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Biological Hydrogen Sulfide and Sulfate Removal from Rubber Smoked Sheet Wastewater for Enhanced Biogas Production
Available online at www.sciencedirect.com
ScienceDirect Availableonline onlineatatwww.sciencedirect.com www.sciencedirect.com Available Energy Procedia 00 (2017) 000–000
ScienceDirect ScienceDirect
www.elsevier.com/locate/procedia
Energy (2017) 000–000 569–574 EnergyProcedia Procedia138 00 (2017) www.elsevier.com/locate/procedia
2017 International Conference on Alternative Energy in Developing Countries and Emerging Economies 2017 AEDCEE, 25‐26 May 2017, Bangkok, Thailand
BiologicalTheHydrogen Sulfide and Sulfate 15th International Symposium on DistrictRemoval Heating and from CoolingRubber Smoked Sheet Wastewater for Enhanced Biogas Production Assessing the feasibility of using the heat demand-outdoor a a,b * Kanathip Promnuan and Sompong O-Thong temperature function for a long-term district heat demand forecast 0F
a
Biotechnology Program, Faculty of Science, Thaksin University, Phatthalung 93210, Thailand.
a,b,c a a b c in Energy and Environment, Faculty of Science, Thaksin.,University, Phatthalung,93210, Thailand. I. Research AndrićCenter *, A. Pina , P. Ferrão , J. Fournier B. Lacarrière O. Le Correc a
a
IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France
Abstract
The sulfate-rich wastewater from rubber smoked sheet industry could generate hydrogen sulfide (H2S) under anaerobic condition, which created bad smell to the community and might cause toxicity and damage to the environment. The H2S can be removed from the biogas by sulfur-oxidizing bacteria (SOB) with the ability to converted H2S to sulfate. Sulfate-reducing Abstract bacteria (SRB) could remove sulfate in wastewater before anaerobic treatment for biogas production. The microbial sludge from wastewater and anaerobic digestion system was collected and test for sulfate and H2S removal efficiency. Anaerobic microbial District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the sludge has a high ability to produced methane from gelatin with a specific methane production rate of 92.4 ml CH4 gVSS-1 day-1. greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat Anaerobic microbial sludge has lower methane production when gelatin and sulfate used as a substrate with a specific methane sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, production rate of 81.4 ml CH4 gVSS-1 day-1. The biomethane potential, hydrogen sulfide removal and sulfate removal in prolonging the investment return period. anaerobic digestion system by addition of enriched cultures of SOB and SRB were investigated. The methane yield of SRB The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand consortium was 60.1 ml CH4/gCOD with 20% sulfate reduction from wastewater and no sulfide reduction. The methane yield of forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 SOB consortium was 41.9 ml CH4/gCOD with no sulfate and sulfide reduction from wastewater. The addition of SRB buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district consortium could increase methane production by reducing sulfate concentration in wastewater consequently to a reduced renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were concentration of H2S in biogas. compared with results from a dynamic heat demand model, previously developed and validated by the authors. results showed that when only weatherLtd. change is considered, the margin of error could be acceptable for some applications ©The 2017 The Authors. Published by Elsevier © 2017 The Authors. Published by Elsevier Ltd. Peer-review responsibility of lower the scientific committee of the 2017 International Conference on Alternative Energy renovation in (the error inunder annual demand was than 20% for all weather scenarios considered). However, after introducing Peer-review under responsibility of the Organizing Committee of 2017 AEDCEE. D eveloping the Countries and Emerging scenarios, error value increased Economies. up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the Keywords: Biogas; Hydrogen sulfide; Sulfur-oxidizing bacteria; Sulfate-reducing bacteria decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations. © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and * Corresponding author. Tel.: +66-74-693-992; fax: +66-74-693-992. Cooling. E-mail address: [email protected]
Keywords: Heat demand; Forecast; Climate change 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Organizing Committee of 2017 AEDCEE.
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 2017 International Conference on Alternative Energy in Developing Countries and Emerging Economies. 10.1016/j.egypro.2017.10.161
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Kanathip Promnuan et al. / Energy Procedia 138 (2017) 569–574 Kanathip Promnuan and Sompong O-Thong./ Energy Procedia 00 (2017) 000–000
1. Introduction Rubber smoked sheet wastewater containing high sulfate and the sulfate could converse to hydrogen sulfide (H2S) under anaerobic condition by sulfate-reducing bacteria. Hydrogen sulfide created a bad smell (rotten egg odor) to public health. If people received a high concentration of H2S, it affects the respiratory system. Biogas production from sulfate-rich wastewaters resulted in high hydrogen sulfide concentration in biogas. It may cause serious problems in the application of biogas because the H2S concentration in the gas phase higher than 1000 ppmv could not direct combustion. The limitation of H2S for internal combustion engine fuel is 100 ppmv and much lower 16 ppmv is set for compressed natural gas for transportation fuel [1]. Moreover, sulfide in the liquid phase (dissolved sulfide) generated during the anaerobic treatment of sulfate-rich wastewater also imposes toxicity to methanogens [2]. Treatment technologies to remove the high concentrations of H2S in the gas phase are physical (adsorption, absorption, and dilution), chemical (chemical absorption, neutralization, and combustion) and biological (activated sludge and biofilter) methods [3]. H2S in Biogas is difficult to remove because of methanogenic archaea and sulfate-reducing bacteria growth in the same condition. Under anaerobic environment with the presence of chemical oxygen demand (COD), the sulfate-reducing bacteria (SRB) can convert sulfate in wastewaters to sulfide. Biological conversion of sulfide to elemental sulfur or sulfate using sulfide-oxidizing bacteria (SOB) is a capable process to remove H2S from biogas [4, 5]. In natural, the SRB and SOB can coexist in hydrothermal vents, microbial mats, marine sediments and wastewater biofilms as a response of high organic input and low dissolved oxygen (DO) concentration [6]. Therefore, the combination of the SRB and SOB for remove sulfide and sulfate in biogas reactor is of practical interest. The aim of this study was to gain more insight into the syntrophic interactions between the different bacterial trophic groups in biogas process. For this purpose, activity tests in the presence of various substrates were carried out to fully elucidate the outcome of competition between the sulfate reducers and the other anaerobic consortia in high sulfate wastewater. The biomethane production, hydrogen sulfide removal and sulfate removal in anaerobic digestion of rubber smoked sheet wastewater by adding enriched cultures of SRB and SOB were investigated. 2. Methodology 2.1. Sampling and Inoculum The rubber smoked sheet wastewater was collected from Yangkaw cooperative rubber sheet plant. The chemical and physical compositions of wastewater were analyzed according to standard water and wastewater examination methods [7]. The sludge inoculum was collected from biogas plant of the Yangkaw cooperative rubber sheet plant. Wastewater adjusting the initial pH in the range of 7-7.5 by ash and NaHCO3 was used as the substrate for seed sludge. Prior to use, the sludge inoculums were incubated for 1-2 weeks to activate microorganism activities. The sulfate-reducing bacteria also enriched from anaerobic sludge collected from the Yangkaw cooperative rubber sheet plant. It was kept at a temperature of 4°C during transport to the laboratory. Postgate medium C was used for enrichment and cultured sulfate-reducing bacteria [8]. Postgate medium C 1 L contained of 6.0 ml Lactic acid, 4.5 g Na2SO4, 1.0 g NH4Cl, 1.0 g Yeast extract, 0.5 g KH2PO4, 0.3 g Sodium citrate·2H2O, 0.06 g CaCl2·6H2O, 0.06 g MgSO4·7H2O, 0.004 g FeSO4·7H2O and pH adjusted at 7.0±2. The sulfide-oxidizing bacteria were enriched from biofilter sludge collecting from Pitak palm oil CO., LTD. Thiosulfate mineral medium was used for enrichment and culturing sulfide-oxidizing bacteria [9]. Thiosulfate mineral medium 1 L contained of 5.1 g Na2S2O3, 2.0 g K2HPO4, 2.0 g KH2PO4, 0.4 g NH4Cl, 0.2 g MgCl2·7H2O, 0.01 g FeSO4·7H2O and pH adjusted at 7.0±2. 2.2. Specific methanogenic activity A specific methanogenic activity (SMA) test was used to determine for microbial activity in anaerobic digestion [10]. SMA tests were carried out in the presence and absence of sulfate (NaSO4 30 mM). The substrates tested including acetic, avicel, glucose and gelatin and combinations at the concentrations of 4 g/L COD. SMA was carried out in test vials (60 ml) with anaerobic sludge and incubated under mesophilic condition (35 °C) for a period of 7 days. All tests were performed in the presence and absence the addition of sulfate into the medium. The biogas
Kanathip Promnuan et al. / Energy Procedia 138 (2017) 569–574 Kanathip Promnuan and Sompong O-thong./ Energy Procedia 00 (2017) 000–000
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production was collected by water displacement (gas counter) and biogas composition analysis by GC-TCD every day. 2.3. Batch assay for sulfide and sulfate removal Batch assay was carried out in a 120-ml vial with working volume of 50 ml. Rubber sheet wastewater, anaerobic sludge (SL), enriched SRB and enriched SOB were mixed as described previously by Angelidaki et al. [11]. The initial pH was adjusted 7.0-8.0 and incubated under mesophilic condition (35 °C) for a period of 20 days by variated proportions of inoculum (%SL: %SOB: %SRB) as follows: 60:20:0, 60:0:20, 60:10:10, 60:15:5 and 60:5:15. The biogas production was collected by water displacement (gas counter) and biogas composition analysis by GC-TCD every day. All tests were run in triplicate for at each condition with avicel as a positive control. 2.4. Analytical methods Biogas composition was daily monitored by gas chromatography. The TS, VS, alkalinity, and pH of the materials were determined using the standard water and wastewater examination methods [7]. Elemental composition (C, H, O, N, and S) of the materials was performed in a CHNS-O Analyzer, CE Instruments Flash EA 1112 Series with dynamic flash combustion at 900 ºC, for C, H, N and S element, at 1060 ºC for O element [12]. Sulfide, Sulfate, and chemical oxygen demand (COD) were measured by Merck Cell test. The pH was measured with Adwa waterproof pH-Temp Pocket tester. 3. Results and Discussion 3.1. Substrate characterization The characteristics of rubber smoked sheet wastewater were shown in Table 1. The wastewater was high sulfate and protein concentrations that can converse to ammonia and hydrogen sulfide. Ammonia is toxic to aquatic animals and methanogens. In addition, ammonia also inhibited anaerobic digestion process. Methanogenesis was completely inhibited at total ammonia nitrogen of higher than 9 g N L-1 [7]. Ammonia nitrogen is less inhibitory in its ionic form (NH4+) than as free ammonia (NH3), but the partitioning between these forms is dependent on temperature and pH. For this reason, ammonia inhibition has been reported in a wide range of total ammonia nitrogen concentrations between 1500 and 7000 mg N L-1 [13]. Wastewater also contains a high amount of sulfate. The sulfate is reduced to sulfide by the sulfate-reducing bacteria (SRB). SRB inhibition is due to competition for common organic and inorganic substrates that suppresses methane production. SRB inhibition also results from the toxicity of sulfide [13]. Therefore, the addition of SOB and/or SRB can be removal sulfate and sulfide by syntrophic between SOB that convert sulfide to element sulfur and SRB that converts sulfate to sulfide. 3.2. Specific methanogenic activity Table 2 summarizes the specific methanogenic activity (SMA) for anaerobic sludge samples from biogas plant of rubber smoked sheet wastewater. The SMA in all substrates demonstrated that methanogens and SRB were competed for consuming of substrates. The SMA of gelatin gave the high specific methane production of 92.41 ml CH4 gVSS-1 day-1. The SMA values from gelatin as a substrate indicated that high growth proteolytic bacteria in the systems [11]. Proteolytic bacteria are a hydrolysis bacterium that converts the insoluble complex organic matter, such as cellulose, into soluble molecules such as sugars, amino acids, and fatty acids. Protease was secreted by proteolytic bacteria and convert proteins into amino acids. The SMA of acetic, avicel and glucose as a substrate was 7.37, 13.96, 32.41 ml CH4 gVSS-1 day-1 respectively. There were very low when compared with the values obtained for gelatin. High acetate degradation in vials containing sulfate was suggesting that acetate-utilizing SRB is a significant role in acetate conversion. The SRB may compete with methanogens, acetogens, or fermentative microorganisms for available acetate, H2, propionate, and butyrate in anaerobic systems [14, 15]. Anaerobic sludge
Kanathip Promnuan et al. / Energy Procedia 138 (2017) 569–574 Kanathip Promnuan and Sompong O-Thong./ Energy Procedia 00 (2017) 000–000
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from Yangkaw cooperative rubber sheet plant can be degraded gelatin better than another substrate. Furthermore, the presence of sulfate in acetic as a substrate shown inhibited methanogens in anaerobic digestion. Table 1. Chemical and physiological characteristics of rubber smoked sheet wastewater Parameter
Influent wastewater
COD (mg/l)
6,500
pH
a
4
Total solid (mg/L)
6,115
Volatile solid (mg/L)
4,367
Sulfate (mg/L SO42-)
5,101
2-
Sulfide (mg/l S )
0.25
Total alkalinity (mg/L. CaCO3)
3,000
Total nitrogen (mg/L)
1,360
a
8,500
Protein (mg/L)
total nitrogen multiplies factor of protein 6.25
Table 2. Specific methanogenic activity and sulfate reduction of sludge from rubber smoked sheet biogas plant Treatment
SMA (ml CH4 gVSS-1 day-1)
Acetic Acetic+ SO4
7.37 2-
Avicel Acetic+ SO4
27.03 13.96
2-
7.58
Glucose
32.41
Glucose+ SO42-
27.32
Gelatin
92.41
Gelatin+ SO4
2-
81.41
3.3. Sulfide and sulfate removal for enhanced methane production The results show that biogas increased was improved with sulfate removal from the wastewater (Table 3). Methane production rate in all experiment was high on Day 2 and gradually decreased until the end of the experiment (Fig 1a). Addition of enriched SRB at 20% into the batch fermentation system can remove sulfate (20%) and increase methane yields (60.07 ml CH4/COD). Methanogens and SRB did not compete for common substrates. Syntrophic propionate and ethanol conversion bacteria were likely performed primarily by SRB, while H2, formate, and acetate were consumed primarily by methanogens. Some cases of sulfate, certain SRB such as Desulfovibrio spp. may grow together with H2-utilizing methanogens to convert ethanol or lactate to acetate syntrophically [16]. Addition of enriched SRB and SOB was shown high methane accumulation more than the control (Fig 1b). Sulfide in all treatments could not be removed by the addition of SOB. It is possible that SOB cannot grow in anaerobic fermentation. Normally, SOB use the energy of oxidized inorganic sulfur compounds (hydrogen sulfide, thiosulfates, sulfites, elemental sulfur) in aerobic condition [17], but some SOB can grow in micro-aeration [18]. Therefore, the conditions of this experiment may not be suitable for growth of SOB. 4. Conclusion The specific methanogenic activity of anaerobic sludge from Yangkaw cooperative rubber sheet biogas plant has a high capacity to degradation of the protein. Addition of enriched SRB could improve biogas volume and biogas quality. Addition of enriched SRB 20%v/v has the capacity to remove sulfate and increase methane production.
Kanathip Promnuan et al. / Energy Procedia 138 (2017) 569–574 Kanathip Promnuan and Sompong O-thong./ Energy Procedia 00 (2017) 000–000
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Table 3. Effect of sulfide sulfate removal and methane yield after added proportions of SRB and SOB No.
Treatment
Methane yield (ml CH4 g-1 COD)
Sulfide (mg/l S2-)
after 5.3
0.6
0
6.6
8.6
0
61
280
0
5.3
4.4
17
54
250
0
4.3
4.7
0
60.07
50
200
0
4.5
3.6
20
SL+ 1SOB + 1SRB
51.72
60
230
0
3.7
3.5
5
7
SL + 2SOB + 1SRB
45.75
51
230
0
4.7
4.2
11
8
SL + 1SOB + 2SRB
56.75
68
230
0
3.7
3.4
8
2
SOB
3
SRB
4
SL + SOB
5
SL + SRB
6
after 62
0
0.5
0 41.93
Sulfate Removal (%)
before 4.6
SL
before 50
Sulfate (g/l SO42-)
0
1
52.58
Sulfide Removal (%)
a
0
b
Fig. 1 Effect of methane production rate (a) and cumulative methane yield (b) after added proportions of SRB and SOB
Acknowledgements The authors would like to thank the Research and Development Institute, Thaksin University, Research Center in Energy and Environment, Faculty of Science, Thaksin University, Research Group for Development of Microbial Hydrogen Production Process, Khon Kaen University, and Thailand Research Fund through grant Research and Researchers for Industries (RRI) (PHD59I0069) for the financial support. References [1] Kanjanarong J, Giri BS, Jaisi DP, Oliveira FR, Boonsawang P, Chaiprapat S, Singh RS, Balakrishna A, Khanal SK. Removal of hydrogen sulfide generated during anaerobic treatment of sulfate-laden wastewater using biochar: Evaluation of efficiency and mechanisms. Bioresource Technology 2017; 234: p. 115-121. [2] Li Y, Khanal SK. Bioenergy: Principles and applications, 1st ed. Canada: John Wiley & Sons; 2016. [3] Namgung HK, Song J. The effect of oxygen supply on the dual growth kinetics of Acidithiobacillus thiooxidans under acidic conditions for biogas desulfurization. Int. J. Environ. Res. Public Health 2015; 12: p. 1368-1386. [4] Xu XJ, Chen C, Wang AJ, Fang N, Yuan Y, Ren NQ, Lee DJ. Enhanced elementary sulfur recovery in integrated sulfate-reducing, sulfurproducing rector under micro-aerobic condition. Bioresource Technology 2012; 116: p. 517-521. [5] Lohwacharin J, Annachhatre AP. Biological sulfide oxidation in an airlift bioreactor. Bioresource Technology 2010; 101: p. 2114-2120. [6] Okabe S, Ito T, Sugita K, Satoh H. Succession of internal sulfur cycles and sulfur-oxidizing bacterial communities in microaerophilic wastewater biofilms. Applied and Environmental Microbiology 2005; 71: p. 2520-2529. [7] APHA. Standard methods for the examination of water and wastewater 22th ed. Washington DC, USA: American Public Health Association; 2012. [8] Postgate JR. The sulfate-reducing bacteria, 2nd ed. United Kingdom: Cambridge University Press; 1984.
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[9] Namgung HK, Ahn H, Song J. Development of a two-phase bioreactor for the biological removal of hydrogen sulfide from biogas. Energy Procedia 2012; 14: p. 1143-1148. [10] O'Reilly C, Colleran E. Effect of influent COD/SO4(2-) ratios on mesophilic anaerobic reactor biomass populations: physico-chemical and microbiological properties. FEMS Microbiol Ecol 2006; 56: p. 141-153. [11] Angelidaki I, Alves M, Bolzonella D, Borzacconi L, Campos JL, Guwy AJ, Kalyuzhnyi S, Jenicek P, Van Lier JB. Defining the biomethane potential (BMP) of solid organic wastes and energy crops: a proposed protocol for batch assays. Water science and technology 2009; 59: p. 927-934. [12] Lesteur, M., Bellon-Maurel, V., Gonzalez, C., Latrille, E., Roger, J. M., Junqua, G., Steyer, J. P. Alternative methods for determining anaerobic biodegradability: a review. Process Biochem 2010; 45: p. 431-440. [13] Chen Y, Cheng J, Creamer KS. Inhibition of anaerobic digestion process: A review. Bioresource Technology 2008; 99: p. 4044-4064. [14] McCartney DM, Oleszkiewicz JA. Competition between methanogens and sulfate reducers: effect of COD: sulfate ratio and acclimation. Water Environment Research 1993; 65: p. 655-664. [15] Colleran E, Finnegan S, Lens P. Anaerobic treatment of sulphate-containing waste streams. Antonie van Leeuwenhoek 1995; 67: p. 29-46. [16] Wu WM, Hickey RF, Zeikus JG. Characterization of metabolic performance of methanogenic granules treating brewery wastewater: role of sulfate-reducing bacteria. Appl Environ Microbiol 1991; 57: p. 3438-3449. [17] Pokorna D, Zabranska J. Sulfur-oxidizing bacteria in environmental technology. Biotechnology Advances 2015; 33: p. 1246-1259. [18] Blázquez E, Gabriel D, Baeza JA, Guisasola A. Treatment of high-strength sulfate wastewater using an autotrophic biocathode in view of elemental sulfur recovery. Water Research 2016; 105: p.395-405
ScienceDirect Availableonline onlineatatwww.sciencedirect.com www.sciencedirect.com Available Energy Procedia 00 (2017) 000–000
ScienceDirect ScienceDirect
www.elsevier.com/locate/procedia
Energy (2017) 000–000 569–574 EnergyProcedia Procedia138 00 (2017) www.elsevier.com/locate/procedia
2017 International Conference on Alternative Energy in Developing Countries and Emerging Economies 2017 AEDCEE, 25‐26 May 2017, Bangkok, Thailand
BiologicalTheHydrogen Sulfide and Sulfate 15th International Symposium on DistrictRemoval Heating and from CoolingRubber Smoked Sheet Wastewater for Enhanced Biogas Production Assessing the feasibility of using the heat demand-outdoor a a,b * Kanathip Promnuan and Sompong O-Thong temperature function for a long-term district heat demand forecast 0F
a
Biotechnology Program, Faculty of Science, Thaksin University, Phatthalung 93210, Thailand.
a,b,c a a b c in Energy and Environment, Faculty of Science, Thaksin.,University, Phatthalung,93210, Thailand. I. Research AndrićCenter *, A. Pina , P. Ferrão , J. Fournier B. Lacarrière O. Le Correc a
a
IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France
Abstract
The sulfate-rich wastewater from rubber smoked sheet industry could generate hydrogen sulfide (H2S) under anaerobic condition, which created bad smell to the community and might cause toxicity and damage to the environment. The H2S can be removed from the biogas by sulfur-oxidizing bacteria (SOB) with the ability to converted H2S to sulfate. Sulfate-reducing Abstract bacteria (SRB) could remove sulfate in wastewater before anaerobic treatment for biogas production. The microbial sludge from wastewater and anaerobic digestion system was collected and test for sulfate and H2S removal efficiency. Anaerobic microbial District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the sludge has a high ability to produced methane from gelatin with a specific methane production rate of 92.4 ml CH4 gVSS-1 day-1. greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat Anaerobic microbial sludge has lower methane production when gelatin and sulfate used as a substrate with a specific methane sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, production rate of 81.4 ml CH4 gVSS-1 day-1. The biomethane potential, hydrogen sulfide removal and sulfate removal in prolonging the investment return period. anaerobic digestion system by addition of enriched cultures of SOB and SRB were investigated. The methane yield of SRB The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand consortium was 60.1 ml CH4/gCOD with 20% sulfate reduction from wastewater and no sulfide reduction. The methane yield of forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 SOB consortium was 41.9 ml CH4/gCOD with no sulfate and sulfide reduction from wastewater. The addition of SRB buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district consortium could increase methane production by reducing sulfate concentration in wastewater consequently to a reduced renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were concentration of H2S in biogas. compared with results from a dynamic heat demand model, previously developed and validated by the authors. results showed that when only weatherLtd. change is considered, the margin of error could be acceptable for some applications ©The 2017 The Authors. Published by Elsevier © 2017 The Authors. Published by Elsevier Ltd. Peer-review responsibility of lower the scientific committee of the 2017 International Conference on Alternative Energy renovation in (the error inunder annual demand was than 20% for all weather scenarios considered). However, after introducing Peer-review under responsibility of the Organizing Committee of 2017 AEDCEE. D eveloping the Countries and Emerging scenarios, error value increased Economies. up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the Keywords: Biogas; Hydrogen sulfide; Sulfur-oxidizing bacteria; Sulfate-reducing bacteria decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations. © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and * Corresponding author. Tel.: +66-74-693-992; fax: +66-74-693-992. Cooling. E-mail address: [email protected]
Keywords: Heat demand; Forecast; Climate change 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Organizing Committee of 2017 AEDCEE.
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 2017 International Conference on Alternative Energy in Developing Countries and Emerging Economies. 10.1016/j.egypro.2017.10.161
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Kanathip Promnuan et al. / Energy Procedia 138 (2017) 569–574 Kanathip Promnuan and Sompong O-Thong./ Energy Procedia 00 (2017) 000–000
1. Introduction Rubber smoked sheet wastewater containing high sulfate and the sulfate could converse to hydrogen sulfide (H2S) under anaerobic condition by sulfate-reducing bacteria. Hydrogen sulfide created a bad smell (rotten egg odor) to public health. If people received a high concentration of H2S, it affects the respiratory system. Biogas production from sulfate-rich wastewaters resulted in high hydrogen sulfide concentration in biogas. It may cause serious problems in the application of biogas because the H2S concentration in the gas phase higher than 1000 ppmv could not direct combustion. The limitation of H2S for internal combustion engine fuel is 100 ppmv and much lower 16 ppmv is set for compressed natural gas for transportation fuel [1]. Moreover, sulfide in the liquid phase (dissolved sulfide) generated during the anaerobic treatment of sulfate-rich wastewater also imposes toxicity to methanogens [2]. Treatment technologies to remove the high concentrations of H2S in the gas phase are physical (adsorption, absorption, and dilution), chemical (chemical absorption, neutralization, and combustion) and biological (activated sludge and biofilter) methods [3]. H2S in Biogas is difficult to remove because of methanogenic archaea and sulfate-reducing bacteria growth in the same condition. Under anaerobic environment with the presence of chemical oxygen demand (COD), the sulfate-reducing bacteria (SRB) can convert sulfate in wastewaters to sulfide. Biological conversion of sulfide to elemental sulfur or sulfate using sulfide-oxidizing bacteria (SOB) is a capable process to remove H2S from biogas [4, 5]. In natural, the SRB and SOB can coexist in hydrothermal vents, microbial mats, marine sediments and wastewater biofilms as a response of high organic input and low dissolved oxygen (DO) concentration [6]. Therefore, the combination of the SRB and SOB for remove sulfide and sulfate in biogas reactor is of practical interest. The aim of this study was to gain more insight into the syntrophic interactions between the different bacterial trophic groups in biogas process. For this purpose, activity tests in the presence of various substrates were carried out to fully elucidate the outcome of competition between the sulfate reducers and the other anaerobic consortia in high sulfate wastewater. The biomethane production, hydrogen sulfide removal and sulfate removal in anaerobic digestion of rubber smoked sheet wastewater by adding enriched cultures of SRB and SOB were investigated. 2. Methodology 2.1. Sampling and Inoculum The rubber smoked sheet wastewater was collected from Yangkaw cooperative rubber sheet plant. The chemical and physical compositions of wastewater were analyzed according to standard water and wastewater examination methods [7]. The sludge inoculum was collected from biogas plant of the Yangkaw cooperative rubber sheet plant. Wastewater adjusting the initial pH in the range of 7-7.5 by ash and NaHCO3 was used as the substrate for seed sludge. Prior to use, the sludge inoculums were incubated for 1-2 weeks to activate microorganism activities. The sulfate-reducing bacteria also enriched from anaerobic sludge collected from the Yangkaw cooperative rubber sheet plant. It was kept at a temperature of 4°C during transport to the laboratory. Postgate medium C was used for enrichment and cultured sulfate-reducing bacteria [8]. Postgate medium C 1 L contained of 6.0 ml Lactic acid, 4.5 g Na2SO4, 1.0 g NH4Cl, 1.0 g Yeast extract, 0.5 g KH2PO4, 0.3 g Sodium citrate·2H2O, 0.06 g CaCl2·6H2O, 0.06 g MgSO4·7H2O, 0.004 g FeSO4·7H2O and pH adjusted at 7.0±2. The sulfide-oxidizing bacteria were enriched from biofilter sludge collecting from Pitak palm oil CO., LTD. Thiosulfate mineral medium was used for enrichment and culturing sulfide-oxidizing bacteria [9]. Thiosulfate mineral medium 1 L contained of 5.1 g Na2S2O3, 2.0 g K2HPO4, 2.0 g KH2PO4, 0.4 g NH4Cl, 0.2 g MgCl2·7H2O, 0.01 g FeSO4·7H2O and pH adjusted at 7.0±2. 2.2. Specific methanogenic activity A specific methanogenic activity (SMA) test was used to determine for microbial activity in anaerobic digestion [10]. SMA tests were carried out in the presence and absence of sulfate (NaSO4 30 mM). The substrates tested including acetic, avicel, glucose and gelatin and combinations at the concentrations of 4 g/L COD. SMA was carried out in test vials (60 ml) with anaerobic sludge and incubated under mesophilic condition (35 °C) for a period of 7 days. All tests were performed in the presence and absence the addition of sulfate into the medium. The biogas
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production was collected by water displacement (gas counter) and biogas composition analysis by GC-TCD every day. 2.3. Batch assay for sulfide and sulfate removal Batch assay was carried out in a 120-ml vial with working volume of 50 ml. Rubber sheet wastewater, anaerobic sludge (SL), enriched SRB and enriched SOB were mixed as described previously by Angelidaki et al. [11]. The initial pH was adjusted 7.0-8.0 and incubated under mesophilic condition (35 °C) for a period of 20 days by variated proportions of inoculum (%SL: %SOB: %SRB) as follows: 60:20:0, 60:0:20, 60:10:10, 60:15:5 and 60:5:15. The biogas production was collected by water displacement (gas counter) and biogas composition analysis by GC-TCD every day. All tests were run in triplicate for at each condition with avicel as a positive control. 2.4. Analytical methods Biogas composition was daily monitored by gas chromatography. The TS, VS, alkalinity, and pH of the materials were determined using the standard water and wastewater examination methods [7]. Elemental composition (C, H, O, N, and S) of the materials was performed in a CHNS-O Analyzer, CE Instruments Flash EA 1112 Series with dynamic flash combustion at 900 ºC, for C, H, N and S element, at 1060 ºC for O element [12]. Sulfide, Sulfate, and chemical oxygen demand (COD) were measured by Merck Cell test. The pH was measured with Adwa waterproof pH-Temp Pocket tester. 3. Results and Discussion 3.1. Substrate characterization The characteristics of rubber smoked sheet wastewater were shown in Table 1. The wastewater was high sulfate and protein concentrations that can converse to ammonia and hydrogen sulfide. Ammonia is toxic to aquatic animals and methanogens. In addition, ammonia also inhibited anaerobic digestion process. Methanogenesis was completely inhibited at total ammonia nitrogen of higher than 9 g N L-1 [7]. Ammonia nitrogen is less inhibitory in its ionic form (NH4+) than as free ammonia (NH3), but the partitioning between these forms is dependent on temperature and pH. For this reason, ammonia inhibition has been reported in a wide range of total ammonia nitrogen concentrations between 1500 and 7000 mg N L-1 [13]. Wastewater also contains a high amount of sulfate. The sulfate is reduced to sulfide by the sulfate-reducing bacteria (SRB). SRB inhibition is due to competition for common organic and inorganic substrates that suppresses methane production. SRB inhibition also results from the toxicity of sulfide [13]. Therefore, the addition of SOB and/or SRB can be removal sulfate and sulfide by syntrophic between SOB that convert sulfide to element sulfur and SRB that converts sulfate to sulfide. 3.2. Specific methanogenic activity Table 2 summarizes the specific methanogenic activity (SMA) for anaerobic sludge samples from biogas plant of rubber smoked sheet wastewater. The SMA in all substrates demonstrated that methanogens and SRB were competed for consuming of substrates. The SMA of gelatin gave the high specific methane production of 92.41 ml CH4 gVSS-1 day-1. The SMA values from gelatin as a substrate indicated that high growth proteolytic bacteria in the systems [11]. Proteolytic bacteria are a hydrolysis bacterium that converts the insoluble complex organic matter, such as cellulose, into soluble molecules such as sugars, amino acids, and fatty acids. Protease was secreted by proteolytic bacteria and convert proteins into amino acids. The SMA of acetic, avicel and glucose as a substrate was 7.37, 13.96, 32.41 ml CH4 gVSS-1 day-1 respectively. There were very low when compared with the values obtained for gelatin. High acetate degradation in vials containing sulfate was suggesting that acetate-utilizing SRB is a significant role in acetate conversion. The SRB may compete with methanogens, acetogens, or fermentative microorganisms for available acetate, H2, propionate, and butyrate in anaerobic systems [14, 15]. Anaerobic sludge
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from Yangkaw cooperative rubber sheet plant can be degraded gelatin better than another substrate. Furthermore, the presence of sulfate in acetic as a substrate shown inhibited methanogens in anaerobic digestion. Table 1. Chemical and physiological characteristics of rubber smoked sheet wastewater Parameter
Influent wastewater
COD (mg/l)
6,500
pH
a
4
Total solid (mg/L)
6,115
Volatile solid (mg/L)
4,367
Sulfate (mg/L SO42-)
5,101
2-
Sulfide (mg/l S )
0.25
Total alkalinity (mg/L. CaCO3)
3,000
Total nitrogen (mg/L)
1,360
a
8,500
Protein (mg/L)
total nitrogen multiplies factor of protein 6.25
Table 2. Specific methanogenic activity and sulfate reduction of sludge from rubber smoked sheet biogas plant Treatment
SMA (ml CH4 gVSS-1 day-1)
Acetic Acetic+ SO4
7.37 2-
Avicel Acetic+ SO4
27.03 13.96
2-
7.58
Glucose
32.41
Glucose+ SO42-
27.32
Gelatin
92.41
Gelatin+ SO4
2-
81.41
3.3. Sulfide and sulfate removal for enhanced methane production The results show that biogas increased was improved with sulfate removal from the wastewater (Table 3). Methane production rate in all experiment was high on Day 2 and gradually decreased until the end of the experiment (Fig 1a). Addition of enriched SRB at 20% into the batch fermentation system can remove sulfate (20%) and increase methane yields (60.07 ml CH4/COD). Methanogens and SRB did not compete for common substrates. Syntrophic propionate and ethanol conversion bacteria were likely performed primarily by SRB, while H2, formate, and acetate were consumed primarily by methanogens. Some cases of sulfate, certain SRB such as Desulfovibrio spp. may grow together with H2-utilizing methanogens to convert ethanol or lactate to acetate syntrophically [16]. Addition of enriched SRB and SOB was shown high methane accumulation more than the control (Fig 1b). Sulfide in all treatments could not be removed by the addition of SOB. It is possible that SOB cannot grow in anaerobic fermentation. Normally, SOB use the energy of oxidized inorganic sulfur compounds (hydrogen sulfide, thiosulfates, sulfites, elemental sulfur) in aerobic condition [17], but some SOB can grow in micro-aeration [18]. Therefore, the conditions of this experiment may not be suitable for growth of SOB. 4. Conclusion The specific methanogenic activity of anaerobic sludge from Yangkaw cooperative rubber sheet biogas plant has a high capacity to degradation of the protein. Addition of enriched SRB could improve biogas volume and biogas quality. Addition of enriched SRB 20%v/v has the capacity to remove sulfate and increase methane production.
Kanathip Promnuan et al. / Energy Procedia 138 (2017) 569–574 Kanathip Promnuan and Sompong O-thong./ Energy Procedia 00 (2017) 000–000
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Table 3. Effect of sulfide sulfate removal and methane yield after added proportions of SRB and SOB No.
Treatment
Methane yield (ml CH4 g-1 COD)
Sulfide (mg/l S2-)
after 5.3
0.6
0
6.6
8.6
0
61
280
0
5.3
4.4
17
54
250
0
4.3
4.7
0
60.07
50
200
0
4.5
3.6
20
SL+ 1SOB + 1SRB
51.72
60
230
0
3.7
3.5
5
7
SL + 2SOB + 1SRB
45.75
51
230
0
4.7
4.2
11
8
SL + 1SOB + 2SRB
56.75
68
230
0
3.7
3.4
8
2
SOB
3
SRB
4
SL + SOB
5
SL + SRB
6
after 62
0
0.5
0 41.93
Sulfate Removal (%)
before 4.6
SL
before 50
Sulfate (g/l SO42-)
0
1
52.58
Sulfide Removal (%)
a
0
b
Fig. 1 Effect of methane production rate (a) and cumulative methane yield (b) after added proportions of SRB and SOB
Acknowledgements The authors would like to thank the Research and Development Institute, Thaksin University, Research Center in Energy and Environment, Faculty of Science, Thaksin University, Research Group for Development of Microbial Hydrogen Production Process, Khon Kaen University, and Thailand Research Fund through grant Research and Researchers for Industries (RRI) (PHD59I0069) for the financial support. References [1] Kanjanarong J, Giri BS, Jaisi DP, Oliveira FR, Boonsawang P, Chaiprapat S, Singh RS, Balakrishna A, Khanal SK. Removal of hydrogen sulfide generated during anaerobic treatment of sulfate-laden wastewater using biochar: Evaluation of efficiency and mechanisms. Bioresource Technology 2017; 234: p. 115-121. [2] Li Y, Khanal SK. Bioenergy: Principles and applications, 1st ed. Canada: John Wiley & Sons; 2016. [3] Namgung HK, Song J. The effect of oxygen supply on the dual growth kinetics of Acidithiobacillus thiooxidans under acidic conditions for biogas desulfurization. Int. J. Environ. Res. Public Health 2015; 12: p. 1368-1386. [4] Xu XJ, Chen C, Wang AJ, Fang N, Yuan Y, Ren NQ, Lee DJ. Enhanced elementary sulfur recovery in integrated sulfate-reducing, sulfurproducing rector under micro-aerobic condition. Bioresource Technology 2012; 116: p. 517-521. [5] Lohwacharin J, Annachhatre AP. Biological sulfide oxidation in an airlift bioreactor. Bioresource Technology 2010; 101: p. 2114-2120. [6] Okabe S, Ito T, Sugita K, Satoh H. Succession of internal sulfur cycles and sulfur-oxidizing bacterial communities in microaerophilic wastewater biofilms. Applied and Environmental Microbiology 2005; 71: p. 2520-2529. [7] APHA. Standard methods for the examination of water and wastewater 22th ed. Washington DC, USA: American Public Health Association; 2012. [8] Postgate JR. The sulfate-reducing bacteria, 2nd ed. United Kingdom: Cambridge University Press; 1984.
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