low concentration. A much better effect in the H2 O2 /UV process was achieved for the wastewater after coagulation and even better results were obtained by the photo-Fenton process, which may be explained by the excitation of UV filters and other compound molecules by means of UV radiation. In the case of the photo-Fenton process, the emission spectrum was broader and this phenomenon was much stronger. The reason for low efficiency of the Fenton process after coagulation for sample A and a small contribution of the oxidation reaction in the Fenton process for raw wastewater might have been the presence of antioxidants (i.e. hyaluronic acid), which are HO radical scavengers.[21] Those substances were used in the production of cosmetics just before sample A collection. Those substances undergo photolysis, which explains the good results of H2 O2 /UV and photo-Fenton processes.[21] Similarly to sample A, in the Fenton process carried out
for sample C, the final neutralization/coagulation plays a significant role. However, a high value of COD removal achieved after 5 min of the process may result from the presence of a certain amount of substances quickly reacting with HO radicals. This is confirmed by high value of COD removal after 5 min in cases of all AOPs carried out for wastewater after coagulation, which is most evident in the case of the photo-Fenton process. Lower values of COD removal in H2 O2 /UV process compared with the value of COD removal in the Fenton process results probably from a significant contribution from coagulation in the Fenton process, which is absent in the H2 O2 /UV process. In the case of sample B, the effect of neutralization/coagulation in the total effect of the Fenton process is significantly lower. It results from the weak effect of coagulation itself. However, this effect exists and most probably consists in the adsorption of pollutants. It is confirmed by the fact that the Fenton process carried out after coagulation in conditions producing the worst effect (FeCl3 , pH 6) gave better results of COD removal than the effect of H2 O2 /UV process. Definitely the best, but worse than in the case of sample A, the effect of the photo-Fenton process may be explained by the contribution of neutralization/coagulation, by the stronger excitation of molecules of UV filters by the UV lamp irradiation and by Fe2+ ions reproduction according to reaction (1).[20] Fe(OH)2+ + hν → Fe2+ + HO• .
(1)
In all Fenton and photo-Fenton processes, the optimal dose of H2 O2 was similar to the COD value, while Fe(II) dose was eight times smaller. Increasing the doses did not improve the effect of the process. In order to estimate the efficiency of the Fenton process, a parameter referred to as ‘efficiency of hydrogen peroxide’ was recommended by Kang and Hwang.[22] η(%) =
COD × 100 , 0.476[H2 O2 ]
(2)
where COD, COD removed (mg/L); [H2 O2 ], dose of H2 O2 (mg/L); 0.476, factor COD theoretically removed (mg) by 1 mg of H2 O2 . The value of this parameter for the Fenton process and sample A was high – 160.0. Such high values of H2 O2 efficiency are caused not only by the oxidation process, but also by the final coagulation. This is proved by a very low value (27.4%) of this parameter for the same wastewater sample, but after the coagulation process. For wastewater B, for which the effect of the Fenton process is smaller, the value of η parameter is also lower, namely 94.7%. The contribution of the final coagulation to this parameter is less significant. For wastewater B after coagulation, this value is slightly lower (80.7%). In the case of wastewater C, for which the effect of the Fenton process is intermediate (closer to the effect for wastewater A), the value of η parameter (144.7%) is close to the value obtained for wastewater A. The contribution of the final coagulation to this parameter
Environmental Technology Table 6.
H2 O2 efficiency (%) in AOP’s for samples A, B and C and process time 60 min. Coagulation + Fenton process
Fenton process for raw wastewater A
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160.0
Coagulation+H2 O2 /UV process
C
A
B
C
A
B
C
A
B
C
94.7
144.7
27.4
80.7
112.3
155.3
114.8
142.8
31.3
14.4
26.0
HO• + RH → R • + H2 O, R + O2 →
RO•2 .
Cosmetic wastewater is generally characterized by high but diversified (37.7–74.6% COD removal) susceptibility to coagulation, which depends on the wastewater composition. The effect of the Fenton process is slightly higher than the coagulation effect (44.7–75.1% COD removal). Contribution of the final neutralization/coagulation to the final effect is significant. Antioxidants present in wastewater lead to the decrease in the effect of the Fenton process. In the case of wastewater after coagulation, the photoFenton process proved to be the most effective of all oxidation processes investigated. In case of wastewater A, the total effect of COD removal was equal to 92.4%.
(3) (4)
Very low values of η parameter for the H2 O2 /UV process for wastewater after coagulation, which are equal to 31.3%, 14.4% and 26.0%, respectively, result not only from the low efficiency of this process. It was achieved using relatively a high (optimal) H2 O2 /COD ratio. Presented results of the studies may be compared only with the results of the studies published by El-Gohary et al. [4] The results obtained by those authors were slightly higher (up to 77.5% COD removal) and similar to the studies presented in this paper, the differences between the coagulants were small. The investigated samples of wastewater were characterized by COD values similar to the value for sample C. However, they contained much more biodegradable substances – i.e. vitamins and sorbitol. The results of the studies on the Fenton process may be compared with the results presented by Bautista et al. [6] The authors treated the pre-coagulated wastewater with a COD value of 2720 mg/L and with a higher susceptibility to biological treatment. The obtained results of COD removal were slightly lower than those reported in the present study. Additionally, they were achieved using almost twofold higher values of H2 O2 /COD ratio. 5.
Coagulation + photoFenton process
B
is low, which is proved by the value of η parameter for the wastewater after coagulation (112.3%). This value is only slightly lower than without the coagulation process. The value of η parameter for the photo-Fenton process and wastewater after coagulation is high for all investigated wastewater samples and is equal to 155.3%, 114.8% and 142.8%, respectively. The values of η for all processes and wastewater, and 60 min reaction time, are presented in Table 6. Since the contribution of the final coagulation to the value of η parameter cannot be significant, the high value of the parameter is caused by the presence of oxygen in the aerated sample and the presence of organic radicals formed in the reactions mentioned below.[23] •
547
Conclusions
Composition and concentration of pollutants in cosmetic wastewater generated by a big cosmetic factory significantly changes in time and according to the changes in the production profile. This type of wastewater is resistant to biological treatment and the pollutant concentration is usually high.
Acknowledgements The authors gratefully acknowledged the financial support provided by the National Science Centre (grant no. 7385/B/ T02/2011/40 ‘Chemical pretreatment of effluents from cosmetic industry’).
References [1] Carballa M, Omil F, Lema JM, Llompard M, Garcia-Jares C, Rodriguez I, Gomez M, Ternes T. Behavior of pharmaceuticals, cosmetics and hormones in a sewage treatment plant. Water Res. 2004;38:2918–2926. [2] Dhanirama D, Gronow J, Voulvoulis N. Cosmetics as a potential source of environmental contamination in the UK. Environ Technol. 2012;33:1597–1608. [3] Tamura I, Kimura K, Kameda Y, Nakada N, Yamamoto H. Ecological risk assessment of urban creek sediments contaminated by untreated domestic wastewater: potential contribution of antimicrobials and a musk fragrance. Environ Technol. 2013. doi:10.1080/09593330.2012.758667 [4] El-Gohary F, Tawfik A, Mahmoud U. Comparative study between chemical coagulation/precipitation (C/P) versus coagulation/dissolved air flotation (C/DAF) for pretreatment of personal care products (PCPs) wastewater. Desalination. 2010;252:106–112. [5] Aloui F, Kchaou S, Sayadi S. Physicochemical treatments of anionic surfactants wastewater: effect on aerobic biodegradability. J Hazard Mater. 2009;164:353–359. [6] Bautista P, Mohedano AF, Gilarranz MA, Casas J, Rodriguez J. Application of Fenton oxidation to cosmetic wastewaters treatment. J Hazard Mater. 2007;143:128–134. [7] Boroski M, Rodrigues AC, Garcia JC, Sampaio LC, Nozaki J, Hioka N. Combined electrocoagulation and TiO2 photoassisted treatment applied to wastewater effluents from pharmaceutical and cosmetic industries. J Hazard Mater. 2009;162:448–454.
Downloaded by [The University of British Columbia] at 04:12 24 November 2014
548
J. Naumczyk et al.
[8] Bautista P, Mohedano A, Menendez N, Casas J, Rodriguez JJ. Catalytic wet peroxide oxidation of cosmetic wastewaters with Fe-bearing catalysts. Catal Today. 2010;151:148–152. [9] Martins RC, Silva AMT, Castro-Silva S, Garção-Nunes P, Quinta-Ferreira RM. Advanced oxidation processes for treatment of effluents from a detergent industry. Environ Technol. 2011;32:1031–1041. [10] Carballa M, Omil F, Lema JM. Removal of cosmetic ingredients and pharmaceuticals in sewage primary treatment. Water Res. 2005;39:4790–4796. [11] Suarez S, Lema JM, Omil F. Pre-treatment of hospital wastewater by coagulation–flocculation and flotation. Biores Technol. 2009;100:2138–2146. [12] Felis E, Alder A, Surmacz-Górska J, Miksch K. Advanced oxidation of the polycyclic musk fragrances with using UV and UV/H2 O2 processes. Arch Environ Prot. 2008;34: 13–23. [13] Rosal R, Rodriguez A, Perdigon-Melon JA, Petre A, GarciaCalvo E, Gomez MJ, Aguera A, Fernandez-Alba R. Occurrence of emerging pollutants in urban wastewater and their removal through biological treatment followed by ozonation. Water Res. 2009;44:578–588. [14] Ternes TA, Stuber J, Herrmann N, McDowell D, Ried A, Kampman M, Teiser B. Ozonation: a tool for removal of pharmaceuticals, contrast media and musk fragrances from wastewater. Water Res. 2003;37:1976–1982. [15] Li W, Ma Y, Guo C, Hu W, Liu K, Wang Y, Zhu T. Occurrence and behavior of the most used sunscreen UV filters in
[16] [17] [18] [19]
[20] [21] [22] [23]
a wastewater reclamation plant. Water Res. 2007;41:3506– 3512. Kaleta J, Elektorowicz M. The removal of anionic surfactants from water in coagulation. Environ Technol. 2013;34:999– 1005. Pagano M, Lopez A, Volpe A, Mascolo G, Ciannarella R. Oxidation of nonionic surfactants by Fenton and H2 O2 /UV processes. Environ Technol. 2008;29:423–433. Kang YW, Cho M-J, Hwang K-Y. Correction of hydrogen peroxide interference on standard chemical oxygen demand test. Water Res. 1999;33:1247–1251. Carballa M, Fink G, Omil F, Lema JM, Ternes T. Determination of the solid-water distribution coefficient (Kd ) for pharmaceuticals, estrogens and musk fragrances in digested sludge. Water Res. 2008;42:287–295. Krzysztoszek A, Naumczyk J. Landfill leachate treatment by Fenton, photo-Fenton processes and their modifications. J Adv Oxid Technol. 2012;15:53–63. Caillet S, Yu H, Lessard S, Lamoureux G, Ajdukovic D, Lacroix M. Fenton reaction applied for screening natural antioxidants. Food Chem. 2007;100:542–552. Kang YW, Hwang K-Y. Effect of re action conditions on the oxidation efficiency in the Fenton process. Water Res. 2000;34:2786–2790. Naumczyk J, Prokurat I, Marcinowski P. Landfill leachates treatment by H2 O2 /UV, O3 /H2 O2 , modified Fenton, and modified photo-Fenton methods. Int J Photoenergy. 2012, Article ID 909157, 9 pages, doi:10.1155/2012/909157
