Abstract:Anaerobic ammonia oxidation (Anammox) is one of the important discoveries in the field of environmental microbiology, and it plays an indispensible role in the nitrogen removal from wastewaters and the biogeochemical nitrogen cycle. Through review research progress in anaerobic ammonia oxidation, an Anammox special issue is published so as to find problems, explore applications and outlook developments. The special issue consists of reviews and original papers, mainly involving in the following aspects: i) enrichment of Anaerobic ammonia oxidation bacteria (AnAOB); ii) community analysis of AnAOB; iii) preservation of granular AnAOB sludge; iv) effect of organic matter on Anammox; v) application of Anammox process, etc.

Abstract:Anaerobic ammonium oxidation (ANAMMOX), as its essential advantages of high efficiency and low cost, is a promising novel biological nitrogen elimination process with attractive application prospects. Over the past two decades, many processes based on the ANAMMOX reaction have been continuously studied and applied to practical engineering, with the perspective of reaching100 full-scale installations in operation worldwide by 2014. Our review summarizes various forms of ANAMMOX processes, including partial nitritation-ANAMMOX, completely autotrophic nitrogen removal over nitrite, oxygen limited autotrophic nitrification and denitrification, denitrifying ammonium oxidation, aerobic deammonification, simultaneous partial nitrification, ANAMMOX and denitrification, single-stage nitrogen removal using ANAMMOX and partial nitritation. We also compare the operating conditions for one-stage and two-stage processes and summarize the obstacles and countermeasures in engineering application of ANAMMOX systems, such as moving bed biofilm reactor, sequencing batch reactor and granular sludge reactor. Finally, we discuss the future research and application direction, which should focus on the optimization of operating conditions and applicability of the process to the actual wastewater, especially on automated control and the impact of special wastewater composition on process performance.

Abstract:Nitrogen removal techniques based on Anammox process are developing rapidly these years. The distribution and diversity of Anammox have become important research directions. A variety of Anammox have been detected till now, of which only Kuenenia and Brocadia are often detected in wastewater treatment systems. In addition, in a single niche there is only one type of Anammox bacteria. However, the distribution mechanism and transformation of Anammox bacteria in different niches are still ambiguous. Therefore, the distribution of Anammox in various conditions was summarized and analyzed in this article. And the key factors influencing the distribution of Anammox were concluded, including substrate concentration and the specific growth rate, sludge properties and microbial niche, the joint action and influence of multiple factors. The engineering significance research on the distribution and influencing factors of Anammox bacteria in the sewage system and proposed research prospects were expounded.

Abstract:We studied the effects of the oxygen on partial nitrification in a membrane bioreactor (MBR), to find out critical dissolved oxygen (DO) concentrations for the optimal partial nitrification by monitoring the oxygen uptake rate (OUR) and oxygen supply rate (OSR). The nitrite accumulation occurred at a DO concentration of 1 mg/L, while the ratio of nitrite to ammonia in effluent was close to 1 at a DO concentration of 0.5 mg/L which was suitable to serve as the feed of an ANNAMOX system. When the mixed liquid suspended?solids(MLSS) was 20 g/L in MBR, OUR and OSR were 19.86 mg O2/(L·s) and 0.369 mg O2/(L·s) respectively, indicating that the oxygen supply was the bottleneck of partial nitrification. “Low DO and high aeration rate” were suggested as a control strategy to further improve the efficiency of partial nitrification.

Abstract:In order to simultaneously remove carbon and nitrogen from organic-rich wastewater, we used an up-flow anaerobic sludge bed/blanket (UASB) reactor that was started up with anammox with high concentration of carbon and nitrogen by gradually raising the organic loading of influent. We optimized the removal of nitrogen and carbon when the chemical oxygen demand (COD) concentration varied from 172 to 620 mg/L. During the entire experiment, the ammonium and total nitrogen removal efficiency was higher than 85%, while the average COD removal efficiency was 56.6%. The high concentration of organic matter did not restrain the activity of anammox bacteria. Based on polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and tapping sequencing analyses, the Planctomycete, Proteobacteria, Chloroflexi, Chlorobi bacteria are detected in the UASB reactor, which indicated complex removal pathway of carbon and nitrogen coexisted in the reactor. However, a part of Planctomycete which referred to anammox bacteria could tolerate a high content of organic carbon, and it provided help for high performance of nitrogen removal in UASB reactor.

Abstract:An expanded-granular sludge bed (EGSB) reactor was set-up with artificial water by seeding a 60–d stored ANAMMOX sludge. The nitrogen removal efficiency of ANAMMOX enrichment culture in the reactor was determined. In addition, the main microbial populations and the relative abundance of ANAMMOX bacteria were investigated by molecular approaches. Results show that the maximum nitrogen removal rate was 3.0 kg-N·m-3·d-1 after 185 d, and the ammonium and nitrite removal efficiencies were all over 85%. Analysis of 16S rRNA gene-cloning indicates that the main microbial population in the ANAMMOX enrichment culture was changed from Candidatus Brocadia fulgid and Candidatus Brocadia brasiliensis (0 day) to Candidatus Jettenia asiatica (185 day). Fluorescence in situ hybridization analysis shows that the relative abundance of ANAMMOX bacteria was increased from (57.69±4.79)% to (83.32±4.40)%. The results of qPCR further indicate that the gene copies of ANAMMOX bacteria in the granules were increased from 1.14×1011copies/g wet weight to 3.69×1011copies/g wet weight.

Abstract:The anaerobic granular sludge from an Internal Circulation (IC) reactor of a paper mill wastewater treatment plant were seeded in an Anammox upflow anaerobic sludge blanket reactor. After 185 days operation, the reactor was finally started up by increasing the influent ammonium and nitrite concentrations to 224 mg/L and 255 mg/L, respectively, with volumetric nitrogen removal rate increasing to 3.76 kg/(m3·d). The physicochemical characteristics of the cultivated Anammox granules were observed by scanning electron microscope, transmission electron microscope and Fourier Transform infrared spectroscopy (FTIR). Results suggested that during the start-up course, the granular sludge initially disintegrated and then re-aggregated. FTIR spectra results revealed that the Anammox granular sludge contained abundant functional groups, indicating that it may also possess good adsorption properties. The ecological structure of the granular sludge, analyzed by the metagenomic sequencing methods, suggested that the relative abundance of the dominant bacterial community in the seeding sludge, i.e., Proteobacteria, Firmicutes, Bacteroidetes, significantly reduced, while Planctomycetes which contains anaerobic ammonium oxidation bacteria remarkably increased from 1.59% to 23.24% in the Anammox granules.

Abstract:An anaerobic sequencing batch reactor (ASBR) was used to treat thermal denitration tail liquid and microbial community was studied. Activated sludge was taken from the reactor for scanning electron microscope analysis. The images showed that the dominant cells in the flora were oval cocci. Its diameter was about 0.7 μm. Through a series of molecular biology methods such as extracting total DNA from the sludge, PCR amplification, positive clone authentication and sequencing, we obtained the 16S rDNA sequences of the flora. Phylogenetic tree and clone library were established. The universal bacteria primers of 27F-1492R PCR amplification system obtained 85 clones and could be divided into 21 OTUS. The proportions were as follows: Proteobacteria 61.18%; Acidobacteria 17.65%; Chlorobi 8.24%; Chlorofexi 5.88%; Gemmatimonadetes 3.53%; Nitrospirae 2.35% and Planctomycetes 1.18%. The specific anammox bacterial primers of pla46rc-630r and AMX368-AMX820 PCR amplification system obtained 45 clones. They were divided into 3 OTUS. Candidatus brocadia sp. occupied 95.6% and unknown strains occupied 4.4%.

Abstract:To study the effect of preservation temperature on the characteristics of anaerobic ammonium oxidation (Anammox) granules and optimize the preservation temperature of anammox granules, the anammox granules were cultivated in an upflow anaerobic sludge bed reactor through adjusting the hydraulic retention times, and the inorganic carbon with KHCO3/NaHCO3 was alternately supplied. Subsequently, the enriched anammox granules were preserved at -40, 4 and 35 °C, and ambient temperature of (27±4) °C. NaHCO3 can be used as the inorganic carbon for the growth of anaerobic ammonium oxidizing bacterium (AnAOB). The best preservation temperature was 4 °C for maintaining anammox biomass, anammox activity, settleability, and the integrity of the anammox granule and AnAOB cell structure. During the preservation period, the first-order exponential decay model can simulate the decay of anammox biomass and activity, and the decay coefficients (bAN) of anammox biomass and activity had positive correlation with the degree of AnAOB cell lysis. Meanwhile, the rate of anammox biomass decay was larger than that of anammox activity. The ratio of protein to polysaccharide in extracellular polymeric substances and heme c cannot effectively indicate the changes of anammox granules settleability and activity, respectively, and the bioactivity has a negative association with the degree of AnAOB cell lysis.

Abstract:In order to broaden the application area of the new nitrogen removal technology, A full-scale system for short-cut nitrification and anaerobic ammonium oxidation (Anammox) was investigated in the nitrogen removal from a strong-ammonium pharmaceutical wastewater. When the influent ammonium concentration was (430.40±55.43) mg/L, ammonia removal efficiency was (81.75±9.10) %. The results showed that the short-cut nitrification and Anammox system could successfully remove nitrogen from the pharmaceutical wastewater. The start-up of short-cut nitrification system took about 74 d and the nitrite accumulation efficiency was (52.11±9.13) %, the two-step mode using synthetic wastewater and actual wastewater was suitable for the start-up of short-cut nitrification system. The start-up of Anammox system took about 145 d and the maximum volumetric nitrogen removal rate was 6.35 kgN/(m3·d), which were dozens of times higher than those for the conventional nitrification–denitrification process. The strategy achieving Anammox sludge by self-growth and biocatalyst addition was suitable for the start-up of Anammox system.

Abstract:Homoacetogens are a group of microorganisms with application potential to produce chemicals and biofuels by the bioconversion of synthesis gas. In this study, we collected waste activated sludge samples to screen homoacetogens by Hungate anaerobic technique, and studied the effect of pH on acetate and alcohol production from H2/CO2 gas. The mixed culture contained Clostridium ljungdahlii, Lysinibacillus fusiformis and Bacillus cereus. Acetate concentration achieved 31.69 mmol/L when the initial pH was 7. The mixed culture containing homoacetogen could converting H2/CO2 to acetate, which provides an efficient microbial resource for the bioconversion of synthesis gas.

Abstract:Methanotrophs could degrade methane and various chlorinated hydrocarbons. The analysis on methane monooxygenase gene cluster sequence would help to understand its catalytic mechanism and enhance the application in pollutants biodegradation. The methanotrophs was enriched and isolated with methane as the sole carbon source in the nitrate mineral salt medium. Then, five chlorinated hydrocarbons were selected as cometabolic substrates to study the biodegradation. The phylogenetic tree of 16S rDNA using MEGE5.05 software was constructed to identify the methanotroph strain. The pmoCAB gene cluster encoding particulate methane monooxygenase (pMMO) was amplified by semi-nested PCR in segments. ExPASy was performed to analyze theoretical molecular weight of the three pMMO subunits. As a result, a strain of methanotroph was isolated. The phylogenetic analysis indicated that the strain belongs to a species of Methylocystis, and it was named as Methylocystis sp. JTC3. The degradation rate of trichloroethylene (TCE) reached 93.79% when its initial concentration was 15.64 μmol/L after 5 days. We obtained the pmoCAB gene cluster of 3 227 bp including pmoC gene of 771 bp, pmoA gene of 759 bp, pmoB gene of 1 260 bp and two noncoding sequences in the middle by semi-nested PCR, T-A cloning and sequencing. The theoretical molecular weight of their corresponding gamma, beta and alpha subunit were 29.1 kDa, 28.6 kDa and 45.6 kDa respectively analyzed using ExPASy tool. The pmoCAB gene cluster of JTC3 was highly identical with that of Methylocystis sp. strain M analyzed by Blast, and pmoA sequences is more conservative than pmoC and pmoB. Finally, Methylocystis sp. JTC3 could degrade TCE efficiently. And the detailed analysis of pmoCAB from Methylocystis sp. JTC3 laid a solid foundation to further study its active sites features and its selectivity to chlorinated hydrocarbon.