This article was downloaded by: [Florida International University] On: 08 September 2014, At: 07:47 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Environmental Technology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tent20
Anaerobic baffled reactor coupled with chemical precipitation for treatment and toxicity reduction of industrial wastewater a
b
Sawanya Laohaprapanon , Marcia Marquesa & William Hogland
a
a
Department of Biology and Environmental Science, Linnaeus University, Kalmar, LNU, Sweden; b
Department of Sanitary and Environmental Engineering, Rio de Janeiro State University – UERJ, Rio de Janeiro, Brazil Accepted author version posted online: 02 Aug 2013.Published online: 01 Oct 2013.
To cite this article: Sawanya Laohaprapanon, Marcia Marquesa & William Hogland (2014) Anaerobic baffled reactor coupled with chemical precipitation for treatment and toxicity reduction of industrial wastewater, Environmental Technology, 35:2, 154-162, DOI: 10.1080/09593330.2013.821142 To link to this article: http://dx.doi.org/10.1080/09593330.2013.821142
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Environmental Technology, 2014 Vol. 35, No. 2, 154–162, http://dx.doi.org/10.1080/09593330.2013.821142
Anaerobic baffled reactor coupled with chemical precipitation for treatment and toxicity reduction of industrial wastewater Sawanya Laohaprapanona∗ , Marcia Marquesab and William Hoglanda a Department
of Biology and Environmental Science, Linnaeus University, Kalmar, LNU, Sweden; b Department of Sanitary and Environmental Engineering, Rio de Janeiro State University – UERJ, Rio de Janeiro, Brazil
Downloaded by [Florida International University] at 07:47 08 September 2014
(Received 28 March 2013; accepted 25 June 2013 ) This study describes the reduction of soluble chemical oxygen demand (CODs ) and the removal of dissolved organic carbon (DOC), formaldehyde (FA) and nitrogen from highly polluted wastewater generated during cleaning procedures in wood floor manufacturing using a laboratory-scale biological anaerobic baffled reactor followed by chemical precipitation using MgCl2 ·6H2 O + Na2 HPO4 . By increasing the hydraulic retention time from 2.5 to 3.7 and 5 days, the reduction rates of FA, DOC and CODs of nearly 100%, 90% and 83%, respectively, were achieved. When the Mg:N:P molar ratio in the chemical treatment was changed from 1:1:1 to 1.3:1:1.3 at pH 8, the NH+ 4 removal rate increased from 80% to 98%. Biologically and chemically treated wastewater had no toxic effects on Vibrio fischeri and Artemia salina whereas chemically treated wastewater inhibited germination of Lactuca sativa owing to a high salt content. Regardless of the high conductivity of the treated wastewater, combined biological and chemical treatment was found to be effective for the removal of the organic load and nitrogen, and to be simple to operate and to maintain. A combined process such as that investigated could be useful for on-site treatment of low volumes of highly polluted wastewater generated by the wood floor and wood furniture industries, for which there is no suitable on-site treatment option available today. Keywords: anaerobic baffled reactor; magnesium ammonium phosphate; toxicity assessment; ammonia removal; urea-formaldehyde wastewater
1. Introduction Urea-formaldehyde (UF) resins are globally used in wood product manufacturing (e.g. the manufacturing of wood furniture and wood floors) and their residues are often transferred into wastewater through the cleaning of machinery and containers from the production line.[1,2] UF resins do not themselves have high toxicity, but chemical dissociation of these compounds in water produces free formaldehyde (FA) and ammonia (NH3 ). These intermediate compounds are much more toxic and are known inhibitors of biological treatment processes.[3] Additionally, a previous investigation [4] showed that the wastewater generated through the cleaning/washing of surfaces and machinery in the wood floor manufacturing industry is strongly toxic to algal growth. Therefore, this wastewater must be treated before being discharged into receiving waters to eliminate adverse effects on the environment and human health. The literature widely reports combinations of anoxic/ anaerobic and aerobic processes for treatment of industrial wastewater with a relatively high content of organic pollutants and nitrogen. Previous studies describe the efficiency of degradation of organic pollutants (FA and urea) employing a coupled biofilm airlift suspension and anoxic
∗ Corresponding
author. Email: [email protected]
© 2013 Taylor & Francis
upflow anaerobic sludge blanket,[5] a continued anaerobic treatment,[6] an anaerobic sequencing batch biofilm reactor,[2,7] a sequencing batch reactor, a sequencing continuous-inflow reactor and a novel modified movingbed sequencing continuous-inflow reactor [8] and denitrification in a multifed upflow filter.[9] Although these combined treatment processes are reliable for the removal of organic pollutants, they face potential problems during nitrification and denitrification processes, such as the requirement of an external carbon source and high-energy consumption for aeration.[10] Moreover, the treatment of wastewater with high ammonia content requires large reaction volumes to eliminate toxicity due to the ammonia. This would not be cost effective for the treatment of small volumes of wastewater, such as those generated by cleaning processes in the wood floor and wood furniture industries. Therefore, a simple combined on-site treatment system is needed for the adequate removal of organic compounds and nitrogen before the wastewater can be discharged into receiving waters or, at least, into the municipal sewerage system, with no further risks to the biological processes carried out in the centralized treatment plant.
Downloaded by [Florida International University] at 07:47 08 September 2014
Environmental Technology Precipitation of ammonia by forming magnesium ammonium phosphate (MAP) has received attention in recent years. MAP or struvite (NH4 MgPO4 ·6H2 O) is a white insoluble crystalline compound composed of magnesium, ammonium and phosphate in equal proportions.[10] Previous studies have shown that this method is highly efficient for ammonia removal from various types of wastewater such as landfill leachate,[11,12] manure,[13,14] industrial wastewater [15] and swine wastewater.[16] Moreover, MAP can be recovered as a slow-release fertilizer for agricultural use.[12,17] The present study investigated the combined processes of a biological anaerobic baffled reactor (ABR) and chemical precipitation for treatment of industrial wastewater. First, the performance and practicality of a continuous ABR for removal of FA and organic pollutants from the UF-based wastewater generated by a wood floor manufacturer were observed over 110 days of operation. Second, the efficiency of using MgCl2 ·6H2 O and Na2 HPO4 to remove ammonia from the effluent of the ABR was tested at different Mg:N:P molar ratios. To ensure the quality of the treated wastewater and the selection of suitable treatment technologies to reclaim wastewater effluent, acute toxicity studies of Vibrio fischeri and Artemia salina and a germination study of Lactuca sativa seeds were also carried out.
2. Materials and methods The laboratory-scale experiments in this study included two sequential processes for cleaning wastewater from the wood floor industry: (i) biological treatment and (ii) ammonia removal by chemical precipitation.
Figure 1.
155
2.1. Biological treatment processes 2.1.1. ABR treatment system and operating conditions A schematic diagram of a continuous-flow ABR specially constructed for this study is shown in Figure 1. The system consists of a feeding tank, followed by a bioreactor ABR unit, settling tank and gas collection unit. The rectangular, transparent ABR glass reactor has external dimensions (height × length × width) of 34 cm × 50 cm × 16 cm and a total working volume of 20 L. Vertical walls divide the reactor into five equal compartments; each compartment has a width ratio of upflow to downflow chambers of 2:1. The lower portion of the compartments is bent 2 cm above the reactor’s base at a 45◦ . This design provides a better water distribution along the reactor. The feed sample was forced to flow up and down through the reactor, and the treated wastewater was collected in the settling tank. The headspace of the reactor was not compartmentalized, which allowed the exhaust gases to be kept in the gas collector tank. The reactor was covered with a water jacket that kept the operational temperature at 25 ± 2◦ C throughout the experiment. Fifty per cent of the reactor volume was seeded with sludge, and the remaining volume was filled with diluted industrial wastewater (soluble chemical oxygen demand CODs concentration of 400 mgL−1 ) and flushed with nitrogen gas to create an oxygen-free condition for anaerobic microorganisms. The primary biomass was taken from a local wastewater treatment plant and inoculated in a UF synthetic medium for 263 days. During the experimental tests, the reactor was initially operated in a continuous mode with a flow rate of 8 Ld−1 , which gave a hydraulic retention time (HRT) of 2.5 days.
Schematic diagram of the laboratory-scale continuous-flow ABR unit.
156
S. Laohaprapanon et al.
Table 1. Physical–chemical composition of the studied wastewater (n = 3). Variable
Downloaded by [Florida International University] at 07:47 08 September 2014
pH Conductivity TS TSS CODs DOC FA TN NH+ 4 −N NO− 3 −N
Unit
Min
Max
Avg. (SD)
– mS cm−1 g L−1 g L−1 mg L−1 mg L−1 mg L−1 mg L−1 mg L−1 mg L−1
1.98 6.15 4.38 0.18 3860 1960 80 813 30 10
2.31 11.74 7.15 0.43 4360 2350 271 1985 107 16
2.08 (0.51) 8.05 (3.2) 5.76 (1.96) 0.21 (0.03) 4155 (166) 2207 (171) 208 (63) 1180 (391) 64 (34) 13 (3)
The concentration of the wastewater was increased stepwise by decreasing the dilution factor and increasing the HRT from 2.5 to 3.7 and 5.0 days. At the given HRTs, the upward velocity of the liquid flow in each compartment was 0.82, 0.55 and 0.41 m d−1 . The variability of the effectiveness of the treatment system, in terms of reducing organic, FA, and nitrogen contents and toxicity, was investigated. 2.1.2. Wastewater sample The wastewater used in the experiment was the effluent from a wood floor manufacturing plant located in southern Sweden. The wastewater was collected at regular intervals for sampling and characterization. The wastewater characteristics are presented in Table 1. 2.2. Ammonium removal by chemical precipitation To promote the removal of ammonia from the ABR effluent, chemical precipitation was applied in a second step using magnesium and phosphate reagents. The investigation was carried out by conducting two-batch experiments at various Mg:N:P molar ratios. The effect of the Mg:N:P molar ratio on the ammonia removal was investigated using MgCl2 ·6H2 O and Na2 HPO4 . The contents of magnesium and phosphorus varied between 1.0 and 1.3 moles per mole of nitrogen. The experimental procedure involved stirring 200 mL of wastewater with phosphate and magnesium reagents in a 300 mL Erlenmeyer flask at 300 rpm for 20 min. After reaction, the pH and conductivity of the samples were determined, and 25 mL of each sample was collected for further analyses. The remaining solution had its pH adjusted to 8 and was then filtered through a 0.45 μm membrane filter for analysis of its components. All experiments were carried out in duplicate. 2.3. Analytical methods The performance of the ABR in treating organic pollutants was assessed by comparing several variables measured in the untreated waste, with measurements made on the
effluent from compartments 1, 3 and 5 of the reactor. Liquid samples of 20 mL were withdrawn from the effluents at each compartment. After measuring the pH with a portable pH meter (Mettler Toledo, SE), the samples were centrifuged (Hettich Universal 16, Andreas Hettich GmbH & Co. KG, Germany) at 4000 rpm for 5 min. Concentrations of CODs , dissolved organic carbon (DOC), FA, volatile acids (VAs), total alkalinity (TA), total nitrogen (TN) and ammonium nitrogen (NH4 N) were regularly monitored with commercial HACH LANGE cuvette test kits (Dr. Bruno Lange, GmbH & CO. KG, Dusseldorf, Germany) and measured spectrophotometrically with a HACH XION 500 spectrophotometer. The standard deviations for all variables measured employing this method were 99%) and other organic compounds (83% CODs and 90% DOC) at an HRT of five days. • Urea hydrolysis is beneficial for treating acidic wastewater since ammonia is a strong base. This effect eliminated the need for additional alkaline application. However, the rapid increase in the
Downloaded by [Florida International University] at 07:47 08 September 2014
162
S. Laohaprapanon et al.
ammonium concentration and pH in the system may induce ammonia inhibition. • Besides the high level of ammonium removal achieved by chemical precipitation, intermittent operation of this process is also possible, which would make the treatment more feasible for a small wastewater volume. • Despite the combined ABR and chemical precipitation process improving the quality of effluent and detoxifying the wastewater for A. salina and V. fischeri, the disposal of the effluent for agricultural use is not recommended as the effluent contains a high level of salt and can inhibit seed germination. • The system is simple to operate and maintain, and the coupled approach could be useful for the on-site treatment of low volumes of highly polluted wastewater generated by cleaning activities in the wood floor or wood furniture industries. Acknowledgements The authors acknowledge the Swedish Knowledge Foundation (KK-Stiftelsen) for the scholarship provided to the first author, and the Swedish Foundation for International Cooperation in Research and Higher Education (STINT). Support from the companies AB Gustaf Kähr and Akzo Nobelare is acknowledged.
References [1] Henze M, Harremoës P, Jansen JLC, Arvin E. Biological and chemical processes. 3rd ed. Berlin: Springer-Verlag; 2002. [2] Kaczala F, Marques M, Hogland W. Biotreatability of wastewater generated during machinery washing in a woodbased industry: COD, formaldehyde and nitrogen removal. Bioresour Technol. 2010;101:8975–8983. [3] Chen Y, Cheng JJ, Creamer KS. Inhibition of anaerobic digestion process: a review. Bioresour Technol. 2008;99:4044–4064. [4] Laohaprapanon S, Kaczala F, Salomon PS, Marques M, Hogland W. Wastewater generated during cleaning/washing procedures in a wood-floor industry: toxicity on the microalgae Desmodesmus subspicatus. Environ Technol. 2012;33:2439–2446. [5] Compos JL, Sanchez M, Mosquer-Corral A, Mendez R, Lema JM. Coupled BAS and anoxic UASB system to removal urea and formaldehyde from wastewater. Water Res. 2003;37:3445–3451. [6] Vidal G, Jiang ZP, Omil F, Thalasso F, Mendez R, Lema JM. Continuous anaerobic treatment of wastewaters containing formaldehyde and urea. Bioresour Technol. 1999;70: 283–291. [7] Pereira NS, Zaiat M. Degradation of formaldehyde in anaerobic sequencing batch biofilm reactor (ASBBR). J Hazard Mater. 2009;163:777–782. [8] Moussavi G, Heidarizad M. The performance of SBR, SCR, and MSCR for simultaneous biodegradation of high concentrations of formaldehyde and ammonia. Sep Purif Technol. 2011;77:187–195. [9] Garrido JM, Méndez R, Lema JM. Simultaneous urea hydrolysis, formaldehyde removal and denitrification in a multifed upflow filter under anoxic and anaerobic conditions. Water Res. 2001;35:691–698.
[10] Khin T, Annachhatre AP. Novel microbial nitrogen removal processes. Biotechnol Adv. 2004;22:519–532. [11] Iaconi CD, Pagano M, Ramadori R, Lopez A. Nitrogen recovery from a stabilized municipal landfill leachate. Bioresour Technol. 2010;101:1732–1736. [12] Li XZ, Zhao QL, Hao XD. Ammonium removal from landfill leachate by chemical precipitation. Waste Manage. 1999;19:409–415. [13] Yetilmezsoy K, Sapci-Zengin Z. Recovery of ammonium nitrogen from the effluent of UASB treating poultry manure wastewater by MAP precipitation as a slow release fertilizer. J Hazard Mater. 2009;166:260–269. [14] Yilmazel YD, Demirer GN. Removal and recovery of nutrients as struvite form anaerobic digestion residues of poultry manure. Environ Technol. 2011;32:783–794. [15] Huang H, Song Q, Wang W, Wu S, Dai J. Treatment of anaerobic digester effluents of nylon wastewater through chemical precipitation and a sequencing batch reactor process. J Environ Manage. 2007;101:68–74. [16] Suzuki K, Tanaka Y, Kuroda K, Hanajima D, Fukumoto Y. Recovery of phosphorus from swine wastewater through crystallization. Bioresour Technol. 2005;96:1544–1550. [17] El Diwani G, El Rafie SH, El Ibiari NN, El Aila HI. Recovery of ammonia nitrogen from industrial wastewater treatment as struvite slow releasing fertilizer. Desalination. 2007;214:200–214. [18] Swedish Standards Institution. Swedish Standard SS028119: determination of calcium content of water. Stockholm: SIS; 1974. [19] Swedish Standards Institution. Swedish Standard SS028121: determination of calcium and magnesium content of water. Stockholm: SIS; 1974. [20] Svensson BM, Athiasson L, Mårtensson L, Bergström S. Artemia salina as test organism for assessment of acute toxicity of leachate water from landfills. Environ Monitor Assess. 2005;102:309–321. [21] Komilis DP, Karatzas E, Halvadakis CP. The effect of olive oil mill wastewater on seed germination after various pretreatment techniques. J Environ Manage. 2005;74: 339–348. [22] Oliveira SV, Moraes EM, Adorno MA, Varesche MB, Foresti E, Zaiat M. Formaldehyde degradation in an anaerobic packed-bed bioreactor. Water Res. 2004;38:1685–1694. [23] Priya KR, Sandy S, Swaminathan K. Kinetic analysis of treatment of formaldehyde containing wastewater in UASB reactor. Chem Eng J. 2009;148:212–216. [24] Wang LK, Shammas NK, Hung YT. Advances in hazardous industrial waste treatment. New York: CRC Press; 2009. [25] Ryu HD, Lim CS, Kang MK, Lee SI. Evaluation of struvite obtained from semiconductor as a fertilizer in cultivating Chinese cabbage. J Hazard Mater. 2012;221–222:248–255. [26] Gunay A, Karadag D, Tosun I, Ozturk M. Use of magnesit as a magnesium source for ammonium removal from leachate. J Hazard Mater. 2008;156:619–623. [27] Sakthivel SR, Tilley E, Udert KM. Wood ash as a magnesium source for phosphorus recovery from source-separated urine. Sci Tot Environ. 2012;419:68–75. [28] Landau M, Sanchez V. Effect of pH and decapsulation on the toxicity of ammonia to the brine shrimp Artemia franciscana. J World Aqua Soc. 1991;22:178–182. [29] Young BJ, Riera NI, Beily ME, Bres PA, Crespo BC, Ronco AE. Toxicity of the effluent from an anaerobic bioreactor treating cereal on Lactuca sativa. Special issue section: SETAC North America 31st annual meeting–advancing the Omics in aquatic toxicology. Ecotoxicol Environ Saf. 2012;76:182–186.
Environmental Technology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tent20
Anaerobic baffled reactor coupled with chemical precipitation for treatment and toxicity reduction of industrial wastewater a
b
Sawanya Laohaprapanon , Marcia Marquesa & William Hogland
a
a
Department of Biology and Environmental Science, Linnaeus University, Kalmar, LNU, Sweden; b
Department of Sanitary and Environmental Engineering, Rio de Janeiro State University – UERJ, Rio de Janeiro, Brazil Accepted author version posted online: 02 Aug 2013.Published online: 01 Oct 2013.
To cite this article: Sawanya Laohaprapanon, Marcia Marquesa & William Hogland (2014) Anaerobic baffled reactor coupled with chemical precipitation for treatment and toxicity reduction of industrial wastewater, Environmental Technology, 35:2, 154-162, DOI: 10.1080/09593330.2013.821142 To link to this article: http://dx.doi.org/10.1080/09593330.2013.821142
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Environmental Technology, 2014 Vol. 35, No. 2, 154–162, http://dx.doi.org/10.1080/09593330.2013.821142
Anaerobic baffled reactor coupled with chemical precipitation for treatment and toxicity reduction of industrial wastewater Sawanya Laohaprapanona∗ , Marcia Marquesab and William Hoglanda a Department
of Biology and Environmental Science, Linnaeus University, Kalmar, LNU, Sweden; b Department of Sanitary and Environmental Engineering, Rio de Janeiro State University – UERJ, Rio de Janeiro, Brazil
Downloaded by [Florida International University] at 07:47 08 September 2014
(Received 28 March 2013; accepted 25 June 2013 ) This study describes the reduction of soluble chemical oxygen demand (CODs ) and the removal of dissolved organic carbon (DOC), formaldehyde (FA) and nitrogen from highly polluted wastewater generated during cleaning procedures in wood floor manufacturing using a laboratory-scale biological anaerobic baffled reactor followed by chemical precipitation using MgCl2 ·6H2 O + Na2 HPO4 . By increasing the hydraulic retention time from 2.5 to 3.7 and 5 days, the reduction rates of FA, DOC and CODs of nearly 100%, 90% and 83%, respectively, were achieved. When the Mg:N:P molar ratio in the chemical treatment was changed from 1:1:1 to 1.3:1:1.3 at pH 8, the NH+ 4 removal rate increased from 80% to 98%. Biologically and chemically treated wastewater had no toxic effects on Vibrio fischeri and Artemia salina whereas chemically treated wastewater inhibited germination of Lactuca sativa owing to a high salt content. Regardless of the high conductivity of the treated wastewater, combined biological and chemical treatment was found to be effective for the removal of the organic load and nitrogen, and to be simple to operate and to maintain. A combined process such as that investigated could be useful for on-site treatment of low volumes of highly polluted wastewater generated by the wood floor and wood furniture industries, for which there is no suitable on-site treatment option available today. Keywords: anaerobic baffled reactor; magnesium ammonium phosphate; toxicity assessment; ammonia removal; urea-formaldehyde wastewater
1. Introduction Urea-formaldehyde (UF) resins are globally used in wood product manufacturing (e.g. the manufacturing of wood furniture and wood floors) and their residues are often transferred into wastewater through the cleaning of machinery and containers from the production line.[1,2] UF resins do not themselves have high toxicity, but chemical dissociation of these compounds in water produces free formaldehyde (FA) and ammonia (NH3 ). These intermediate compounds are much more toxic and are known inhibitors of biological treatment processes.[3] Additionally, a previous investigation [4] showed that the wastewater generated through the cleaning/washing of surfaces and machinery in the wood floor manufacturing industry is strongly toxic to algal growth. Therefore, this wastewater must be treated before being discharged into receiving waters to eliminate adverse effects on the environment and human health. The literature widely reports combinations of anoxic/ anaerobic and aerobic processes for treatment of industrial wastewater with a relatively high content of organic pollutants and nitrogen. Previous studies describe the efficiency of degradation of organic pollutants (FA and urea) employing a coupled biofilm airlift suspension and anoxic
∗ Corresponding
author. Email: [email protected]
© 2013 Taylor & Francis
upflow anaerobic sludge blanket,[5] a continued anaerobic treatment,[6] an anaerobic sequencing batch biofilm reactor,[2,7] a sequencing batch reactor, a sequencing continuous-inflow reactor and a novel modified movingbed sequencing continuous-inflow reactor [8] and denitrification in a multifed upflow filter.[9] Although these combined treatment processes are reliable for the removal of organic pollutants, they face potential problems during nitrification and denitrification processes, such as the requirement of an external carbon source and high-energy consumption for aeration.[10] Moreover, the treatment of wastewater with high ammonia content requires large reaction volumes to eliminate toxicity due to the ammonia. This would not be cost effective for the treatment of small volumes of wastewater, such as those generated by cleaning processes in the wood floor and wood furniture industries. Therefore, a simple combined on-site treatment system is needed for the adequate removal of organic compounds and nitrogen before the wastewater can be discharged into receiving waters or, at least, into the municipal sewerage system, with no further risks to the biological processes carried out in the centralized treatment plant.
Downloaded by [Florida International University] at 07:47 08 September 2014
Environmental Technology Precipitation of ammonia by forming magnesium ammonium phosphate (MAP) has received attention in recent years. MAP or struvite (NH4 MgPO4 ·6H2 O) is a white insoluble crystalline compound composed of magnesium, ammonium and phosphate in equal proportions.[10] Previous studies have shown that this method is highly efficient for ammonia removal from various types of wastewater such as landfill leachate,[11,12] manure,[13,14] industrial wastewater [15] and swine wastewater.[16] Moreover, MAP can be recovered as a slow-release fertilizer for agricultural use.[12,17] The present study investigated the combined processes of a biological anaerobic baffled reactor (ABR) and chemical precipitation for treatment of industrial wastewater. First, the performance and practicality of a continuous ABR for removal of FA and organic pollutants from the UF-based wastewater generated by a wood floor manufacturer were observed over 110 days of operation. Second, the efficiency of using MgCl2 ·6H2 O and Na2 HPO4 to remove ammonia from the effluent of the ABR was tested at different Mg:N:P molar ratios. To ensure the quality of the treated wastewater and the selection of suitable treatment technologies to reclaim wastewater effluent, acute toxicity studies of Vibrio fischeri and Artemia salina and a germination study of Lactuca sativa seeds were also carried out.
2. Materials and methods The laboratory-scale experiments in this study included two sequential processes for cleaning wastewater from the wood floor industry: (i) biological treatment and (ii) ammonia removal by chemical precipitation.
Figure 1.
155
2.1. Biological treatment processes 2.1.1. ABR treatment system and operating conditions A schematic diagram of a continuous-flow ABR specially constructed for this study is shown in Figure 1. The system consists of a feeding tank, followed by a bioreactor ABR unit, settling tank and gas collection unit. The rectangular, transparent ABR glass reactor has external dimensions (height × length × width) of 34 cm × 50 cm × 16 cm and a total working volume of 20 L. Vertical walls divide the reactor into five equal compartments; each compartment has a width ratio of upflow to downflow chambers of 2:1. The lower portion of the compartments is bent 2 cm above the reactor’s base at a 45◦ . This design provides a better water distribution along the reactor. The feed sample was forced to flow up and down through the reactor, and the treated wastewater was collected in the settling tank. The headspace of the reactor was not compartmentalized, which allowed the exhaust gases to be kept in the gas collector tank. The reactor was covered with a water jacket that kept the operational temperature at 25 ± 2◦ C throughout the experiment. Fifty per cent of the reactor volume was seeded with sludge, and the remaining volume was filled with diluted industrial wastewater (soluble chemical oxygen demand CODs concentration of 400 mgL−1 ) and flushed with nitrogen gas to create an oxygen-free condition for anaerobic microorganisms. The primary biomass was taken from a local wastewater treatment plant and inoculated in a UF synthetic medium for 263 days. During the experimental tests, the reactor was initially operated in a continuous mode with a flow rate of 8 Ld−1 , which gave a hydraulic retention time (HRT) of 2.5 days.
Schematic diagram of the laboratory-scale continuous-flow ABR unit.
156
S. Laohaprapanon et al.
Table 1. Physical–chemical composition of the studied wastewater (n = 3). Variable
Downloaded by [Florida International University] at 07:47 08 September 2014
pH Conductivity TS TSS CODs DOC FA TN NH+ 4 −N NO− 3 −N
Unit
Min
Max
Avg. (SD)
– mS cm−1 g L−1 g L−1 mg L−1 mg L−1 mg L−1 mg L−1 mg L−1 mg L−1
1.98 6.15 4.38 0.18 3860 1960 80 813 30 10
2.31 11.74 7.15 0.43 4360 2350 271 1985 107 16
2.08 (0.51) 8.05 (3.2) 5.76 (1.96) 0.21 (0.03) 4155 (166) 2207 (171) 208 (63) 1180 (391) 64 (34) 13 (3)
The concentration of the wastewater was increased stepwise by decreasing the dilution factor and increasing the HRT from 2.5 to 3.7 and 5.0 days. At the given HRTs, the upward velocity of the liquid flow in each compartment was 0.82, 0.55 and 0.41 m d−1 . The variability of the effectiveness of the treatment system, in terms of reducing organic, FA, and nitrogen contents and toxicity, was investigated. 2.1.2. Wastewater sample The wastewater used in the experiment was the effluent from a wood floor manufacturing plant located in southern Sweden. The wastewater was collected at regular intervals for sampling and characterization. The wastewater characteristics are presented in Table 1. 2.2. Ammonium removal by chemical precipitation To promote the removal of ammonia from the ABR effluent, chemical precipitation was applied in a second step using magnesium and phosphate reagents. The investigation was carried out by conducting two-batch experiments at various Mg:N:P molar ratios. The effect of the Mg:N:P molar ratio on the ammonia removal was investigated using MgCl2 ·6H2 O and Na2 HPO4 . The contents of magnesium and phosphorus varied between 1.0 and 1.3 moles per mole of nitrogen. The experimental procedure involved stirring 200 mL of wastewater with phosphate and magnesium reagents in a 300 mL Erlenmeyer flask at 300 rpm for 20 min. After reaction, the pH and conductivity of the samples were determined, and 25 mL of each sample was collected for further analyses. The remaining solution had its pH adjusted to 8 and was then filtered through a 0.45 μm membrane filter for analysis of its components. All experiments were carried out in duplicate. 2.3. Analytical methods The performance of the ABR in treating organic pollutants was assessed by comparing several variables measured in the untreated waste, with measurements made on the
effluent from compartments 1, 3 and 5 of the reactor. Liquid samples of 20 mL were withdrawn from the effluents at each compartment. After measuring the pH with a portable pH meter (Mettler Toledo, SE), the samples were centrifuged (Hettich Universal 16, Andreas Hettich GmbH & Co. KG, Germany) at 4000 rpm for 5 min. Concentrations of CODs , dissolved organic carbon (DOC), FA, volatile acids (VAs), total alkalinity (TA), total nitrogen (TN) and ammonium nitrogen (NH4 N) were regularly monitored with commercial HACH LANGE cuvette test kits (Dr. Bruno Lange, GmbH & CO. KG, Dusseldorf, Germany) and measured spectrophotometrically with a HACH XION 500 spectrophotometer. The standard deviations for all variables measured employing this method were 99%) and other organic compounds (83% CODs and 90% DOC) at an HRT of five days. • Urea hydrolysis is beneficial for treating acidic wastewater since ammonia is a strong base. This effect eliminated the need for additional alkaline application. However, the rapid increase in the
Downloaded by [Florida International University] at 07:47 08 September 2014
162
S. Laohaprapanon et al.
ammonium concentration and pH in the system may induce ammonia inhibition. • Besides the high level of ammonium removal achieved by chemical precipitation, intermittent operation of this process is also possible, which would make the treatment more feasible for a small wastewater volume. • Despite the combined ABR and chemical precipitation process improving the quality of effluent and detoxifying the wastewater for A. salina and V. fischeri, the disposal of the effluent for agricultural use is not recommended as the effluent contains a high level of salt and can inhibit seed germination. • The system is simple to operate and maintain, and the coupled approach could be useful for the on-site treatment of low volumes of highly polluted wastewater generated by cleaning activities in the wood floor or wood furniture industries. Acknowledgements The authors acknowledge the Swedish Knowledge Foundation (KK-Stiftelsen) for the scholarship provided to the first author, and the Swedish Foundation for International Cooperation in Research and Higher Education (STINT). Support from the companies AB Gustaf Kähr and Akzo Nobelare is acknowledged.
References [1] Henze M, Harremoës P, Jansen JLC, Arvin E. Biological and chemical processes. 3rd ed. Berlin: Springer-Verlag; 2002. [2] Kaczala F, Marques M, Hogland W. Biotreatability of wastewater generated during machinery washing in a woodbased industry: COD, formaldehyde and nitrogen removal. Bioresour Technol. 2010;101:8975–8983. [3] Chen Y, Cheng JJ, Creamer KS. Inhibition of anaerobic digestion process: a review. Bioresour Technol. 2008;99:4044–4064. [4] Laohaprapanon S, Kaczala F, Salomon PS, Marques M, Hogland W. Wastewater generated during cleaning/washing procedures in a wood-floor industry: toxicity on the microalgae Desmodesmus subspicatus. Environ Technol. 2012;33:2439–2446. [5] Compos JL, Sanchez M, Mosquer-Corral A, Mendez R, Lema JM. Coupled BAS and anoxic UASB system to removal urea and formaldehyde from wastewater. Water Res. 2003;37:3445–3451. [6] Vidal G, Jiang ZP, Omil F, Thalasso F, Mendez R, Lema JM. Continuous anaerobic treatment of wastewaters containing formaldehyde and urea. Bioresour Technol. 1999;70: 283–291. [7] Pereira NS, Zaiat M. Degradation of formaldehyde in anaerobic sequencing batch biofilm reactor (ASBBR). J Hazard Mater. 2009;163:777–782. [8] Moussavi G, Heidarizad M. The performance of SBR, SCR, and MSCR for simultaneous biodegradation of high concentrations of formaldehyde and ammonia. Sep Purif Technol. 2011;77:187–195. [9] Garrido JM, Méndez R, Lema JM. Simultaneous urea hydrolysis, formaldehyde removal and denitrification in a multifed upflow filter under anoxic and anaerobic conditions. Water Res. 2001;35:691–698.
[10] Khin T, Annachhatre AP. Novel microbial nitrogen removal processes. Biotechnol Adv. 2004;22:519–532. [11] Iaconi CD, Pagano M, Ramadori R, Lopez A. Nitrogen recovery from a stabilized municipal landfill leachate. Bioresour Technol. 2010;101:1732–1736. [12] Li XZ, Zhao QL, Hao XD. Ammonium removal from landfill leachate by chemical precipitation. Waste Manage. 1999;19:409–415. [13] Yetilmezsoy K, Sapci-Zengin Z. Recovery of ammonium nitrogen from the effluent of UASB treating poultry manure wastewater by MAP precipitation as a slow release fertilizer. J Hazard Mater. 2009;166:260–269. [14] Yilmazel YD, Demirer GN. Removal and recovery of nutrients as struvite form anaerobic digestion residues of poultry manure. Environ Technol. 2011;32:783–794. [15] Huang H, Song Q, Wang W, Wu S, Dai J. Treatment of anaerobic digester effluents of nylon wastewater through chemical precipitation and a sequencing batch reactor process. J Environ Manage. 2007;101:68–74. [16] Suzuki K, Tanaka Y, Kuroda K, Hanajima D, Fukumoto Y. Recovery of phosphorus from swine wastewater through crystallization. Bioresour Technol. 2005;96:1544–1550. [17] El Diwani G, El Rafie SH, El Ibiari NN, El Aila HI. Recovery of ammonia nitrogen from industrial wastewater treatment as struvite slow releasing fertilizer. Desalination. 2007;214:200–214. [18] Swedish Standards Institution. Swedish Standard SS028119: determination of calcium content of water. Stockholm: SIS; 1974. [19] Swedish Standards Institution. Swedish Standard SS028121: determination of calcium and magnesium content of water. Stockholm: SIS; 1974. [20] Svensson BM, Athiasson L, Mårtensson L, Bergström S. Artemia salina as test organism for assessment of acute toxicity of leachate water from landfills. Environ Monitor Assess. 2005;102:309–321. [21] Komilis DP, Karatzas E, Halvadakis CP. The effect of olive oil mill wastewater on seed germination after various pretreatment techniques. J Environ Manage. 2005;74: 339–348. [22] Oliveira SV, Moraes EM, Adorno MA, Varesche MB, Foresti E, Zaiat M. Formaldehyde degradation in an anaerobic packed-bed bioreactor. Water Res. 2004;38:1685–1694. [23] Priya KR, Sandy S, Swaminathan K. Kinetic analysis of treatment of formaldehyde containing wastewater in UASB reactor. Chem Eng J. 2009;148:212–216. [24] Wang LK, Shammas NK, Hung YT. Advances in hazardous industrial waste treatment. New York: CRC Press; 2009. [25] Ryu HD, Lim CS, Kang MK, Lee SI. Evaluation of struvite obtained from semiconductor as a fertilizer in cultivating Chinese cabbage. J Hazard Mater. 2012;221–222:248–255. [26] Gunay A, Karadag D, Tosun I, Ozturk M. Use of magnesit as a magnesium source for ammonium removal from leachate. J Hazard Mater. 2008;156:619–623. [27] Sakthivel SR, Tilley E, Udert KM. Wood ash as a magnesium source for phosphorus recovery from source-separated urine. Sci Tot Environ. 2012;419:68–75. [28] Landau M, Sanchez V. Effect of pH and decapsulation on the toxicity of ammonia to the brine shrimp Artemia franciscana. J World Aqua Soc. 1991;22:178–182. [29] Young BJ, Riera NI, Beily ME, Bres PA, Crespo BC, Ronco AE. Toxicity of the effluent from an anaerobic bioreactor treating cereal on Lactuca sativa. Special issue section: SETAC North America 31st annual meeting–advancing the Omics in aquatic toxicology. Ecotoxicol Environ Saf. 2012;76:182–186.
