过酸化失稳是困扰有机废物厌氧消化(AD)过程高效稳定运行的一大难题.为探析不同诱导方式造成过酸化的AD系统微生态特征差异,在餐厨垃圾中温AD反应器中分别引人负荷扰动(R2)、温度及搅拌扰动(R3)以诱发系统过酸化,利用宏基因组学测序技术,对比考察稳定与酸化系统微生物群落结构及主要产甲烷功能路径差异.结果表明,两种方式均成功诱发系统过酸化失稳,过酸化系统中挥发性脂肪酸(VFA)过量富集(R2、R3系统中分别高达(12.53±1.96)g·L-1和(8.00±0.81)g·L-1)的同时,丙酸等多碳VFA组分比例大幅升高.R2、R3系统酸化后其产甲烷菌及相关酶受到高浓度VFA的显著抑制,酸积累程度更高的R2受抑制更为明显.且经相关性分析发现,多碳酸尤其是丙酸是抑制产甲烷作用的关键因素.与R2相比,R3具有更高的耗氢能力,耗氢微生物如可耗H2产酸的Treponema属和氢营养型产甲烷菌Methanoculleus属、Methanospirillum属等相对丰度显著高于R2.酸化系统均以乙酸营养型产甲烷为主要的产甲烷途径,并以Methanosaeta属为主要的乙酸型产甲烷菌.酸化系统中更高含量的乙酸产甲烷途径的AK-PTA酶有利于促进对乙酸的利用,增强厌氧消化微生物菌群对高浓度乙酸的耐受能力.本研究中的相关结果可为提高有机废物AD微生态抗酸化能力提供理论依据和数据支撑.

A modified Anaerobic Digestion Model No. 1 (ADM1) with optimized kinetic parameters was presented to model methane production in the anaerobic digestion of food waste. Experimental data from batch and semi-continuous fermentations were used to calibrate and verify the model. Modified ADM1 simulation was carried out using AQUASIM 2.0 software. Sensitivity analysis was used to identify and evaluate the most sensitive kinetic parameters during biogas production. The decay constant of microorganisms, the disintegration constant, the hydrolysis constant of carbohydrates, the Monod maximum specific substrate uptake rate, and the half-saturation constants affected biogas production significantly. The optimized values of these parameters were 0.001, 0.16, 3, 1 and 0.23, respectively. Optimization results were validated using batch and semi-continuous experiments. The modified ADM1 well-predicted methane production, with R-2 values for the validation experiments all above 90%. These results can be used as basic data to simulate methane production in full-scale reactors.

Biogas plants can effectively treat organic wastes from various sources and recover energy from biomass for commercial use. However, anaerobic digestion (AD) can suffer from process instability, which can affect efficiency of biogas production. Process monitoring can be used to ensure stable and efficient biogas production process. In recent years, researchers have paid increasing attention to process monitoring as a means of stabilizing anaerobic reactors and ensuring high biogas production. This review of process monitoring of AD focuses on recent progress related to effective early-warning indicators and robust, applicable monitoring methods. A review of the literature revealed that explorations of process monitoring parameters have mainly focused on the metabolic process of AD itself, while the importance of monitoring the feeding substrate as a means of optimizing process stability has not been valued sufficiently. In addition, the application of robust online monitoring methods developed in the laboratory to real-world applications in biogas plants has been limited by high costs. In the future, on the premise of strict cost control, better understanding of the mechanisms underlying AD instability and increased attention focused on online monitoring of the feeding substrate will facilitate optimization of the production process at biogas plants to achieve efficient and stable production.

推广生活垃圾分类收集与资源化利用有助于促进资源节约型?环境友好型社会建设.本文综述了我国生活垃圾分类发展历程;收集了国家和地方在推广生活垃圾分类过程中所做的工作;提炼出了生活垃圾分类过程中还存在的障碍和瓶颈;并给出了相应的对策.本文分析表明,我国生活垃圾分类经历了开始(20世纪90年代)?试点探索(2000～2015年)和快速发展(2016年至今)3个阶段.目前国家和地方正逐步采用可操作性强的垃圾分类方法?融合互联网+的宣传方式?实用性的法规章程?完善的分类收集-分类运输-分类处理循环链来推进生活垃圾分类,甚至生活垃圾分类工作还逐步向市场化方向发展.我国将走出一条切实可行?可复制?可推广的高效生活垃圾分类模式.后期加强全民参与及大众自觉回收的责任意识?出台更细化具体?操作性强的实施方案?重视学校儿童的垃圾分类教育?充分利用国内拾荒人员,对快速推进我国生活垃圾分类进程具有重要意义.

A long-term high solids anaerobic digestion of food waste was conducted to identify microbial mechanisms of ammonia inhibition during digestion and to clarify correlations between ammonia accumulation, microbial community dynamics (diversity, composition, and interactions), and process stability. Results show that the effects of ammonia on process performance and microbial community were indirectly caused by volatile fatty acid accumulation. Excess free ammonia blocked acetate metabolism, leading to process instability. Accumulated acetate caused feedback inhibition at the acetogenesis stage, which resulted in considerable accumulation of propionate, valerate, and other long-chain fatty acids. This high concentration of volatile fatty acids reduced the abundance of syntrophic acetogenic bacteria and allowed hydrolytic fermentative bacteria to dominate. The normally interactive and orderly metabolic network was broken, which further exacerbated the process instability. These results improve the understanding of microbial mechanisms which contribute to process instability and provide guidance for the microbial management of anaerobic digesters.

A plug-flow reactor (PFR) (R1) and a completely-stirred tank reactor (CSTR) (R2) were operated under mesophilic temperature (37±1℃) for high-solids digestion of kitchen waste to investigate the microbial community characteristics before and after sludge-bulking using MiSeq high-throughput sequencing technology. The results showed that the archaeal community structure changed little after sludge-bulking, and acetoclastic methanogen Methanosaeta and mixotrophic methanogen Methanosarcina dominated in both reactors. There was a marked increase in the relative abundance of bacteria genera that might be related to sludge bulking. Those proliferated bacteria genera are those capable of producing biosurfactants (Corynebacterium, Lactobacillus, etc.) and those containing mycolic acids in cell walls (Actinomyces, Corynebacterium, etc.). In addition, volatile fatty acids (VFAs) and total ammonia nitrogen (TAN) were accumulated in these reactors before sludge-bulking. Accordingly, bacteria that can contribute to the accumulation of VFAs (Petrimonas, Anaerosalibacter and Fastidiosipila, etc.) and TAN (Proteiniphilum, Tepidimicrobium and Aminobacterium, etc.) were observed to proliferate.

To identify the most efficient system for conversion of food waste (FW) into biogas,FW fermentation was investigated in two types of reactors:a completely-stirred tank reactor (CSTR) and a plug-flow reactor with a reflux ratio (R-PFR).The efficiency,stability,and microbial community structure in the reactors were compared.Stable fermentation was achieved under an organic loading rate (OLR) of 3.0 kgVS· m-3· d-1 in both reactors.Compared with the CSTR,total alkalinity (TA) and ratio of volatile fatty acids (VFA) to TA (VFA/TA) were more stable,and inhibitors such as total ammonia-nitrogen (TAN) and free ammonia-nitrogen (FAN) concentrations were lower in R-PFR.However,specific methane production (SMP) was higher in the CSTR.The phyla Chloroflexi (37.35％) and Firmicutes (31.22％) were predominant in the R-PFR,whereas Firmicutes (44.41％) and Bacteroidetes (31.14％) were more abundant in the CSTR.The genus Methanosaeta accounted for 98.72％ and 84.90％ of the total population in the CSTR and R-PFR,respectively,indicating that the main methanogenic pathway in both reactors was acetoclastic methanogenesis.In addition to Methanosaeta,mixotrophic methanogens such as Methanosarcina (9.72％) and hydrogenotrophic methanogens such as Methanospirillum and Methanolinea were detected in the CSTR.The methanogenic community obtained in the CSTR had a greater tolerance to high ammonia and VFA levels,which is conducive to stable and efficient methanogenesis.R-PFR may be more appropriate for highly variable substrate,as shock loads can vary spatially in the reactor.However,R-PFR systems are not suitable for long-term treatment of highly degradable substrate such as FW,as local acidification may occur.Our results provide a basis for the optimization of anaerobic FW digestion.

The correlations between kinetic parameters and both operational conditions and process performance during the anaerobic digestion of food waste were investigated. Substrate concentration (SC), biomass concentration (BC), and substrate-inoculum ratio (S/I) were selected as the operational conditions, while first-order and modified Gompertz models were introduced to evaluate digestion kinetics. The results indicated that no significant correlations between both hydrolysis and methanogenesis kinetic parameters (k and R-m) relative to the operational conditions and process parameters could be determined; however, k/R'(m) was observed to significantly correlate with these parameters. Specifically, substrate load (both SC and S/I) positively influenced k/R'(m) via its impact on volatile fatty acid (VFA) and pH, while BC reduced k/R'(m) by increasing the alkalinity of the system. Moreover, k/R'(m) was negatively correlated with process efficiency. The methane recovery rate exceeded 90% when 1.55 4.64 (p = 0.05). These findings provide a scientific foundation for predicting the behavior of anaerobic systems and optimizing the digestion process. (C) 2017 Elsevier B.V. All rights reserved.

Foaming negatively affects anaerobic digestion of food waste (FW). To identify the causes of foaming, reactor performance and microbial community dynamics were investigated in three mesophilic digesters treating FW. The digesters were operated under different modes, and foaming was induced with several methods. Proliferation of specific bacteria and accumulation of surface active materials may be the main causes of foaming. Volatile fatty acids (VFAs) and total ammonia nitrogen (TAN) accumulated in these reactors before foaming, which may have contributed to foam formation by decreasing the surface tension of sludge and increasing foam stability. The relative abundance of acid-producing bacteria (Petrimonas, Fastidiosipila, etc.) and ammonia producers (Proteiniphilum, Gelria, Aminobacterium, etc.) significantly increased after foaming, which explained the rapid accumulation of VFAs and NH4 + after foaming. In addition, the proportions of microbial genera known to contribute to foam formation and stabilization significantly increased in foaming samples, including bacteria containing mycolic acid in cell walls (Actinomyces, Corynebacterium, etc.) and those capable of producing biosurfactants (Corynebacterium, Lactobacillus, 060F05-B-SD-P93, etc.). These findings improve the understanding of foaming mechanisms in FW digesters and provide a theoretical basis for further research on effective suppression and early warning of foaming.

A serious foaming incident occurred in a mesophilic food waste digester. The effects of foaming on reactor efficiency parameters were investigated, including specific biogas production (SBP), specific methane production (SMP) and volatile solids (VS) removal rate. The possible causes of foaming were evaluated according to a series of stability parameters including volatile fatty acids (VFAs), the ratio of VFA to total alkalinity (VFA/TA) combined with the ammonia nitrogen concentration (TAN), as well as the bacterial community structure in pre- and post-foaming system. The SBP, SMP and VS removal rate during the stable stage were (0.950 ± 0.104) m3/kg VS, (0.574 ± 0.072) m3CH4/kg VS and (87.14 ± 2.76)%, respectively. However, those parameters decreased to (0.717 ± 0.100) m3/kg VS, (0.432 ± 0.070) m3CH4/kg VS and (84.24 ± 4.44)% with the appearance of the foaming incident, which indicated that the efficiency of the digester had been significantly influenced by the foaming incident. Prior to the foaming, there appeared to be a rapid accumulation of VFAs along with a reduction in the proportion of acetic acid in VFAs. The propionic acid, which is believed to play a major role in enhancing the foaming tendency, increased in its proportion in VFAs as well. The filamentous bacteriaLongilinea arvoryzae,Levilineaand the myxobacteriumCytophaga fermentans had stronger band intensities after foaming. Their filamentous structure or mucilage can be a significant contributor to the initiation of foaming to some extent. In conclusion, foaming may be caused by the combination of VFAs accumulation and the proliferation of specific bacteria.

To explore the relationship between process stability and microbial community in anaerobic digestion, organic loading rate (OLR) disturbances were introduced into an anaerobic digester treating food waste (FW) to induce different process stages. Physico-chemical analysis along with the 454-pyrosequencing microbial technique were performed to monitor the responses of state parameters as well as the dynamics of microbial community. Results showed that balanced community structure ensured the stable operation of the digester. Under steady-state conditions, the methane yield reached (0.50±0.01) LCH4/gVS and volatile solids (VS) removal rate reached (89.58±0.08) %. Under high OLR conditions, the relative abundance of acid-producing bacteria (phyla Tenericutes and Actinobacteria) increased dramatically, which induced the proliferation of syntrophic fatty acid degrading bacteria (class Clostridia), while the abundance and activity of syntrophic hydrogenotrophic methanogens decreased. The imbalance relationship between methanogens and syntrophic fatty acid degrading bacteria caused their inefficient syntrophy, eventually resulting in volatile fatty acid (VFA) accumulation and process deterioration. Moreover, the accumulated VFA and ammonia reduced the specific acetoclastic methanogenic activity (SAMA) and specific methanogenic activity (SMA) by 60.12% and 72.51%, respectively, which further deteriorated the digestion process. Although the digester afterwards recovered to its original operational conditions and process performance, the microbial community profile changed and achieved new steady-state conditions.

In recent years , the quantity of harmless treatment of domestic garbage in Chongqing city has been increasing at 9%annually , but the processing capacity is relatively lagging behind .Based on the analysis of the current situation of domestic garbage disposal in Chongqing , this paper discussed the main problems existed in the process , and proposed further improving and perfecting disposal measures.Firstly, further promote the amount of incineration disposal in order to increase the rate of resource treatment and utilization . Secondly, accelerate the reconstruction and extension of landfill to improve the treatment capacity of emergency .Thirdly, rebuild the leachate treatment facilities of landfill aiming at reducing secondary pollution .Fourthly, improve the collection and transportation systems , and expand the coverage of municipal domestic garbage disposal facilities .Lastly, promote the classification of domestic garbage to improve the level of reduction .