- Email: [email protected]
Brewery wastewater treatment using laboratory scale aerobic sequencing batch reactor
Accepted Manuscript Brewery Wastewater Treatment using Laboratory Scale Aerobic Sequencing Batch Reactor B.F. Bakare, K. Shabangu, M. Chetty PII:
S1026-9185(16)30049-X
DOI:
10.1016/j.sajce.2017.08.001
Reference:
SAJCE 43
To appear in:
South African Journal of Chemical Engineering
Received Date: 3 September 2016 Revised Date:
28 June 2017
Accepted Date: 11 August 2017
Please cite this article as: Bakare, B.F., Shabangu, K., Chetty, M., Brewery Wastewater Treatment using Laboratory Scale Aerobic Sequencing Batch Reactor, South African Journal of Chemical Engineering (2017), doi: 10.1016/j.sajce.2017.08.001. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Brewery Wastewater Treatment using Laboratory Scale Aerobic Sequencing Batch Reactor B.F. Bakare1, K. Shabangu1, 2 and M. Chetty2 1
Faculty of Engineering, Department of Chemical Engineering, Mangosuthu University of
2
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Technology, P.O. Box 12363 Jacobs, Durban 4026, South Africa, Email: [email protected]. Faculty of Engineering and built Environment, Department of Chemical Engineering, Durban University of Technology, P.O. Box 1334, Durban, 4000, South Africa ABSTRACT
SC
This study evaluates the performance of two laboratory scale aerobic sequencing batch reactor operated under continuous low aeration and cyclic aeration scheme for the treatment
M AN U
of wastewater generated from a local brewery in Durban South Africa. The continuous low aeration scheme was intended to determine its effect on the performance of the reactor in terms of organic material removal compared to a typical cyclic aeration reactor for biological organic material removal. The performance of the two laboratory scale reactor was determined in terms of removals of chemical oxygen demand and biological oxygen demand. These two parameters were selected because they are priority pollutants and organic
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components in brewery wastewater. The experimental results demonstrated that reductions in chemical oxygen demand and biological oxygen demand in wastewater generated from the breweries can be successfully achieved using both aeration configurations. However, the
EP
treatment efficiencies in terms of the removal of chemical oxygen demand was consistently maintained above 90 % and for biological oxygen demand it was observed to be above 80 % with the reactor operated under the continuous low aeration scheme performing significantly
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better than the reactor operated under the cyclic aeration scheme. Keywords:
continuous low aeration, cyclic aeration, sequencing batch reactor, organic
components, treatment efficiencies, sludge INTRODUCTION
One of the major effects of socio-economic change due to industrialisation is the generation of industrial wastewater, which requires treatment before being released into the environment. In South Africa, most of the municipality has wastewater treatment plants originally designed for the treatment of domestic wastewater. The discharge of industrial wastewater in these treatment plants introduces various difficulties in the treatment process
ACCEPTED MANUSCRIPT due to the complex and varying nature of industrial wastewater. There has been a rise in environmental pollution caused by the discharge of industrial effluents into the environment. Wastewater generated from breweries is among the major industrial effluents contributing to such pollution, due to its high strength in terms of the presence of organic material and biological nutrients (Simate et al. 2011). Despite the discharge of large volumes of highly
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polluted effluents, the brewing industry constitutes an important segment of any country (Braeken et al, 2004).
The composition of wastewater generated from the brewery fluctuates significantly as a result of the various processes that take place within the brewery. Wastewater from the brewery
SC
usually contains high levels of organic components which are generally easily biodegradable (Sinbuathong et al. 2007; Xu et al. 2013). Previous studies conducted on brewery wastewater
M AN U
indicated that a continuous monitoring of effluent from a brewery plant presented considerable variation in the wastewater characteristics in terms of chemical oxygen demand, biological oxygen demand, biological nutrients and solids concentrations (ling, 1998; Driessen and Vereijken, 2003; Jones et al. 2011; Enitan, 2015). Chemical oxygen demand ranges from 2000-6000 mg/L and biological oxygen demand ranges from 1200-3600 mg/L leading to high ratios of BOD: COD which indicates the magnitude of biodegradable soluble
TE D
materials presents in brewery wastewater.
Historically, sequencing batch reactor (SBR) has been employed as an efficient technology for wastewater treatment, especially for domestic wastewater because of its simple
EP
configuration and high treatment efficiency in terms of organic compounds and solid removal (Merzouki et al, 1999; Simate et al. 2011). Previous studies conducted has indicated that the
AC C
sequencing batch reactor concept is a viable and economically attractive alternative to the conventional continuous flow activated-sludge process in Biochemical Oxygen Demand, Suspended solids and nitrogen removal, as well as in the chemical precipitation of phosphorus. The dynamic and flexible nature of SBR systems allows ample room for expansion and operational adjustments at minimal costs (Irvine et al, 1989; Fernandes, 1994 and Jang et al, 2013). Thus due to the high organic content and high biodegradability of wastewater generated from the brewery, sequencing batch reactor is ideally an appropriate treatment method to be considered for the removal of the organic materials found in brewery wastewater. This paper therefore evaluates the performance of the two laboratory scale sequencing batch reactor
ACCEPTED MANUSCRIPT operated under different aeration configuration in treating wastewater generated from a local brewery in Durban South Africa. MATERIALS AND METHODS Sample collection and Preparation
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Wastewater samples from the brewery was collected for two main purposes; initially to characterise the wastewater generated from the brewery in order to identify the pollutant strength of the wastewater and secondly, for the operation of the two laboratory scale sequencing batch reactor in order to investigate the performance of the two rectors in terms of
SC
the removal of chemical oxygen demand, biological oxygen demand, total solids, volatile solids and total suspended solids. Samples were collected on a daily basis from the brewery
M AN U
for a month. This allow for the evaluation of the pollutant strength and fluctuations in the quality of the wastewater generated from the brewery. Samples collected were transported to the laboratory immediately in a cooler box full of ice and analyses were conducted immediately, where possible. However, if it was not possible to conduct the analysis immediately, samples were kept in the cold room in the laboratory at 4oC and analysis was conducted within 48 hours of sample collection. A mixed culture of activated sludge was
TE D
used as seed for both sequencing batch reactors. The activated sludge was allowed to acclimate after inoculation in brewery wastewater for 21 days. Samples collected for the operation of the two sequencing batch reactors was carried out once a week, fed into the
EP
SBRs and treatment proceeded immediately. Equipment Set up
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The two laboratory scale sequencing batch reactors used for this study were identical with a total volume of 25 litres and a working volume of 15 litres. The reactors consisted of a closed cylindrical clear PVC vessel with a height of 0.45 m and a diameter of 0.35 m, with the bottom of each tank having a slope of 60º. Figure 1 presents the sectional view of the reactors.
Sectional view of the sequencing batch reactors
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Figure 1:
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ACCEPTED MANUSCRIPT
Portable shaft mixers kept the solids suspended in the reactors. The motors were mounted on rubber gaskets and the shafts entered the reactors via 7.62 cm diameter holes in each reactor lid. The mixer shafts descended vertically into the tanks. The rubber gaskets were modified rubber end-caps for 7.62 cm PVC piping. The modifications consisted of removing the
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thinner portion of the cap, leaving a 1.27 cm thick disk, and then cutting a hole to allow passage of the mixer blade through the newly-formed rubber ring. These rubber gaskets acted as seals to minimise leakage of odorous gases and absorb noisy vibrations from the motors during mixing. Each mixer blade was positioned a few centimetres above the bottom outlet,
EP
allowing for the dispersion of the larger solids. The motor operated at 10.0 W and 2000 rpm. The shaft was stainless steel with a length of 45.7 cm and a diameter of 0.79 cm. The
AC C
propeller blade was also stainless steel, with a diameter of 6.35 cm. The mixers operated continuously, except during the short time allowed for settling and supernatant draining. The mixer switches were also operated manually. Temperature and pH were measured by means of a digital analyser attached directly to each of the reactors. Air was supplied to both reactors by means of an air pump connected to the air diffusing copper pipes. To keep the small diffusers from floating freely in the tank, they were fitted to the end of a solid, copper pipe tube, which descended vertically into the reactor through a hole in the lid. This provided the reactors with adequate oxygenation. Influent to the reactors was introduced through an opening located at the middle of each reactor by means of a centrifugal pump. In order to drain the treated water after solids settling, two spigots were
ACCEPTED MANUSCRIPT added to the side of each tank. The use of this spigot is intended to minimise the occurrence of scouring during the removal of the supernatant. Tank drainage occurred manually by opening the spigot valve and draining the required volume of sample. Operational Scheme The two sequencing batch reactor were seeded with equal volumes of activated sludge and
RI PT
was fed with brewery wastewater without aeration and mechanical mixing during the filling period. This was done in order to prevent sludge bulking. The sequencing batch reactor were operated following the basic SBR operation scheme (fill, react, settling and decanting), however the aeration sequence differs from one another. The reactor was run for 15
SC
consecutive weeks with a 5 day hydraulic retention time for each batch run. The sequencing batch reactor operated under the continuous low aeration scheme employed the air pump
M AN U
which supplied air at a fixed rate of 2.5 litres/mins which allowed a dissolved oxygen concentration of 1.5 mg/l maintained in the reactor throughout the 5 day hydraulic retention time for each batch runs. Air supply was only terminated during the 3 hour settling period for each batch runs before samples were collected for analytical purposes. The sequencing batch reactor operated under cyclic aeration scheme requires adequate amount of oxygen during the aeration stage in order to meet the oxygen requirement while allowing the condition within
TE D
the reactor to return to anoxic condition when the aeration is stopped. Air was supplied to the reactor by means of the same type of air pump at a fixed rate of 7.5 litres/mins which allowed a dissolved oxygen concentration of 3 mg/l maintained in the reactor for 9 hours in a day over
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Figure 2.
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the 5 days hydraulic retention time. The piping and instrumentation layout is presented in
Figure 2:
Piping and instrumentation layout of the laboratory scale sequencing batch reactor treating brewery wastewater.
ACCEPTED MANUSCRIPT The two reactors operated at room temperatures (20 -25 ºC) without controlling the pH, however the pH within the two reactor remained fairly constant (6-8) throughout the operation. Analytical Methods
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Analyses were conducted before the brewery wastewater was fed into the reactors and after treatment had taken place. This allowed for the evaluation of the treatment efficiencies achieved in both reactors. The monitoring parameters that were used to determine the treatment efficiencies of the reactors are chemical oxygen demand and biological oxygen
SC
demand. These parameters are priority pollutants and organic constituent found in brewery wastewater. The monitoring parameters were determined according to the standard methods
Treatment efficiency % =
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(APHA, 1998). The treatment efficiencies were determined using the following equation; –
RESULTS AND DISCUSSIONS
× 100
Brewery wastewater characterization results
presented in Table 1.
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The characterization results for the brewery wastewater collected over a 4 week period is
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Table 1: Brewery Wastewater Characteristics
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Parameters Mean Range of Concentration 382 Total Suspended Solids (mg/L) 200 - 563.8 6.74 pH 5-11 8.10 Ammonical Nitrogen(mg/L) 0.84-15.31 2746 Biological Oxygen Demand (mg/L) 2180 - 3018 11214 Chemical Oxygen Demand(mg/L) 2280 - 10210 5600 Total Solids (mg/L) 2000-9200 The characteristic of the collected brewery wastewater was similar to characteristics documented from previous studies (Ling, 1998; Dai, 2002; Rao et al. 2007; Enitan et al, 2015). It was also observed that the characteristics of the brewery wastewater fluctuated considerably over the 4 week sampling period. This is an indication that there were wide variations in the strength of the wastewater generated from the brewery. The characterisation
ACCEPTED MANUSCRIPT results clearly demonstrate that the generated wastewater samples from the brewery were high in organic components with a BOD to COD ratio of 0.6.
Chemical Oxygen Demand Results
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Figure 3 presents the chemical oxygen demand results for both the sequencing batch reactors.
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(a)
(b)
ACCEPTED MANUSCRIPT Figure 3:
Chemical Oxygen Demand results indicating the influent concentration, effluent concentration and the removal efficiencies for the sequencing batch reactors. (a) SBR 1 is the sequencing batch reactor operated under continuous low aeration scheme (b) SBR 2 is the sequencing batch reactor operated under cyclic aeration scheme.
As presented in Figure 3 (a) & (b) for both sequencing batch reactor, the influent brewery
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wastewater into the sequencing batch reactors over the 15 weeks of operation varied considerably in terms of the Chemical Oxygen demand. This observation conforms to previous study on brewery wastewater which had been attributed to the various processes taking place within the brewery (Ling, 1998; Sinbuathong et al. 2007; Jones et al. 2011; Xu et al. 2013; Enitan et al, 2015). The influent chemical oxygen demand over the 15 weeks of
SC
operation of the sequencing batch reactors ranged between 2976 – 10860 mg/l, this is an indication of the fact that the wastewater from the brewery which was used in this study
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contains high levels of organic components which could be easily biodegradable. The obtained chemical oxygen demand values ranged from between 232 – 1000 mg/l after treatment under the continuous low aeration scheme during the 15 weeks duration while that of the sequencing batch reactor operated under cyclic aeration scheme ranged from 964 – 4136 mg/l. A significant reduction in terms of Chemical Oxygen Demand was observed in both reactors; however the reduction in chemical oxygen demand observed from the
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sequencing batch reactor operated under continuous low aeration scheme was significantly higher statistically than that of the reactor operated under cyclic aeration scheme. The chemical oxygen demand removal efficiency was consistently maintained above 90 % for the
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sequencing batch reactor operated under continuous low aeration scheme while that of the reactor operated under cyclic aeration scheme did not exceed 78 % over the entire 15 weeks
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duration of the investigation conducted. Biological Oxygen Demand Results The results for both sequencing batch reactor in terms biological oxygen demand is presented in Figure 4 (a) & (b). As shown in this figure, the biological oxygen demand concentration in the influent brewery wastewater also varied considerably as observed for the chemical oxygen demand. The influent biological oxygen demand into both sequencing batch reactor over the 15 weeks of operation ranged from 2291 – 3764 mg/l. However, the operation of the sequencing batch reactor under the continuous low aeration scheme resulted into an effluent biological oxygen demand which ranged from 372 – 764 mg/l. The biological oxygen demand removal efficiency was found to be consistently above 80 %. The reactor operated
ACCEPTED MANUSCRIPT under cyclic aeration scheme produced an effluent with biological oxygen demand ranging between 890 – 1259 mg/l over the entire duration of the investigation conducted. This resulted to a biological oxygen demand removal efficiency not exceeding 65%. Again the sequencing batch reactor operated under continuous low aeration scheme performed better
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SC
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statistically when compared to the reactor operated under cyclic aeration scheme.
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(a)
(b)
ACCEPTED MANUSCRIPT Chemical Oxygen Demand results indicating the influent concentration, effluent concentration and the removal efficiencies for the sequencing batch reactors. (a) SBR 1 is the sequencing batch reactor operated under continuous low aeration scheme (b) SBR 2 is the sequencing batch reactor operated under cyclic aeration scheme.
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Figure 4:
CONCLUSIONS
The purpose of this paper was to investigate the treatment of wastewater collected from a local brewery in Durban South Africa using laboratory scale aerobic sequencing batch
SC
reactor. The characteristics of the brewery wastewater used in this study confirm the findings from previous studies that have been conducted on brewery wastewater (Ling, 1998; Dai,
M AN U
2002; Rao et al. 2007; Enitan et al, 2015). The brewery wastewater used in this study indicated a wastewater quality that is high in organic constituents, which is highly biodegradable and one that will require prior treatment before discharge into the environment to avoid pollution that may arise if discharged into the environment without prior treatment. Thus in view of this finding, there is a need for appropriate technology to be used for efficiently treating the increasing volumes and strength of wastewater generated from the
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brewery plants.
The performance of two laboratory-scale aerobic sequencing batch reactors treating wastewater collected from the brewery under continuous low aeration scheme and cyclic
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aeration scheme was therefore investigated. The investigation has demonstrated that it is feasible to treat brewery wastewater using aerobic sequencing batch reactor without the need to enhance the activity of microorganisms in both sequencing batch reactors by providing
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supplementary nitrogen and phosphorus nutrients. The performance of the sequencing batch reactor operated under continuous low aeration scheme was significantly higher than that of the sequencing batch reactor operated under cyclic aeration scheme in terms of the chemical oxygen demand and biological oxygen demand reduction. It was therefore concluded that the better performance observed in the sequencing batch reactor operated under continuous low aeration scheme was because, microbial activity degrading organic materials in the reactor was enhance because of the constant availability of oxygen compared to the reactor operated under cyclic aeration scheme. Thus, the finding from this investigation is an indication that there is a potential for the equipment and energy
ACCEPTED MANUSCRIPT savings by operating aerobic sequencing batch reactors under continuous low aeration scheme for the treatment of wastewater generated from the breweries. ACKNOWLEDGEMENTS The author will like to gratefully acknowledge the participation of Sthembile Mzimela and the support received from the Research Directorate at Mangosuthu University of Technology
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Durban South Africa. REFERENCES
American Public Health Association, APHA. (2012). Standards methods for the examination
Environmental Federation, Washington, DC.
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of water and wastewater, 20th edition. American Water Works Association and Water
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Braeken, L., Van Der Bruggen, B. & Vandecasteele, C. (2004). Regeneration of brewery waste water using nanofiltration. Water research, 38, 3075-3082.
DAI, H. (2002). Carbon nanotubes: opportunities and challenges. Surface Science, 500, 218241.
Driessen, W. & Vereijken, T. (2003). Recent developments in biological treatment of
of Brew.
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brewery effluent. Proceedings 9th Brewing Convention, Victoria Falls, Zambia, Inst. & Guild
Enitan, A. M., Adeyemo, J., Kumari, S., Swalaha, F. M. & Bux, F. (2015). Characterization
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of Brewery Wastewater Composition. World Academy of Science, Engineering and Technology, International Journal of Environmental, Chemical, Ecological, Geological and
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Geophysical Engineering, 9, 1015-1018. Fernandes, L. (1994). Effect of temperature on the performance of an SBR treating liquid swine-manure. Bioresource technology, 47, 219-227. Irvine, R. L., Ketchum JR, L. H. & Asano, T. (1989). Sequencing batch reactors for biological wastewater treatment. Critical Reviews in Environmental Science and Technology, 18, 255-294. Jang, H. M., Lee, J. W., Ha, J. H. & Park, J. M. (2013). Effects of organic loading rates on reactor performance and microbial community changes during thermophillic aerobic digestion process of high-strength food wastewater. Bioresource technology, 148, 261-269.
ACCEPTED MANUSCRIPT Jones, C. L. W., Britz, P., Davies, M. T. T., Scheepers, R., Cilliers, A., Crous, L. & Laubscher, R. (2011). The wealth in brewery effluent – Water and nutrient recovery using alternative technologies In: Proceedings of Fifteenth International Water Technology Conference, IWTC-15 2011. Alexandria, Egypt Ling, L. (1998). Brewery Wastewater Treatment Using Aerobic Sequencing Batch Reactors
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with Mixed Culture Activated Sludge. University of British Columbia
Merzouki, M., Delgenes, J., Bernet, N., Moletta, R., and Benlemlih, M. (1999). Polyphosphate-accumulating and denitrifying bacteria isolated from anaerobic-anoxic and
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anaerobic-aerobic sequencing batch reactors. Current Microbiology, 38, 9-17.
Rao, A. G., Reddy, T., Prakash, S. S., Vanajakshi, J., Joseph, J. & Sarma, P. (2007). pH
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regulation of alkaline wastewater with carbon dioxide: A case study of treatment of brewery wastewater in UASB reactor coupled with absorber. Bioresource technology, 98, 2131-2136. Simate, G. S., Cluett, J., Iyuke, S. E., Musapatika, E. T., Ndlovu, S., Walubita, L. F. & Alvarez, A. E. (2011). The treatment of brewery wastewater for reuse: State of the art. Desalination, 273, 235-247.
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Sinbuathong, N., Khaodhiar, S., Liengcharernsit, W., Sirirote, P. & Watts, D. (2007). Effect of sulphate on the methanogenic activity of a bacterial culture from a brewery wastewater during glucose degradation. Journal of Environmental Sciences, 19, 1025-1027.
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Xu, F., Huang, Z., Miao, H., Ren, H., Zhao, M. & Ruan, W. 2013. Identical full-scale biogaslift reactors (BLRs) with anaerobic granular sludge and residual activated sludge for brewery
2040.
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wastewater treatment and kinetic modelling. Journal of Environmental Sciences, 25, 2031-
ACCEPTED MANUSCRIPT HIGHLIGHTS
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SC M AN U
•
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•
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•
Wastewater generated from the brewery contains high amount of organic constituents which are highly biodegradable and requires appropriate technology for efficient treatment. The findings demonstrated that wastewater from the brewery can be successfully treated using sequencing batch reactor. The reactor operated under continuous low aeration scheme performed significantly better than the reactor operated under cyclic aeration scheme. No additional nutrient was supplied to both reactors.
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•
S1026-9185(16)30049-X
DOI:
10.1016/j.sajce.2017.08.001
Reference:
SAJCE 43
To appear in:
South African Journal of Chemical Engineering
Received Date: 3 September 2016 Revised Date:
28 June 2017
Accepted Date: 11 August 2017
Please cite this article as: Bakare, B.F., Shabangu, K., Chetty, M., Brewery Wastewater Treatment using Laboratory Scale Aerobic Sequencing Batch Reactor, South African Journal of Chemical Engineering (2017), doi: 10.1016/j.sajce.2017.08.001. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Brewery Wastewater Treatment using Laboratory Scale Aerobic Sequencing Batch Reactor B.F. Bakare1, K. Shabangu1, 2 and M. Chetty2 1
Faculty of Engineering, Department of Chemical Engineering, Mangosuthu University of
2
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Technology, P.O. Box 12363 Jacobs, Durban 4026, South Africa, Email: [email protected]. Faculty of Engineering and built Environment, Department of Chemical Engineering, Durban University of Technology, P.O. Box 1334, Durban, 4000, South Africa ABSTRACT
SC
This study evaluates the performance of two laboratory scale aerobic sequencing batch reactor operated under continuous low aeration and cyclic aeration scheme for the treatment
M AN U
of wastewater generated from a local brewery in Durban South Africa. The continuous low aeration scheme was intended to determine its effect on the performance of the reactor in terms of organic material removal compared to a typical cyclic aeration reactor for biological organic material removal. The performance of the two laboratory scale reactor was determined in terms of removals of chemical oxygen demand and biological oxygen demand. These two parameters were selected because they are priority pollutants and organic
TE D
components in brewery wastewater. The experimental results demonstrated that reductions in chemical oxygen demand and biological oxygen demand in wastewater generated from the breweries can be successfully achieved using both aeration configurations. However, the
EP
treatment efficiencies in terms of the removal of chemical oxygen demand was consistently maintained above 90 % and for biological oxygen demand it was observed to be above 80 % with the reactor operated under the continuous low aeration scheme performing significantly
AC C
better than the reactor operated under the cyclic aeration scheme. Keywords:
continuous low aeration, cyclic aeration, sequencing batch reactor, organic
components, treatment efficiencies, sludge INTRODUCTION
One of the major effects of socio-economic change due to industrialisation is the generation of industrial wastewater, which requires treatment before being released into the environment. In South Africa, most of the municipality has wastewater treatment plants originally designed for the treatment of domestic wastewater. The discharge of industrial wastewater in these treatment plants introduces various difficulties in the treatment process
ACCEPTED MANUSCRIPT due to the complex and varying nature of industrial wastewater. There has been a rise in environmental pollution caused by the discharge of industrial effluents into the environment. Wastewater generated from breweries is among the major industrial effluents contributing to such pollution, due to its high strength in terms of the presence of organic material and biological nutrients (Simate et al. 2011). Despite the discharge of large volumes of highly
RI PT
polluted effluents, the brewing industry constitutes an important segment of any country (Braeken et al, 2004).
The composition of wastewater generated from the brewery fluctuates significantly as a result of the various processes that take place within the brewery. Wastewater from the brewery
SC
usually contains high levels of organic components which are generally easily biodegradable (Sinbuathong et al. 2007; Xu et al. 2013). Previous studies conducted on brewery wastewater
M AN U
indicated that a continuous monitoring of effluent from a brewery plant presented considerable variation in the wastewater characteristics in terms of chemical oxygen demand, biological oxygen demand, biological nutrients and solids concentrations (ling, 1998; Driessen and Vereijken, 2003; Jones et al. 2011; Enitan, 2015). Chemical oxygen demand ranges from 2000-6000 mg/L and biological oxygen demand ranges from 1200-3600 mg/L leading to high ratios of BOD: COD which indicates the magnitude of biodegradable soluble
TE D
materials presents in brewery wastewater.
Historically, sequencing batch reactor (SBR) has been employed as an efficient technology for wastewater treatment, especially for domestic wastewater because of its simple
EP
configuration and high treatment efficiency in terms of organic compounds and solid removal (Merzouki et al, 1999; Simate et al. 2011). Previous studies conducted has indicated that the
AC C
sequencing batch reactor concept is a viable and economically attractive alternative to the conventional continuous flow activated-sludge process in Biochemical Oxygen Demand, Suspended solids and nitrogen removal, as well as in the chemical precipitation of phosphorus. The dynamic and flexible nature of SBR systems allows ample room for expansion and operational adjustments at minimal costs (Irvine et al, 1989; Fernandes, 1994 and Jang et al, 2013). Thus due to the high organic content and high biodegradability of wastewater generated from the brewery, sequencing batch reactor is ideally an appropriate treatment method to be considered for the removal of the organic materials found in brewery wastewater. This paper therefore evaluates the performance of the two laboratory scale sequencing batch reactor
ACCEPTED MANUSCRIPT operated under different aeration configuration in treating wastewater generated from a local brewery in Durban South Africa. MATERIALS AND METHODS Sample collection and Preparation
RI PT
Wastewater samples from the brewery was collected for two main purposes; initially to characterise the wastewater generated from the brewery in order to identify the pollutant strength of the wastewater and secondly, for the operation of the two laboratory scale sequencing batch reactor in order to investigate the performance of the two rectors in terms of
SC
the removal of chemical oxygen demand, biological oxygen demand, total solids, volatile solids and total suspended solids. Samples were collected on a daily basis from the brewery
M AN U
for a month. This allow for the evaluation of the pollutant strength and fluctuations in the quality of the wastewater generated from the brewery. Samples collected were transported to the laboratory immediately in a cooler box full of ice and analyses were conducted immediately, where possible. However, if it was not possible to conduct the analysis immediately, samples were kept in the cold room in the laboratory at 4oC and analysis was conducted within 48 hours of sample collection. A mixed culture of activated sludge was
TE D
used as seed for both sequencing batch reactors. The activated sludge was allowed to acclimate after inoculation in brewery wastewater for 21 days. Samples collected for the operation of the two sequencing batch reactors was carried out once a week, fed into the
EP
SBRs and treatment proceeded immediately. Equipment Set up
AC C
The two laboratory scale sequencing batch reactors used for this study were identical with a total volume of 25 litres and a working volume of 15 litres. The reactors consisted of a closed cylindrical clear PVC vessel with a height of 0.45 m and a diameter of 0.35 m, with the bottom of each tank having a slope of 60º. Figure 1 presents the sectional view of the reactors.
Sectional view of the sequencing batch reactors
M AN U
Figure 1:
SC
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ACCEPTED MANUSCRIPT
Portable shaft mixers kept the solids suspended in the reactors. The motors were mounted on rubber gaskets and the shafts entered the reactors via 7.62 cm diameter holes in each reactor lid. The mixer shafts descended vertically into the tanks. The rubber gaskets were modified rubber end-caps for 7.62 cm PVC piping. The modifications consisted of removing the
TE D
thinner portion of the cap, leaving a 1.27 cm thick disk, and then cutting a hole to allow passage of the mixer blade through the newly-formed rubber ring. These rubber gaskets acted as seals to minimise leakage of odorous gases and absorb noisy vibrations from the motors during mixing. Each mixer blade was positioned a few centimetres above the bottom outlet,
EP
allowing for the dispersion of the larger solids. The motor operated at 10.0 W and 2000 rpm. The shaft was stainless steel with a length of 45.7 cm and a diameter of 0.79 cm. The
AC C
propeller blade was also stainless steel, with a diameter of 6.35 cm. The mixers operated continuously, except during the short time allowed for settling and supernatant draining. The mixer switches were also operated manually. Temperature and pH were measured by means of a digital analyser attached directly to each of the reactors. Air was supplied to both reactors by means of an air pump connected to the air diffusing copper pipes. To keep the small diffusers from floating freely in the tank, they were fitted to the end of a solid, copper pipe tube, which descended vertically into the reactor through a hole in the lid. This provided the reactors with adequate oxygenation. Influent to the reactors was introduced through an opening located at the middle of each reactor by means of a centrifugal pump. In order to drain the treated water after solids settling, two spigots were
ACCEPTED MANUSCRIPT added to the side of each tank. The use of this spigot is intended to minimise the occurrence of scouring during the removal of the supernatant. Tank drainage occurred manually by opening the spigot valve and draining the required volume of sample. Operational Scheme The two sequencing batch reactor were seeded with equal volumes of activated sludge and
RI PT
was fed with brewery wastewater without aeration and mechanical mixing during the filling period. This was done in order to prevent sludge bulking. The sequencing batch reactor were operated following the basic SBR operation scheme (fill, react, settling and decanting), however the aeration sequence differs from one another. The reactor was run for 15
SC
consecutive weeks with a 5 day hydraulic retention time for each batch run. The sequencing batch reactor operated under the continuous low aeration scheme employed the air pump
M AN U
which supplied air at a fixed rate of 2.5 litres/mins which allowed a dissolved oxygen concentration of 1.5 mg/l maintained in the reactor throughout the 5 day hydraulic retention time for each batch runs. Air supply was only terminated during the 3 hour settling period for each batch runs before samples were collected for analytical purposes. The sequencing batch reactor operated under cyclic aeration scheme requires adequate amount of oxygen during the aeration stage in order to meet the oxygen requirement while allowing the condition within
TE D
the reactor to return to anoxic condition when the aeration is stopped. Air was supplied to the reactor by means of the same type of air pump at a fixed rate of 7.5 litres/mins which allowed a dissolved oxygen concentration of 3 mg/l maintained in the reactor for 9 hours in a day over
AC C
Figure 2.
EP
the 5 days hydraulic retention time. The piping and instrumentation layout is presented in
Figure 2:
Piping and instrumentation layout of the laboratory scale sequencing batch reactor treating brewery wastewater.
ACCEPTED MANUSCRIPT The two reactors operated at room temperatures (20 -25 ºC) without controlling the pH, however the pH within the two reactor remained fairly constant (6-8) throughout the operation. Analytical Methods
RI PT
Analyses were conducted before the brewery wastewater was fed into the reactors and after treatment had taken place. This allowed for the evaluation of the treatment efficiencies achieved in both reactors. The monitoring parameters that were used to determine the treatment efficiencies of the reactors are chemical oxygen demand and biological oxygen
SC
demand. These parameters are priority pollutants and organic constituent found in brewery wastewater. The monitoring parameters were determined according to the standard methods
Treatment efficiency % =
M AN U
(APHA, 1998). The treatment efficiencies were determined using the following equation; –
RESULTS AND DISCUSSIONS
× 100
Brewery wastewater characterization results
presented in Table 1.
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The characterization results for the brewery wastewater collected over a 4 week period is
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Table 1: Brewery Wastewater Characteristics
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Parameters Mean Range of Concentration 382 Total Suspended Solids (mg/L) 200 - 563.8 6.74 pH 5-11 8.10 Ammonical Nitrogen(mg/L) 0.84-15.31 2746 Biological Oxygen Demand (mg/L) 2180 - 3018 11214 Chemical Oxygen Demand(mg/L) 2280 - 10210 5600 Total Solids (mg/L) 2000-9200 The characteristic of the collected brewery wastewater was similar to characteristics documented from previous studies (Ling, 1998; Dai, 2002; Rao et al. 2007; Enitan et al, 2015). It was also observed that the characteristics of the brewery wastewater fluctuated considerably over the 4 week sampling period. This is an indication that there were wide variations in the strength of the wastewater generated from the brewery. The characterisation
ACCEPTED MANUSCRIPT results clearly demonstrate that the generated wastewater samples from the brewery were high in organic components with a BOD to COD ratio of 0.6.
Chemical Oxygen Demand Results
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Figure 3 presents the chemical oxygen demand results for both the sequencing batch reactors.
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Chemical Oxygen Demand results indicating the influent concentration, effluent concentration and the removal efficiencies for the sequencing batch reactors. (a) SBR 1 is the sequencing batch reactor operated under continuous low aeration scheme (b) SBR 2 is the sequencing batch reactor operated under cyclic aeration scheme.
As presented in Figure 3 (a) & (b) for both sequencing batch reactor, the influent brewery
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wastewater into the sequencing batch reactors over the 15 weeks of operation varied considerably in terms of the Chemical Oxygen demand. This observation conforms to previous study on brewery wastewater which had been attributed to the various processes taking place within the brewery (Ling, 1998; Sinbuathong et al. 2007; Jones et al. 2011; Xu et al. 2013; Enitan et al, 2015). The influent chemical oxygen demand over the 15 weeks of
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operation of the sequencing batch reactors ranged between 2976 – 10860 mg/l, this is an indication of the fact that the wastewater from the brewery which was used in this study
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contains high levels of organic components which could be easily biodegradable. The obtained chemical oxygen demand values ranged from between 232 – 1000 mg/l after treatment under the continuous low aeration scheme during the 15 weeks duration while that of the sequencing batch reactor operated under cyclic aeration scheme ranged from 964 – 4136 mg/l. A significant reduction in terms of Chemical Oxygen Demand was observed in both reactors; however the reduction in chemical oxygen demand observed from the
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sequencing batch reactor operated under continuous low aeration scheme was significantly higher statistically than that of the reactor operated under cyclic aeration scheme. The chemical oxygen demand removal efficiency was consistently maintained above 90 % for the
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sequencing batch reactor operated under continuous low aeration scheme while that of the reactor operated under cyclic aeration scheme did not exceed 78 % over the entire 15 weeks
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duration of the investigation conducted. Biological Oxygen Demand Results The results for both sequencing batch reactor in terms biological oxygen demand is presented in Figure 4 (a) & (b). As shown in this figure, the biological oxygen demand concentration in the influent brewery wastewater also varied considerably as observed for the chemical oxygen demand. The influent biological oxygen demand into both sequencing batch reactor over the 15 weeks of operation ranged from 2291 – 3764 mg/l. However, the operation of the sequencing batch reactor under the continuous low aeration scheme resulted into an effluent biological oxygen demand which ranged from 372 – 764 mg/l. The biological oxygen demand removal efficiency was found to be consistently above 80 %. The reactor operated
ACCEPTED MANUSCRIPT under cyclic aeration scheme produced an effluent with biological oxygen demand ranging between 890 – 1259 mg/l over the entire duration of the investigation conducted. This resulted to a biological oxygen demand removal efficiency not exceeding 65%. Again the sequencing batch reactor operated under continuous low aeration scheme performed better
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statistically when compared to the reactor operated under cyclic aeration scheme.
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(b)
ACCEPTED MANUSCRIPT Chemical Oxygen Demand results indicating the influent concentration, effluent concentration and the removal efficiencies for the sequencing batch reactors. (a) SBR 1 is the sequencing batch reactor operated under continuous low aeration scheme (b) SBR 2 is the sequencing batch reactor operated under cyclic aeration scheme.
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Figure 4:
CONCLUSIONS
The purpose of this paper was to investigate the treatment of wastewater collected from a local brewery in Durban South Africa using laboratory scale aerobic sequencing batch
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reactor. The characteristics of the brewery wastewater used in this study confirm the findings from previous studies that have been conducted on brewery wastewater (Ling, 1998; Dai,
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2002; Rao et al. 2007; Enitan et al, 2015). The brewery wastewater used in this study indicated a wastewater quality that is high in organic constituents, which is highly biodegradable and one that will require prior treatment before discharge into the environment to avoid pollution that may arise if discharged into the environment without prior treatment. Thus in view of this finding, there is a need for appropriate technology to be used for efficiently treating the increasing volumes and strength of wastewater generated from the
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brewery plants.
The performance of two laboratory-scale aerobic sequencing batch reactors treating wastewater collected from the brewery under continuous low aeration scheme and cyclic
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aeration scheme was therefore investigated. The investigation has demonstrated that it is feasible to treat brewery wastewater using aerobic sequencing batch reactor without the need to enhance the activity of microorganisms in both sequencing batch reactors by providing
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supplementary nitrogen and phosphorus nutrients. The performance of the sequencing batch reactor operated under continuous low aeration scheme was significantly higher than that of the sequencing batch reactor operated under cyclic aeration scheme in terms of the chemical oxygen demand and biological oxygen demand reduction. It was therefore concluded that the better performance observed in the sequencing batch reactor operated under continuous low aeration scheme was because, microbial activity degrading organic materials in the reactor was enhance because of the constant availability of oxygen compared to the reactor operated under cyclic aeration scheme. Thus, the finding from this investigation is an indication that there is a potential for the equipment and energy
ACCEPTED MANUSCRIPT savings by operating aerobic sequencing batch reactors under continuous low aeration scheme for the treatment of wastewater generated from the breweries. ACKNOWLEDGEMENTS The author will like to gratefully acknowledge the participation of Sthembile Mzimela and the support received from the Research Directorate at Mangosuthu University of Technology
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Durban South Africa. REFERENCES
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Environmental Federation, Washington, DC.
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of water and wastewater, 20th edition. American Water Works Association and Water
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Braeken, L., Van Der Bruggen, B. & Vandecasteele, C. (2004). Regeneration of brewery waste water using nanofiltration. Water research, 38, 3075-3082.
DAI, H. (2002). Carbon nanotubes: opportunities and challenges. Surface Science, 500, 218241.
Driessen, W. & Vereijken, T. (2003). Recent developments in biological treatment of
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brewery effluent. Proceedings 9th Brewing Convention, Victoria Falls, Zambia, Inst. & Guild
Enitan, A. M., Adeyemo, J., Kumari, S., Swalaha, F. M. & Bux, F. (2015). Characterization
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of Brewery Wastewater Composition. World Academy of Science, Engineering and Technology, International Journal of Environmental, Chemical, Ecological, Geological and
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Geophysical Engineering, 9, 1015-1018. Fernandes, L. (1994). Effect of temperature on the performance of an SBR treating liquid swine-manure. Bioresource technology, 47, 219-227. Irvine, R. L., Ketchum JR, L. H. & Asano, T. (1989). Sequencing batch reactors for biological wastewater treatment. Critical Reviews in Environmental Science and Technology, 18, 255-294. Jang, H. M., Lee, J. W., Ha, J. H. & Park, J. M. (2013). Effects of organic loading rates on reactor performance and microbial community changes during thermophillic aerobic digestion process of high-strength food wastewater. Bioresource technology, 148, 261-269.
ACCEPTED MANUSCRIPT Jones, C. L. W., Britz, P., Davies, M. T. T., Scheepers, R., Cilliers, A., Crous, L. & Laubscher, R. (2011). The wealth in brewery effluent – Water and nutrient recovery using alternative technologies In: Proceedings of Fifteenth International Water Technology Conference, IWTC-15 2011. Alexandria, Egypt Ling, L. (1998). Brewery Wastewater Treatment Using Aerobic Sequencing Batch Reactors
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with Mixed Culture Activated Sludge. University of British Columbia
Merzouki, M., Delgenes, J., Bernet, N., Moletta, R., and Benlemlih, M. (1999). Polyphosphate-accumulating and denitrifying bacteria isolated from anaerobic-anoxic and
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Rao, A. G., Reddy, T., Prakash, S. S., Vanajakshi, J., Joseph, J. & Sarma, P. (2007). pH
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regulation of alkaline wastewater with carbon dioxide: A case study of treatment of brewery wastewater in UASB reactor coupled with absorber. Bioresource technology, 98, 2131-2136. Simate, G. S., Cluett, J., Iyuke, S. E., Musapatika, E. T., Ndlovu, S., Walubita, L. F. & Alvarez, A. E. (2011). The treatment of brewery wastewater for reuse: State of the art. Desalination, 273, 235-247.
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Sinbuathong, N., Khaodhiar, S., Liengcharernsit, W., Sirirote, P. & Watts, D. (2007). Effect of sulphate on the methanogenic activity of a bacterial culture from a brewery wastewater during glucose degradation. Journal of Environmental Sciences, 19, 1025-1027.
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Xu, F., Huang, Z., Miao, H., Ren, H., Zhao, M. & Ruan, W. 2013. Identical full-scale biogaslift reactors (BLRs) with anaerobic granular sludge and residual activated sludge for brewery
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wastewater treatment and kinetic modelling. Journal of Environmental Sciences, 25, 2031-
ACCEPTED MANUSCRIPT HIGHLIGHTS
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Wastewater generated from the brewery contains high amount of organic constituents which are highly biodegradable and requires appropriate technology for efficient treatment. The findings demonstrated that wastewater from the brewery can be successfully treated using sequencing batch reactor. The reactor operated under continuous low aeration scheme performed significantly better than the reactor operated under cyclic aeration scheme. No additional nutrient was supplied to both reactors.
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