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Ind. Eng. Chem. Res. 2006, 45, 6854-6859
Electrolytic Treatment of Beer Brewery Wastewater Krishnan Vijayaraghavan,* Desa Ahmad, and Renny Lesa Department of Biological & Agricultural Engineering, Faculty of Engineering, UniVersity Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
A novel method of beer brewery wastewater treatment was developed based on in situ hypochlorous acid generation. The hypochlorous acid was generated in an undivided electrolytic cell that consisted of two sets of graphite as the anode and stainless sheets as the cathode. The generated hypochlorous acid served as an oxidizing agent to destroy the organic present in the brewery wastewater. An influent chemical oxygen demand (COD) concentration of 2470 mg/L at an initial pH 4.5, a current density of 74.5 mA/cm2, a sodium chloride content of 3%, and an electrolysis period of 50 min resulted in the following values: pH, 6.7; COD, 64 mg/L; biochemical oxygen demand (BOD5), 30 mg/L; total organic carbon (TOC), 40 mg/L; residual total chlorine, 162 mg/L; turbidity, 20 NTU (nephelometric turbidity units); ammonia nitrogen (NH3-N), below the detectable limit; and temperature, 40 °C. The energy requirements were determined to be 56 and 39 W/L, while treating 24 L of beer brewery wastewater with sodium chloride concentrations of 2% and 3% and at a current density of 74.5 mA/cm2. The observed energy difference was due to the improved conductivity at high sodium chloride contents. The cost incurred in treating 1 m3 of beer brewery wastewater was determined to be RM 8, when the electrolytic reactor was operated at a current density of 74.5 mA/cm2 and the sodium chloride content was 3%. 1. Introduction
Table 1. Characteristics of Raw Beer Brewery Wastewater
Because the conventional method of beer brewery wastewater treatment is based on biological methods, it naturally leads to longer hydraulic retention time and is subject to failures due to shock loading and improper maintenance. Moreover, the biodegradation of flavonoids present in the brewery requires specific bacterial strains to achieve higher removal efficiencies. The electrochemical method of treatment is well-suited for degrading biorefractory organic pollutants, because it is possible to achieve partial or complete decomposition of the organic substance. The electrochemical methods of treatment are favored, because they are neither subject to failures due to variation in wastewater strength nor due to the presence of toxic substances and require less hydraulic retention time. The in situ generation of hypochlorous acid in wastewater treatment is advantageous, because aqueous solutions of sodium hypochlorite are much safer to use than chlorine gas. In the case of chlorine or chlorine-containing chemicals, the storage and transportation costs are great, because of the requirement of having safety equipment present, to tackle any mishap. The electrochemical method of waste treatment came into existence when it was first used to treat sewage generated onboard by ships, by mixing sewage and seawater in a 3:1 ratio and subjecting them to electrolysis.1 Thereafter, the application of electrochemical treatment was widely received in treating industrial wastewaters that are rich in refractory organics and chloride content. Electrochemical oxidation of effluents from textiles,2-6 olive mills,7,8 tanneries,9-11 distilleries,12 and syntan facilities13 had been successfully treated. The electrochemical oxidation of swine manure resulted in the simultaneous removal of chemical oxygen demand (COD) and ammonia nitrogen (NH3-N).14 The electrochemical oxidation of phenol and chlorinated phenol was studied using porous carbon felt,15 borondoped diamond,16 ruthenium mixed oxide,17 DSA, and graphite felt as electrode material.18 * To whom correspondence should be addressed. Tel.: 00-60389466416. Fax: 00-603-8946 6425. E-mail address: vijay@ eng.upm.edu.my.
parameter
value
pH concentration of COD concentration of BOD concentration of TOC concentration of TKN concentration of NH3-N concentration of phosphate concentration of suspended solids
8.5 ( 0.2 2470 mg/L 1457 mg/L 820 mg/L 97 mg/L 62 mg/L 56 mg/L 350 mg/L
To the best of our knowledge, there are no published scientific reports that are based on in situ hypochlorous oxidation for beer brewery wastewater. Hence, in this article, electrolytic oxidation based on in situ hypochlorous acid generation is being proposed as a method of treatment for beer brewery wastewater. The hypochlorous acid is generated using a graphite anode and stainless steel sheet as a cathode in an undivided electrolytic reactor. The beer brewery wastewater was obtained from the Carlsberg Brewery Malaysia Berhad. 2. Material and Methods 2.1. Beer Brewery Wastewater Characteristics. The raw beer brewery wastewater was collected from the Carlsberg Brewery Malaysia Berhad, and the characteristics of the wastewater are presented in Table 1. The brewery wastewater was preserved at a temperature of 7.5, the generated hypochlorous acid will be converted to hypochlorite ion, which is a weak oxidizing agent. Hence, the reactor pH determines the efficiency of generated chlorine toward oxidizing the organic matter. In the case of electrolytic treatment of raw brewery wastewater, the initial pH was determined to be 8.7; hence, it was subjected to pH adjustment at 4.5. 3.2. Effect of Anodic Oxidation and Chlorine-Based Oxidation of Beer Wastewater. The anodic oxidation experiments were performed in the absence of an additional source of chloride. Because of the poor conductance of the beer wastewater, a maximum current density (12 mA/cm2) was achieved for an input voltage of 17 V. To compare the effect of anodic and chlorine-based oxidation on beer wastewater treatment, investigations were performed in the absence of any chloride addition and at 3% sodium chloride addition for a fixed current density of 12 mA/cm2 (Figure 2). During the anodic oxidation process in the absence of chloride, the COD removal was marginal; however, the chlorine-based oxidation process was more pronounced in regard to destroying the organic matter present in the beer wastewater, thus leading to a lower residual COD concentration with an increase in electrolysis period. As shown in Figure 2, the average COD reduction during anodic oxidation in the absence of sodium chloride addition and with 3% sodium chloride addition were determined to be 18% and 35%, respectively, at the end of 50 min of electrolysis. Hence, further experiments were conducted with the addition of sodium chloride to the beer wastewater. 3.3. Chlorine-Based Oxidation of Beer Wastewater. Figure 3 shows the residual COD concentration during the electrolysis period for an initial COD concentration of 2470 mg/L at a
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Figure 3. Residual chemical oxygen demand (COD) concentration versus electrolysis period.
Figure 5. Residual total organic carbon (TOC) concentration versus electrolysis period.
Figure 4. Residual biochemical oxygen demand (BOD5) concentration versus electrolysis period.
Figure 6. Residual total chlorine concentration versus electrolysis period.
current density of 37.2 and 74.5 mA/cm2 and for sodium chloride concentrations of 1%, 2%, and 3%. For example, at a current density of 37.2 mA/cm2 for sodium chloride contents of 1%, 2%, and 3%, at the end of 30 min of electrolysis, the residual COD values were 1405, 915, and 730 mg/L, respectively. In the case of electrolysis at a current density 74.5 mA/cm2 for the aforementioned sodium chloride contents and electrolysis period, the residual COD values were 1130, 470, and 360 mg/L, respectively. Further increases in the electrolysis period showed a decrease in residual COD concentration, irrespective of the current densities. In the case where 3% sodium chloride was used as an electrolyte at a current density of 37.2 and 74.5 mA/cm2, for an electrolysis period of 50 min, residual COD concentrations of 170 and 64 mg/L, respectively, resulted. At higher current densities, more hypochlorous acid was generated, leading to the oxidation of organic present in the wastewater in shorter period. The residual BOD5 concentration versus the electrolysis period is shown in Figure 4 for current densities of 37.2 and 74.5 mA/cm2 at sodium chloride concentrations of 1%, 2%, and 3%, respectively. As shown in Figure 4, with the increase in current density resulted in lower residual BOD5 concentration. For example, at the end of 50 min of electrolysis with 3% sodium chloride as an electrolyte for current densities of 37.2 and 74.5 mA/cm2, the residual BOD was determined to be 90 and 30 mg/L, respectively.
The TOC removal during the electrolysis period is shown in Figure 5 for current densities of 37.2 and 74.5 mA/cm2 at a sodium chloride concentration of 1%, 2%, and 3%, respectively. As the electrolysis period increased, the TOC also decreased, and a higher removal in TOC was observed with the increase in current density. For example, at the end of 50 min of electrolysis with 3% sodium chloride as an electrolyte for current densities of 37.2 and 74.5 mA/cm2, the residual TOC was determined to be 94 and 40 mg/L, respectively. For the aforementioned electrolysis period and sodium chloride content at a current density 37.2 mA/cm2, the COD/TOC ratio decreased from 3.0 to 1.8. In the case where the current density was 74.5 mA/cm2, the COD/TOC ratio decreased from 3.0 to 1.6, respectively. The decrease in COD/TOC ratio shows that the carbon was destroyed, because of the oxidizing action of the generated hypochlorous acid. In the case of phenol-formaldehyde resin wastewater, treatment based on hypochlorus oxidation resulted in a decrease in the COD/TOC ratio, from 4.3 to 1.3.22 Electrochemical oxidation of the effluents originated from flavor manufacturing facility showed a decrease in COD/TOC ratio from 3.3 to 1.7.23 The total residual chlorine concentration during the electrolysis period is shown in Figure 6, for an initial COD concentration of 2470 mg/L at varying sodium chloride content (1%, 2%, and 3%) and at a current density of 37.2 and 74.5 mA/cm2. For example, at a current density of 37.2 mA/cm2 for sodium chloride contents of 1%, 2%, and 3%, at the end of 30
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Figure 7. Residual turbidity versus electrolysis period.
min of electrolysis, the total residual chlorine concentration was 27, 40, and 50 mg/L, respectively. In the case where the current density is 74.5 mA/cm2, for the aforementioned condition resulted in a total residual chlorine concentration of 42, 78, and 96 mg/L, respectively. In the case of 3% sodium chloride as an electrolyte at current densities of 37.2 and 74.5 mA/cm2, for an electrolysis period of 50 min, resulted in total residual chlorine concentrations of 92 and 162 mg/L, respectively. The increase in total residual chlorine concentration during the electrolysis at a current density 74.5 mA/cm2 was due to the greater amount of chlorine generation at higher current density in comparison to that at a current density of 37.2 mA/cm2. Moreover, the accumulation of hypochlorous acid was relative low, because it has been utilized to destroy the organic content of the brewery wastewater, as shown in Figure 3. During electrolysis, the chloride was converted to chlorine gas at the graphite anode. As a result of disproportionation reaction, the generated chlorine was converted to hypochlorous acid, which oxidizes the organic matter and reduces to chloride. In the absence of an organic substance, the accumulation of residual chorine was remarkable as the same was illustrated when electrolysis was conducted using potable water. Figure 7 shows the residual turbidity level during the electrolysis period at varying sodium chloride contents (1%, 2%, and 3%) at current densities of 37.2 and 74.5 mA/cm2 for an initial COD concentration of 2470 mg/L. At the end of 30 min of electrolysis, for a current density of 37.2 mA/cm2, the residual turbidity was determined to be 250, 170, and 145 NTU (nephelometric turbidity units), respectively. In the case of a current density of 74.5 mA/cm2, for the aforementioned electrolyte concentrations and electrolysis period, the residual turbidity was 150, 100, and 67 NTU, respectively. Further increases in the electrolysis period showed a gradual decrease in turbidity. As shown in Figure 7, a minimum residual turbidity was observed at a sodium chloride content of 3% for a given current density. For example, current densities of 37.2 and 74.5 mA/cm2 with 3% sodium chloride as the electrolyte resulted in residual turbidity values of 58 and 20 NTU, respectively. The residual turbidity of 20 NTU, which resulted during the electrolysis at a current density of 74.5 mA/cm2 and at 3% sodium chloride, was due to the presence of fine suspended solids. The sample, when subjected to clarification for a settling time of 30 min, yielded a turbidity value of 13 NTU, with a residual COD concentration of 42 mg/L. The effluent temperature during the electrolysis of brewery wastewater that has an influent COD of 2470 mg/L is shown
Figure 8. Effluent temperature versus electrolysis period.
Figure 9. Residual pH versus electrolysis period.
in Figure 8, under varying sodium chloride contents (1%, 2%, and 3%) and at fixed current densities of 37.2 and 74.5 mA/cm2. For example, at a current density of 37.2 mA/cm2 for a sodium chloride content of 1%, 2%, and 3% at the end of 30 min of electrolysis, the effluent temperature was determined to be 32, 30, and 28 °C, respectively. However, a current density of 74.5 mA/cm2, for the aforementioned condition, resulted in an effluent temperature of 42, 37, and 32 °C, respectively. Further increases in the electrolysis period showed a gradual increase in electrolyte temperature. In the case of 3% sodium chloride as the electrolyte at a current density of 37.2 and 74.5 mA/cm2, an electrolysis period of 50 min resulted in an effluent temperature of 35 and 40 °C, respectively. However, in the case of 1% sodium chloride as the electrolyte, current densities of 37.2 and 74.5 mA/cm2 at the end of 50 min of electrolysis resulted in an effluent temperature of 40 and 51 °C, respectively. The residual pH during the electrolysis of brewery wastewater is shown in Figure 9 for an influent COD concentration of 2470 mg/L under varying sodium chloride contents (1%, 2%, and 3%) at current densities of 37.2 and 74.5 mA/cm2. For example, at a current density of 37.2 mA/cm2 for a sodium chloride content of 1%, 2%, and 3% at the end of 30 min of electrolysis, the electrolyte pH was observed to be 4.7, 4.8, and 4.9, respectively. However, in the case of a current density at 74.5 mA/cm2, the aforementioned condition resulted in an electrolyte pH value of 4.9, 5.2, and 5.3, respectively. Further increases in the electrolysis period showed a gradual increase in electrolyte
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Conclusion
Figure 10. Residual ammonia nitrogen (NH3-N) and total kjeldhal nitrogen (TKN) concentration versus electrolysis period.
pH. In the case of 3% sodium chloride as the electrolyte at current densities of 37.2 and 74.5 mA/cm2, an electrolysis period of 50 min resulted in an electrolyte pH of 5.8 and 6.7, respectively. However, in the case of 1% sodium chloride as the electrolyte, an electrolysis period of 50 min at current densities of 37.2 and 74.5 mA/cm2 resulted in a residual pH value of 5.2 and 6.0, respectively. The rise in pH during the electrolysis could be due to the loss of hydrogen gas at the cathode, resulting in hydroxide ion accumulation. The electrolyte pH was below 7.5 and the temperature was below 75 °C; therefore, the formation of ClO3- was negligible in the present investigation.24 Figure 10 shows the effect of hypochlorous acid oxidation on the NH3-N and TKN concentrations, with initial values of 62 and 97 mg/L, respectively. For example, at the end of 5 min of electrolysis, for a current density of 74.5 mA/cm2 at 3% sodium chloride, the residual NH3-N and TKN concentrations were determined to be 12 and 92 mg/L, respectively. Further increases in the electrolysis period above 10 min resulted in a residual NH3-N concentration that was below the detectable limit. However, in the case of 50 min of electrolysis for the aforementioned condition, the residual TKN concentration was observed to be 29 mg/L. The possible mechanism for the destruction of nitrogen compounds could be super chlorination, which occurred in the immediate vicinity of the anode electrode area during the initial period of electrolysis. As the electrochemical oxidation progressed, the nitrogen compounds were converted to monochloramines, dichloroamines, and nitrogen trichloride. Further chlorination led to the oxidation of chloramines into nitrous oxide (N2O) and nitrogen (N2), while hypochlorous acid was reduced to chloride.25 The energy requirement for treating brewery wastewater was investigated at various sodium chloride concentrations (1%, 2%, and 3%) and at a fixed current density of 37.2 and 74.5 mA/ cm2. The results showed that, at a current density of 37.2 mA/ cm2, for an electrolyte concentration of 1%, 2%, and 3%, the energy requirements were determined to be 25, 21, and 17 W/L, respectively. In the case of electrolytic treatment at a current density 74.5 mA/cm2, for the aforementioned condition resulted in energy requirement values of 77, 56, and 39 W/L, respectively. The observed low-energy requirement at 3% electrolyte was due to the improved conductivity, in comparison to 1% and 2% electrolyte additions.
The present investigation has revealed that the in situ generation of hypochlorous acid is effective toward the treatment of beer brewery wastewater. During the electrochemical oxidation process, the beer brewery wastewater also undergoes in situ disinfection, because of the hypochlorous acid that is generated. An influent COD concentration of 2470 mg/L at an initial pH 4.5, a current density of 74.5 mA/cm2, a sodium chloride content of 3%, and an electrolysis period of 50 min resulted in the following values: pH, 6.7; COD, 64 mg/L; BOD5, 30 mg/L; TOC, 40 mg/L; residual total chlorine, 162 mg/L; turbidity, 20 NTU; NH3-N, below the detectable limit; and temperature, 40 °C. The energy requirements were determined to be 56 and 39 W/L while treating 24 L of beer brewery wastewater at sodium chloride concentrations of 2% and 3% and at a current density of 74.5 mA/cm2. The observed energy difference was due to the improved conductivity at high sodium chloride contents. The excess chlorine concentration can be reduced by the addition of bisulfite. The chlorinated organics formed during the electrolytic treatment can be removed by passing them through activated carbon before the discharge of the treated effluent. The reuse of treated effluent can be achieved by subjecting it to reverse osmosis, whereby the total dissolved solids level can be decreased to meet the reuse standard. Literature Cited (1) Bockris, J. O. H. EnVironmental Chemistry; Plenum Press: New York, 1977. (2) Vijayaraghavan, K.; Ramanujam, T. K.; Balasubramanian, N. Insitu hypochlorous acid generation for treatment of textile wastewater. Color. Technol. 2001, 117, 49. (3) Kim, T. H.; Park, C.; Lee, J.; Shin, E. B.; Kim, S. Pilot scale treatment of textile wastewater by combined process (fluidized biofilm processchemical coagulation-electrochemical oxidation). Water Res. 2002, 36, 3979. (4) Dogan, D.; Tu¨rkdemir, H. Electrochemical oxidation of textile dye indigo. J. Chem. Technol. Biotechnol. 2005, 80, 916. (5) Szpyrkowicz, L.; Juzzolino, C.; Daniele, S.; De Faveri, M. D. Electrochemical destruction of thiourea dioxide in an undivided parallel plate electrodes batch reactor. Catal. Today 2001, 66, 519. (6) Lo´pez-Grimau, V.; Gutie´rrez, M. C. Decolourisation of simulated reactive dyebath effluents by electrochemical oxidation assisted by UV light. Chemosphere 2006, 62, 106. (7) Gotsi, M.; Kalogerakis, N.; Psillakis, E.; Samaras, P.; Mantzavinos, D. Electrochemical oxidation of olive oil mill wastewaters. Water Res. 2005, 39, 4177. (8) Kyriacou, A.; Lasaridi, K. E.; Kotsou, M.; Balis, C.; Pilidis, G. Combined bioremediation and advanced oxidation of green table olive processing wastewater. Process Biochem. 2005, 40, 1401. (9) Vijayaraghavan, K.; Ramanujam, T. K.; Balasubramanian, N. Insitu hypochlorous acid generation for treatment of tannery wastewaters. J. EnViron. Eng. DiV. (Am. Soc. CiV. Eng.) 1998, 124 (9), 887. (10) Rao, N. N.; Somasekhar, K. M.; Kaul, S. N.; Szpyrkowicz, L. Electrochemical oxidation of tannery wastewater. J. Chem. Technol. Biotechnol. 2001, 76 (11), 1124. (11) Szpyrkowicz, L.; Kaul, S. N.; Neti, R. N.; Satyanarayan, S. Infuence of anode material on electrochemical oxidation for the treatment of tannery wastewater. Water Res. 2005, 39, 1601. (12) Vijayaraghavan, K.; Ramanujam, T. K.; Balasubramanian, N. In situ hypochlorous acid generation for the treatment of distillery spentwash. Ind. Eng. Chem. Res. 1999, 38, 2264. (13) Vijayaraghavan, K.; Ramanujam, T. K.; Balasubramanian, N. In situ hypochlorous acid generation for the treatment of syntan wastewater. Waste Manage. 1999, 19, 319. (14) Chae, K. J.; Yim, S. K.; Choi, K. H.; Kim, S. K.; Park, W. K. Integrated biological and electro-chemical treatment of swine manure. Water Sci. Technol. 2004, 49 (5-6), 427. (15) Polcaro, A. M.; Palmas, S. Electrochemical oxidation of chlorophenols. Ind. Eng. Chem. Res. 1997, 36, 1791.
Ind. Eng. Chem. Res., Vol. 45, No. 20, 2006 6859 (16) Diniz, A. V.; Ferreira, N. G.; Corat, E. J.; Trava-Airoldi, V. J. Efficiency study of perforated diamond electrodes for organic compounds oxidation process. Diamond Relat. Mater. 2003, 12, 577. (17) Yavuz, Y.; Koparal, A. S. Electrochemical oxidation of phenol in a parallel plate reactor using ruthenium mixed metal oxide electrode. J. Hazard. Mater. 2006, 136 (2), 296. (18) Jiang, J. Q.; Yin, Q.; Zhou, J. L.; Pearce, P. Occurrence and treatment trials of endocrine disrupting chemicals (EDCs) in wastewaters. Chemosphere 2005, 61, 544. (19) Standard Methods for the Examination of Water and Wastewater, 16th Edition; American Public Health Association (APHA): Washington, DC, 1985. (20) Wastewater Analysis User Manual, In-house Edition, Hach: Loveland, CO, 1997. (21) Sawyer, C. N.; McCarty, P. L. Chemistry for EnVironmental Engineers, 3rd Edition; McGraw-Hill: Singapore, 1987.
(22) Rajkumar, D.; Palanivelu, K. Electrochemical treatment of industrial wastewater. J. Hazard. Mater. 2004, B113, 123. (23) Ribordy, P.; Pulgarin, C.; Kiwi, J.; Pe´ringer, P. Electrochemical versus photochemical pretreatment of industrial wastewaters. Water Sci. Technol. 1997, 35 (4), 293. (24) Cotton, F. A.; Wilkinson, G. AdVanced Inorganic Chemistry; Wiley: New York, 1988. (25) Tchobanoglous, G., Burton, F. L., Stensel, H. D., Eds. Wastewater Engineering Treatment and Reuse, 4th Edition; McGraw-Hill: New Delhi, India, 2003.
ReceiVed for reView April 7, 2006 ReVised manuscript receiVed July 24, 2006 Accepted August 10, 2006 IE0604371
