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As an intermediate form of microbial denitrification, nitrite serves as a key substrate for anaerobic ammonium oxidation (ANAMMOX). This study investigated the partial dentification (PD) characteristics and the coupling feasibility of PD+ANAMMOX in the biofilm system, using a moving bed biofilm reactor which was operated for 120 days. After 40 days of operation with a C/N ratio of 3.0 and filling fraction of 20%, the nitrate-to-nitrite transformation ratio (NTR) reached (69.38±3.53)%, and enzymatic assays indicated that the activities of nitrate reductase (NAR) had increased from 0.03 to 0.45 μmol·(min·mg)

The specific ammonia uptake rates (SAUR) and ammonia oxidizing bacteria (AOB) community of influent sewage and activated sludge in the 2

The long-term effects of a decreasing temperature on the nitrification performance, biofilm characteristics, and nitrifier community in a moving-bed biofilm reactor (MBBR) and integrated fixed-film activated sludge (IFAS) system were investigated at various temperatures (20, 15, and 10℃) to explore the adaptability of nitrifying biofilm systems to low temperatures. During the experiment, the extracellular polymeric substances (EPS) in the biofilms increased with decreasing temperature, which resulted in an increased biofilm mass and thickness. As there was only a biofilm phase in the MBBR to remove ammonia, the part of the carriers in the MBBR at 10℃ became plugged, which partially led to a deterioration in the effluent water quality. This indicated that the IFAS system was more adaptable to low temperatures than was the MBBR. Meanwhile, the results for the nitrifier activities showed that, although the nitrification contribution rate of the suspended phase in the IFAS system always dominated during the experiment, that of the fixed phase with regards to the ammonia uptake rate (AUR) gradually increased from 30.72% at 20℃ to 39.85% at 10℃. This indicated that the biofilm played an enhanced role in nitrification in the IFAS system. Moreover, the qPCR results revealed that the nitrifier copies of the number of biofilms increased slightly with decreased temperature, and coincided with an increase in biomass, which partially compensated for the decreased nitrification activity. These findings provide a theoretical basis for the application of the biofilm systems to wastewater treatment.

In recent years, the integrated ultrafiltration (UF) membrane process has been widely used due to its high removal efficiency, slight membrane fouling, and small land use. However, a number of problems gradually occurred regarding the integrated UF process caused by the granular adsorbents used, such as powdered activated carbon, carbon nano-tube, nanoscale zerovalent iron, etc. Severe membrane surface damage was easily caused by these granular adsorbents after a long running time, and the cost of most adsorbents was very high. In this study, to effectively overcome these problems, cheap and loose aluminum hydrolyzed flocs were directly injected into the membrane tank in the presence of humic acid (HA), with the aim of investigating the removal efficiency of HA and the corresponding membrane behavior. The results showed that the removal efficiency of HA could be influenced by aeration mode, floc injection frequency, and floc dosage. Compared with intermittent aeration and one-time injection, a loose "protection membrane" layer was formed with continuous aeration and batch injections. Therefore, HA molecules were largely removed, leading to the dramatic alleviation of membrane fouling. The transmembrane pressure significantly increased to 74.8 kPa in the absence of flocs after running for 5 days, but that only increased by 6.3 kPa with continuous aeration and an injection frequency of once every 2 d (each addition consisted of 5.4 mmol·L

The communities and activity of nitrifiers collected from the raw sewage of the 2

A nitrifying sequencing batch reactor (SBR) and continuous stirred-tank reactor (CSTR) were operated at 15℃ under the same conditions to investigate the effect of two typical flow patterns (plug flow and complete mixing) on the efficiency of nitrification enhancement. The results show that, during bioaugmentation, the ammonia utilized rate(AUR)and nitrite utilized rate(NUR)in the SBR were 2.34 and 2.39 times of that before bioaugmentation, and after bioaugmentation ceased, the AUR and NUR slightly decreased to 2.01 and 1.78 times of that before bioaugmentation. Meanwhile, the AUR and NUR in the CSTR were 2.63 and 2.44 times that before bioaugmentation, and after bioaugmentation ceased, the AUR and NUR decreased to 1.48 and 1.31 times that before bioaugmentation. Fluorescence In-Situ Hybridization (FISH) results showed that during bioaugmentation, the ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) in the SBR were 2.67 and 2.71 times of that before bioaugmentation, and after bioaugmentation ceased, the AUR and NUR slightly decreased to 2.14 and 1.95 times that before bioaugmentation. Meanwhile, the AUR and NUR in the CSTR were 2.91 and 1.77 times of that before bioaugmentation, and after bioaugmentation ceased, the AUR and NUR decreased to 1.25 and 1.50 times of that before bioaugmentation. Therefore, the efficiency of nitrification enhancement was similar between the two types of flow patterns during bioaugmentation, but the seeded nitrifiers were much more vulnerable to wash out in the CSTR than that in the SBR due to r/K selectivity of the flow patterns.

The community of nitrifiers cultivated with reject water were investigated by fluorescent in situ hybridization (FISH) performed with 16S rRNA-targeted oligonucleotide probes, and the kinetic properties such as temperature correction factor tauN and the half saturation coefficient K(N) were also investigated. The results showed that the percentage of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) in the activated sludge was 15.7% +/- 3.7% and 12.9% +/- 3.2%, Nitrosomonas europaea-Nitrosococcus mobilis lineage were the dominant AOB, Nitrobacter spp. were the dominant NOB. The temperature correction factors of ammonium utilized rate (AUR) and nitrite utilized rate (NUR) were 1.092 and 1.061 respectively; the K(N) of AOB and NOB were (1.60 +/- 0.29) mg/L (NH4(+) -N), (2.78 +/- 0.30) mg/L (NO2(-) -N) respectively.

Sequencing batch reactor, treating simulated municipal wastewater for N removal and operated at near the minimum SRT (solids retention time) for nitrification (in reactor 2), was seeded daily with nitrifying biomass accumulated with reject water (in reactor 1) came from Xi' an Dengjiacun wastewater treatment plant. Comparison of the nitrification ability, the characteristics of the activated sludge before seeding and after seeding was made. The experiment result shows that, the maximum nitrification rate of the activated sludge in the reactor 1 reached 81.4 mg/(L x h). The effluent concentration of NH4+ -N of the reactor 2 decreased at a rate of 0.992 mg/(L x d) (R2 = 0.903), and the maximum nitrification rate increased 1.36 times. Once seeding was terminated, the effluent concentration of NH4+ -N increased at a rate of 1.956 mg/(L x d) (R2 = 0.999), and nitrification caused by seeding was not completely disappeared after seeding was stopped for 34 d. The amount and varieties of protozoa and the value of SVI in the reactor seeded with nitrifiers increased during the initial time of seeding, but were recovered when the reactor 2 reached stable state.