Kinetic Modelling and Characterization of Microbial Community Present in a Full-Scale UASB Reactor Treating Brewery Effluent

The performance of a full-scale upflow anaerobic sludge blanket (UASB) reactor treating brewery wastewater was investigated by microbial analysis and kinetic modelling. The microbial community present in the granular sludge was detected using fluorescent in situ hybridization (FISH) and further confirmed using polymerase chain reaction. A group of 16S rRNA based fluorescent probes and primers targeting Archaea and Eubacteria were selected for microbial analysis. FISH results indicated the presence and dominance of a significant amount of Eubacteria and diverse group of methanogenic Archaea belonging to the order Methanococcales, Methanobacteriales, and Methanomicrobiales within in the UASB reactor. The influent brewery wastewater had a relatively high amount of volatile fatty acids chemical oxygen demand (COD), 2005 mg/l and the final COD concentration of the reactor was 457 mg/l. The biogas analysis showed 60–69 % of methane, confirming the presence and activities of methanogens within the reactor. Biokinetics of the degradable organic substrate present in the brewery wastewater was further explored using Stover and Kincannon kinetic model, with the aim of predicting the final effluent quality. The maximum utilization rate constant U _max and the saturation constant (K _B) in the model were estimated as 18.51 and 13.64 g/l/day, respectively. The model showed an excellent fit between the predicted and the observed effluent COD concentrations. Applicability of this model to predict the effluent quality of the UASB reactor treating brewery wastewater was evident from the regression analysis (R ²?=?0.957) which could be used for optimizing the reactor performance.     

Novel membrane bioreactor: Able to cope with fluctuating loads, poorly water soluble VOCs, and biomass accumulation

We determined the effect of different mixing intensities on the performance, methanogenic population dynamics, and juxtaposition of syntrophic microbes in anaerobic digesters treating cow manure from a dairy farm. Computer automated radioactive particle tracking in conjunction with computational fluid dynamics was performed to quantify the shear levels locally. Four continuously stirred anaerobic digesters were operated at different mixing intensities of 1,500, 500, 250, and 50 revolutions per min (RPM) over a 260-day period at a temperature of 34 +/- 1 degrees C. Animal manure at a volatile solids (VS) concentration of 50 g/L was fed into the digesters daily at five different organic loading rates between 0.6 and 3.5 g VS/L day. The different mixing intensities had no effect on the biogas production rates and yields at steady-state conditions. A methane yield of 0.241 +/- 0.007 L CH(4)/g VS fed was obtained by pooling the data of all four digesters during steady-state periods. However, digester performance was affected negatively by mixing intensity during startup of the digesters, with lower biogas production rates and higher volatile fatty acids concentrations observed for the 1,500-RPM digester. Despite similar methane production yields and rates, the acetoclastic methanogenic populations were different for the high- and low-intensity mixed digesters with Methanosarcina spp. and Methanosaeta concilii as the predominant methanogens, respectively. For all four digesters, epifluorescence microscopy revealed decreasing microbial floc sizes beginning at week 4 and continuing through week 26 after which no microbial flocs remained. This decrease in size, and subsequent loss of microbial flocs did not, however, produce any long-term upsets in digester performance.     

Anaerobic digestion and co-digestion processes of vegetable and fruit residues: process and microbial ecology

This study evaluated the feasibility of methane production from fruit and vegetable waste (FVW) obtained from the central food distribution market in Mexico City using an anaerobic digestion (AD) process. Batch systems showed that pH control and nitrogen addition had significant effects on biogas production, methane yield, and volatile solids (VS) removal from the FVW (0.42 m(biogas)(3)/kg VS, 50%, and 80%, respectively). Co-digestion of the FVW with meat residues (MR) enhanced the process performance and was also evaluated in a 30 L AD system. When the system reached stable operation, its methane yield was 0.25 (m(3)/kg TS), and the removal of the organic matter measured as the total chemical demand (tCOD) was 65%. The microbial population (general Bacteria and Archaea) in the 30 L system was also determined and characterized and was closely correlated with its potential function in the AD system.     

Characterization of the methanogenic Archaea within two-phase biogas reactor systems operated with plant biomass

The two-phase leach-bed system is a biogas reactor system optimized for the utilization of energy crop silages at maximized loading rates under maintenance of an optimal microbial activity. In this study, a characterization of the methanogenic microbial community within this reactor system was conducted for the first time. Accordingly, effluent samples from the anaerobic filter and the silage digesting leach-bed reactors of both a laboratory-scale two-phase biogas reactor system and a scaled-up commercial on-farm pilot plant were investigated. In total, five Archaea-specific 16S rDNA libraries were constructed and analyzed by amplified rDNA restriction analysis (ARDRA), with subsequent phylogenetic analysis of nucleotide sequences for individual ARDRA patterns. A quantification of major methanogenic Archaea groups was conducted by real-time PCR. A total of 663 clones were analyzed and 45 operational taxonomic units (OTUs) related to methanogenic Archaea were detected. These OTUs were related to the orders Methanosarcinales, Methanomicrobiales and Methanobacteriales, as well as the hitherto uncultured CA-11 and ARC-I groups, and most of them occurred throughout all the compartments of both two-phase biogas reactors. The proportion of acetotrophic to hydrogenotrophic methanogens differed between the laboratory and the pilot scale system. A total of 56% of the clones from the 16S rDNA library derived from the laboratory biogas system were assigned to presumably acetotrophic members of Methanosarcinales. In contrast, these OTUs were less abundant in the 16S rDNA library derived from samples of the pilot plant. Therein, the most dominant OTUs were Methanoculleus-related OTUs, which presumably indicated the predominant presence of hydrogenotrophic methanogens. These findings were confirmed by group-specific quantitative real-time PCR assays. The results indicated that the fraction of acetotrophic and hydrogenotrophic methanogens within a biogas reactor caused certain variations, which may reflect varying substrate utilization during methanogenesis.     

Modeling effects of granules on the start-up of anaerobic digestion of dairy wastewater with Langmuir and extended Freundlich equations

The effects of granules-inocula on the start-up of anaerobic reactors treating dairy manure were studied in a batch-fed reactor. The effects of start-up period and ratio of granules to feed were analyzed. Results indicated that the effects of start-up period could be described by Langmuir model, while the Extended Freundlich model could be used to model the effects of ratio of granules to feed on cumulative biogas production. In addition, transmission electron microscopes (TEM) and scanning electron microscope analysis were conducted to elucidate the distribution of microbial population and micro-colonies in granules and manure. From the TEM micrographs analyses, the ratios the Syntrophobacter and methanogens in granule and manure were shown to be 1.57 ± 0.42 and 0.22 ± 0.20, respectively. These results demonstrated that granules-inocula could reduce the period required for onset of biogas by 25%.     

Microbial community in granules from a high-rate EGSB reactor

The spatial distribution, quantity and diversity of different microorganisms within anaerobic granular sludge from a lab-scale expanded granular sludge bed (EGSB) reactor operated at different organic loading rates were studied using florescent in situ hybridization (FISH), real time quantitative — polymerase chain reaction (RTQ-PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The results indicated that most Eubacteria were located in the outer layer of granule, while the Archaea which mainly were methanogens and more sensible to the environmental conditions were located in the inner layer of the granule. The quantity of Archaea was obviously less than that of Eubacteria in the granules, but increased with the increasing of organic loading rates of the reactor. As the organic loading rate of the reactor increased and the operating time elapsed, the Archaea community in the granules changed significantly. Seven typical DGGE bands were collected and sequenced, and found that the dominant species of Archaea in the granules operated in the last period were mainly Methanocorpusculum, Methanobacterium, Methanosaeta.     

Molecular Monitoring of Microbial Population Dynamics During Operational Periods of Anaerobic Hybrid Reactor Treating Cassava Starch Wastewater

This study characterized the microbial community and population dynamics in an anaerobic hybrid reactor (AHR) treating cassava starch wastewater. Methanogens and nonmethanogens were followed during the start-up and operation of the reactor, and linked to operational and performance data. Biomass samples taken from the sludge bed and packed bed zones of the AHR at intervals throughout the operational period were examined by 16S rRNA fluorescence in situ hybridization (FISH). The start-up seed and the reactor biomass were sampled during the feeding of the wastewater with a chemical oxygen demand (COD) value of 8 g L⁻¹ and a hydraulic retention time (HRT) of 8 days. These samples were characterized by the predominance of cells with long-rod morphology similar to Methanosaeta spp. Following a sharp operational change, accomplished by increasing the COD concentration of the organic influent from 8 to 10 g L⁻¹ and reducing the HRT from 8 to 5 days, there was a doubling of the organic loading rate, a reduction of the COD removal efficiency, as well as decreased methane content in the biogas and an accumulation of total volatile acids in the reactor. Moreover, this operational change resulted in a significant population shift from long-rod Methanosaeta-like cells to tetrad-forming Methanosarcina-like cells. The distributions of microbial populations involved in different zones of the AHR were determined. The results showed that nonmethanogens became the predominant population in both sludge and the packed bed zone. However, the percentage of methanogens in the packed bed zone was higher than that in the sludge bed zone. This higher percentage of methanogens was likely caused by the fact that the packed bed zone provided a suitable environmental condition with an appropriate nutrient availability for methanogen growth.     

Methanogenic population dynamics during start-up of anaerobic digesters treating municipal solid waste and biosolids

An aggressive start-up strategy was used to initiate codigestion in two anaerobic, continuously mixed bench-top reactors at mesophilic (37 degrees C) and thermophilic (55 degrees C) conditions. The digesters were inoculated with mesophilic anaerobic sewage sludge and cattle manure and were fed a mixture of simulated municipal solid waste and biosolids in proportions that reflect U.S. production rates. The design organic loading rate was 3.1 kg volatile solids/m3/day and the retention time was 20 days. Ribosomal RNA-targeted oligonucleotide probes were used to determine the methanogenic community structure in the inocula and the digesters. Chemical analyses were performed to evaluate digester performance. The aggressive start-up strategy was successful for the thermophilic reactor, despite the use of a mesophilic inoculum. After a short start-up period (20 days), stable performance was observed with high gas production rates (1.52 m3/m3/day), high levels of methane in the biogas (59%), and substantial volatile solids (54%) and cellulose (58%) removals. In contrast, the mesophilic digester did not respond favorably to the start-up method. The concentrations of volatile fatty acids increased dramatically and pH control was difficult. After several weeks of operation, the mesophilic digester became more stable, but propionate levels remained very high. Methanogenic population dynamics correlated well with performance measures. Large fluctuations were observed in methanogenic population levels during the start-up period as volatile fatty acids accumulated and were subsequently consumed. Methanosaeta species were the most abundant methanogens in the inoculum, but their levels decreased rapidly as acetate built up. The increase in acetate levels was paralleled by an increase in Methanosarcina species abundance (up to 11.6 and 4.8% of total ribosomal RNA consisted of Methanosarcina species ribosomal RNA in mesophilic and thermophilic digesters, respectively). Methanobacteriaceae were the most abundant hydrogenotrophic methanogens in both digesters, but their levels were higher in the thermophilic digester.     

Influence of environmental conditions on methanogenic compositions in anaerobic biogas reactors

The influence of environmental parameters on the diversity of methanogenic communities in 15 full-scale biogas plants operating under different conditions with either manure or sludge as feedstock was studied. Fluorescence in situ hybridization was used to identify dominant methanogenic members of the Archaea in the reactor samples; enriched and pure cultures were used to support the in situ identification. Dominance could be identified by a positive response by more than 90% of the total members of the Archaea to a specific group- or order-level probe. There was a clear dichotomy between the manure digesters and the sludge digesters. The manure digesters contained high levels of ammonia and of volatile fatty acids (VFA) and were dominated by members of the Methanosarcinaceae, while the sludge digesters contained low levels of ammonia and of VFA and were dominated by members of the Methanosaetaceae. The methanogenic diversity was greater in reactors operating under mesophilic temperatures. The impact of the original inoculum used for the reactor start-up was also investigated by assessment of the present population in the reactor. The inoculum population appeared to have no influence on the eventual population.     

Microbial population dynamics during start-up and overload conditions of anaerobic digesters treating municipal solid waste and sewage sludge

Microbial population dynamics were investigated during start-up and during periods of overload conditions in anaerobic co-digesters treating municipal solid waste and sewage sludge. Changes in community structure were monitored using ribosomal RNA-based oligonucleotide probe hybridization to measure the abundance of syntrophic propionate-oxidizing bacteria (SPOB), saturated fatty acid-beta-oxidizing syntrophs (SFAS), and methanogens. These changes were linked to traditional performance parameters such as biogas production and volatile fatty acid (VFA) concentrations. Digesters with high levels of Archaea started up successfully. Methanosaeta concilii was the dominant aceticlastic methanogen in these systems. In contrast, digesters that experienced a difficult start-up period had lower levels of Archaea with proportionally more abundant Methanosarcina spp. Syntrophic propionate-oxidizing bacteria and saturated fatty acid-beta-oxidizing syntrophs were present at low levels in all digesters, and SPOB appeared to play a role in stabilizing propionate levels during start-up of one digester. Digesters with a history of poor performance tolerated a severe organic overload event better than digesters that had previously performed well. It is hypothesized that higher levels of SPOB and SFAS and their methanogenic partners in previously unstable digesters are responsible for this behavior.     

Competition and Coexistence of Sulfate-Reducing and Methanogenic Populations in Anaerobic Biofilms

The microbial population structure and function of natural anaerobic communities maintained in laboratory fixed-bed biofilm reactors were tracked before and after a major perturbation, which involved the addition of sulfate to the influent of a reactor that had previously been fed only glucose (methanogenic), while sulfate was withheld from a reactor that had been fed both glucose and sulfate (sulfidogenic). The population structure, determined by using phylogenetically based oligonucleotide probes for methanogens and sulfate-reducing bacteria, was linked to the functional performance of the biofilm reactors. Before the perturbation, the methanogenic reactor contained up to 25% methanogens as well as 15% sulfate-reducing bacteria, even though sulfate was not present in the influent of this reactor. Methanobacteriales and Desulfovibrio spp. were the most abundant methanogens and sulfate-reducing bacteria, respectively. The presence of sulfate-reducing bacteria (primarily Desulfovibrio spp. and Desulfobacterium spp.) in the absence of sulfate may be explained by their ability to function as proton-reducing acetogens and/or fermenters. Sulfate reduction began immediately following the addition of sulfate consistent with the presence of significant levels of sulfate-reducing bacteria in the methanogenic reactor, and levels of sulfate-reducing bacteria increased to a new steady-state level of 30 to 40%; coincidentally, effluent acetate concentrations decreased. Notably, some sulfate-reducing bacteria (Desulfococcus/Desulfosarcina/Desulfobotulus group) were more competitive without sulfate. Methane production decreased immediately following the addition of sulfate; this was later followed by a decrease in the relative concentration of methanogens, which reached a new steady-state level of approximately 8%. The changeover to sulfate-free medium in the sulfidogenic reactor did not cause a rapid shift to methanogenesis. Methane production and a substantial increase in the levels of methanogens were observed only after approximately 50 days following the perturbation.     

Thermophilic anaerobic digestion of source-sorted organic fraction of municipal solid waste

The influence of different organic fraction of municipal solid wastes during anaerobic thermophilic (55 degrees C) treatment of organic matter was studied in this work: food waste (FW), organic fraction of municipal solid waste (OFMSW) and shredded OFMSW (SH_OFMSW). All digester operated at dry conditions (20% total solids content) and were inoculated with 30% (in volume) of mesophilic digested sludge. Experimental results showed important different behaviours patterns in these wastes related with the organic matter biodegradation and biogas and methane production. The FW reactor showed the smallest waste biodegradation (32.4% VS removal) with high methane production (0.18 LCH4/gVS); in contrast the SH_OFMSW showed higher waste biodegradation (73.7% VS removal) with small methane production (0.05 LCH4/g VS). Finally, OFMSW showed the highest VS removal (79.5%) and the methane yield reached 0.08 LCH4/g VS. Therefore, the nature of organic substrate has an important influence on the biodegradation process and methane yield. Pre-treatment of waste is not necessary for OFMSW.     

Potential of biogas recirculation to enhance biomass accumulation on supporting media

Two lab-scale anaerobic hybrid reactors (AHR) were operated to investigate the effect of recirculated biogas on the development of biomass on supporting media during the start-up. The reactor comprised of two distinct zones; sludge bed on the bottom and packed bed using nylon fiber as the media on the upper half of the reactor. Both reactors were continuously fed with cassava starch wastewater. The organic loading rate (OLR) was increased from 0.3 to 5.5 g COD/L/day by gradually decreasing the hydraulic retention time (HRT) from 37 to 3.5 days in two months. The biogas at 2.6 L/L/day was recirculated merely in the first month of the operation in order to allow the attached biomass to grow according to the organic matters present in the reactor at the final stage of the start up. Chemical oxygen demand (COD) removal efficiency of over 80% was achieved throughout the study. The result demonstrated a better COD removal efficiency for the reactor with biogas recirculation, especially at low HRTs. The amounts of biomass accumulated on the media in both reactors were slightly different with 11.9 gVSS found on the one with biogas recirculation compared to 9.8 gVSS on the other. In addition, 16.3% increase of the sludge bed was achieved with biogas recirculation as opposed to 9% in the control one. The attached biomass activity test indicated a greater amount and more favorable ratio of the methanogenic bacterial group on the media with the recirculation correlating well to a relatively higher methane content in biogas. As a result, the recirculation of biogas has a potential of improving the characteristics of the AHR especially in terms of biomass accumulation.     

Research on soybean protein wastewater treatment by the integrated two-phase anaerobic reactor

The start-up tests of treating soybean protein wastewater by the integrated two-phase anaerobic reactor were studied. The results showed that the soybean protein wastewater could be successfully processed around 30 days when running under the situation of dosing seed sludge with the influent of approximately 2000 mg/L and an HRT of 40 h. When the start-up was finished, the removal rate of COD by the reactor was about 80%. In the zone I, biogas mainly revealed carbon dioxide (CO₂) and hydrogen (H₂). Methane was the main component in the zone 2 which ranged from 53% to 59% with an average of 55%. The methane content in biogas increased from the zone I to II. It indicated that the methane-producing capacity of the anaerobic sludge increased. It was found that the uniquely designed two-phase integrated anaerobic reactor played a key role in treating soybean protein wastewater. The acidogenic fermentation bacteria dominated in the zone I, while methanogen became dominant in the zone II. It realized the relatively effective separation of hydrolysis acidification and methanogenesis process in the reactor, which was benefit to promote a more reasonable space distribution of the microbial communities in the reactor. There were some differences between the activities of the sludge in the two reaction zones of the integrated two-phase anaerobic reactor. The activity of protease was higher in the reaction zone I. And the coenzyme F₄₂₀ in the reaction zone II was twice than that in the reaction zone I, which indicated that the activity of the methanogens was stronger in the reaction zone II.     

Anaerobic Digestion of Dairy Manure in a Hybrid Reactor with Biogas Recirculation

Summary A novel anaerobic hybrid reactor (AHR) configuration incorporating floating support media for biomass immobilization and biogas recirculation for enhanced mixing was used for anaerobic digestion of dairy manure. No pretreatment or solid liquid separation was applied. The reactor was operated at high influent volatile solids (VS) and organic loading rates (OLR) of up to 9.87% and 7.30 g VS/l day, respectively. After 149 days of continuous operation the results revealed that a high amount (38.1 g VSS) of biomass was able to attach itself to the support medium being used. The investigated AHR configuration achieved COD, BOD, TS, and VS removal efficiencies of 48–63, 64–78, 55–65, and 59–68%, respectively, at a hydraulic retention time (HRT) of 15 days. The corresponding average methane production value obtained in this study was 0.191 l/g VS added.     

Changes in microbial ecology in an anaerobic reactor

This study examined the behaviour of the microbial population in an anaerobic reactor, in terms of changes in numbers of total bacterial community, autofluorescent methanogens, non-methanogens and morphology of the autofluorescent methanogens, using epifluorescence microscopy and microbiological enumeration techniques. A laboratory-scale, continuous flow-completely mixed anaerobic reactor, coupled with a conventional gravity settling tank and a continuous recycling system, was operated at an HRT range between 24 and 12 h, using dairy wastewater as the substrate. The numbers of the total bacterial community and autofluorescent methanogens both decreased during start-up. Also, the proportion of the number of autofluorescent methanogens in the total bacterial community varied from 5% to 16% during operation. In particular, the activity of the methane-forming bacteria decreased significantly at HRTs of 16 and 12 h. A membrane module, instead of a conventional settling tank, would obviously have been a more effective method if recycling were required in the anaerobic treatment system.     

Effect of medium composition and sludge removal on the production, composition, and architecture of thermophilic (55 degrees C) acetate-utilizing granules from an upflow anaerobic sludge blanket reactor.

A thermophilic upflow anaerobic sludge blanket (UASB) reactor degrading acetate was started by applying published methods (W. M. Wiegant and A. W. A. de Man, Biotechnol. Bioeng. 28:718-77, 1986) for production of granules dominated by Methanothrix spp. The reactor was inoculated with thermophilic digested sludge. No granules were observed during the first 7 months of start-up of the UASB reactor. However, after the concentrations of potassium, phosphate, ammonium, and magnesium in the medium were gradually increased, granules developed, indicating that there was a critical concentration of one or more of the ions required for production of granules from the starting material. After several years of stable operation, the effect of removing 60% of the granular sludge was investigated. Immunologic qualitative and quantitative studies showed that removal of the granular sludge resulted in an increase in the number of the predominant methanogens, antigenically related to Methanosarcina thermophila TM-1 and Methanosarcina mazeii S-6, and Methanobacterium thermoautotrophicum delta H and GC1. These changes were accompanied by modifications of the microanatomy of the granules, as demonstrated histochemically and immunohistochemically. The results indicated that different catabolic pathways dominated in different regions of the granules, i.e., acetate oxidation in the middle of the granules, where there is a low acetate concentration, and an aceticlastic reaction in the outer surfaces, with a high acetate concentration. The results also showed that removal of granules from a UASB reactor which has been under steady-state operation for a long period can improve the reactor's performance via formation of denser and larger granules with improved microbial activities.     

Archaea diversity within a commercial biogas plant utilizing herbal biomass determined by 16S rDNA and mcrA analysis

Aims: The Archaea diversity was evaluated in an agricultural biogas plant supplied with cattle liquid manure and maize silage under mesophilic conditions. Methods and Results: Two different genes (16S rRNA; methyl‐coenzyme‐M‐reductase, MCR) targeted by three different PCR primer sets were selected and used for the construction of three clone libraries comprising between 104 and 118 clones. The clone libraries were analysed by restriction fragment polymorphism (RFLP). Between 11 and 31 operational taxonomic units (OTUs) were detected and assigned to orders Methanomicrobiales, Methanosarcinales and Methanobacteriales. Over 70% of all Archaea OTUs belong to the order Methanomicrobiales which mostly include hydrogenotrophic methanogens. Acetotrophic methanogens were detected in minor rates. Similar relative values were obtained by a quantitative real‐time PCR analysis. Conclusions: The results implied that in this biogas plant the most of the methane formation resulted from the conversion of H₂ and CO₂. Significance and Impact of the Study: This study reports, for the first time, a molecular analysis of the archaeal community in this type of agricultural biogas plants. Therein the hydrogenotrophic methanogenesis seems to be the major pathway of methane formation. These results are in contrast with the common thesis that in biogas fermentations the primary substrate for methanogenesis is acetate.     

Development of mixed inoculum for methane enriched biogas production

Inocula were collected from four different sources such as Jajmau tannery waste treatment plant (ITW), Jajmau municipal waste treatment (IMW), Unnao distillery (IDW) and a batch reactor, in which the sludge of a field scale biogas reactor was added to cow dung slurry to develop inoculum (IBS). A combination of these mixed inocula were used for biogas production at 35°C in laboratory scale reactor (10 L capacity) and the average yield of biogas (0.547 Lg^?1 volatile solid (VS)) and methane (0.323 Lg^?1VS) in 41 d was higher in case of mixed inoculum IMW ₁ (IMW+IBS), with maximum methane content in biogas (68% during 27–30 d), as compared to other mixed inocula as well as control i.e. ITW ₁ (ITW+IBS), IDW₁ (IDW+IBS) and IBS. The corresponding yields of gas were biogas (0.505, 0.536 and 0.456 Lg^?1VS), methane (0.288, 0.305, and 0.245 Lg^?1VS) where as, the corresponding maximum methane content in biogas was 62% during 29–33d, 64% during 29–33 d and 62% during 27–29 d in ITW₁, IDW₁ and IBS.     

对硝基苯酚冲击对UASB反应器中污泥活性和微生物种群的影响

研究了在稳定运行的上流式厌氧污泥床(Upflow Anaerobic Sludge Blanket,UASB)反应器中,对硝基苯酚(p-NP)冲击对反应器活性的影响。采用PCR-DGGE技术监测了反应器受对硝基苯酚冲击后微生物种群多样性的变化。实验结果表明,p-NP冲击对污泥的产甲烷活性和COD去除活性均有严重的抑制,污泥活性的恢复需要较长时间;高浓度冲击比低浓度冲击产生更严重的影响,20mg/L和40mg/Lp-NP冲击后污泥活性的恢复期分别为16d和27d。p-NP冲击后,真细菌和古菌的多样性均发生了显著的变化,而且p-NP冲击对真细菌的影响大于对古菌的影响。p-NP冲击后甲烷产量下降的主要与Methanosaetasp.的活性下降以及Methanomicrobia sp.丰度的下降有关。而冲击后真细菌的主要变化表现为Chloroflexisp.、Bacteroidesp.和Anaerovibrio sp.的丰度均下降;Rheinheimera sp.在受到20mg/Lp-NP冲击时丰度下降,继续受到40mg/Lp-NP冲击时该种群消失。Flavobacteria sp.是p-NP冲击后新出现的细菌种群,可能与p-NP的降解有关。