陈琳, 李东, 文昊深, 冯立森, 黄亚军, 刘晓风. 蔬菜废弃物中温厌氧发酵酸化失稳预警指标筛选[J]. 农业工程学报, 2017, 33(1): 225-230. DOI: 10.11975/j.issn.1002-6819.2017.01.031
    引用本文: 陈琳, 李东, 文昊深, 冯立森, 黄亚军, 刘晓风. 蔬菜废弃物中温厌氧发酵酸化失稳预警指标筛选[J]. 农业工程学报, 2017, 33(1): 225-230. DOI: 10.11975/j.issn.1002-6819.2017.01.031
    Chen Lin, Li Dong, Wen Haoshen, Feng Lisen, Huang Yajun, Liu Xiaofeng. Screening of early warning indicators of instability in anaerobic digestion of vegetable waste under mesophilic condition[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2017, 33(1): 225-230. DOI: 10.11975/j.issn.1002-6819.2017.01.031
    Citation: Chen Lin, Li Dong, Wen Haoshen, Feng Lisen, Huang Yajun, Liu Xiaofeng. Screening of early warning indicators of instability in anaerobic digestion of vegetable waste under mesophilic condition[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2017, 33(1): 225-230. DOI: 10.11975/j.issn.1002-6819.2017.01.031

    蔬菜废弃物中温厌氧发酵酸化失稳预警指标筛选

    Screening of early warning indicators of instability in anaerobic digestion of vegetable waste under mesophilic condition

    • 摘要: 厌氧消化是一种可以较好地将有机废弃物处理和能源回收结合的生物技术,它是多种厌氧微生物共同参与、分阶段有序进行的复杂串联代谢过程。其中产甲烷菌对环境最敏感、代谢速率最慢,产甲烷阶段往往是厌氧消化系统的瓶颈,水解酸化与产甲烷两阶段不能较好地匹配,极易受到抑制。针对蔬菜废弃物厌氧发酵易酸化的特点,该试验旨在筛选发酵体系酸化失稳预警指标,采用自行设计的70 L反应装置,在中温35 ℃条件下进行蔬菜废弃物厌氧发酵的连续冲击负荷试验。通过对发酵过程中的气相及液相指标监测,该研究筛选出4类失稳预警指标,分别为:1)甲烷与二氧化碳的比值。当CH4/CO2<1.06时,系统出现酸化现象,提前18 d对厌氧发酵系统做出预警指示,具有最强的失稳预警性;2)挥发性脂肪酸。当丙酸、正/异丁酸、正/异戊酸出现突变时,系统出现酸化征兆,分别在17、15和15 d对厌氧消化体系做出失稳预警;3)碱度。包括总碱度(total alkalinity,TA)、碳酸氢盐碱度(bicarbonate alkalinity,BA)、及挥发酸盐碱度(intermediate alkalinity,IA)的耦合性指标,当BA<1 500 mg/L、BA/TA<0.8或IA/BA>0.4时,系统提前13、12和12 d做出酸化预警指示,此时发酵体系缓冲性能较差,系统极易出现挥发性脂肪酸的累积进而导致系统酸化失稳;4)氧化还原电位和pH值在整个厌氧消化过程中均持续微弱变化,利用其绝对值很难做出失稳判断,利用其相对变化值可做出失稳判断,骤变分别发生在产气彻底停止前第5天和第4天,预警能力较弱。在工程实际应用中,相比液相指标而言,气相指标的监测更容易实现,建议CH4/CO2作为预警指标。

       

      Abstract: Abstract: Anaerobic digestion (AD) is a kind of biological technology, which can combine organic waste treatment and energy recovery together. AD is a complex and well-organized metabolic process with a series of ordered biochemical reactions participated by multiple anaerobic microorganisms. Compared to other microbes in AD process, Methanogenic archaea are most sensitive to environment and have the lowest metabolism rate, so the methanogenic stage is the bottleneck step of anaerobic digestion system. The characteristics of vegetable waste, such as high content of moisture and organic matter, make it suitable for anaerobic digestion. Vegetable wastes are easily perishable materials. It is difficult to realize the balance between hydrolysis/acidification and methanogenesis during the digestion of vegetable waste. The methanogens are easily inhibited by cumulative volatile fatty acids, especially under high organic loading rate (OLR). Therefore, to stably running biogas plant, the digestion system with vegetable waste as substrate is always operated under low OLR. However, the lower OLR always results in a low efficiency of digester and low treatment capacity of plant. Taking into account the efficiency and stability, it is necessary to find effective instability early warning indicators and control strategies. In order to select a set of early-warning indicators for the acidification of the digestion system, continuous anaerobic digestions of vegetable waste were carried out at OLR of 0.5, 1.0 and 1.5 g/(L·d) in the self-designed 70 L reactors under mesophilic conditions (35 ℃). During the digestion, the primary parameter of the gas and liquid phase were directly monitored by on-line analyzer (daily biogas production, CH4 and CO2 content, pH value and oxidation-reduction potential (ORP)), and off-line analytical instrument (total alkalinity (TA), bicarbonate alkalinity (BA), intermediate alkalinity (IA) and volatile fatty acids, including acetate, propionate, n-butyrate, iso-butyrate, n-valerate, and iso-valerate). Secondary parameters, such as the value of CH4/CO2, total volatile fatty acids/BA, BA/TA, IA/BA, were indirectly monitored by data processing. Four types of parameters were selected as the indicator of the instability early-warning for mesophilic anaerobic fermentation with vegetable waste as substrate. According to the early-warning ability, the four types of indicators were as followings: 1) CH4/CO2. When CH4/CO2<1.06, the system tended to be unstable. It was the best early-warning indicator for the mesophilic anaerobic digestion of the vegetable waste and could warn the instability of the system 18 d ahead of complete failure of digestion system. 2) The propionic acid, butyrate, iso-butyrate, valerate and iso-valerate concentrations. When the concentrations of these acids increased suddenly, the digestion system also tended to be unstable. The sudden increasing occurred 17, 15 and 15 d ahead for propionate, butyrate and valerate, respectively. 3) The values of BA, BA/TA or IA/BA. When BA<1 500 mg/L, BA/TA <0.8 or IA/BA>0.4 occurred 13, 12 and 12 d ahead, the buffering capacity of the system was very poor, and the system would be inhibited by accumulative volatile fatty acids. 4) ORP and pH value. The values of ORP and pH changed slowly and continuously. The absolute values of ORP and pH were difficult to be used as indicators. The relative change value, such as daily increasing of ORP or daily decreasing of pH value, could be used as early-warning indicator. The sharp increasing of ORP and decreasing of pH value occurred 5 and 4 d ahead. For engineering application, CH4/CO2 is recommended as indicator due to its convenience and on-line determination.

       

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