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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) -1 while the activities of nitrite reductase (NIR) had decreased from 0.18 to 0.02 μmol·(min·mg) -1 . Illumina high-throughput sequencing analysis revealed that the proportion of genus of Thauera bacteria to total microorganism increased from 0.3% (d1) to 37.27% (d64). Finally, the effluent had a total nitrogen (TN) concentration of (6.41±1.50) mg·L -1 , indicating a total nitrogen removal ratio of (88.16±2.71)% and confirming the feasibility of PD+ANAMMOX in the biofilm system.

A SMBBR was established to treat medium ammonium under room temperature. Results showed that TN load can reach 0.16 kg·(m 3 ·d) -1 , and the average TN removal efficiency was (51.58±6.80)% in the SMBBR with an influent ammonia concentration of 100 mg·L -1 and DO of 0.4-0.7 mg·L -1 . AOB, ANAMMOX, and NOB activity reached (2253.21±502.10) mg·(m 2 ·d) -1 , (4847.46±332.89) mg·(m 2 ·d) -1 , and (1455.17±473.83) mg·(m 2 ·d) -1 , and ANAMMOX and AOB bacteria were found to develop a good collaborative relationship. Quantitative PCR results showed that the relative abundance of ANAMMOX, AOB and NOB were 11.57%, 1.01% and 0.94%, respectively. The stable operation of single stage partial nitritation-ANAMMOX process provide an alternative technology for medium ammonia wastewater.

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.

To evaluate the influence of Fe/S ratio and pH on sulfide removal efficiency and interactions between Fe/S and pH, anaerobic hydrogen sulfide in situ depression tests and digested sludge liquor sulfide removal tests were carried out by using dewatering sludge from a wastewater treatment plant (WWTP). Results showed that the concentration of hydrogen sulfide in biogas from the thermal pretreatment following anaerobic digestion process could be reduced from 170.4×10 -6 to 14.09×10 -6 at Fe/S=7.75, which means the biogas desulfurization treatment is not required. Under the condition of pH 7.00-7.50 and Fe/S 1-11, pH is the main influencing factor for sulfide removal. Improving the pH of anaerobic digestion is beneficial in reducing the dosage of Fe(Ⅲ). An Fe/S ratio of 7.0 is the minimum to meet the biogas hydrogen sulfide emission standards during high solid sludge anaerobic digestion. The concentration of hydrogen sulfide was not up to standards if pH was below 7.30.

Nitrospira was enriched from activated sludge by using fed-batch cultivation, and its related kinetic characterization was studied. The results showed that Nitrospira could be successfully enriched from the activated sludge for a controlled nitrite concentration no higher than 2 mg·L -1 . The maximum nitrate oxidation rate was 48.72 mg·(g·h) -1 . The fluorescence for the in situ hybridization results showed that Nitrospira accounted for about 75% of the total biomass, while Nitrobacter accounted for only 0.1%. In addition, the kinetic parameters of Nitrospira at 20℃ were also investigated. The results showed that the optimum growth temperature for Nitrospira was 30-35℃. The temperature correction coefficient τ N was 1.046. The nitrite half-saturation constant K S and oxygen half-saturation constant K O were (0.32±0.03)mg·L -1 and (1.52±0.09)mg·L -1 , respectively. This study on the kinetic characterization of Nitrospira provided a theoretical foundation for the treatment plant design and process optimization.

An anaerobic sequencing batch reactor(ASBR) inoculated with activated sludge was employed to investigate the start-up of anaerobic ammonium oxidation(ANAMMOX) process and the spatial distribution of extracellular polymeric substances(EPS) in ANAMMOX granules. The results showed that the removal rates of NH 4 + -N and NO 2 - -N reached more than 99%. The removal rate of total nitrogen(TN) was 89.87%±0.43% and the TN removal load in the ASBR was 1.7 kg·(m 3 ·d) -1 . The ratios of nitrite consumption and nitrate production to ammonium consumption were 1.32±0.08 and 0.24±0.03, respectively. Besides, the pH and the effluent nitrate concentration in bulk liquid were considered as two simple indicators for rapid diagnosis of ANAMMOX performance. The proteins(PN) was the main component of EPS in ANAMMOX granular sludge. The PN and polysaccharides(PS) in ANAMMOX granules were (59.61±5.64) mg·g -1 and (12.21±2.04) mg·g -1 , respectively, with the ratio of PN/PS reaching approximately 4.88±1.39. β -D-glucofuranose and dead cells were distributed in the outermost layer of granules, while living cells, PN, lipids, α -glucosamine and α-mannose were distributed throughout the granules and mainly concentrated on the outside of granules. PN and lipids constituted the framework of ANAMMOX granules and ANAMMOX bacteria were embedded among the PN and lipids matrix.

To investigate the effect of temperature on the activity of high-temperature phosphate accumulating organisms (PAO HT ) and their competitive ability for the substrate, the sludge from an enhanced biological phosphorus removal (EBPR) reactor stably operated at the high temperature of 30℃ was used. The results showed that PAO HT activity and their competitive ability for the substrate increased with temperature increasing from 15℃ to 30℃. When the temperature was as higher as 30℃, the rates of anaerobic phosphorus release, aerobic phosphorus uptake and acetate uptake of PAO HT were 239.46 mg·(g·h) -1 , 79.90 mg·(g·h) -1 , 357.47 mg·(g·h) -1 , respectively. The corresponding value of ΔP/ΔHAc was 0.628, which was considerably higher than that of PAO reported in literatures. A simplified Arrhenius equation was used to describe the effect of temperature on the rates of anaerobic phosphorus release, aerobic phosphorus uptake and acetate uptake, and the temperature coefficients were 1.08, 1.07 and 1.05, respectively.

Two SBRs which were under high ammonia loading[1 kg·(m 3 ·d) -1 ] and different dual inhibition with feed-batch were employed to study how to control the stability of partial nitritation system. The experimental result showed that the dual inhibition of FNA and DO or FA and DO could implement partial nitrification process at 35℃±1℃ and the ammonia concentration of 1000 mg·L -1 . The effluent NO 2 - -N/NH 4 + -N ratio was about 1, and the effluent NO 3 - -N concentration was close to 0, which was suitable for the appropriate influent for the ANAMMOX. In R1, under the dual inhibition of high FA and low DO concentration, the nitrite oxidizing rate was reduced from 28.16 mg·(g·h) -1 to 0.3 mg·(g·h) -1 (calculated as NO 2 - -N, the same as below). The ammonia oxidizing rate decreased by 43.60%, which was stable at about 20 mg·(g·h) -1 (calculated as NH 4 + -N, the same as below). In R2,under the dual inhibition of high FNA and low DO concentration, the nitrite oxidizing rate reduced from 12.37 mg·(g·h) -1 to 0.02 mg·(g·h) -1 . But the ammonia oxidizing rate remained at a higher level[45 mg·(g·h) -1 ]. Comparing the nitrification performance of the two SBRs under different control strategies, the dual inhibition of high FNA and low DO concentration had the advantages of short cultivation period, high biological activity and stable operation. It is therefore more suitable for the achievement of the partial nitrification.

Methane (CH 4 ) and nitrous oxide (N 2 O) are two of the most important non-CO 2 greenhouse gases. And municipal sewage treatment plant is an important anthropogenic source of CH 4 and N 2 O. Therefore, it is essential to measure the production and emission of CH 4 and N 2 O during biological wastewater treatment process. The surface emission flux isolation chamber was employed to collect the gas sample from the Xi'an No.3 WWTP (the Orbal oxidation ditch process) and Xi'an NO.4 WWTP (A/A/O process) to determine the contents of methane and nitrous oxide. And the effects of temperature and dissolved oxygen concentration on non-CO 2 greenhouse gases emission from Xi'an NO.4 WWTP were discussed. The results showed that methane and nitrous oxide emission factors from No.3 WWTP were 1181 mg CH 4 per m 3 influent and 36.20 mg N 2 O per m 3 influent, respectively while those from the No.4 WWTP were 209 mg CH 4 per m 3 influent and 54.64 mg N 2 O per m 3 influent. In addition, the important influencing factors which affected methane and nitrous oxide emission were temperature, aeration strategy, DO, nitrite oxidation rate and specific methanogenic activity.

The communities and activity of nitrifiers collected from the raw sewage of the 2 nd and 3 rd wastewater treatment plants (WWTP) in Xi'an were investigated. FISH results indicated that the (AOB+NOB)/EUB percentages were (5.35±2.1)% and(6.0±2.8)% in the 2 nd and 3 rd WWTP, respectively. The dominant AOB was Nitrosomonas europaea/Nitrosococcus mobilis lineage and the dominant NOB was Nitrospira , the sub-dominant NOB was Nitrobacter , and coexisted with Nitrococcus, Nitrospina . Respirometric assays showed that the influent nitrifiers were active following a 2-16 hour period of metabolic induction. The ammonium utilized rate was (0.32±0.12) mg·(L·h) -1 and (0.43±0.17) mg·(L·h) -1 , nitrite utilized rate was (0.71±0.18) mg·(L·h) -1 and (0.58±0.27) mg·(L·h) -1 for nitrifers in raw sewage fed to the 2 nd and 3 rd WWTP, respectively. Therefore, nitrifiers were present and active in the raw sewage, and played the role of natural continuous seeding in the activated sludge system. Based on the nitrification activity, the estimated continuous seeding intensity of AOB and NOB was 0.08-0.09 g·(g·d) -1 and 0.11-0.24 g·(g·d) -1 , respectively.

The transformation characteristics of carbon, nitrogen, phosphorus and sulfur in dewatering sludge from municipal wastewater treatment plant (WWTP) were investigated after thermal hydrolysis pretreatment at 165 degress C for 50 min. The results showed that the hydrolysis efficiency of VSS could reach as high as 43.35%, 54.36% of protein and 65.12% of carbohydrate were transferred to dissolved organics, respectively, and the main component of dissolved organic matter in hydrolysate was dissolved protein (52.18% ), 54.23% of insoluble organic nitrogen was turned into dissolved nitrogen and 22.13% of dissolved nitrogen in hydrolysate was converted to ammonia. The transformation rate of insoluble phosphorus was 30.52%. Dissolved phosphorus was mostly transformed to phosphate (79.84%) as phosphorus-accumulating bacteria cells were crushed. 50.03% of insoluble organic sulfur was hydrolyzed, and little change was detected in sulfide (0.50%). The analysis results of the organic compounds transformation are valuable for treatment of the thermal hydrolysis pretreated sludge with high solid content.

Effects of carbon sources, temperature and electron acceptors on phosphorus uptake and release were investigated in a pilot-scale oxidation ditch. Phosphorus uptake and release rates were measured with different carbon sources (domestic sewage, sodium acetate, glucose) at 25 degrees C. The results showed that the minimum phosphorus uptake and release rates of glucose were 5.12 mg x (g x h)(-1) and 6.43 mg x (g x h)(-1), respectively, and those of domestic sewage are similar to those of sodium acetate. Phosphorus uptake and release rates increased with the increase of temperature (12, 16, 20 and 25 degrees C) using sodium acetate as carbon sources. Anoxic phosphorus uptake rate decreased with added COD. Electron acceptors (oxygen, nitrate, nitrite) had significant effects on phosphorus uptake rate and their order was in accordance with oxygen > nitrate > nitrite. The mass ratio of anoxic P uptake and N consumption (P(uptake)/N (consumption)) of nitrate and nitrite were 0.96 and 0.65, respectively.

The oxidation ditch operation mode was simulated by sequencing batch reactor (SBR) system with alternate stirring and aeration. The nitrogen and phosphorus removal efficiencies were investigated in two different aeration modes: point aeration and step aeration. Experimental results show that oxygen is dissolved more efficiently in point aeration mode with a longer aerobic region in the same air supply capacity, but dissolved oxygen (DO) utilization efficiency for nitrogen and phosphorus removal is high in step aeration mode. Nitrification abilities of the two modes are equal with ammonia-nitrogen (NH4(+) -N) removal efficiency of 96.68% and 97.03%, respectively. Nitrifier activities are 4.65 and 4.66 mg x (g x h)(-1) respectively. When the ratio of anoxic zones and the aerobic zones were 1, the total nitrogen (TN) removal efficiency of point aeration mode in 2, 4 or 7 partitions was respectively 60.14%, 47.93% and 33.7%. The total phosphorus (TP) removal efficiency was respectively 28.96%, 23.75% and 24.31%. The less the partitions, the higher the nitrogen and phosphorus removal efficiencies, but it is in more favor of TN removal. As for step aeration mode with only one partitioning zone, the TN and TP removal efficiencies are respectively 64.21% and 49.09%, which is better than in point aeration mode, but more conducive to the improvement of TP removal efficiency. Under the condition of sufficient nitrification in step aeration mode, the nitrogen and phosphorus removal is better with the increase of anoxic zone. The removal efficiencies of TN and TP respectively rose to 73.94% and 54.18% when the ratio of anoxic zones and the aerobic zones was increased from 1 : 1 to 1. 8 : 1. As the proportion of anoxic zones was enlarged further, nitrification and operation stability were weakened so as to affect the nitrogen and phosphorus removal efficiencies.

Phosphorous removal & denitrifying phosphate uptake of the granular sludge was investigated in this study. Inoculated with flocculation sludge, the granulation of the biological phosphorous removal sludge was realized in a sequencing batch reactor (SBR) fed with sodium acetate by means of hydraulic selection under an anaerobic/oxic alternating operation (referred to as an A/O). Then the biological phosphorous removal granular sludge was induced into the denitrifying phosphate uptake granular sludge under an anaerobic/anoxic/oxic alternating operation (referred to as an A/A/O). The properties of the two kinds of granular sludge were studied. The biological phosphorus removal granular sludge was completed on the 82nd day. The biological phosphorus removal granule sludge showed some characteristics, e.g. pallideflavens in color, 0.5-1.5 mm in diameter, 20-30 m/h in settling velocity, 94% in water content, 1.043 9 in specific gravity, and below 50 mL/g in SVI. The max. specific release phosphorus rate (SRPR), the max. specific uptake phosphorus rate (SUPR) and the phosphorus content of the MLSS (TP/SS) was 67.7 mg/(g x h), 43.2 mg/(g x h) and 6.5% respectively on the 437th day. On the 448th day the operation of the reactor was changed into A/A/O. The max. SRPR, the max. anoxic SUPR and the TP/SS of the denitrifying phosphate uptake granular sludge was 30 mg/(g x h), 27.9 mg/(g x h) and 6.3% respectively on the 653rd day. The two kinds of granular sludge had potential to carry out phosphorus removal.

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.

Substrate utilization in a glucose-fed anaerobic sequencing batch reactor (ASBR) under different F/M ratios was investigated. Glucose added was quickly taken up by fermentation bacterial in anaerobic digestion, then partly degraded directly to volatile fatty acid (VFA, accounted for 34%-38% of COD-fed) and partly accumulated transiently in the cell as glycogen (accounted for 41%-46% of COD-fed) and degraded to VFA in the following. The bacterial accumulation capacities increased with F/M. The maximum specific storage capacities could reach as high as 116.8, 81.1 and 62.4 mg/g as F/M (COD/VSS) was controlled in 0.27, 0.20 and 0.14 respectively. VFA production rate slowed down due to glucose storage, which resulted in low VFA accumulation and guaranteed a stable operation in ASBR under high loading rate.

The denitrification and excessive P removal can be realized by denitrifying phosphate-accumulating organisms (DNPAOs) under low carbon condition. DNPAOs use poly-3-hydroxy- butyrate (PHB) as electron donor, and use nitrate and nitrite as electron acceptor during the denitrifying phosphate uptake. In this study the biological phosphorus removal granular sludge was induced into the denitrifying and phosphate uptake granular sludge under an anaerobic/anoxic/aerobic alternating operation (referred to as an A/A/O) in a sequencing batch reactor (SBR). When the system is stable, the P and N removal ratio is over 90% and 93% respectively; the release phosphorus is 25-33 mg/L at anaerobic stage; 1g NOx-N approximately takes up P 1.3 g at anoxic stage. In the typical cycle the anaerobic maximum specific release phosphorus rate (max. SRPR) is 18.39 mg/(g x h); the anoxic max. specific uptake phosphorus rate (SUPR) and the max. specific denitrification rate (SDNR) is 23.72 mg/(g x h) and 18.19 mg/(g x h) respectively; the aerobic max. SUPR is 17.15 mg/(g x h). The fraction of DNPAOs rises from 14.9% to 80.7%. Compared with the physical-chemical property of the biological phosphorus removal granular sludge, the settling velocity and the specific gravity of the denitrifying phosphate uptake granular sludge is elevated 0.16-0.7 times and 0.0031 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.