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The continuous aerobic granular sludge (AGS) process is promising for upgrading existing wastewater treatment facilities. However, this approach is still challenging because of its complicated structure and operation. To address this issue, a novel separate aeration self-circulating technology (abbreviated as Zier) was proposed, which is promising for cultivating AGS by its outstanding upflow velocity and circulation multiplier (more than 30 m/h and 200, respectively). This study elaborated on the Zier reactor's feasibility, optimization, and control strategy through computational fluid dynamics simulations, theoretical calculations, and experiments. An appropriate flow regime for efficient removal of pollutant and granulation of sludge was attained at a superficial gas velocity of 1.3 cm/s. Moreover, optimizing the aeration column diameter to half of the reaction column and increasing the height/diameter ratio to 20 dramatically boosted the nitrogen removal capacity over 1.6 kg N/m3/d. Utilizing a smaller circulation pipe diameter ensured granulation under a consistent flow regime. By judiciously regulating, multiple CSTRs and PFRs seamlessly integrated within the Zier reactor across a broad spectrum of particle sludge. The validity of these findings was further substantiated through experimental and theoretical validations. Drawing from these findings, a multi-scenario control strategy was proposed as Zier's map. With all the superiorities shown by the Zier reactor, this study could offer new insights into an efficient continuous AGS process.
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Reatores Biológicos , Hidrodinâmica , Esgotos , Eliminação de Resíduos Líquidos , Eliminação de Resíduos Líquidos/métodos , Aerobiose , NitrogênioRESUMO
Aerobic granular sludge (AGS) capable of nitrogen and phosphorus removal is mainly limited to the applications in sequencing batch reactors. This study introduced an innovative continuous self-circulating up-flow fluidized bed process (Zier process) using separate aeration. The process was composed of an anoxic column (Zier-A), aeration column (Zier-OO) and aerobic column (Zier-O), and was used to treat actual municipal sewage continuously for 170 days. The process achieved self-circulation of 20-32 times and an up-flow velocity within the reactor of 7-16 m/h which were accurately controlled with only separate aeration. The larger proportion of self-circulating multiple times contributed to particle formation and stability, providing hydraulic shear conditions, and screened the precipitation performance of the granular sludge (GS). Meanwhile, the dissolved oxygen (DO) of Zier-O was controlled at 0.1-0.3 mg/L, and the DO of Zier-A input water was zero. The accurate oxygen supply enhanced simultaneous nitrification and denitrification (SND) as well as short-cut nitrification and denitrification in Zier-O and improved the COD utilization rate and the nitrogen removal rate in Zier-A. The COD treatment capacity reached 2.46 kg-COD/(m³·d). With a hydraulic retention time of 10 h, the process consistently ensured that the average concentrations of ammonia nitrogen and total nitrogen in the effluent were maintained below 5 and 15 mg/L, respectively. Moreover, the process maintained the shape and stability of GS, the median diameter of GS ranged between 300-1210 µm, the percentage of mass with particle size distribution < 200 µm at a height of 150 cm within Zier-A and Zier-O accounted for as low as 0.04%-0.05%, and showed good settling performance. The suspended solids in effluent can be maintained at 50-80 mg/L. Overall, the unique structural setting and control method of the Zier process provide another approach for the application of continuous AGS treatment for municipal sewage.
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Reatores Biológicos , Nitrogênio , Esgotos , Eliminação de Resíduos Líquidos , Eliminação de Resíduos Líquidos/métodos , Aerobiose , Fósforo , Desnitrificação , Análise da Demanda Biológica de Oxigênio , NitrificaçãoRESUMO
Anammox is a green, economical and efficient nitrogen removal process. Most successful anammox studies are based on biofilm- or granule-based systems, but pure floc sludge partial nitrification (PN) and anammox (A) systems that are not inoculated with anaerobic ammonia oxidizing bacteria (AnAOB) are rarely reported. If the anammox process occurs in floc-based systems, the large specific surface areas provide more efficient nitrogen removal, and are much more economical in terms of construction and investment. This study investigated the establishment, performance and sludge characteristics of a one-stage PN/A system with pure floc sludge and exhibited a short sludge retention time (SRT) and low mixed liquor suspended solids (SS) content. The experiment was run for approximately 1260 days and divided into five stages based on the SRTs and influent ammonia concentrations treating synthetic wastewater with no organic matter. The results showed that the AnAOB were successfully cultivated and enriched with ordinary nitrification and denitrification sludge, which formed a pure floc-based anammox system with a short SRT (at least 14 days) and a low SS control. The maximum nitrogen removal efficiency and sludge removal loading rate reached 87.1 % and 3.16 kg N/(kg VSS·d) with ammonia loading rates = 0.55 and 0.56 kg-N/(m3·d), dissolved oxygen = 0.2 and 0 mg/L, temperature = 30 and 28 °C, mixed liquor volatile suspended solid (VSS) = 800 and 130 mg/L, free ammonia (FA)/VSS = 3.5 and 47.5 mg NH3-N/g VSS and SRT = 30 and 15 days, respectively. Moreover, the FA/VSS ratio was used to determine the operating performance of the PN/A system, and the thresholds for inhibiting nitrite-oxidizing bacteria and ammonia-oxidizing bacteria, including AnAOB, were 0.5-50 and above 50 mg NH3-N/g VSS, respectively. The floc-based one-stage PN/A systems proposed in this study provide reductions in the volumes, and floor areas for the reactor tanks, and in the cost of the carrier.
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Nitrificação , Esgotos , Esgotos/microbiologia , Amônia , Oxidação Anaeróbia da Amônia , Reatores Biológicos/microbiologia , Bactérias , Nitrogênio , Oxirredução , DesnitrificaçãoRESUMO
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(NOx--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.
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Microbiota , Nitrogênio , Bactérias , Carbono/química , Desnitrificação , Etanol/química , Glucose , Metanol/química , Nitrogênio/química , Acetato de SódioRESUMO
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 SV30/SV5 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, NH4+-N, and TN were 94%, 99%, and 35% and 92%, 97%, and 30%, respectively, in SBR1 of bulking sludge and SBR2 of flocculated sludge, and the removal rates of TP were 60% and 30%, respectively.
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Microbiota , Esgotos , Bactérias , Reatores Biológicos/microbiologia , Esgotos/microbiologia , Eliminação de Resíduos Líquidos/métodosRESUMO
Odor emissions from intensive livestock farms have attracted increased attention due to their adverse impacts on the environment and human health. Nevertheless, a systematic summary regarding the characteristics, sampling detection, and control technology for odor emissions from livestock farms is currently lacking. This paper compares the development of odor standards in different countries and summarizes the odor emission characteristics of livestock farms. Ammonia, the most common odor substance, can reach as high as 4100 ppm in the compost area. Sampling methods for point and area source odor emissions are introduced in this paper, and odor analysis methods are compared. Olfactometers, odorometers, and the triangle odor bag method are usually used to measure odor concentration. Odor control technologies are divided into three categories: physical (activated carbon adsorption, masking, and dilution diffusion), chemical (plant extract spraying, wet scrubbing, combustion, non-thermal plasma, and photocatalytic oxidation), and biological (biofiltration, biotrickling, and bioscrubbing). Each technology is elucidated, and the performance in the removal of different pollutants is summarized. The application scopes, costs, operational stability, and secondary pollution of the technologies are compared. The generation of secondary pollution and long-term operation stability are issues that should be considered in future technological development. Lastly, a case analysis for engineering application is conducted.
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Compostagem , Odorantes , Amônia , Animais , Fazendas , Humanos , GadoRESUMO
This study investigated the effects of denitrification sludge EPS enhanced (DS-EPSCN) by a fluctuating carbon and nitrogen ratio (C/N) cultivation strategy on the properties of Anammox granules under extreme acid or alkaline shock. The results showed that the DS-EPSCN significantly improved the nitrogen removal performance of low-density Anammox granular sludge (Granules-L) and high-density Anammox granular sludge (Granules-H) under extreme acid shock (pH 5.0). The contents of high-molecular-weight substances (such as aromatic proteins and polysaccharides) in the DS-EPSCN rose markedly, contributing to a substantial increase in the flocculation efficiency under acidic conditions and increasing the granule stability. In addition, abundant amounts of N-butyryl-dl-homoserine lactone (C4-HSL) and N-hexanoyl-dl-homoserine lactone (C6-HSL) in the DS-EPSCN promoted the granule activity. However, under extreme alkaline shock (pH 10.5), the flocculation efficiency of the DS-EPSCN was poor, and the addition of DS-EPSCN had no influence on the stability of the granules but improved the activity of the Granules-H. The reason was that the release mechanism of the endogenous acyl-homoserine lactone (AHL) signals in the Granules-H was activated by the exogenous C4-HSL and C6-HSL in the DS-EPSCN under alkaline conditions, leading to increased Granules-H activity. This research provides a novel approach to enhance the resistance of Anammox granular sludge to extreme pH shock.
Assuntos
Desnitrificação , Esgotos , Acil-Butirolactonas , Reatores Biológicos , Concentração de Íons de Hidrogênio , Percepção de QuorumRESUMO
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 (NH2 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 NH2 OH. The results showed that when 5 mg·L-1 of NH2 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 NN4+-N dropped from 26.05 mg·L-1 to 8.06 mg·L-1, thus producing 9.02 mg·L-1 of NO2--N and 6.70 mg·L-1 of NO3--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 NH2 OH is expected to provide a feasible application for the rapid start-up nitritation of municipal wastewater.
Assuntos
Amônia , Nitritos , Bactérias/genética , Reatores Biológicos , Hidroxilamina , Hidroxilaminas , Nitrificação , Oxirredução , EsgotosRESUMO
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.
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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.
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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 R2 was 0.90 and 0.94, respectively. FHA may be the main reason for inhibiting the activity of Nitrobacter and Nitrospira.
Assuntos
Nitritos , Nitrobacter , Bactérias , Reatores Biológicos , Hidroxilamina , Hidroxilaminas , OxirreduçãoRESUMO
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)â, 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.
Assuntos
Bactérias , Esgotos , Reatores Biológicos , Temperatura Baixa , Fósforo , Temperatura , Eliminação de Resíduos LíquidosRESUMO
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 Cu2+, 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 Cu2+ on denitrification using NO2- as an electron acceptor. The results showed that Cu2+ had a significant inhibitory effect on denitrification process using NO2- as an electron acceptor, and the semi-inhibitory concentration EC50 of sludge activity was 4.79 mg·L-1. In the long-term experiment, the concentration of Cu2+ was gradually increased. When the concentration of Cu2+ was 0.5 mg·L-1and 1 mg·L-1, the denitrification activity of the sludge could be restored to the original level after acclimation. When the concentration of Cu2+ was increased to 3 mg·L-1, the denitrification performance was destroyed and difficult to recover, at which point the NO2--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 Cu2+ had been stopped for 14 days. At the same time, during the long-term effect of Cu2+, the EPS content increased, which played an important role in protecting the microorganism against Cu2+ toxicity, and increased the sludge particle size and, as a result, sludge sedimentation.
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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 4.37×107 copies·g-1 to 2.28×1010 copies·g-1. This study demonstrates that anoxic carrier biofilms may have potential applications in anammox bacterial enrichment to enhance denitrification from municipal wastewater.
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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.
Assuntos
Reatores Biológicos , Nitrificação , Bactérias , Nitritos , Nitrogênio , Esgotos , Eliminação de Resíduos LíquidosRESUMO
Under transient conditions, a biotrickling filter was developed to treat gaseous H2S 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 7.8-32.5â, and an inlet concentration of 2.02-319.19 mg·m-3, an average removal efficiency of 91.8% was achieved with a maximum H2S elimination capacity of 78.37 g·(m3·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 H2S 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 H2S, but the elimination capacity could be increased.
Assuntos
Biodegradação Ambiental , Sulfeto de Hidrogênio , Microbiota , Águas Residuárias , Reatores Biológicos , Filtração , PolipropilenosRESUMO
Shortcut nitrification sludge, which was set aside for two months, was recovered using Reactors â , â ¡, â ¢, and â £. The aeration rates of Reactors â , â ¡, â ¢, and â £ 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 25â. 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 12th, 18th, 21st, and 21st cycles. The removal ratio of ammonia nitrogen was about 95%. The highest concentrations of nitrite for Reactors â , â ¡, â ¢, and â £ were 20.83, 22.81, 21.50, and 20.73 mg·L-1, respectively, which occurred in the 30th, 35th, 38th, and 42nd 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.
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Amônia/química , Reatores Biológicos , Nitrificação , Nitritos/química , Nitrogênio/química , Bactérias/metabolismo , EsgotosRESUMO
A modification of the two sludge A2/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, NH4+-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 A2/O-BAF system to treat low C/N waste water.
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Reatores Biológicos/microbiologia , Desnitrificação , Nitratos/isolamento & purificação , Fósforo/química , Eliminação de Resíduos Líquidos/métodos , Nitrogênio , EsgotosRESUMO
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 NH4+-N and NO2--N increased from 54.4% and 65.3% to 95.8% and 92.5%, respectively, at a temperature of 30â and an influent concentration of NO2--N of (30±0.2)mg·L-1. The substrate ratio (NO2--N/NH4+-N) increased from 0.9 to 1.4.However, the removal efficiency of NH4+-N was affected negligibly, and the average removal efficiency of NO2--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 NH4+-N and NO2--N decreased from 97.5% and 98.5% to 35.2% and 40.1%, respectively, when the temperature of the reactor dropped from 30â to 15â at one time. The average removal efficiencies of NH4+-N and NO2--N dropped from 97.7% and 98.6% to 52.7% and 62.4%, respectively, when the ladder cooling method(30ââ25ââ20ââ15â) was used. The average removal efficiencies of NH4+-N and NO2--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 NO2--N/NH4+-N equal to 1.4.
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Amônia/metabolismo , Nitrogênio/isolamento & purificação , Eliminação de Resíduos Líquidos , Águas Residuárias , Anaerobiose , Reatores Biológicos , OxirreduçãoRESUMO
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 NH3·H2O with almost no ammonia escape. With high FA concentration (FA>687.1 mg·L-1), ammonia nitrogen is not oxidized to oxidized nitrogen (NO2--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, NH4+-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.