Abstract：To clarify the influence of substrates composition on the production characteristics and foaming performance of extracellular polymer (EPS) in anaerobic digestion system, three types of food waste, namely high-carbohydrate, high-protein and high-fat, were tested in batch experiments. The EPS production characteristics (concentration, composition, structure, functional groups, etc.), and parameters characterizing the foaming properties (viscosity, surface tension and relative hydrophobicity) and potential (foaming tendency, foam stability, foam diameter and liquid film thickness) of various types of EPS and sludge, were examined in different test groups. The correlation between EPS characteristics and sludge characteristics was also analyzed. The test groups with different substrates produced EPS with different properties. Specifically, the more balanced the substrate composition, the more it tended to be used for gas production, while the high carbohydrate and control groups had significantly higher total EPS concentrations than the rest experimental groups due to the excess carbohydrate content. Carbohydrates, proteins and oils influenced EPS morphology and composition by altering intermediate metabolites, affecting enzyme production and proliferation of microorganisms, respectively. In terms of EPS structure, more humic-like substances were produced under high carbohydrate conditions in the high-carbohydrate and control groups. In terms of functional groups, the alkyl group was reduced in the high-carbohydrate group, the high-protein group produced more hydrophilic nitrogenous functional groups, and the carboxylic acid content increased in the high-fat group. In addition, the relative hydrophobicity of EPS was reduced to varying degrees in all three experimental groups compared to the control group. The correlation analysis revealed that the sludge foaming capacity was significantly more correlated with EPS-related parameters than with substrate categories. Sludge foaming tendency (FP) was strongly correlated with loosely bound EPS (P < 0.01, r=0.979) and soluble EPS (P < 0.05, r=0.678). EPS viscosity also had a positive effect on both FP and foam stability (FS) (P < 0.05), and increased EPS surface tension favored the FS (P < 0.05). In terms of the role of substrates on foaming, carbohydrates may be responsible for the production of larger diameter, more stable foams from the sludge by increasing EPS viscosity and hydrophilicity. Proteins use enzymes to reduce the surface tension of EPS, resulting in smaller diameter and less stable foams, and thus alleviated the foaming phenomenon. Fat reduced the loosely bound EPS (P < 0.05, r =-0.649) and its intermediate metabolite LCFA altered the viscosity of tightly bound EPS (P < 0.01, r=0.788), both contributing to increase the FP.
周滢月, 张智, 李蕾, 杨屏锦, 王小铭, 彭绪亚. 底物对厌氧消化系统EPS产生及起泡的影响[J]. 中国环境科学, 2023, 43(8): 4046-4056.
ZHOU Ying-yue, ZHANG Zhi, LI Lei, YANG Ping-jin, WANG Xiao-ming, PENG Xu-ya. Influence of substrate composition on the production characteristics of extracellular polymers and foaming performance in anaerobic digestion systems. CHINA ENVIRONMENTAL SCIENCECE, 2023, 43(8): 4046-4056.
李蕾,黄茜,杨屏锦,等.有机垃圾厌氧消化泡沫产生机理及控制方法[J].中国环境科学, 2020,8(40):3475-3485. Li L, Huang Q, Yang P J, et al. Occurrence mechanisms and control methods of foaming in anaerobic digesters treating organic wastes[J]. China Environmental Sciences, 2020,40(8):3475-3485.
[2]
靳晨曦,孙士强,盛维杰,等.中国厨余垃圾处理技术及资源化方案选择[J].中国环境科学, 2022,42(3):1240-1251. Jin C X, Sun S Q, Sheng W J, et al. Food waste treatment technology and resource solution options in China[J]. China Environmental Sciences, 2022,42(3):1240-1251.
[3]
张星星,焦彭博,杨汇莹,等.剩余污泥与餐厨垃圾协同厌氧消化研究进展[J].中国环境科学, 2022,42(5):2179-2194. Zhang X X, Jio P B, Yang H Y, et al. Recent advances in anaerobic co-digestion of excess sludge and food waste[J]. China Environmental Sciences, 2022,42(5):2179-2194.
[4]
Meng Y, Li S, Yuan H, et al. Effect of lipase addition on hydrolysis and biomethane production of Chinese food waste[J]. Bioresource Technology, 2015,179:452-459.
[5]
Yang P, Peng Y, Liu H, et al. Multi-scale analysis of the foaming mechanism in anaerobic digestion of food waste:From physicochemical parameter, microbial community to metabolite response[J]. Water Research, 2022,218:118482.
[6]
Lienen T, Kleyböcker A, Verstraete W, et al. Foam formation in a downstream digester of a cascade running full-scale biogas plant:Influence of fat, oil and grease addition and abundance of the filamentous bacterium Microthrix parvicella[J]. Bioresource Technology, 2014,153:1-7.
[7]
Moeller L, Lehnig M, Schenk J, et al. Foam formation in biogas plants caused by anaerobic digestion of sugar beet[J]. Bioresource Technology, 2015,178:270-277.
[8]
Nouha K, Kumar R S, Balasubramanian S, et al. Critical review of EPS production, synthesis and composition for sludge flocculation[J]. Journal of Environmental Sciences, 2018,66:225-245.
[9]
Yuksekdag Z N, Aslim B. Influence of different carbon sources on exopolysaccharide production by Lactobacillus delbrueckii sub sp. bulgaricus(B3, G12)and Streptococcus thermophilus(W22)[J]. Brazilian Archives of Biology and Technology, 2008,51(3):581-585.
[10]
Arshad Z, Maqbool T, Shin K H, et al. Using stable isotope probing and fluorescence spectroscopy to examine the roles of substrate and soluble microbial products in extracellular polymeric substance formation in activated sludge process[J]. Science of the Total Environment, 2021,788:147875.
[11]
Le C, Stuckey D C. Influence of Feed Composition on the monomeric structure of free bacterial extracellular polysaccharides in anaerobic digestion[J]. Environmental Science & Technology, 2017,51(12):7009-7017.
[12]
Chen X, Zhou W, Li G, et al. Anaerobic biodegradation of soybean-process wastewater:Operation strategy and sludge bed characteristics of a high-performance Spiral Symmetric Stream Anaerobic Bioreactor[J]. Water Research, 2021,197:117095.
[13]
Frolund B, Griebe T, Nielsen P H. Enzymatic activity in the activated-sludge floc matrix[J]. Applied Microbiology and Biotechnology, 1995, 43(4):755-761.
[14]
Boleij M, Pabst M, Neu T R, et al. Identification of glycoproteins isolated from extracellular polymeric substances of full-scale anammox granular sludge[J]. Environmental Science & Technology, 2018,52(22):13127-13135.
[15]
Cao F, Bourven I, Lens P N L, et al. Hydrophobic features of EPS extracted from anaerobic granular sludge:an investigation based on DAX-8resin fractionation and size exclusion chromatography[J]. Applied Microbiology and Biotechnology, 2017,101(8):3427-3438.
[16]
李蕾,张智,黄茜,等.厨余垃圾厌氧消化反应器起泡的驱动因子[J].中国环境科学, 2023,43(3):1244-1255. Li L, Zhang Z, Huang Q, et al. Driving factors of foaming in anaerobic digestion of food waste[J]. China Environmental Sciences, 2023,43(3):1244-1255.
[17]
Grau R A, Heiskanen K. Visual technique for measuring bubble size in flotation machines[J]. Minerals Engineering, 2002,15(7):507-513.
[18]
张靖雪,李盼盼,于洋,等.基于固液分离预处理的餐厨垃圾厌氧发酵[J].中国环境科学, 2022,42(3):1252-1258. Zhang Q X, Li P P, Yu Y, et al. Study on anaerobic digestion of kitchen waste based on solid-liquid separation pretreatment[J]. China Environmental Sciences, 2022,42(3):1252-1258.
[19]
Wang S, Yang Q Q, Shi W X, et al. Performance and evaluation of aerobic granular sludge in oily wastewater treatment[J]. Desalination and Water Treatment, 2017,72:112-118.
[20]
Kougias P G, Boe K, Einarsdottir E S, et al. Counteracting foaming caused by lipids or proteins in biogas reactors using rapeseed oil or oleic acid as antifoaming agents[J]. Water Research, 2015,79:119-127.
[21]
Stoyanova E, Forsthuber B, Pohn S, et al. Reducing the risk of foaming and decreasing viscosity by two-stage anaerobic digestion of sugar beet pressed pulp[J]. Biodegradation, 2014,25(2):277-289.
[22]
He Q, Li L, Zhao X, et al. Investigation of foaming causes in three mesophilic food waste digesters:reactor performance and microbial analysis[J]. Scientific Reports, 2017,7:13701.
[23]
苏燕,赵勇胜,李璐璐,等.多孔介质中泡沫的迁移特性和影响因素研究[J].中国环境科学, 2015,35(3):817-824. Su Y, Zhao Y S, Li L L, et al. Study on transport characteristics of foams and affecting factors in porous media[J]. China Environmental Sciences, 2015,35(3):817-824.
[24]
张虹,李蕾,彭韵,等.氨氮对餐厨垃圾厌氧消化性能及微生物群落的影响[J].中国环境科学, 2020,40(8):3465-3474. Zhang H, Li L, Peng Y, et al. Effects of ammonia on anaerobic digestion of food waste:Process performance and microbial community[J]. China Environmental Sciences, 2020,40(8):3465-3474.
[25]
胡小兵,叶星,周元凯,等.胞外聚合物对活性污泥吸附生活污水碳源的影响[J].环境科学学报, 2016,36(11):4062-4069. Hu X B, Ye X, Zhou Y K, et al. The effect of extracellular polymeric substances on adsorption of the carbon source in sewage by activated sludge[J]. Acta Scientiae Circumstantiae, 2016,36(11):4062-4069.
[26]
Laspidou C S, Rittmann B E. A unified theory for extracellular polymeric substances, soluble microbial products, and active and inert biomass[J]. Water research (Oxford), 2002,36(11):2711-2720.
[27]
Pt H, L N, C V. The effect of nutrients on extracellular polymeric substance production and its influence on sludge properties[J]. Water SA, 2022,29(4):437-442.
[28]
Hargreaves S K, Hofmockel K S. Physiological shifts in the microbial community drive changes in enzyme activity in a perennial agroecosystem[J]. Biogeochemistry, 2014,117(1):67-79.
[29]
Li W, Liao X, Guo J, et al. New insights into filamentous sludge bulking:The potential role of extracellular polymeric substances in sludge bulking in the activated sludge process[J]. Chemosphere, 2020,248:126012.
[30]
Ye F, Peng G, Li Y. Influences of influent carbon source on extracellular polymeric substances (EPS) and physicochemical properties of activated sludge[J]. Chemosphere, 2011,84(9):1250-1255.
[31]
Deng Y, Li W, Ruan W, et al. Applying EEM-PARAFAC analysis with quantitative real-time PCR to monitor methanogenic activity of high-solid anaerobic digestion of rice straw[J]. Frontiers in Microbiology, 2021,12.
[32]
Wei D, Yan T, Zhang K, et al. Qualitative and quantitative analysis of extracellular polymeric substances in partial nitrification and full nitrification reactors[J]. Bioresource Technology, 2017,240:171-176.
[33]
Zhang Y, Liu Y, Zhou A, et al. Identification of groundwater pollution from livestock farming using fluorescence spectroscopy coupled with multivariate statistical methods[J]. Water Research, 2021,206:117754.
[34]
Liu S, Lin C, Diao X, et al. Interactions between tetracycline and extracellular polymeric substances in anammox granular sludge[J]. Bioresource Technology, 2019,293:122069.
[35]
Zhu L, Zhou J, Lv M, et al. Specific component comparison of extracellular polymeric substances (EPS) in flocs and granular sludge using EEM and SDS-PAGE[J]. Chemosphere, 2015,121:26-32.
[36]
Diehl B G, Watts H D, Kubicki J D, et al. Correction to:Towards lignin-protein crosslinking:amino acid adducts of a lignin model quinone methide[J]. Cellulose, 2019,26(11):7025.
[37]
Zhang W, Dai X, Dong B, et al. New insights into the effect of sludge proteins on the hydrophilic/hydrophobic properties that improve sludge dewaterability during anaerobic digestion[J]. Water Research, 2020, 173:115503.
[38]
Cao B, Zhang T, Zhang W, et al. Enhanced technology based for sewage sludge deep dewatering:A critical review[J]. Water Research, 2021, 189:116650.
[39]
Yuan D, Wang Y. Effects of solution conditions on the physicochemical properties of stratification components of extracellular polymeric substances in anaerobic digested sludge[J]. Journal of Environmental Sciences, 2013,25(1):155-162.
[40]
Zhang D, Li W, Hou C, et al. Aerobic granulation accelerated by biochar for the treatment of refractory wastewater[J]. Chemical Engineering Journal, 2017,314:88-97.
[41]
Tao C, Parker W, Bérubé P. Characterization and modelling of soluble microbial products in activated sludge systems treating municipal wastewater with special emphasis on temperature effect[J]. Science of the Total Environment, 2021,779:146471.
[42]
Ekstrand E, Svensson B H,šafarič L, et al. Viscosity dynamics and the production of extracellular polymeric substances and soluble microbial products during anaerobic digestion of pulp and paper mill wastewater sludges[J]. Bioprocess and Biosystems Engineering, 2020,43(2):283-291.
[43]
Pham P L, Dupont I, Roy D, et al. Production of exopolysaccharide by Lactobacillus rhamnosus R and analysis of its enzymatic degradation during prolonged fermentation[J]. Applied and Environmental Microbiology, 2000, 66(6):2302-2310.
[44]
van der Ven C, Gruppen H, de Bont D B A, et al. Correlations between biochemical characteristics and foam-forming and-stabilizing ability of whey and casein hydrolysates[J]. Journal of Agricultural and Food Chemistry, 2002,50(10):2938-2946.
