| 1. |
- Jonstrup, Maria, et al.
(författare)
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Comparison of anaerobic pre-treatment and aerobic post-treatment coupled to photo-Fenton oxidation for degradation of azo dyes
- 2011
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Ingår i: Journal of Photochemistry and Photobiology, A: Chemistry. - : Elsevier BV. - 1873-2666 .- 1010-6030. ; 224:1, s. 55-61
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Tidskriftsartikel (refereegranskat)abstract
- Photo-Fenton oxidation was used for treatment of synthetic textile wastewater as stand alone treatment, as pre-treatment before aerobic biological treatment and as post-treatment after anaerobic biological treatment. The processes were compared with regards to decolorization, chemical oxygen demand (COD) reduction and chemical consumption. When applying photo-Fenton alone for treatment of Remazol Red RR (100 mg/l), optimal conditions were 3.0 mM H2O2 and 0.25 mM Fe2+. These conditions resulted in complete decolorization and a residual COD of 2.9 mg/l. When reducing the H2O2 dose to 1 mM, residual COD was 22 mg/l. In the combined photo-Fenton/aerobic treatment complete decolorization and COD removal was achieved at 3 mM H2O2 and 0.25 mM Fe2+, while 9 mg/l of residual COD remained at the H2O2 concentration 1 mM. When applying photo-Fenton as post-treatment after the anaerobic step, the residual COD was 14 mg/l independent of the H2O2 concentration being set to 1 or 3 mM, however the Fe2+ concentration needed to be increased to 2 mM, due to complex formation with the phosphate added as a macronutrient. Phytotoxicity tests showed higher residual toxicity after the photo-Fenton treatment alone than after the combined processes. Our results thereby show that incorporation of a biological step leads to improved mineralization and reduced residual toxicity at lower H2O2 doses. (C) 2011 Elsevier B.V. All rights reserved.
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| 2. |
- Kanders, Linda, 1979-, et al.
(författare)
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Impact of seeding on the start-up of one-stage deammonification MBBRs
- 2014
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Ingår i: Environmental technology. - : Taylor & Francis. - 0959-3330 .- 1479-487X. ; 35:22, s. 2767-2773
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Tidskriftsartikel (refereegranskat)abstract
- Treating nitrogen-rich reject water from anaerobically digested sludge with deammonification has become a very beneficial side stream process. One common technique is the one-stage moving bed bioreactors (MBBRs), which in comparison with the other deammonification techniques can be started up without seeding anammox bacteria. This study investigated the impact of biofilm seeding on the start-up of one-stage deammonification MBBRs. Two lab-scale reactors were run in parallel with partial nitritation for 56 days until 11% of the carrier area in one reactor was replaced with fully developed deammonification biofilm to work as the seeding material. The seeded reactor started nitrogen reduction immediately up to a plateau of 1.3gNm−2 d−1; after another 54 days on day 110, the reduction significantly increased. At the same time, the non-seeded reactor also started to reduce nitrogen due to deammonification. The development was followed with both nitrogen analyses and fluorescence in situ hybridization analyses. On day 134, the biofilm in both reactors contained >90% anammox bacteria and reached maximum nitrogen removal rates of 7.5 and 5.6gNm−2 d−1 in the seeded and non-seeded reactor, respectively. Over 80% of the inorganic nitrogen was reduced. In conclusion, the seeding did not contribute to a shorter start-up time or the achieved anammox enrichment, although it did contribute to a partial, immediate nitrogen reduction. The boundary conditions are the most important factors for a successful start-up in a deammonification MBBR system.
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| 3. |
- Punzi, Marisa, et al.
(författare)
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Combined anaerobic-ozonation process for treatment of textile wastewater : Removal of acute toxicity and mutagenicity
- 2015
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Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 292, s. 52-60
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Tidskriftsartikel (refereegranskat)abstract
- A novel set up composed of an anaerobic biofilm reactor followed by ozonation was used for treatment of artificial and real textile effluents containing azo dyes. The biological treatment efficiently removed chemical oxygen demand and color. Ozonation further reduced the organic content of the effluents and was very important for the degradation of aromatic compounds, as shown by the reduction of UV absorbance. The acute toxicity toward Vibrio fischeri and the shrimp Artemia salina increased after the biological treatment. No toxicity was detected after ozonation with the exception of the synthetic effluent containing the highest concentration, 1. g/l, of the azo dye Remazol Red. Both untreated and biologically treated textile effluents were found to have mutagenic effects. The mutagenicity increased even further after 1. min of ozonation. No mutagenicity was however detected in the effluents subjected to longer exposure to ozone. The results of this study suggest that the use of ozonation as short post-treatment after a biological process can be beneficial for the degradation of recalcitrant compounds and the removal of toxicity of textile wastewater. However, monitoring of toxicity and especially mutagenicity is crucial and should always be used to assess the success of a treatment strategy. © 2015 Elsevier B.V.
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| 4. |
- Punzi, Marisa, et al.
(författare)
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Degradation of a textile azo dye using biological treatment followed by photo-Fenton oxidation : Evaluation of toxicity and microbial community structure
- 2015
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 270, s. 290-299
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Tidskriftsartikel (refereegranskat)abstract
- Many commercial dye preparations are cocktails of active dyes and various by-products that are recalcitrant to biological degradation and end up in significant amounts in the effluent after the dyeing process. Conventional wastewater treatment processes are not able to degrade such compounds and detoxify the effluent, thus alternative treatments should be developed.In our work we suggest to use photo-Fenton oxidation as post-treatment after an anaerobic biofilm process, in a way to minimize the reagents needed. This process was used for treatment of synthetic textile wastewater containing the commercial azo dyestuff Remazol Red, starch and sodium chloride. The treated textile effluent had COD lower than 18. mg/l even when using initial Fenton reagents concentration as low as 1. mM ferrous ions and 10. mM hydrogen peroxide. The acute toxicity was higher in the biologically treated than in the untreated effluent. Photo-Fenton oxidation successfully reduced the toxicity and the final effluent was non-toxic to Artemia salina and Microtox, with the exception of the effluent containing high concentration of sodium chloride, which was moderately toxic to Microtox. For the first time the presence of algae was detected in a reactor treating textile wastewater using denaturing gradient gel electrophoresis (DGGE); bacteria and fungi were also abundant.The results of this study suggest that using advanced oxidation after biological treatment is an effective way to degrade the organic compounds and remove toxicity from textile effluents.
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| 5. |
- Punzi, Marisa, et al.
(författare)
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Treatment of synthetic textile wastewater by homogeneous and heterogeneous photo-Fenton oxidation
- 2012
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Ingår i: Journal of Photochemistry and Photobiology, A: Chemistry. - : Elsevier BV. - 1873-2666 .- 1010-6030. ; 248, s. 30-35
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Tidskriftsartikel (refereegranskat)abstract
- The efficiencies of homogeneous and heterogeneous photo-Fenton oxidation were compared for treatment of azo dye containing synthetic textile wastewater. The influence of parameters such as the presence of NaCl and starch was evaluated and optimal iron and H2O2 dosage determined. Complete decolorization of Remazol Red RR was achieved at all investigated NaCl and starch concentration. Mineralization, in terms of COD reduction, was 96% in the homogeneous and 93% in the heterogeneous reaction, but decreased with increasing NaCl and starch concentrations. The homogeneous oxidation showed the highest efficiency in treating synthetic wastewater containing Remazol Blue RR or a mixture of Remazol Red RR and Remazol Blue RR. Nevertheless, the mineralization was significantly lower than for Remazol Red RR, which shows the dependence on dye structure. Similar amounts of iron-containing sludge were produced in the two processes, while the release of iron ions was reduced by 50% when using heterogeneous photo-Fenton. Promising results were obtained when reusing the iron powder as catalyst; complete decolorization was achieved during 20 batches. (C) 2012 Elsevier B.V. All rights reserved.
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| 6. |
- Punzi, Marisa
(författare)
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Treatment of Textile Wastewater by Combining Biological Processes and Advanced Oxidation
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Treatment of textile wastewater is challenging because the water contains toxic compounds that have low biodegradability. Dyes, detergents, surfactants, biocides and more are used to improve the textile process and to make the clothes resistant to physical, chemical and biological agents. New technologies have been developed in the last decades and in particular Advanced Oxidation Processes (AOPs) have shown considerable potential for treatment of industrial effluents. These processes however are expensive and full scale applications are still scarce. In addition, the complex oxidation chemistry transforms the pollutants into a very large number of degradation intermediates which may be even more toxic than the original compounds. This thesis presents a novel treatment approach where two AOPs, photo-Fenton oxidation and ozonation, are used after an anaerobic biofilm process for treatment of textile wastewater, azo dyes degradation and removal of toxicity. The biological treatment cleaves the azo bonds of the dyes and consumes the biodegradable compounds whereas the following advanced oxidation degrades the aromatic amines and other by-products that are recalcitrant to biological degradation. The approach that includes photo-Fenton oxidation resulted in higher reduction of chemical oxygen demand (COD) than that with ozonation when treating real textile wastewater. The latter however resulted in higher reduction of toxicity towards the bacteria Vibrio fischeri and the shrimp Artemia salina. Mutagenic effects were detected in the untreated and biologically treated effluent, but not after photo-Fenton oxidation and ozonation. Environmental impact and costs of the two treatment strategies, at the operating conditions used in this study, are high compared with the full-scale biological process used in the Netherlands, where the wastewater is actually treated. Substitution of artificial light with sunlight and upscaling would result in great improvements in terms of electricity requirements and ozone consumption hence would bring down the environmental impact to values that are comparable to the biological process, suggesting that full scale implementation can be achieved. Further research should look into combining this treatment approach with technologies that allow water and salt recovery and reuse, to make the textile industry more sustainable.
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