Energy Procedia 52 ( 2014 ) 328 – 336

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1876-6102 © 2014 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).Selection and peer-review under responsibility of the Organizing Committee of 2013 AEDCEE doi: 10.1016/j.egypro.2014.07.084

2013 Alternative Energy in Developing Countries and Emerging Economies

Anaerobic Co-digestion of Canned Seafood Wastewater with Glycerol Waste for Enhanced Biogas Production

Kiattisak Panponga,, Galaya Srisuwana, Sompong O-Thonga,b,c*, Prawit Kongjand aSchool of Engineering and Resources, Walailak University, Nakornsrithamarat 80161, Thailand

bDepartment of Biology, c Research Center in Energy and Environment, Faculty of Science, Thaksin University, Phatthalung 93110, Thailand

dDepartment of Science, Faculty of Science and Technology, Prince of Songkla University, Pattani 94000, Thailand

Abstract

The potentiality in biogas production from anaerobic co-digestion of canned seafood wastewater (CSW) with glycerol waste (GW) was investigated. Methane yields from anaerobic co-digestion of CSW with 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10% (v/v) of GW were 577, 265, 101, 51, 11, 9, 4, 3, 2 and 2 mLCH4/g VS-added, respectively. The anaerobic co-digestion of 99% CSW with 1%GW was the optimal mixture ratio for methane production with a maximum methane yield was 577 mLCH4/g VS-added and 97% biodegradability. Meanwhile, the maximum methane yield of 1%GW and 100%CSW were 211 and 278 mLCH4/g VS-added. Methane yield increased by 108% when compared with digested CSW alone. The maximum methane production from anaerobic co-digestion of 99%CSW with 1%GW was 5.8 m3 CH4/m3 of mixed wastewater and electricity production of 1 m3 mixed wastewater would be 207 MJ or 58 kWh of electricity. Continuous methane production from anaerobic co-digestion of CSW with 1% GW in up-flow anaerobic sludge blanket (UASB) reactors gave methane production rate of 2.33 LCH4/L-reactor.day. © 2013 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the Research Center in Energy and Environment, Thaksin University. Keyword: Co-digestion, Biogas production, Canned seafood wastewater, Glycerol waste, Synergistic effect ;

1. Introduction

Canned seafood industry (tuna, sardine, mackerel, etc.) is one of the major exports of Thailand. Most of the seafood processing plants are located in the southern and eastern coast of Thailand. The amount of wastewater from canned seafood industry ranges from 300 to 500 m3/day [1]. Canned seafood industry

* Corresponding author. Tel.: +66 746 93992 ; fax: +66 746 93992. E-mail address: sompong.o@gmail.com

© 2014 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).Selection and peer-review under responsibility of the Organizing Committee of 2013 AEDCEE

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discharges the wastewater around 14 to 22 m3/ton of raw material (from washing (9%), cooling (34%), thawing (26%), ice removal (21%) and sterilization (10%) [1, 2]. Presently, wastewater treatment systems operating in the canned seafood industry are activated sludge, aerated lagoon, oxidation pond and anaerobic lagoon, but anaerobic reactors are used less [2]. The wastewater treatment is particularly difficult because of the high content salts protein and oil [2]. As a result, anaerobic reactor was not popular due to the problem of high content of organic nitrogen in wastewater which inhibited the anaerobic process [3]. The inhibitors generally occur in the canned seafood wastewater consisting of salts, fat, oil, grease and ammonia [2]. Compositions of canned seafood wastewaters were contained of BOD5 (100–3,000 mg/L), COD (1,000–18,000 mg/L) and nitrogen content (80–1,000 mg/L) [4]. The total ammonia nitrogen (TAN) is a combination of free ammonia nitrogen (NH3) and ionized ammonia nitrogen (NH4

+) which will be inhibited methanogenic activity by the concentrations of TAN in the range of 0.17 to 14 g/L reduced the methane production about 50% [5-7]. Guerrero et al. [8] reported that the toxicity of free ammonia nitrogen (NH3) for mesophilic conditions was in the range of 25 - 140 mg NH3/L. Additionally, the anaerobic treatment of canned seafood wastewater is inhibited by the presence of high sodium or chloride concentrations [2]. Methanogenesis is strongly inhibited by a sodium concentration of more than 10 g/L [4]. The maximal biogas yield was 0.75 m3/kg COD for anaerobic filter treatment of fishery wastewater which was operated at OLR of 1.3 kg COD/m3.day and HRT of 11days [3]. Therefore, the investment construction of biogas system in the canned seafood industry is not worth due to the low biogas production and also poor quality of biogas. One approach to increase the biogas production in the canned seafood wastewaters is the use the co-digestion process. Glycerol waste (GW) is a by-product of biodiesel production. By one kilogram of biodiesel production generated glycerol waste about 100 g or approximate 10% of raw material [9, 10]. Currently, glycerol waste has a low price because of excessive supplies [9]. Advantages of glycerol are easily digested, high COD, low prices and stored at room temperature for a long time [11]. Glycerol waste was used as a co-substrate to improve the biogas production in the anaerobic fermentation process [12]. Glycerol waste could improve C/N ratio and dilute the toxic compounds by the values of C/N and COD/N ratios were 20 and 70 which suggested a value in the process of anaerobic digestion [13]. Astals et al. [14] reported that the co-digestion between pig manure and 4% of glycerol waste can be increased the biogas production of about 400%. The maximum methane yield of 0.32 ml CH4/g COD-removed was achieved at a mixing ratio of 80:20 (glycerol: pig manure) [15]. Co-digestion of pig manure (PM) with fish waste (FW) or biodiesel waste (BW) could upgrade biogas volume and composition with compared to sole PM digestion [16]. The addition of 2 ml of glycerol waste per litter of potato wastewater could be increased biogas production by 0.74 L biogas/mL glycerol product [11]. Additionally, the glycerol is an intermediate product of anaerobic degradation of fats. Lipids are hydrolysed to glycerol and free long chain fatty acids (LCFAs) as the first step in anaerobic conditions [17]. This study aimed to enhance biogas production from canned seafood wastewater (CSW) by co-digestion with glycerol waste from biodiesel industry.

2. Methodology

2.1 Granule sludge

The granular sludge samples were collected from wastewater treatment plant of the Kiang Huat Sea Gull Trading Frozen Food Public Company Limited (KST in Hat-Yai District (Songkhla, Thailand). The granular size was used in the experiment between 0.8 and 1 mm. The volatile suspended solid (VSS) of the granular sludge was 33.876 g VSS/L.

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2.2 Canned seafood wastewater and glycerol waste

The wastewater sample was collected from Kuang Pei San Food Products Public Co., Ltd. in Muang Trang district, Trang Province, Thailand. The sample was stored at a temperature of 40C before it was analyzed and used in the experiment. The glycerol waste was collected from the biodiesel plant at Prince of Songkla University in Hat-Yai District, Songkhla Province, Thailand. The main characteristics of the canned seafood wastewater and glycerol waste were shown in Table 1.

Table 1. Characteristics of CSW and GW used in the experiments

Parameter CSW GW pH 6.3 8.8 COD(g/L) 10.4 1,760 VFA(mg/L) 2,230 6,650 ALK(mg/L) 2,560 35,050 TN(mg/L) 870 1,670 TP(mg/L) 53.6 71,500 TS(g/L) 9.37 969 VS(g/L) 7.76 910 Protein(g/L) 3.90 1.28 Carbohydrate(g/L) 1.91 845 Fat(g/L) 0.13 63.76 C/N ratio 11 949 Na+(mg/L) 560 20 K+(mg/L) - 40

2.3 Batch reactor

Anaerobic co-digestions of canned seafood wastewater (CSW) with glycerol waste (GW) were tested in 1,000 ml serum bottle with a working volume of 900 ml. The serum bottles were fitted with gas sampling septa closed with rubber stoppers and sealed with aluminium caps. Initially, the digestion mixtures were flushed with nitrogen gas for 5 min to replace the air (oxygen) in order to achieve anaerobic conditions. All batch experiments were conducted under mesophilic condition with 11 different concentrations of GW in the range of 0-10 % (v/v) to determine the appropriate amount of glycerol waste for the best methane production. The volume of granular sludge of 125 mL (4.23 g VSS) was added in all experiments. The mixed ratio of CSW with GW had the concentrations of VS in the range of 9.98 – 90.96 g VS/L (Table 2). During the experiments, biogas was daily collected by water displacement. The composition of biogas was analysed periodically by GC-TCD. COD, VS, VFA, Alkalinity, VFA/Alk ratio, pH and Alk/COD ratio were determined from liquid samples at the end. In the continuous operation, the optimum condition from the batch experiment was selected to operate in continuous reactor (UASB).

2.4 Continuous reactor

Continuous anaerobic co-digestion of CSW with GW was operated in up-flow anaerobic sludge blanket (UASB) at working volume 2.58 L. UASB reactor constructed by using clear acrylic in thickness about 0.5 mm. The experiment operated in the optimum condition of batch test (99%CSW+ 1%GW) and organic loading rate (OLR) of 2 g COD/L. day. The start-up of UASB system was started at OLR of 0.5 g COD/L. day then gradually increased to 2 g COD/L. day by adjusting the flow rate of feeding. The HRT was gradually reduced from 51 to 13 days. The biogas production was collected by water displacement (gas counter) every day. The biogas samples were taken from the UASB reactor everyday for biogas composition analysis by GC-TCD. The liquid samples were taken from the UASB reactor everyday to analyze the pH and VFA.

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Table 2. Initial conditions used in the experiments

Experiment pH COD (g/L)

VS (g/L)

TN (g/L)

C/N ratio

COD/VS (g COD/g VS)

CSW 6.30 10.4 7.76 0.870 11 1.34 GW(1%) 8.00 16.0 4.50 0.019 758 3.56 CSW+ GW(1%) 6.90 25.6 9.98 0.887 26 2.57 CSW +GW(2%) 7.10 35.2 12.20 0.993 32 2.89 CSW +GW(3%) 7.40 64.0 24.42 1.004 57 2.62 CSW +GW(4%) 7.60 88.0 36.64 1.027 77 2.40 CSW +GW(5%) 7.80 112 48.86 1.047 96 2.29 CSW +GW(6%) 7.90 128 51.08 1.037 111 2.51 CSW +GW(7%) 8.00 144 63.30 1.049 124 2.27 CSW +GW(8%) 8.10 160 75.52 1.061 136 2.12 CSW +GW(9%) 8.20 176 83.74 1.072 148 2.10 CSW +GW(10%) 8.30 192 90.96 1.083 160 2.11

2.5 Analytical methods

pH was measured by using Sartorius Docu - pH meter. Chemical oxygen demand (COD), total solid (VS), volatile suspended solid (VSS), total nitrogen (TN), total phosphorus (TP), volatile fatty acid, alkalinity, protein, carbohydrate and fat were analyzed according to standard method for the examination of water and wastewater [18]. The methane content was analyzed by a gas chromatography (GC) equipped with a thermal conductivity detector [19]. The synergism calculated using the methane production of the optimal mixture ratio of CSW with GW (%) in batch test by comparing with the methane production of CSW and GW(%) alone [20]. Theoretical methane potential calculated according Bushwell’s formula which derived from stoichiometric conversion of the compound to CH4, CO2 and NH3 [21].

3. Result and Discussion

3.1 Substrate characterization

The characteristics of CSW and GW before and after mixing were shown in Table 1 and 2. The CSW was high protein and had a C/N ratio as 11 which was very low when compared to GW. GW consisted mainly of carbohydrate and had a C/N ratio very high which had a value as 949. Additionally, adding of GW into CSW at a concentration of 1-10% (v/v) could be increased the C/N ratio between 26 and 160. Li et al. [22] reported that the suitable C/N ratio for anaerobic digestion in the range 20 – 30. As a co-substrate, GW can be adjusted the C/N ratio and pH of CSW. Particularly, it can be balanced the C/N ratio of the mixed wastewater and it can be diluted the ammonium nitrogen concentration in the anaerobic digester [23]. It was found that CSW had a COD concentration of 10.4 g/L which not economic feasibility for biogas production. However, the COD concentration of GW was very high which had a value as 1,760 g/L. So, using GW co-digested with CSW can be increased the COD concentration.

3.2 Methane potential of co-digestion CSW with GW The accumulative methane production and methane yield by the co-digestion of the CSW and GW were shown in Fig 1 and 2. Methane yields of co-digestion CSW with 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10% (v/v) of GW were 577, 265, 101, 51, 11, 9, 4, 3, 2 and 2 mLCH4/g VS-added, respectively. The co-digestion of 99%CSW with 1%GW was the optimal mixture ratio for methane production which had a cumulative methane production of 5,184 mLCH4 and methane yield of 577 mLCH4/g VS-added with 97%

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biodegradability (Table 3). The maximum methane yield of 100%CSW was 278 mL CH4/g VS-added with 95% biodegradability. Meanwhile, the maximum methane yield of 1%GW was 211 mL CH4/g VS-added with 70% biodegradability. Methane yield was increased by 108% when comparing with digested CSW alone. These results showed that adding 1% GW into CSW can be enhanced biogas production. Maldenovska et al. [24] reported that the co-digestion between manure and lipids gave a methane yield of 382 mLCH4/g VS-added. Additionally, adding 1%GW into CSW also increased the C/N ratio from 11 to 26 (Table 2). Addition of GW at 2-10% (v/v) into CSW increased C/N ratio between 32 and 160 but had a negative effect on methane production due to system overload. The methanogenic process was inhibited when increased glycerol waste concentration up to 2%. Fountoulakis et al. [25] reported that adding GW not exceeded a limiting 1% (v/v) can be boosted the biogas yield. The initial pH after adding GW into CSW ranged 6.9 – 8.3 which had suitable for the methanogenic process more than CSW alone (pH 6.3) (Table 2). In addition, the advantage in using GW as a co-substrate can be adjusted the pH of CSW which could save the cost of chemicals in adjusting the pH value. The final volatile fatty acid and alkalinity were in the range of 1,100 – 7,100 mg/L and 3,100 – 4,450 mg/L. As a result, the VFA/Alk ratio had a value in the range of 0.25 – 2.29 which indicated the efficiency of anaerobic digestion (Table 3). The suitable VFA/Alk ratio for anaerobic digestion must be no greater than 0.4 [26].

Table 3. Summary of methane yield, biodegradability and pH of anaerobic co-digestion of CSW with GW.

Exp. Initial

Loading (gVS/L)

CH4 Yield (mL CH4/g VS

added)

biodegradability (%)

pH After digestion

VFA/Alk ratio

CSW 7.76 278 95 6.7 0.31 GW(1%) 4.50 211 70 5.1 3.26 CSW+ GW(1%) 9.98 577 97 7.3 0.25 CSW+GW(2%) 12.20 265 80 6.8 0.76 CSW+GW(3%) 24.42 101 78 5.3 1.71 CSW+GW(4%) 36.64 51 77 5.0 1.92 CSW+GW(5%) 48.86 11 70 4.8 1.81 CSW+GW(6%) 51.08 9 70 4.8 1.69 CSW+GW(7%) 63.30 4 62 4.7 1.83 CSW +GW(8%) 75.52 3 56 4.8 1.99 CSW +GW(9%) 83.74 2 36 4.9 2.12 CSW+GW(10%) 90.96 2 33 4.8 2.29

Fig. 1. Cumulative methane production from anaerobic co-digestion of CSW with GW.

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Kiattisak Panpong et al. / Energy Procedia 52 ( 2014 ) 328 – 336 333

Fig. 2. Methane production from anaerobic co-digestion of CSW with GW.

3.3 Synergism of co-digestion between CSW and GW

The anaerobic co-digestion of 99%CSW with 1%GW resulted in positive synergism by increasing the methane production, methane yield and degradation efficiency. The total methane production was 5,184 mLCH4 while total methane production from CSW and GW alone were 1,945 and 951 mLCH4. The synergistic methane production (Syn-MP) of co-digestion between CSW and GW was 2,288 mLCH4 (Fig 3A). Additionally, the methane yield of co-digestion was 577 mLCH4/g VS-added (Theoretical methane yield = 630 mLCH4/g VS-added). Methane yield was increased by 108% when compared to the methane yield of CSW (278 mLCH4/g VS-added) and GW (211 mLCH4/g VS-added). The synergistic methane yield (Syn-MY) was 88 mLCH4/g VS-added (Fig 3B). The degradation efficiency increased from 95% to 97% after adding 1%GW into CSW. The maximum methane production from anaerobic co-digestion of CSW with 1% GW was 5.8 m3 CH4/ m3 of mixed wastewater. Meanwhile, the maximum methane production of CSW and GW alone was 2.2 m3 CH4/m3 of CSW wastewater and 0.2 m3 CH4/m3 of 1%GW wastewater. Finally, the electricity production of 1 m3 of mixed wastewater would be 207 MJ or 58 kWh of electricity by calculation from the content of energy as 36 MJ/m3 CH4 and 10 kWh/m3 CH4 which had a conversion efficiency of approximate 40% in a gas motor [20].

3.4 Continuous methane production of co-digestion CSW with GW in UASB reactor

Anaerobic co-digestion of 99%CSW and 1%GW was selected to operate in the UASB reactor. Granular sludge in the UASB could adapt quickly because the granular sludge was taken from the UASB treating the same type of wastewater. The first phase, the wastewater entering into the UASB system at OLR 0.5 g COD/L. day was acclimatized phase. The OLR was gradually increased up to 2 g COD/L. day by adjusting the inflow rate of wastewater (fixed initial COD was 25,600 mg/L). The results showed that the biogas production rate, methane composition and pH were 2.33 L/L reactor-day, 60% and 6.9 -7.2 in steady state (Fig 5A). Khanal [27] reported that the optimal pH for anaerobic process in the range 6.8 – 7.4. The methane yield of 309 mLCH4/g COD-removed (640 mL CH4/g VS-added) with 80% COD removal achieved under steady state (Fig 5B). The result of this experiment was nearby to that of Nuchdang and Phalakornkule [15] which reported that the maximum methane yield of 320 mL CH4/g COD-removed at an OLR of 1.6 g COD/L. day in a case of the co-digestion between glycerol and pig manure. Volatile fatty acids (VFAs) were important mid-products in the production of methane; their

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concentrations affected the efficiency of fermentation and their effected on methane yield and methanogenic bacteria growth [28]. The results in Fig 4 showed that when the system go to steady state, the VFA and alkalinity values were in the range 1,100 – 1,250 mg/ L and 2,600 – 2,850 mg/L. Additionally, the VFA/Alk ratio was less than 0.4 and Alk/COD ratio was in the range of 0.5 - 0.65 when the system went into a steady state. The suitable VFA for the anaerobic digestion must be had a maximum of 2,000 mg/L and should have the VFA/Alk ratio less than 0.4 for the buffer capacity of a good system and should have the Alk/COD ratio greater than 0.5 to keep the pH of the system decreased [26, 28].

Fig. 3. Methane production from anaerobic co-digestion of CSW with GW at ratio of 99:1; (A) cumulative methane production and (B) methane yield: T-MP (Total methane production), CSW-MP (Canned seafood wastewater methane production), GW-MP (Glycerol waste (1%) methane production and Syn-MY (Synergistic methane yield)

Fig. 4. Total VFA, alkalinity, VFA/alkalinity ratio and Alk/COD ratio at an OLR of 2 g COD/L. day in UASB reactor

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Kiattisak Panpong et al. / Energy Procedia 52 ( 2014 ) 328 – 336 335

Fig. 5. (A) Biogas and methane production, methane element (%) and pH at an OLR of 2 g COD/L. day in UASB reactor (B) COD (in), COD (out) and COD remove (%)

4. Conclusion

Anaerobic co-digestion of CSW with 1%GW had potential to improve the quality and quantity of biogas. The cumulative methane production and methane yield were 5,184 mLCH4 and 577 mLCH4/g VS-added. The cumulative methane production and methane yield was increased by 167% and 108% when compared with digested CSW alone. The results also showed that the methane production in continuous reactor was achieved with methane production rate of 2.33 LCH4/L-reactor.day and methane yield was 309 mLCH4/g COD-removed (640 mLCH4/g VS-added) of removal COD 80%. Adding GW as a carbon source into CSW was resulted in increasing C/N ratio from 11 to 26 and also diluted the toxicity of ammonia in the system. The maximum methane production of co-digestion between 99%CSW and 1% GW was 5.8 m3 CH4/ m3 of mixed wastewater and electricity production of 1 m3 of mixed wastewater would be 207 MJ or 58 kWh of electricity. So, GW can be used a co-substrate because it enhanced a potential the methane production in CSW.

Acknowledgements

I would like to thank the Office of the Higher Education Commission (OHEC) for support the funding in this research.

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