[Microbial Community Characteristics of Shortcut Nitrification Start-up in Different MBR-Inoculated Sludges].

In order to clarify the microbial community characteristics of the shortcut nitrification start-up with different inoculated sludges in the membrane bioreactor (MBR), the MBR was inoculated with nitrification sludge (R1), anaerobic nitrification sludge (R2) and 1:1 mixed inoculated anaerobic nitrification and denitrification sludge (R3). The results showed that the combination of intermittent aeration and shortened hydraulic retention time (HRT) successfully achieved the shortcut nitrification by R1, R2 and R3 reactors after 46 d, 8 d and 30 d respectively, with the R2 reactor exhibiting the shortest start-up period. During stable operations, the average nitrite accumulation rates of R1, R2 and R3 reactors were 92%, 93% and 94% respectively, and the R3 reactor showed a more stable shortcut nitrification. The results of analyses using ACE, Chao, Shannon, and Simpson diversity indices showed that the microbial abundance and diversity levels of R1 and R2 were significantly lower than that of the inoculant during the stable operation period, while the species abundance in the R3 reactor was slightly reduced and the diversity level was slightly changed. The main bacteria in the three reactors were Proteobacteria and Bacteroidetes after the successful start-up of shortcut nitrification, and the relative abundance of Proteobacteria was increased compared with the inoculated sludge. Proteobacteria were the main denitrifying bacteria, with ß-Proteobacteria being the dominant bacteria of the shortcut nitrification system in the three reactors, accounting for 59.6%, 63.6% and 69.3% respectively. Through further analysis, the next dominant bacteria in R1, R2 and R3 were all Nitrosomonas, with 12.8%, 20.2% and 19.7% respectively. Compared with the R1 reactor, there was a certain proportion of shortcut nitrification bacteria in the sludge of the R2 and R3 reactors, which was more favorable to the operation of the shortcut nitrification system.

[Start-up and Characteristics of the Microbial Community Structure of ANAMMOX].

An anaerobic ammonium oxidation (ANAMMOX) reactor was successfully started up in 17 days, with the up-flow anaerobic sludge blanket (UASB) reactor being seeded with mixed anaerobic sludge from laboratory cultures with an ANAMMOX function and aerobic activated sludge from a municipal sewage treatment plant in a volume ratio of 1:2. The processes could be divided into two phases of hydrolysis, enhanced and steady. Anaerobic ammonium oxidation bacteria (AAOB) were enriched by improving the reactor volume load gradually after the steady phase. When the volume load increased from 0.10 kg·(m3·d)-1 to 0.44 kg·(m3·d)-1, the removal of total nitrogen (TN) also increased from 0.09 kg·(m3·d)-1 to 0.42 kg·(m3·d)-1. The color of the sludge changed from a light red that deepened gradually in the UASB reactor. At that time, the proportion of the sludge particle size greater than 0.2 mm increased from 10.90% to 38.37%.The sludges from the inoculation phase and from the phase when the volume load was increasing were analyzed by high-throughput sequencing, indicating that Chloroflexi, Proteobacteria, WWE3, Actinobacteria, Planctomycetes, and so on were the dominant species. The proportion of Proteobacteriain the denitrification bacteria was gradually reduced from 21.60% to 14.20% with an increase in the degree of AAOB enrichment, while the Planctomycetes increased from 0.73% to 15.50%. Candidatus Brocadia, Candidatus Jettenia, and Candidatus Kuenenia were the main species of Planctomyceteswhen the volume load increased to 0.44 kg·(m3·d)-1 in the reactor, and the Candidatus Brocadia was the main species of AAOB, which accounted for 13.40%.

[Fast Start-up of Shortcut Nitrification in a CSTR and an MBR].

In order to achieve fast start-up of shortcut nitrification, a continuous stirred tank reactor (CSTR) and a membrane bioreactor (MBR) were selected for a comparative study about the start-up characteristic of shortcut nitrification. The differences in three aspects of the two reactors were investigated, namely start-up time, nitrogen transformation, and sludge performance. The results showed that the start-up of shortcut nitrification was successfully achieved in the CSTR and MBR after 44 and 56 days of operation, respectively, with influent C/N=1, temperature around 30℃±1℃, pH of 7.5-8.0, and dissolved oxygen (DO) of 0.6-1.0 mg·L-1, as well as combining anoxic/aerobic ratio 1:3 (15 min:45 min) with shortened hydraulic retention time (HRT). The start-up period of the MBR was shorter. On the 14th, 28th, and 56th day, the average nitrite accumulation efficiencies in the CSTR were 51%, 66%, and 89%, respectively, and 50%, 71%, and 93% in the MBR, and nitrate formation rates of the CSTR was successively 7.4, 4.0, and 1.7 mg·(g·h)-1 (NO3--N/MLVSS), respectively, and 7.6, 3.5, and 1.0 mg·(g·h)-1 (NO3--N/MLVSS) for the MBR. A higher nitrite accumulation efficiency and a lower nitrate formation rate were detected in the MBR on the 28th and 56th day, respectively, which could be beneficial to the fast start-up of shortcut nitrification. During the operation period, the shortcut nitrification sludge in the two reactors was yellow, the sludge volume index (SVI) was between 55 and 110 mL·g-1, and the mixed liquor volatile suspended solids (MLVSS)/mixed liquor suspended solids (MLSS) ratio was around 0.6-0.8. The good sludge performance created favorable conditions for the fast start-up of shortcut nitrification in both the CSTR and MBR. In conclusion, the MBR exhibited better performance in the fast start-up of shortcut nitrification.

[Quick Start-up and Sustaining of Shortcut Nitrification in Continuous Flow Reactor].

How to achieve fast and stable startup of shortcut nitrification has a very important practical value for treatment of low C/N ratio wastewater. Thus, the quick start-up and sustaining of shortcut nitrification were investigated in continuous flow reactor targeting at the current situation of urban wastewater treatment plant using a continuous flow process. The results showed that quick start-up of shortcut nitrification could be successfully achieved in a continuous flow reactor after 60 days' operation with intermittent aeration and controlling of three stages of stop/aeration time (15 min/45 min, 45 min/45 min and 30 min/30 min). The nitrification rates could reach 90% or 95% respectively, while influent ammonia concentrations were 50 or 100 mg · L⁻¹ with stop/aeration time of 30 min/30 min. In addition, intermittent aeration could inhibit the activity of nitrite oxidizing bacteria (NOB), while short hydraulic retention time (HRT) may wash out NOB. And a combined use of both measures was beneficial to sustain shortcut nitrification.

[Nitrogen Removal of Municipal Wastewater by ANAMMOX Coupled Shortcut Nitrification in Anaerobic Baffled Reactor].

If the technology of anaerobic ammonium oxidation(ANAMMOX) can substitute the mainstream technology of municipal wastewater treatment plant, the energy of municipal wastewater treatment will be decreased significantly. Thus, anaerobic baffled reactor(ABR) was used to build carbon system, shortcut nitrification system and anaerobic ammonia oxidation system. And the three systems were coupled to shortcut nitrification-anaerobic ammonia oxidation reactor to treat municipal wastewater. The results showed that the average effluent COD concentration of carbon removal system was 80 mg·L-1 when the hydraulic retention time of carbon removal system was 4.5 h. And the subsequent shortcut nitrification system would not be adversely affected by the effluent COD. Finally, the average effluent total nitrogen concentration was 10 mg·L-1, with total nitrogen volume load of ANAMMOX system of 0.36 kg·(m3·d)-1. When the dissolved oxygen was controlled between 1 to 2 mg·L-1, the nitrite accumulation rate could be maintained around 90%, ensuring the stable operation of the subsequent anaerobic ammonia oxidation system. The nitrogen of municipal wastewater could be stable and efficiently removed by the shortcut nitrification -ANAMMOX integration ABR with temperature of 30℃ and dissolved oxygen of 1-2 mg·L-1.

[Optimization of Energy Saving Measures with ABR-MBR Integrated Process].

High energy consumption and membrane fouling are important factors that limit the wide use of membrane bioreactor (MBR). In order to reduce energy consumption and delay the process of membrane fouling, the process of anaerobic baffled reactor (ABR)-MBR was used to treat domestic sewage. The structure of the process and conditions of nitrogen and phosphorus removal were optimized in this study. The results showed that energy consumption was reduced by 43% through optimizing the structure of ABR-MBR process. Meanwhile, the process achieved a high level of COD, NH: -N, TN and TP removal, with the average removal efficiencies of 91%, 85%, 76% and 86%, respectively. In addition, the added particulate media could effectively delay membrane fouling, while the formation process of membrane fouling was changed. The extracted amount of carbohydrates increased while the amount of proteins decreased. Finally, the potential was enhanced for the practical application of MBR.

[Formation Mechanism of Aerobic Granular Sludge and Removal Efficiencies in Integrated ABR-CSTR Reactor].

Anaerobic Baffled Reactor (ABR) was altered to make an integrated anaerobic-aerobic reactor. The research investigated the mechanism of aerobic sludge granulation, under the condition of continuous-flow. The last two compartments of the ABR were altered into aeration tank and sedimentation tank respectively with seeded sludge of anaerobic granular sludge in anaerobic zone and conventional activated sludge in aerobic zone. The HRT was gradually decreased in sedimentation tank from 2.0 h to 0.75 h and organic loading rate was increased from 1.5 kg x (M3 x d)(-1) to 2.0 kg x (M3 x d)(-1) while the C/N of 2 was controlled in aerobic zone. When the system operated for 110 days, the mature granular sludge in aerobic zone were characterized by compact structure, excellent sedimentation performance (average sedimentation rate was 20.8 m x h(-1)) and slight yellow color. The system performed well in nitrogen and phosphorus removal under the conditions of setting time of 0.75 h and organic loading rate of 2.0 kg (m3 x d)(-1) in aerobic zone, the removal efficiencies of COD, NH4+ -N, TP and TN were 90%, 80%, 65% and 45%, respectively. The results showed that the increasing selection pressure and the high organic loading rate were the main propulsions of the aerobic sludge granulation.

[Research on Cultivation and Stability of Nitritation Granular Sludge in Integrated ABR-CSTR Reactor].

Abstract: The last two compartments of the Anaerobic Baffled Readtor ( ABR) were altered into aeration tank and sedimentation tank respectively to get an integrated anaerobic-aerobic reactor, using anaerobic granular sludge in anaerobic zone and aerobic granular sludge in aerobic zone as seed sludge. The research explored the condition to cultivate nitritation granular sludge, under the condition of continuous flow. The C/N rate was decreased from 1 to 0.4 and the ammonia nitrogen volumetric loading rate was increased from 0.89 kg x ( m3 x d)(-1) to 2.23 kg x (m3 x d)(-1) while the setting time of 1 h was controlled in the aerobic zone. After the system was operated for 45 days, the mature nitritation granular sludge in aerobic zone showed a compact structure and yellow color while the nitrite accumulation rate was about 80% in the effluent. The associated inhibition of free ammonia (FA) and free nitrous acid (FNA) dominated the nitritation. Part of granules lost stability during the initial period of operation and flocs appeared in the aerobic zone. However, the flocs were transformed into newly generated small particles in the following reactor operation, demonstrating that organic carbon was benefit to granulation and the enrichment of slow-growing nitrifying played an important role in the stability of granules.

[Effects of temperature on combined process of ABR and MBR for domestic sewage treatment and analysis of microbial community].

Effects of temperature on the combined process of ABR and MBR ( CAMBR) for domestic sewage treatment were investigated and the changes in the bacterial community structure were analyzed by PCR-DGGE technique. The HRT, recycle ratio 1, recycle ratio 2, pH and DO were 7.5 h, 200% , 50%, 6.5~8.5 and 3 mg.L-1, respectively. The temperature were controlled at three gradients: middle (25°C ±5°C ), low (10°C±5°C) and high (35°C±5°C ). The results showed that the change of temperature had little influence on COD removal, and the CAMBR in stable state showed good performance in COD removal. In addition, the CAMBR achieved good effluent quality in middle or high temperature environment, and the average TN removal efficiency was 70% with an effluent TN of 9 mg L-1, and the average TP removal efficiency was 73% with the effluent TP below 0. 8 mg L-1. For the process operated in low temperature environment, the average TN removal efficiency was only 57% with an effluent TN of 15 mg L-1, and the average TP removal efficiency was decreased to 67% with an effluent TP of 1 mg.L-1. DGGE analysis indicated that throughout the process, the microbial population within the system maintained its diversity in distribution, while the dominant flora was prominent. During the same period, microbial populations in each compartment were similar. However, the structure of microbial community had significant differences between the ABR and the MBR due to the change of microenvironment in each compartment. Thus, the contributions of the ABR and the MBR were intensified, guaranteeing the efficiency of nitrogen and phosphorus removal in the system.

Experimental Tibetan monkey domestication and its application for intraocular pressure measurement.

AIM: To train Tibetan monkey (Macaca thibetana) for intraocular pressure (IOP) measurement in conscious state and obtain normal IOP in conscious Tibetan Macaque. METHODS: The training was based on award-conditioned behavior. Food stimulation and human-animal interaction were used in this training. RESULTS: Trained Tibetan monkeys calmly accepted IOP measurement by the TonoVet® rebound tonometer without sedation or anesthesia and their IOP values were similar to other primates. CONCLUSION: Human-cultivated Thibetan monkeys are tamable, and can be used for biomedical research such as ophthalmic research without anesthesia.