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The research trend of FA inhibitions on nitrifies were introduced, including the inhibition mechanism and inhibition mathematic model of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, as well as the strategy to reduce or avoid inhibition effects. In addition, the selective inhibition effects of FA on the start-up and stability of partial nitrification were illuminated. In particular, the combinative effects of FA inhibition and other factors (such as dissolved oxygen and temperature) on short-cut nitrification were presented in the review. [ABSTRACT FROM AUTHOR]

Partial nitritation is the basis of anoxic ammonium oxidation (Anammox), however, very limited research has been undertaken on this field. In this study, an A/O reactor was used to investigate the feasibility of the partial nitritation and the performance of biological phosphorus removal from municipal wastewater. The obtained results showed that the partial nitritation could be achieved in A/O reactor with nitrite accumulation rate of 85%. It was possible that nitrite-to-ammonium ratio in the effluent from the A/O reactor was approximately controlled at 1.0 by adjusting hydraulic retention time, which was beneficial to the Anammox reaction. The fluctuation of temperature and DO concentration might lead to the deterioration of nitritation. After the achievement of partial nitritation, the biological phosphorus removal was not stable, which might relate to the increase of FNA concentration in the effluent of A/O reactor, and needed further experimental investigation. [ABSTRACT FROM AUTHOR]

To study the long-term effect of dissolved oxygen (DO) on phosphorus removal process, the characteristics of enhanced biological phosphorus removal (EBPR) under the DO level of 5.5 -7.0 mg/L and 0.5 - 1.5 mg/L were investigated systematically using sequencing batch reactor (SBR). The results showed that, when pH was in 7.2 - 7.6 and temperature was at (23 ± 0.5 ) °C , high DO had adverse impact on both phosphorus release process and phosphorus uptake process. The amount of released phosphorus in anaerobic period was 43.08% lower than that under low DO condition. Phosphorus uptake process went fast during the initial 30 rain in aerobic period. The maximum specific phosphorus uptake rate was 6.27, 11.45 mg ⋅ g-1 ⋅ h-1 under high DO and low DO conditions, respectively. Analysis indicated that the main reason of deterioration of phosphorus removal process was deficiency of poly - β - hydroxybutyrate (PHB) caused by excessive aeration and more influent carbon source used for densification process. High DO did not have obvious advantage on restraining filamentous sludge bulking than low DO. The improvement of phosphorus removal was usually associated with the improvement of sludge settleability. [ABSTRACT FROM AUTHOR]

In order to solve the problem of sludge bulking which happened in wastewater treatment plant frequently, a notion named low DO limited filamentous bulking was put forward. It is a new energy-saving and high-efficient method to treat wastewater with the characteristics of morphology and physiology of filamentous bacteria under low DO concentration condition. The impact of DO concentration and organic loading rate (OLR) on sludge settleability and the removal characteristics of nitrogen, phosphorus and COD under limited filamentous bulking were investigated by using sequencing batch reactor (SBR) through operation in aerobic-anoxic pattern. The results show that OLR and DO concentration affect sludge settleability in special range respectively. When OLR is larger than 0. 25 d-1, limited filamentous bulking state can not be maintained by low DO concentration alone. Nitrification will not be deteriorated under low DO limited filamentous bulking condition, and about 20% nitrogen is removed through simultaneous nitrification and denitrification (SND) based on the mass balance of nitrogen. Aerobic phosphorus release is found in the initial stage of low aeration rate, and the system can enrich phosphorus accumulating organisms (PAOs). [ABSTRACT FROM AUTHOR]

The shift of nitrifier population within a partial nitrification reactor was investigated using fluorescence in-situ hybridization (FISH) techniques and the floc morphology was observed using scan electron microscope (SEM). Partial nitrification to nitrite was achieved quickly by using real-time aeration duration control when domestic wastewater was treated in a lab-scale sequencing batch reactor (SBR). The average nitrite accumulation ratio was above 93%. The morphology photographs observed using SEM indicated that the sludge showed a shift towards spherical and small rod-shaped clusters from the diverse morphology. FISH analysis showed that ammonia-oxidizing bacteria (AOB) gradually out-competed nitrite-oxidizing bacteria (NOB). AOB population percentage increased from 3.5% (during the start-up period) to 8.5% (after achieving nitritation for 102 days), while NOB population percentage decreased from 3.1% to less than 0. 5%. Accordingly, the long-term operation with the use of real-time aeration duration control was not only favorable for AOB community optimisation, but also for the achievement of partial nitrification in practice. [ABSTRACT FROM AUTHOR]

The combination of chromatogram and chemical analysis was adopted to optimize the methods selected to measure poly - P, glycogen and PHA intracellular polymer in EBPR system. PHA was measured by GC system, glycogen was degraded by dilute hydrochloric acid and analyzed by glucose commercial kit, and poly - P was oxidized by potassium persulfate and analyzed by molybdenum - antimony anti-spectrophotometric method. Testing of the proposed method for PHA analysis shows that 4% sulfuric acid concentration and degradation for 20 h are required for optimal PHB and PHV extraction, while 0.6 mol/L HCl and digestion for 5 h produce the highest recovery of glycogen, and the medical glucose kit can be used in this research. Oxidation for 30 min at 120 °C is recommended for the recovery of poly - P. The results of precision analysis and recovery test with standard addition of these methods show that they possess high precision and are convenient for laboratory research and practical application. [ABSTRACT FROM AUTHOR]

Adding external carbon sources is an important method for advanced nitrogen removal of secondary effluent in wastewater treatment plants (WWTPs). In order to compare the denitrification performance and economy of different carbon sources sufficiently, as well as the effect of long-term addition of carbon sources on the microbial population structure, four single carbon sources (methanol, ethanol, glucose, and sodium acetate) and four types of composite carbon sources were prepared by mixing sodium acetate and ethanol with a higher reaction rate and cheap glucose. The results showed that the effluent ρ (NO x - -N) concentration of all systems was less than 1.0 mg·L -1 during the experiment. For single-carbon source systems, ethanol had the fastest denitrification rate, followed by sodium acetate and methanol; that of the glucose was the slowest. In the composite carbon source systems, the sodium acetate/glucose (1:1) with COD/ ρ (N) was 6, which was equivalent to the results of sodium acetate/glucose (1:3), ethanol/glucose(1:1), and ethanol/glucose (1:3) with COD/ ρ (N) of 9, 10, and 10, respectively. The sodium acetate/glucose (1:1) system had the fastest reaction rate and the best economy. High-throughput sequencing results showed that after more than 70 days of operation, the structure of the microbial community had changed completely. In the glucose-related system, the abundance of Candidatus Saccharibacteria, which is not popular in typical nitrogen removal systems, increased from 1.16% of seed sludge to 47.37%, and Saccharibacteria_genera_incertae_sedis correspondingly became the dominant community. This study not only provides a more comprehensive comparison for the selection of carbon sources in WWTPs with ultimate nitrogen removal but also provides basic data for the role of carbon sources in the domestication of microbial communities.

Filamentous bacteria, as one of the common bacteria types in wastewater biological treatment, are considered to be the main factor to induce sludge bulking. However, because of its special filamentous shape, it plays a crucial role in the formation of sludge particles. Taking filamentous bulking sludge as the research object, the effect of filamentous bacteria on the sludge granulation process and maintaining the stability of sludge granules was studied, and the microbial diversity of the sludge system was analyzed. Filamentous bulking sludge (SVI=241.56 mL·g -1 ) and flocculated sludge (SVI=64.22 mL·g -1 ) were respectively inoculated to carry out granulation culture. The results showed that the time of particle appearance of bulking sludge and flocculated sludge was 20 days and 40 days, respectively; the mature particle sizes were 650 μm and 700 μm, respectively; and the granulation time of bulking sludge was only half that of flocculated sludge. After adding the anoxic zone, the granules were broken to differing degrees, but the SV 30 /SV 5 value of mature granules recovered to 1 after short-term fluctuation, and the stability of the mature granules was stronger. The analysis of microbial community structure showed that the relative abundance of norank_o__Saccharimonadales , unclassified_o__Saccharimonadales , and unclassified_f__Saccharimonadaceae increased from 0.05%, 0.01%, and 0.01% to 4.09%, 3.15%, and 1.12%. The existence and accumulations of these hydrophobic bacteria were important for rapid granulation. The removal rates of COD, NH 4 + -N, and TN were 94%, 99%, and 35% and 92%, 97%, and 30%, respectively, in SBR 1 of bulking sludge and SBR 2 of flocculated sludge, and the removal rates of TP were 60% and 30%, respectively.

The effective inhibition of nitrite oxidizing bacteria (NOB) is the key to realizing satisfactory nitrite accumulation and achieving effective nitritation. In order to explore the selective effect of hydroxylamine (NH 2 OH) on ammonia oxidizing bacteria (AOB) and NOB, a sequencing batch reactor (SBR) with the operation mode of anaerobic/aerobic/anoxia (A/O/A) was used to observe the start-up of nitritation at different concentrations and frequencies of NH 2 OH. The results showed that when 5 mg·L -1 of NH 2 OH was added once every 2 cycles, the nitrite accumulation rate (NAR) increased from 0.1% to 57.4% in 6 days, and was maintained at (62.0±4.6)% until the end of the trials. In the typical cycle on day 6, the NN 4 + -N dropped from 26.05 mg·L -1 to 8.06 mg·L -1 , thus producing 9.02 mg·L -1 of NO 2 - -N and 6.70 mg·L -1 of NO 3 - -N. Meanwhile, the ratio of the maximum activity of AOB (rAOB) to NOB (rNOB) increased from 1.05 on day 1 to 4.22 on day 9. Moreover, qPCR results indicated that the abundance of AOB and NOB decreased to 30.2% and 19.1%, respectively, on day 9 in comparison to the original sample. The results indicate that the selective effect of AOB and NOB based on NH 2 OH is expected to provide a feasible application for the rapid start-up nitritation of municipal wastewater.

To investigate the characteristics of microbial diversity during filamentous bulking at low temperature, the induction of sludge bulking was successfully carried out using a low-temperature sequencing batch reactor(SBR). With the help of Illumina MiSeq high-throughput sequencing technology, the overall changes in the microbial community structure of activated sludge, the characteristics of each specific microbial community, and the specific genera were all investigated under different sludge sedimentation performances. The results showed that filamentous bulking can be successfully induced after the system operating temperature drops to (14±1)℃, and the COD and TN removal rates can still be maintained at approximately 90% and 86%, respectively, with the sludge volume index deteriorating to 663.99 mL·g -1 . The occurrence of sludge bulking at low temperature will not only reduce the overall diversity and uniformity of microorganisms in the system and increase the abundance of filamentous bacteria from 0.49% to 26.04% but also cause the abundance of denitrifying bacteria to reduce from 21.04% to 13.99% and that of dephosphorization bacteria to reduce from 4.25% to 1.93%. Of the five filamentous genera founded, the abundances of three filamentous bacteria represented by Thiothrix increased, whereas only that of the Haliscomenobacter decreased. Of the 19 denitrifier genera founded, the abundances of five species represented by Nitrosomonas increased, whereas those of seven species represented by Nitrospira decreased. Moreover, the abundances of Pseudomonas and Tetrasphaera increased out of the eight phosphorus-removing bacteria genera, whereas the abundances of the five bacteria genera represented by Candidatus_Competibacter decreased. Although sludge bulking has a significant impact on the structure of the microbial community, the 477 operational taxonomic units and 227 bacterial species that are always present in the different sludge samples indicate that the main microorganisms in the reactor are still relatively stable during the bulking process.

The sludge from enrichment of Nitrobacter and Nitrospira was used as a research object and batch tests were performed. The inhibitory effects of hydroxylamine on Nitrobacter and Nitrospira under the same pH and different hydroxylamine concentration gradients, the same hydroxylamine concentration, and different pH gradients were investigated. The results showed that under the same pH condition, the activity of Nitrobacter decreased with increasing hydroxylamine concentration. Under the same hydroxylamine concentration (HA=5 mg·L -1 ) at a higher pH environment (pH ≥ 7.5), hydroxylamine produced more free hydroxylamine (FHA) and the inhibitory effect on Nitrobacter was improved. At a low pH environment (pH≤7), ionic hydroxylamine promoted the activity of Nitrobacter . The inhibitory effect of hydroxylamine on Nitrospira was limited. When pH=7.5 and hydroxylamine concentration was 45 mg·L -1 , the relative activity of Nitrospira was 82%. The NOB growth rate kinetics model and the non-substrate inhibition linear equation were used to describe the effect of FHA on Nitrobacter and Nitrospira activity. The coefficient of determination R 2 was 0.90 and 0.94, respectively. FHA may be the main reason for inhibiting the activity of Nitrobacter and Nitrospira .

The aim of the present study was to investigate the effect of alkaline sludge fermentation products as a carbon source on the nitrification process and performance. During the operation of a biological nitrogen removal (BNR) system with sludge fermentation mixture as the carbon source, the activities of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were inhibited at the beginning. After 16 days, the activity of AOB began to recover rapidly, but the activity of NOB was still inhibited. The specific nitrate production rate (SNaPR, N/VSS) decreased from 0.1791 g·(g·d) -1 to 0.0078 g·(g·d) -1 . At the same time, the nitrite accumulation rate increased from 8.12% to 91.42% and remained stable. The sludge fermentation mixture was separated into sludge fermentation liquid and sludge fermentation sediment. The changes in nitrification activity by adding different types of fermentation products were investigated. The results showed that the activity of NOB decreased in the experimental group fed with the sludge fermentation mixture and the fermentation liquid. The SNaPR decreased from an initial 0.1793 g·(g·d) -1 to 0.1510 g·(g·d) -1 and 0.1617 g·(g·d) -1 , respectively. In the experimental group fed with fermentation sediment, the activity of NOB increased. SNaPR rose from 0.1793 g·(g·d) -1 to 0.1864 g·(g·d) -1 . Therefore, the activity of the NOB can be inhibited when the sludge fermentation mixture and the fermentation liquid are used as a carbon source in the nitrification process. In addition, the short-range nitrification process can be realized, which is beneficial to accelerating the reaction speed and saving investment in this type of carbon source.

Partial-denitrification coupled with ANAMMOX is a novel biological nitrogen removal technology, which is expected to significantly reduce the external carbon source dosage for advanced nitrogen removal from municipal wastewater. In this study, ANAMMOX sludge was inoculated to investigate advanced nitrogen removal performance and sludge characteristics in a partial-denitrification/ANAMMOX reactor. The results showed that inoculation of ANAMMOX sludge could quickly start the partial-denitrification/ANAMMOX reactor. The effluent total nitrogen concentrations were (4.82±1.84) mg·L -1 with a chemical oxygen demand of 2.19±0.08. Sludge particles larger than 0.20 mm accounted for 86.16% in the reactor. This meant that granular sludge was formed, which was conducive to good retention of ANAMMOX bacteria in the reactor. The external carbon source dosage and the oxygen requirement for nitrification can be reduced by applying partial-denitrification coupled with ANAMMOX to advanced nitrogen removal from the effluent of secondary clarifier in municipal wastewater treatment plants.

Under transient conditions, a biotrickling filter was developed to treat gaseous H 2 S produced from the fine-grid reservoir of a municipal wastewater treatment plant (WWTP) with AAO excess sludge as the inoculum and polypropylene rings as the packing material. The start-up process and steady-state operation of the biotrickling filter were studied. With an empty bed retention time of 14 s, an ambient temperature of 7.8-32.5℃, and an inlet concentration of 2.02-319.19 mg·m -3 , an average removal efficiency of 91.8% was achieved with a maximum H 2 S elimination capacity of 78.37 g·(m 3 ·h) -1 . Over a 247-day period, the pressure drop across the biotrickling filter was maintained at 96 Pa·m -1 . Microbial analysis using high-throughput sequencing technology showed a variation in the microbial community during the experiment; the Shannon index dropped from 4.99 to 3.75, and the functional genera Pseudomonas and Thiobacillus were identified as good performers in the biotrickling filter system. These results indicate that the application of AAO excess sludge as an inoculum for biotrickling filters is feasible for effective H 2 S removal. A steady pressure drop was achieved using polypropylene rings as the packing material. The diversity of the microbial community showed a downward trend when exposed to H 2 S, but the elimination capacity could be increased.

Anoxic MBBR is a process to achieve advanced denitrification from municipal wastewater. Here, anoxic MBBR was applied as a post-denitrification SBR to achieve advanced denitrification by partial anammox (anaerobic ammonium oxidation). During a 250-day operation, denitrification performance gradually improved and the total nitrogen concentration of the effluent was approximately 5 mg·L -1 . The average nitrate, ammonia, and total inorganic nitrogen removal efficiencies were (97.7±2.9)%, (93.3±2.9)%, and (94.3±2.7)%, respectively, between day 211 and 250. The simultaneous removal of ammonia and nitrate was observed in the anoxic reactor. Analysis of the ammonia removal pathway revealed that assimilation and nitrification were poor in the anoxic MBBR. The anammox activity test and the denitrification performance showed that anammox occurred and played a not insignificant role in the anoxic MBBR. The results of real-time quantitative PCR showed that anammox bacteria enriched in anoxic MBBR, especially in the anoxic carrier biofilms, where the abundance of anammox bacteria increased from 4.37×10 7 copies·g -1 to 2.28×10 10 copies·g -1 . This study demonstrates that anoxic carrier biofilms may have potential applications in anammox bacterial enrichment to enhance denitrification from municipal wastewater.

Type 0092 filamentous bacteria generally do not result in excessive sludge bulking. To take advantage of this, domestic sewage was used to inoculate shortcut nitrification sludge in a sequencing batch reactor (SBR). Sludge settleability, the nitrite accumulation ratio (NAR), pollutant removal characteristics, and the dynamic variation of microbial communities during the system startup and maintenance were investigated. The results indicated that limited filamentous bulking (LFB)with Type 0092 filamentous bacteria combined with shortcut nitrification could be achieved under alternating anoxic and aerobic (four times/cycle;the ratio of anoxic/aerobic was 20 min/60 min) with low dissolved oxygen (DO) content (0.3-0.8 mg·L -1 ) and a low food/microorganism (F/M) ratio[0.24 kg·(kg·d) -1 , COD/MLSS]. The removal rate of COD and total nitrogen (TN) were increased by 13% and 5% when the sludge volume index (SVI) and NAR were maintained at approximately 180 mL·g -1 and 99%, respectively, and aeration consumption was reduced by 62.5% compared to general whole-run nitrification. When the ratio of anoxic/aerobic changed to be 10 min/30 min as alternating times increased to 6 times per cycle, the activity of the nitrite oxidizing bacteria (NOB) recovered, causing shortcut nitrification to be destroyed. In addition, low DO, alternate anoxic/aerobic modes, and low loading rates were the key factors in achieving LFB with Type 0092 filamentous bacteria as the dominant filamentous bacteria. Limited filamentous bulking could not be maintained under low DO and alternating anoxic/aerobic conditions with loading rates above 0.25 kg·(kg·d) -1 , COD/MLSS.

The short-cut biological nitrogen removal process has been widely used in industrial wastewater treatment, and denitrification is a crucial step for removing nitrogen on which the effect of Cu 2+ , a common heavy metal ion in wastewater, has not been studied. In this study, sludge with good short-range biological nitrogen removal characteristics in an A/O reactor was selected to investigate the short-term and long-term effects of Cu 2+ on denitrification using NO 2 - as an electron acceptor. The results showed that Cu 2+ had a significant inhibitory effect on denitrification process using NO 2 - as an electron acceptor, and the semi-inhibitory concentration EC 50 of sludge activity was 4.79 mg·L -1 . In the long-term experiment, the concentration of Cu 2+ was gradually increased. When the concentration of Cu 2+ was 0.5 mg·L -1 and 1 mg·L -1 , the denitrification activity of the sludge could be restored to the original level after acclimation. When the concentration of Cu 2+ was increased to 3 mg·L -1 , the denitrification performance was destroyed and difficult to recover, at which point the NO 2 - -N removal rate was reduced to less than 10% and the denitrification system was severely inhibited. However, there was some recovery of sludge denitrification capacity after the addition of Cu 2+ had been stopped for 14 days. At the same time, during the long-term effect of Cu 2+ , the EPS content increased, which played an important role in protecting the microorganism against Cu 2+ toxicity, and increased the sludge particle size and, as a result, sludge sedimentation.

The effects of low substrate ratio, cooling methods, and pH on nitrogen removal performance were studied in a laboratory-scale anaerobic ammonium oxidation reactor (ASBR) while treating simulated domestic waste water. The results illustrated that the average removal efficiencies of NH 4 + -N and NO 2 - -N increased from 54.4% and 65.3% to 95.8% and 92.5%, respectively, at a temperature of 30℃ and an influent concentration of NO 2 - -N of (30±0.2)mg·L -1 . The substrate ratio (NO 2 - -N/NH 4 + -N) increased from 0.9 to 1.4.However, the removal efficiency of NH 4 + -N was affected negligibly, and the average removal efficiency of NO 2 - -N decreased to 54.6% when the substrate ratio was increased to 1.6, suggesting that the nitrogen removal performance of anaerobic ammonium oxidation was best when the substrate ratio was close to the theoretical value of 1.32.The average removal efficiencies of NH 4 + -N and NO 2 - -N decreased from 97.5% and 98.5% to 35.2% and 40.1%, respectively, when the temperature of the reactor dropped from 30℃ to 15℃ at one time. The average removal efficiencies of NH 4 + -N and NO 2 - -N dropped from 97.7% and 98.6% to 52.7% and 62.4%, respectively, when the ladder cooling method(30℃→25℃→20℃→15℃) was used. The average removal efficiencies of NH 4 + -N and NO 2 - -N increased initially and then decreased when the pH was increased gradually from 7.7 to 8.5.The highest nitrogen removal efficiency was achieved when the pH was controlled at 8.3 with a substrate ratio of NO 2 - -N/NH 4 + -N equal to 1.4.

A modification of the two sludge A 2 /O-BAF system was used to treat low C/N real domestic sewage. In order to improve the utilization of the carbon source, the effects of two step feeds (pre-anoxic zone and anoxic zone) on denitrifying phosphorus and nitrate removal were studied. According to the formula of material balance for COD, the utilization of carbon source was analyzed and evaluated under different ratios of step feed, simultaneously. The results showed that when the ratio of step feed was 7:3 and the influent concentrations of COD, NH 4 + -N, TN, and TP were 174.99, 58.19, 59.10, and 5.15 mg·L -1 , respectively, their effluent concentrations were 29.48, 4.07, 14.10, and 0.40 mg·L -1 , and the removal rates were 82.12%, 92.76%, 75.45%, and 91.20%, respectively. It was found that when the ratio of the denitrifying phosphorus accumulation organisms to the phosphorus accumulation organisms(DPAOs/PAOs) was 98.81%, the efficiencies of denitrifying phosphorus and nitrate removal were optimum. By optimizing step feed, the carbon source was utilized effectively, and the efficiencies of nitrogen and phosphorus removal were improved simultaneously. The theoretical basis has thus been provided for the modification of the two sludge A 2 /O-BAF system to treat low C/N waste water.

Shortcut nitrification sludge, which was set aside for two months, was recovered using Reactors Ⅰ, Ⅱ, Ⅲ, and Ⅳ. The aeration rates of Reactors Ⅰ, Ⅱ, Ⅲ, and Ⅳ were 120, 100, 80, and 60 L·h -1 , respectively, while treating real domestic sewage, and the ratio of aerobic/anoxic was 30 min/30 min at the temperature of 25℃. The influent of ammonia was 50-80 mg·L -1 , and the concentration of effluent ammonia was stable, at below 5 mg·L -1 , after the 12 th , 18 th , 21 st , and 21 st cycles. The removal ratio of ammonia nitrogen was about 95%. The highest concentrations of nitrite for Reactors Ⅰ, Ⅱ, Ⅲ, and Ⅳ were 20.83, 22.81, 21.50, and 20.73 mg·L -1 , respectively, which occurred in the 30 th , 35 th , 38 th , and 42 nd cycles, respectively. The concentrations of effluent nitrate were lower than 0.5 mg·L -1 , and the nitrite accumulation rates were higher than 99%. The activity of ammonia-oxidizing bacteria (AOB) increased gradually and finally stabilized at 100.00%; however, the activity of nitrite-oxidizing bacteria (NOB) was gradually inhibited. The recovery of shortcut nitrification was achieved successfully in the different aeration modes.

This study used short process nitrification sludge to investigate the effect of high free ammonia (FA) on ammonia escape during ammonia oxidation. A sequencing batch reactor (SBR) was used to study the ammonia escape process under different FA concentrations. The results indicate that FA in water is usually combined with water molecules at lower FA concentrations to produce stable NH 3 ·H 2 O with almost no ammonia escape. With high FA concentration (FA>687.1 mg·L -1 ), ammonia nitrogen is not oxidized to oxidized nitrogen (NO 2 - -N concentration is <0.1 mg·L -1 at the end of aeration), but the total nitrogen (TN) reached 269.7 mg·L -1 . Therefore, when there is a high FA concentration, NH 4 + -N will evaporate in the form of FA, resulting in ammonia escape. In addition, when 226.6 ≤ FA ≤ 711.8 mg·L -1 , the free ammonia escape rate (FEV) grows rapidly with the increase in FA concentration.

Real domestic sewage was treated with sequencing batch reactors (SBR). The aerobic/anoxic modes were alternated 4 times at 30℃ and 7 times at 18℃ in a single-cycle, respectively, and the ratio of aerobic/anoxic cycles was 30 min/30 min. The influent concentration of ammonia and nitrite was 61.44 mg·L -1 and 0.77 mg·L -1 , respectively. After the experiments were run for 61 and 90 cycles, the effluent of the ammonia was 0.68 mg·L -1 and 1.28 mg·L -1 and the removal rate for ammonia was 98.94% and 99.57%, respectively. The nitrite concentrations were 20.57 mg·L -1 and 20.18 mg·L -1 , and the nitrite accumulation rate reached 95.92% and 99.58%, respectively. During shortcut nitrification, the activity of the ammonia oxidizing bacteria (AOB) increased gradually before finally stabilizing at 100.00%, however the activity of nitrite oxidizing bacteria (NOB) increased first and then decreased gradually, the activity of AOB exceeded NOB at 32 and 74 cycles respectively, where the AOB became the dominant bacteria and the activity of NOB was completely inhibited at 61 and 90 cycles.

Nitrogen removal by a newly discovered Pseudomons sp. strain, DK1, isolated from activated sludge was investigated. Using glucose as a carbon source and a n (C)/ n (N) ratio of five, batch experiments showed that the aerobic denitrification removal rate was 4.09 mg·(L·h) -1 and 4.43 mg·(L·h) -1 with NaNO 3 or NaNO 2 , respectively. Completely nitrogen removal was achieved when using these two nitrogen sources. DK1 was also found to heterotrophically remove NH 4 + -N at a rate of 2.32 mg·(L·h) -1 and to carry out anoxic denitrification of a range of concentrations of NO 2 - -N (from about 100 to 300 mg·L -1 ) within a maximum of 36 hours of inoculation. In the presence of both NO 3 - -N and NO 2 - -N, DK1 was found to preferentially denitrify NO 3 - -N. Simultaneous nitrification and denitrification (SND) capacity of the DK1 strain was observed when using ammonium and nitrate or ammonium and nitrite and the corresponding nitrogen removal rates reached as high as 95.06% and 94.69% within 30 hours of inoculation, respectively. Ammonium with both nitrate and nitrite resulted in a 100% nitrogen removal within the same time frame. The ability to achieve SND and to denitrify both NO 3 - -N and NO 2 - -N makes the DK1 strain potentially useful for future application in nitrogenous wastewater treatment.

To improve the hydrolysis and acidification of activated sludge, two new ways, which were adding fermented sludge or sterilized fermented sludge to batch-mode activated sludge alkaline fermentation system, were investigated in this study. Temperature effect was also studied (10 degrees C and 35 degrees C). Result showed that mesophilic condition greatly enhanced sludge hydrolysis and acidification, which resulted in an obvious volatile fatty acids (VFAs) accumulation in the system. These two new ways could improve both sludge hydrolysis and acidification. The hydrolysis and acidification efficiencies of adding sterilized fermented sludge system were 2 and 1.5 times higher than those of adding fermented sludge system, respectively. In addition, VFAs content was nearly constant in a long time in sterilized fermented sludge addition system while it greatly consumed in fermented sludge addition system. The reason for this enhancement of two new ways were different, fermented sludge addition increased the amount of hydrolytic enzyme and acid-forming bacteria, while sterilized fermented sludge addition increased the amount of degradable substances, and the result also demonstrated that strengthen hydrolysis was more important than acidification. Therefore, mesophilic condition together with sterilized fermented sludge addition was a more effective way to enhance VFAs accumulation in alkaline sludge fermentation process.

The long-term stability of nitrogen removal from municipal landfill with high ammonia nitrogen (NH(4+)-N) content was investigated by using a biological system consisting of a first-stage up-flow anaerobic sludge bed (UASB) and sequencing batch reactor (SBR) under normal and low temperature conditions. The 623 days experimental results clearly showed: the efficient denitrification and methanogenesis were conducted in a same UASB reactor, and almost 100% of denitrification was obtained, when feed COD concentration ranged from 1,000 mg x L(-1) to 13 800 mg x L(-1), effluent COD concentration was between 150 mg x L(-1) and 1,234 mg x L(-1), and when the influent ammonia nitrogen (NH(4+)-N) changed from 574 mg x L(-1) to 2,360 mg-L(-1), the effluent NH:-N was below 10 mg x L(-1), the removal efficiency reached 90% and 98%, respectively. Especially, above 99.2% removal efficiency of TN was obtained, and effluent TN concentration was below 30 mg L(-1)), advanced and efficient nitrogen and organic removal were achieved in the biological system. Furthermore, stable nitrification and denitrification were achieved during the entire experiment period, especially, were maintained successfully for 171 days at the temperature below 15 degrees C and the lowest temperature of 10. 2 degrees C during two winters.

In order to test the start-up and maintain method for short-cut advanced nitrogen removal process at low temperature, this study used a pilot-scale SBR process with a working volume of 7.0 m3 to treat domestic wastewater. Real-time control strategy based on blower frequency (BF) and pH was applied to control the pilot-scale SBR process. Results showed that short-cut nitrification process achieved within 50 days at low temperature (11-16 degrees C), and the nitrite accumulation rate (NAR) of SBR process increased from 19.8% to 90%. Short-cut nitrification process in pilot-scale SBR was maintained for as long as 550 days in the temperature range of 9-28 degrees C, and NAR was maintained above 95%. Meanwhile, the total nitrogen (TN) in effluent was 3 mg x L(-1) and the TN removal efficiency was above 95%. Therefore, it is feasible to start-up and maintain the short-cut advanced nitrogen removal process under low temperature condition in the SBR process.

The performance of denitrifying phosphorus removal under nitrification and nitritation was investigated in a lab-scale Modified University of Cape Town (MUCT) process treating real domestic wastewater with low C/N ratio. The experimental results of 180 days showed that nitritation was achieved at short hydraulic retention time (HRT) and low dissolved oxygen (DO) of 0.3-0.5 mg x L(-1), and an average nitrite accumulation rate (NAR) of above 70% was achieved during nitritation stage. The MUCT process showed a good performance of denitrifying phosphorus removal. Under nitritation mode, total and denitrifying phosphorus removal efficiencies were 90% and 91%, respectively; under nitrification mode, total and denitrifying phosphorus removal efficiencies were 60% and 88%, respectively. Although phosphorus removal performance under nitritation was better than that under nitrification, the results of fluorescence in situ hybridization (FISH) indicated that the percentage of phosphorus accumulating organisms (PAOs) in biomass was about 37% under two modes. The effluent COD concentration was below 50 mg x L(-1) during the experimental period. Batch tests of different nitrifying sludges showed that the percentage of denitrifying phosphorus removal bacteria (DPBs) in PAOs using NO2(-)-N as an electron acceptor under nitritation mode was almost the same as that using NO3(-)-N as an electron acceptor under nitrification mode, with an average percentage of 38%. Compared with nitrification mode with conventional phosphorus removal, nitritation mode with denitrifying phosphorus removal has a superior performance treating limited carbon source wastewater.

Limited filamentous bulking under low dissolved oxygen (DO) is a new technology for energy saving and high quality effluent. In order to investigate the feasibility of this technology, four sequence batch reactors (SBRs) were occupied to operate at different regimes to stimulate different processes under low DO (0.5 mg/L). Sludge settleability, floc structure, pollutant removal and aerated energy consumption were investigated. The results showed that limited filamentous bulking under low DO was hard to realize in the single-stage aerobic reactors for they were prone to bulking severely, while it could be achieved stably in the pre-denitrification reactors when the feed length was between 60 and 90 minutes. Compared with normal sludge at the same DO, limited filamentous bulking sludge acquired by low DO displayed its high energy-saving effect. In addition, the specific ammonia consumption rate of limited filamentous bulking sludge was about 2 times higher than the one of normal sludge. On the contrary, the total nitrogen removal efficiency was lower. Further analysis indicated that stable limited sludge bulking could be achieved in a good alternative anoxic/anaerobic/aerobic condition without too high organic loading.

A pilot-scale modified UCT step feed process was proposed to treat the municipal wastewater with lower COD/N in a large-scale wastewater treatment plant. Effects of influent distribution ratios and nutrients ratios (COD/N, COD/P and TN/P) on nutrients removal capabilities were importantly investigated. The removal mechanisms of organics and nutrients and sludge characteristics were ultimately discussed. According to the continuous experiments, the stable and high process performance was obtained. The average COD removal efficiencies and effluent concentration of (83.8 +/- 3.86)% and (43.7 +/- 8.35) mg/L were achieved in the influent COD loading of 0.79-0.93 kg/(m3 x d). The COD removal in anaerobic and anoxic zones accounted for 60.2% - 76.2%. With the influent distribution ratio of 40%: 30%: 30%, as much as 88.2% of TN removal efficiency was observed. It should be considered the removal of 32.8% through simultaneous nitrification and denitrification process. The average effluent NH(4+)-N and TN were (0.21 +/- 0.20) mg/L and (7.90 +/- 1.27) mg/L, respectively. It was extremely important that as much as 32.6% - 39.5% of the denitrifying phosphorus accumulation organisms contributed to the high phosphorus removal efficiency of 97.2%. A linear positive relationship was observed between nitrogen removal efficiency and COD/N in the range of 4.64 and 7.41 (R2 = 0.96). Phosphorus removal efficiency was found to be a function of the influent COD/P and TN/P, varying from 35.0 to 92.5 and from 6.24 to 12.5, respectively (R2 = 0.87 and R2 = 0.89). In addition, the great sludge settleability was obtained with the mean SVI of (82.6 +/- 4.99) mL/g.

The behaviors of biological phosphorus (P) and nitrogen (N) removal in a lab-scaled anaerobic/anoxic/oxic-biological aerated filter (A2/O-BAF) combined system were investigated during the treatment of real domestic wastewater with the temperature at 15 degrees C, the C/N ratio of 4.9 and internal recycle ratio of 100%, 200%, 300% and 400%. Experimental results clearly showed that COD, N and P can be simultaneously deeply removed in this combined system. When the total HRT was 8.0 h, SRT was 15 d,sludge recycle ratio was 100% and MLSS was 4.0 mg x L(-1), the concentrations of COD, total phosphorus (TP) and ammonia nitrogen could be reached to less than 50.0, 0.5 and 1.0 mg x L(-1) in the effluent, respectively. The concentrations of total nitrogen (TN) could be reduced from 70.9, 72.1, 70.6 and 73.3 mg x L(-1) in the raw wastewater to that of 24.8, 16.5, 9.6 and 8.7 mg x L(-1) in the effluent, respectively. The removal efficiencies of TN were 65.0%, 77.1%, 86.4% and 88.1%, respectively. There was no distinct relationship between the internal recycle ratio and the removal efficiencies of COD, TP and ammonia nitrogen. However, the removal efficiencies of TN increased with the increasing of the internal recycle ratio, the rising rate was descending. Both the capacity of denitrifying and phosphorus removal in anoxic zone increased simultaneously with the increasing of the internal recycle ratio. Batch tests indicated that the population of denitrifying polyphosphate-accumulating organisms (DPAOs) was up to 40.5% of the total phosphate-accumulating organisms (PAOs).

Using a three-sludge system consisted of anaerobic/oxic (A/O) process, partial nitritation and anaerobic ammonium oxidation (ANAMMOX) reactors, cost-effective removal of nitrogen and phosphate from municipal wastewater was achieved. The experimental results showed that effluent total phosphorus (TP) of the A/O system was less than 0.5 mg/L under hydraulic retention time (HRT) of 3.6 h. Partial nitritation with nitrite accumulation efficiency of 75% -96% was realized in the partial nitritation system under room temperature, DO < 0.2 mg/L and HRT of 4.6 h. Under temperature of 27-30 degrees C and HRT of 1.4 h, effluent total nitrogen (TN) and TN removal rate of ANAMMOX reactor were less than 8 mg/L with the minimum value of 1.6 mg/L and 0.57 kg/(m3 x d), respectively. In the three-sludge system, phosphate accumulating organisms, ammonia-oxidizing bacteria and Anammox bacteria existed under suitably environmental condition to optimize the microbial community structure and improve treatment efficiency of various units. Autotrophic nitrogen removal can reduce 62.5% of the oxygen supply, save 100% of denitrification carbon sources theoretically, lower the sludge production, and greatly decrease carbon dioxide emission. As compared to traditional biological nutrient removal process, the three-sludge system has great advantages and potential in energy saving and carbon dioxide emission reduction to realize sustainable development of water resources.

The effects of different COD/TN and HRT(s) (hydraulic retention time of select) on nutrients removal were investigated by using an alternating anoxic/oxic CAST (cyclic activated sludge technology) fed with municipal wastewater. The results showed that various COD/TN and HRT(s) had a bigger influence on the nitrogen removal efficiency rather than the COD removal efficiency. As the influent C/N ratios were about 2.6 and 3.5, ammonia was removed by 98% and TN removal efficiency was increased from 62.9% to 76.2% and 72.1% to 84.6%, respectively, by increasing the HRT(s) from 1.8 h to 5 h. When the COD/TN ratio was increased to about 4.4, TN removal efficiency was decreased from 86.3% to 58.2% by enlarging the HRT(s), which was due to the incomplete nitrification of ammonia. It was also observed that both of increasing the COD/TN and HRT(s) could improve the phosphorus removal performance of the system. Furthermore, effluent of CAST reached the demanded A of integrated wastewater discharge standards (GB 18918-2002) when the COD/TN and HRT(s) were 4.4 and 1.8 h, respectively.

At normal temperature, short-cut nitrification and denitrification was achieved in a lab-scale A2O process treating low C/N ratio domestic wastewater by controlling DO concentration of 0.3-0.5 mg/L and increasing the internal reflux ratio to decrease the actual aerobic HRT. However, the phosphorus removal in A2O process was deteriorated with the increasing of the nitrite concentration in the effluent. The factors causing phosphorus removal deterioration, such as the influent COD concentrations, temperature, pH and free nitrous acid (FNA) were systematically analyzed. Experimental results showed that the nitrite accumulation resulting from short-cut nitrification affected anaerobic P release and aerobic P uptake. Especially, the higher FNA concentration (HNO2-N 0.002-0.003 mg/L) in the aerobic zone significantly inhibited the aerobic P uptake, which was the major reason causing P removal deterioration. Through adding the carbon sources in influent to enhance anaerobic P release and denitrification, the nitrite and FNA concentrations in the aerobic zone were decreased, and the P removal was recovered. More than 96% of PO4(3-) -P could be removed in A2O process.

In order to characterize the dense and regular level of aerobic granular sludge (AGS) which was cultivated by different carbon sources, the SEM images of mature AGS were used in the study. The calculation process using Photoshop and Fips2 on fractal characteristics of these granules was built. The lowest box-counting dimension was bulking aerobic granular sludge cultivated by glucose (No. 1), which was 1.794 +/- 0.011; the box-counting dimension of AGS cultivated by peptone (No. 3) and domestic sewage (No. 5) were reached up to 1.866 +/- 0.018 and 1.880 +/- 0.015. The boundary box-counting dimension of the AGS was also calculated and the average value was 1.14. The AGS cultivated by beer (No. 6) was more regular in shape and the boundary box-counting dimension was 1.115 +/- 0.003. The AGS cultivated by landfill leachate (No. 7) was the most irregular in shape. This study indicates that fractal dimension provides an approach for quantification of dense and regular level of AGS, furthermore, it could be used to characterize the status of AGS, such as bulking.

Aerobic granular sludge (AGS) for simultaneous nitrogen and phosphorus removal (SNPR) was cultivated and studied in two lab-scale sequencing batch reactors (named as A & B) treating real domestic wastewater, additional carbon (sodium propionate and sodium acetate for A, glucose for B) was added to make the ratio of COD:N:P as 360:60:6, good SNPR was achieved at normal (18-27 degrees C) and low temperature (9-13 degrees C). The microbial community composition and distribution, distribution of cells and extracellular polymeric substances (EPS) and morphologies of the AGS were investigated using fluorescence in situ hybridization (FISH), in situ fluorescent staining and scanning electron microscope (SEM), respectively. FISH results showed that ammonium-oxidizing bacteria comprised 12% of all the bacteria and were mainly located at the outer parts of the granules; phosphates accumulating organisms comprised 40% of all the bacteria and were mainly located in the inner parts of the granules. Nitrification was the rate controlling step; denitrifying phosphate accumulating organisms inside the granular sludge might be responsible for denitrification in the aerobic phase, which enabled effective SNPR. Live/dead fluorescent staining results showed that dead cells were distributed throughout the granules and live cells were principally distribution of polysaccharide (including alpha-mannopyranosyl, alpha-glucopyranosyl sugars and beta-D-glucopyranose polysaccharides) of EPS in AGS were influenced by different carbon sources, but the contents and distributions of protein and lipids were not, the contents of protein was the largest. Polysaccharide was responsible for the formation and maintenance of aerobic granular sludge. SEM results showed that bacilli and cocci were the main bacteria in the granules of A and B, respectively. Carbon sources affected the bacteria type and the SNPR efficiency, sodium propionate and sodium acetate were better than glucose.

Nitrite and nitrate have been generally recognized to have an inhibitory effect on metabolism of denitrifiers. The nitrite inhibition on nitrate reduction under various pH conditions and the cross effect of the both electron acceptors on each other were investigated through a series of batch tests by using a biological nutrient removal (BNR) sludge. The results showed that the nitrate reduction activity had a much stronger relationship with the free nitrous acid (FNA) than that of nitrite concentration, suggesting that FNA, rather than nitrite is likely the actual inhibitor on nitrate reduction. Sixty percent inhibition of nitrate reduction was observed at an FNA concentration of 0.01-0.025 mg x L(-1), while total inhibition occurred when the FNA concentration was greater than 0.2 mg x L(-1). Furthermore, nitrite reduction by the BNR sludge was also found to be inhibited by HNO2. The reduction rate decreased by approximately 80% when the FNA concentration was increased from 0.01 mg x L(-1) to 0.2 mg x L(-1). The inhibitory effect of nitrate on nitrite reduction was found to be insignificant, with the most recovery rates under different nitrate concentrations larger than 90%. However, the nitrate reduction rate was observed to recover only 3.04%-72.54%. The recovery rate from inhibition was independent of the duration of the inhibition and the feeding mode of inhibitor, but strongly dependent on the concentration of inhibitor the biomass was exposed to during the inhibition period.

The secondary effluent of three WWTPs was treated by ozonation to investigate organic biodegradability enhancement. The bulk experimental method was used. Ozone adding dosage was controlled to be 2, 4, 6, 8, 10 mg/L by adjusting the adding time. Results showed, UV254 and SUVA(UV254/DOC)decreased with the increasing of the ozone dosage. When ozone adding dosage was 6 mg/L, UV254 and SUVA decreased about 54.4% and 56.6% respectively; while BOD5/COD, BDOC and BDOC/DOC were improved above 30%, 360% and 360% respectively. It could be concluded that suitable ozonation could improve the biodegradation of the organic substances in the secondary effluent. The organic substance was analyzed by the excitation-emission matrix (EEM) to investigate the variation regularity of organic matter changes of the ozoned and non-ozoned secondary effluent. The main organic substances of the secondary effluent in the plant were aromatic protein like substances and humic substances, ozone could significantly remove these types of organic substance.

Aerobic sludge granules with compact structure, wide diverse microbial species and excellent settling capabilities have drawn interest of researchers engaging in work in the area of biological wastewater treatment. This review provides recent advances on aerobic biogranulation technology and application. Granulation mechanism, characteristics and its microbial phase, influence of different environmental factors, granulation model and its application in treating the municipal and toxic industrial wastewater were discussed. Then a prospect concerned for future research is also put forward.

The treatment of real leachate from municipal landfill with high ammonia nitrogen (NH4(+) -N) content was investigated by using lab-scale first-stage up-flow anaerobic sludge bed (UASB)-SBR biological system. The denitritation kinetics characteristics of microbial population in the SBR reactor was also studied. Experimental results clearly showed that the average organic loading rate of UASB reactor reached 6.5 kg/(m x d), the average organic removal rate was 5.3 kg/(m3 x d). High concentrations of COD and nitrogen contained in landfill leachate were removed efficiently, average COD and NH4(+) -N of influent could be reduced from 6 537 mg x L(-1) and 2 021 mg x L(-1) to 354 mg x L(-1) and 2.8 mg x L(-1), respectively, the removal efficiencies reached 94.6% and 99.8%, respectively. Especially, above 99.2% removal efficiency of TN was obtained, and effluent TN concentration below 20 mg x L(-1), so advanced nitrogen removal was achieved in the biological system. Ammonia nitrogen was removed by high effective partial nitrification with above 90% nitrite accumulation ratio, and the denitritation kinetics characteristics of the microbial population was fit well for Monod Equation.

Nitrite accumulation during the denitration process with SBR treating pre-treated by anoxic/anaerobic up-flow anaerobic sludge bed (UASB) was observed at low temperatures. The effects of types of carbon sources on nitrite accumulation were investigated for comprehensive understanding the mechanism of nitrite accumulation. Experimental results clearly showed that nitrite accumulated obviously when five carbon sources (methanol, ethanol, sodium acetate, sodium propinoate and glucose), except for glucose, were used as electron donor. Additionally, nitrite accumulations were observed at four different initial nitrate concentrations and lower temperatures. The maximum concentrations of nitrite accumulation were 37.8, 21.5, 25.2 and 18.8 mg/L, respectively, and the corresponding nitrite accumulation rates (N/VSS x t) were 0.117, 0.136, 0.235 and 0.068 g/(g x d) during the nitrite accumulation period. Two break points of "nitrate knee" and "nitrite knee" on oxidation reduction potential (ORP) profile indicated that the reduction reactions of nitrate and nitrite were completed, respectively.

SBR reactors were used to investigate the N2O emission in shortcut nitrification and simultaneous nitrification and denitrification (SND). Shortcut nitrification with nitrosation rate above 90% was realized by real-time control strategy. The N2O emission and variation of nitrosation rate were investigated under 4 DO levels (0.5, 1.0, 1.5, 2.0 mg/L). The results turned out that the optimal DO to maintain high nitrosation rate and minimum N2O emission was 1.5 mg/L and the N4O emission was 0.06 g per ammonium removed. The SBR filled with carbon fiber performed under low DO and pulse feeding. The SND rate was over 79% during the experiment. The N2O emission was studied under DO 0.2, 0.4, 1.0 and 1.5 mg/L. It turned out that the optimal DO was 1.0 mg/L and the N2O emission was 0.021 g per ammonium removed. Compared to the shortcut nitrification, the N2O emission of SND was 1/3 of the short-cut nitrification under optimal DO.

SBR reactor was performed to incubate polyphosphate accumulating organism (PAO), and it was checked out of the system by fluorescence in situ hybridization. As PAO is a kind of ordinary heterotrophic bacteria, it was excluded the ability of phosphate release and uptake and it was considered only the capacity of denitrification of the target biomass. The results indicated that acetate and PHB can be the electron donors of PAO to denitrify. When fed with acetate, the denitrifying rate and PHB producing rate were independent of initial nitrate concentration. However, served as more nitrate in the reactor, it would be less PHB produced and fewer nitrate reducing when using same amount of acetate. In view of PHB stored as an internal carbon and energy source, it presented as a reaction of zero-order to the substrate by PAO to denitrify, such as nitrate, besides, the specific denitrifying rate was 0.9733 mg/(g x h) and the specific PHB consuming rate was 2.4626 mg/(g x h).

A pilot-scale step-feed A/O system was used to treat low C/N municipal wastewater. To obtain high quality simultaneous nitrogen and phosphorus removal, a modified step-feed A/O system was developed and the nitrogen and phosphorus removal efficiency was evaluated between the original and modified system. The result showed that TN removal efficiency was 66.52% and TP removal efficiency was only 29.24% before the modified configuration was applied. When the modified system was adopted, the satisfied simultaneous nitrogen and phosphorus removal was achieved. TP removal efficiency increased to 89.81% and TN removal efficiency was 73.61% when the optimal feeding ratio (0.45:0.35:0.20) was applied. Compared to the original configuration, TN removal efficiency increased about 7.09% due to the enhanced denitrifying phosphorus removal, which saved the carbon source for denitrification. To evaluate the selection and dominance of polyphosphate-accumulating organisms (PAOs) and denitrifying polyphosphate-accumulating organisms (DNPAOs), batch test was explored to examine the anaerobic phosphorus release, aerobic and anoxic phosphorus uptake. The result showed that both PAOs and DNPAOs were accumulated gradually when the modified system was applied. The maximal aerobic P uptake rate [P/(MLSS x t)] was increased from 2.34 mg/(g x h) to 10.67 mg/(g x h) and the anoxic P uptake rate was increased from 0.33 mg/(g x h) to 2.81 mg/(g x h) when the modified system was operated.

Appropriate change of the traditional operation modes was investigated in a UniFed SBR lab-scale apparatus treating actual domestic wastewater with low C/N and C/P. Results showed that when the feed/decant time was extended from 2 h to 3 h and 4 h, the phosphorous removal efficiency increased from 59.93% to 88.45% without any external carbon source. In the mode of anoxic-aerobic condition, TIN of the effluent reduced obviously, the removal efficiency increased from 49.54% to 60.75% for utilizing limited substrate in influents with low C/N = 2.57, adequately. In the mode of alternation of anoxic-aerobic condition, the nitrogen and phosphorous removal efficiency increased clearly. The carbon source in the influent can be used adequately and it occurred denitrifying dephosphatation in anoxic segment 2. This mode was optimal for the treatment of actual domestic wastewater with low C/N and C/P.

In order to realize the combination of "low oxygen limited filamentous sludge bulking" and short cut nitrification,the startup method of short cut nitrification and the maintenance strategies of sludge settleability were investigated under limited filamentous sludge bulking condition by using sequencing batch reactor (SBR). The effects of environmental factors like water quality, pH, DO,temperature and operation methods like mixture flow pattern, aeration mode, influent pattern on sludge settleability were analyzed. The results show that, when pH is between 7.2 and 8.0 and temperature is between 20 degrees C and 25 degrees C, short cut nitrification can be gradually realized through maintaining low DO and controlling the aeration time accurately. Nitrite accumulating ratio can increase from 28% to 80% after operating 160 cycles. Sludge settleability can be maintained effectively by changing the influent volume exchanging ratio (VER) assisted by aeration rate .The sludge volume index (SVI) can be maintained around 150 mL/g by adjusting the VER from 0.25 to 0.33 under limited sludge bulking. At the end of the aerobic phase, dissolved total nitrogen concentration increase slightly.

The experiment investigated the nitrous oxide production under different C/N ratios during denitrification, taking nitrate and nitrite as electron acceptor respectively. Ethanol was selected as carbon source. The C/N ratios were 0, 1.2, 2.4, 3.5, 5.0 and 20 when nitrate was taken as electron acceptor and C/N ratios 0, 1.8, 2.4, 3.0, 4.3, 5.2, 6.6, 20.6 when electron acceptor was nitrite. The results indicated that: the optimum C/N ratio was 3.0 taking nitrite as electron acceptor and the N2O production was 0.044 mg x L(-1); the optimum C/N ratio was 5.0 taking nitrate as electron acceptor and the N2O production was 0.135 mg x L(-1) which was 3 times higher than that of nitrite as electron acceptor. Though the electron acceptor changed, the trend of N2O production was similar: when carbon source was badly insufficient, the production of N2O and denitrification rate were both quite small; the N2O production increased with the increasing of the quantity of carbon source; when the carbon source was excessive, the N2O production sharply raised. Consequently, compared to complete nitrification and denitrification, short-cut nitrification and denitrification could save 40% carbon source. Moreover, controlling C/N = 3 could reduce the production of N2O in short-cut nitrification.

A SBR was used in this study for investigating the influence of carbon source on EBPR metabolism and microorganism communities when feeding with acetate and propionate. The SBR was operated with a cycle time of 8 h and each cycle consisted of 4 min feeding, 2 h anaerobic period, 5 h aerobic period, 35 min setting, 15 min decanting and 6 min waiting. The COD of influent was kept at 300 mg/L during the experiment. Acetate and propionate were used as the sole carbon source for operation of 60 days, respectively. The phosphorus release/ COD consumption in the end of anaerobic phase were 0.35 and 0.27 when acetate and propionate were used as the carbon source, respectively. The PHA composition was different when different carbon source was dosed. PHB accounted for 92.6% in the end of anaerobic phase but the value for PHV was only 7.4% when acetate was selected as the carbon source. No PH2MV was detected during this process. The compositions of PHA were PHB (10.2%), PHV (35.8%) and PH2MV (54.0%) in the end of anaerobic cycle when propionate was used as the sole carbon source. There was variation of microorganism communities during this process for the results of DGGE combined with SEM micrographs and PHA staining. Coccus morphotype PAOs were accumulated in acetate-fed phase and rod morphotype PAOs were accumulated in propionate-fed stage. Different PAOs were accumulated and the metabolic pathways were different when different carbon sources were used, but good EBPR could be achieved during all these conditions.

Under the well-controlled experimental conditions, the biological treatability of real municipal landfill leachate with high strength nitrogen and high chemical oxygen demand (COD) concentration using anoxic/anaerobic upflow anaerobic sludge bed (UASB) -sequencing batch reactor (SBR) combined process was conducted in laboratory. The results indicated: stable anoxic/anaerobic UASB-SBR process performance was developed during running continuously for five phase (116 d) when feed COD concentration was range from 1 237.2 mg/L to 12596.8 mg/L, effluent COD concentration was between 108.4 mg/L and 528.26 mg/L, and when the influent ammonia nitrogen (NH4(+) -N) was changed from 155.8 mg/L to 1298.0 mg/L, the effluent NH4(+) -N was varied from 0.12 mg/L to 4.1 mg/L, it achieved high COD and NH4(+) -N removal efficiency. In this present study, it is noted that the anoxic UASB1 has two significant effects: firstly, denitrification reaction of high efficiency was conducted for SBR nitrified effluent recirculated by using the abundant organic matters in the raw leachate as carbon source. Secondly, its removal COD was highly effected by anaerobic biodegradation. The effluent COD of anoxic UASB1 was biodegraded further in the anaerobic UASB2 and aerobic SBR, the maximum organic loading rates (OLR) (as COD) were 13.0, 2.09, 2.14 kg/(m3 x d), respectively. In addition, the correlation between OLR with OLRrem and COD removal efficiency of three reactors was studied, relation between nitrogen loading rate (NLR) with NH4(+) -N removal efficiency of SBR was tested by linear regression analysis, it was found that the OLR of anoxic UASB1, anaerobic UASB2 and aerobic SBR increased linearly with OLRrem. As to SBR, the correlation was significant between NLR (as N) with NLRrem. In addition, the OLR of three reactors shows second order exponential correlation with COD removal efficiency. At last, when the water temperature of SBR ranged from 20.7 degrees C to 10.3 degrees C, and dissolved oxygen was controlled below 1.0 mg/L, the efficiencies of nitrification and denitrification were above 98.5% and 97.7% during the whole experimental running period, it achieved advanced nitrogen removal.

The experimental system consisted of anoxic filter and aerobic suspended carrier biofilm reactor. The partial nitrification was achieved and maintained stably in the aerobic reactor under normal temperature (15-29 degrees C) and high DO (6-9 mg/L). The nitritation with 70%-80% nitrite accumulation efficiency was obtained when FA concentration was in the range of 1.0-10.3 mg/L by controlling influent ammonia loading rate (ALR), ratio of alkalinity and ammonia and HRT in the aerobic reactor. The effluent nitrite/ammonia ratio was about 1.25 when the average influent ammonia, influent ALR and influent ratio of alkalinity and ammonia were 315.80 mg/L, 0.43 kg/(m3 x d) and 5.25, respectively. So the effluent of partial nitrification process provided the influent substrate demand for the following ANAMMOX process. The integrative analysis indicated that the proper FA concentration was the main factor achieving the partial nitrification. The study developed a novel partial nitrification technology adapt to water characteristics of digested sludge liquor.

The affecting factors and controlling methods of how realizing and maintaining half-nitrosofication of dewatering liquid of digested sludge were investigated in an A/O process. The experimental results showed that the nitritation was obtained in 29 d under bulk liquid temperature of 9-20 degrees C, average DO of 5.4 mg/L, SRT of about 30 d and influent ammonia loading rate of 0.64 kg/(m3 x d). The nitritation with 70% nitrite accumulation efficiency was maintained during 65 d when average FA concentration in A/O reactor was more than 4 mg/L. Furthermore, the half-nitrosofication with effluent ammonia and nitrite ratio of 1:1.32 was obtained. When the ammonia loading rate reduced to 0.19 kg/(m3 x d) (FA < 1 mg/L), the nitritation disappeared, and the high FA as a main factor of maintaining half-nitrosofication was proved again with FISH under the condition of different FA. TN removal concentration was about 91 mg/L under influent COD of 282 mg/L and raw C/N ratio of 0.85 in the A/O system, which due to nitritation saving much carbon sources. The study showed that the half-nitrosofication of the dewatering liquid was obtained and stably maintained when FA was more than 4 mg/L in the A/O reactor by dynamic controlling influent ammonia loading rate and pH value in the system under middle or low temperature, high DO, long SRT.