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This study characterized the nitrification in a reclaimed water distribution system (DS) and the population size of ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) distributed along the flow course by a series of mixed reactors. The series reactors were initially adopted to study the DS of the reclaimed water and can be used as a feasible method for a similar investigation. This method was easy to model, control, and sample the biofilm formed in the DS. The series reactors were assembled in the Qingyuan Wastewater Treatment and Reuse Company of Xi'an, where the finished water was drawn directly. A mean of 85.0% NH4+-N removal was obtained during a continuous operation of 239 days, when the influent concentration of NH4+-N was 5.21 mg/L on average. The measurement of inorganic nitrogen and nitrification rate along the flow course indicated high activities of the nitrifiers that mainly existed at the initial segment of DS, whereas the pH value and dissolved oxygen concentration decreased. The analysis of the fluorescence in situ hybridization exhibited that the population of the nitrifiers was the highest (an average of 14.33-41.75%) of all bacteria in the biofilm. The dominating species of AOB were Nitrosospira, which presented an increasing trend along the DS course. The dominant shift of NOB, from Nitrobacter to Nitrospira, along the DS may be attributed to the variance of the nutrient condition. This shift confirmed the K/r hypothesis. [ABSTRACT FROM AUTHOR]

This study aims to investigate the diagnosis of acidification and efficient recovery of a laboratory-scale anaerobic sequencing batch reactor (ASBR) which treats synthetic glucose wastewater under mesophilic conditions (35°C). The diagnosis of the ASBR showed that acidification occurred on the seventh day after adding 20 mmol/L of sodium 2-bromoethanesulfonate into the reactor. A three-step recovery strategy was employed to recover the acidified reactor efficiently and to study its restoration process. Results indicated that the acidified ASBR can be revived in approximately 50 d. The specific methanogenic activities of the sludge, which were based on the substrate of acetate, propionate, and butyrate, were restored at 0.85, 0.67, and 0.51 (gCOD-CH4)/(gVSS∙d), respectively. The fluorescent observation images revealed large amounts of Methanosarcina-like and rod-shaped methanogens distributed in the sludge flocs after reactor restoration, thus ensuring that the fermentative, acidogenic, and methanogenic processes proceeded effectively in the anaerobic system. [ABSTRACT FROM AUTHOR]

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.