异养硝化菌的分离及其强化活性污泥脱氮效果

为提高水处理过程中的脱氮率，实现好氧条件下对总氮的去除。通过试验分离出一株异养硝化菌，该菌株为白色革兰氏阴性球状菌。将该菌扩大培养后接种于活性污泥系统并进行了处理模拟废水的试验。结果表明：该菌能在好氧条件下分别代谢氨氮、亚硝酸盐氮、硝酸盐氮，并通过好氧反硝化实现对总氮的去除。用该菌株强化的活性污泥系统对以氨氮、亚硝酸盐氮、硝酸盐氮为惟一氮源的模拟废水进行处理，4h的总氮去除率分别为85％、60％、70％。     

臭氧破解活性污泥的试验研究

采用鼓泡型臭氧接触反应柱,探讨了臭氧氧化对活性污泥性状的影响。结果表明,反应初期MLSS降幅不大,在臭氧投量为0.04～0.10 gO3/gMLSS阶段,臭氧直接作用于污泥,MLSS下降明显;MLVSS呈现与MLSS类似的下降趋势;随着臭氧投量的增加,MLVSS/MLSS值从初期的0.75降至试验末期的0.60。臭氧溶胞引起上清液中SCOD浓度的上升,但同时由于臭氧的矿化作用导致其增加量低于经验值,为0.628 4 gSCOD/gMLVSS。另外,上清液中硝态氮和总氮浓度呈上升趋势,氨氮浓度先上升后下降,在臭氧投量为0.08 gO3/gMLSS时达到最大。     

Controlling sludge settleability in the oxidation ditch process

This paper describes an investigation aimed at developing an operating technique for controlling sludge settleability in the oxidation ditch form of the nitrification denitrification activated sludge process. It was hypothesized that specific sludge volume index (SSVI) is lowest at an optimum process anoxic fraction and increases at higher and lower fractions. Using effluent ammonia:nitrate ratio as a surrogate for anoxic fraction, it was found that a simple empirical model based on a three solids retention time moving average nitrogen ratio was able to replicate the long-term SSVI variations in two independent oxidation ditches at a full-scale plant. Operating data from a second oxidation ditch plant during periods when a prefermenter was on- or off-line showed that SSVI also varies with RBCOD, greater RBCOD giving lower SSVI. It was concluded that best settleability occurs at about the same anoxic fraction as lowest effluent total nitrogen concentration, with an ammonia:nitrate ratio of about 1. An operating rule of thumb is to use dissolved oxygen control to maintain effluent ammonia and nitrate nitrogen concentrations about equal. A third oxidation ditch plant deliberately operated in this manner achieved 15-month median operating values for SSVI of 60mL/g and for effluent ammonia, nitrate and total N, respectively, of 0.2, 0.3 and 2.0mgN/L.     

Anaerobic/oxic/anoxic granular sludge process as an effective nutrient removal process utilizing denitrifying polyphosphate-accumulating organisms

In a biological nutrient removal (BNR) process, the utilization of denitrifying polyphosphate-accumulating organisms (DNPAOs) has many advantages such as effective use of organic carbon substrates and low sludge production. As a suitable process for the utilization of DNPAOs in BNR, an anaerobic/oxic/anoxic granular sludge (AOAGS) process was proposed in this study. In spite of performing aeration for nitrifying bacteria, the AOAGS process can create anaerobic/anoxic conditions suitable for the cultivation of DNPAOs because anoxic zones exist inside the granular sludge in the oxic phase. Thus, DNPAOs can coexist with nitrifying bacteria in a single reactor. In addition, the usability of DNPAOs in the reactor can be improved by adding the anoxic phase after the oxic phase. These characteristics enable the AOAGS process to attain effective removal of both nitrogen and phosphorus. When acetate-based synthetic wastewater (COD: 600 mg/L, NH4-N: 60 mg/L, PO(4)-P: 10 mg/L) was supplied to a laboratory-scale sequencing batch reactor under the operation of anaerobic/oxic/anoxic cycles, granular sludge with a diameter of 500 microm was successfully formed within 1 month. Although the removal of both nitrogen and phosphorus was almost complete at the end of the oxic phase, a short anoxic period subsequent to the oxic phase was necessary for further removal of nitrogen and phosphorus. As a result, effluent concentrations of NH(4)-N, NO(x)-N and PO(4)-P were always lower than 1 mg/L. It was found that penetration depth of oxygen inside the granular sludge was approximately 100 microm by microsensor measurements. In addition, from the microbiological analysis by fluorescence in situ hybridization, existence depth of polyphosphate-accumulating organisms was further than the maximum oxygen penetration depth. The water quality data, oxygen profiles and microbial community structure demonstrated that DNPAOs inside the granular sludge may be responsible for denitrification in the oxic phase, which enables effective nutrient removal in the AOAGS process.     

无外加碳源SBBR脱氮工艺及其控制方法研究

为提高脱氮效果并实现利用内碳源进行反硝化,开展了SBBR（以好氧-缺氧方式运行）处理生活污水的脱氮研究.在好氧阶段,SBBR中的生物膜能创造缺氧微环境并吸收、储存碳,实现了同步硝化反硝化,降低了硝态氮的浓度;在缺氧阶段,可利用内碳源实现剩余硝态氮的反硝化.溶解氧浓度的大小对好氧时间、好氧剩余硝态氮浓度和缺氧反应时间有较大影响,因而可以利用在线检测的DO作为曝气量控制参数.DO、pH和ORP值的变化具有规律性,反映了生物脱氮过程中耗氧和供氧、产酸和产碱、氧化和还原过程的变化.为准确判断好氧和缺氧反应过程的终点,并减少控制的滞后时间,建议以pH值的＂氨谷＂和ORP的＂硝酸盐膝＂作为主控制特征点分别指示硝化和反硝化的终点,而以ORP的＂氨肘＂和pH值的＂硝酸盐峰＂作为参考或辅助控制特征点.     

Simultaneous nitrogen and phosphate removal in aerobic granular sludge reactors operated at different temperatures

The main biological conversions taking place in two lab-scale aerobic granular sludge sequencing batch reactors were evaluated. Reactors were operated at different temperatures (20 and 30 °C) and accomplished simultaneous COD, nitrogen and phosphate removal. Nitrogen and phosphate conversions were linked to the microbial community structure as assessed by fluorescent in situ hybridization (FISH) analysis. Anoxic tests were performed to evaluate the contribution of anoxic phosphate uptake to the overall phosphate removal and to clarify the denitrification pathway. Complete nitrification/denitrification and phosphate removal were achieved in both systems. A considerable fraction of the phosphate removal was coupled to denitrification (denitrifying dephosphatation). From the results obtained in anoxic batch experiments dosing either nitrite or nitrate, denitrification was proposed to proceed mainly via the nitrate pathway. Denitrifying glycogen-accumulating organisms (DGAOs) were observed to be the main organisms responsible for the reduction of nitrate to nitrite. A significant fraction of the nitrite was further reduced to nitrogen gas while being used as electron acceptor by denitrifying polyphosphate-accumulating organisms (PAO clade II) for anoxic phosphate uptake.     

Anoxic growth of phosphate-accumulating organisms (PAOs) in biological nutrient removal activated sludge systems

In this paper, research on the growth performance of phosphate-accumulating organisms (PAOs) was conducted based on literature and experimental investigations on biological nutrient removal (BNR) activated sludge (BNRAS) systems. The research aims at presenting the occurrence of denitrifying PAOs (DPAOs), abstracting information on the kinetics and stoichiometry of PAOs under anoxic conditions and determining the conditions that stimulate the PAO growth under anoxic conditions. The research results indicate that the PAOs are capable of utilizing nitrate as electron acceptor instead of oxygen in BNRAS systems, particularly in external nitrification BNRAS (ENBNRAS) systems. However, the growth yield of PAOs under anoxic conditions should be reduced to about 70% of that under aerobic conditions, and further the stoichiometric coefficient for anoxic P uptake per PHB COD utilized should be reduced to about 80% of that under aerobic conditions as the DPAOs show a significantly lower BEPR performance and use the influent RBCOD less "efficiently" compared with aerobic PAOs (APAOs). The research results also indicate that the major factor influencing the occurrence of DPAOs and associated anoxic P uptake is the nitrate load into the anoxic reactor, i.e. the nitrate load should be large enough or exceeds the denitrification potential of ordinary heterotrophic organisms (OHOs), i.e. non-PAO organisms in the anoxic reactor to stimulate DPAOs in the system as the specific denitrification rate of OHOs (K'2 OHO) is significantly larger than that of PAOs (K'2 PAO). In terms of this competition, if the nitrate load into the main anoxic reactor is less than the denitrification potential of OHOs, then the OHOs will outcompete PAOs for using the limited nitrate, while if the nitrate load in the main anoxic reactor exceeds the denitrification potential of OHOs, then the PAOs would have opportunities to use the "excess" nitrate and so develop in the system. The other factors that influence DPAOs include the system aerobic mass fraction, sequence of reactors and frequency of sludge alternation between the aerobic and anoxic states. Although it does appear that these factors above may significantly influence the fraction of DPAOs (etaG), the quantitative relationship between these factors and etaG is not known, and the experimental observations indicate that this will be system-specific, and require calibration for each situation.     

污泥减量工艺:HA-A/A-MCO的好氧脱氮机制分析

针对污泥减量技术存在对氮、磷去除能力低的问题,开发了一种具有强化脱氮除磷功能并可实现污泥减量化的HA-A/A-MCO工艺。在该工艺取得同步脱氮除磷和污泥减量优异效果的条件下,采用其处理校园生活污水,当进水TN平均为47 mg/L时,出水TN为10.9 mg/L,系统的总脱氮率为76.8%,其中好氧脱氮量占总脱氮量的50%,缺氧脱氮量占26%;HA-A/A-MCO系统存在着在好氧条件下具有反硝化能力的菌属,对好氧脱氮有一定贡献,且DO浓度对其反硝化能力没有抑制作用;好氧池中的DO浓度梯度有利于在污泥絮体内形成缺氧环境,从而促进同步硝化反硝化(SND)的发生,但减小污泥絮体尺寸会削弱絮体内部缺氧区域比例、降低SND的脱氮效率。     

A novel sulfate reduction, autotrophic denitrification, nitrification integrated (SANI) process for saline wastewater treatment

This paper reports on a lab-scale evaluation of a novel and integrated biological nitrogen removal process: the sulfate reduction, autotrophic denitrification and nitrification integrated (SANI) process that was recently proposed for saline sewage treatment. The process consisted of an up-flow anaerobic sludge bed (UASB) for sulfate reduction, an anoxic filter for autotrophic denitrification and an aerobic filter for nitrification. The experiments were conducted to evaluate the performance of the lab-scale SANI system with synthetic saline wastewater at various hydraulic retention times, nitrate concentrations, dissolved oxygen levels and recirculation ratios for over 500 days. The system successfully demonstrated 95% chemical oxygen demand (COD) and 74% nitrogen removal efficiency without excess sludge withdrawal throughout the 500 days of operation. The organic removal efficiency was dependent on the hydraulic retention time, up-flow velocity, and mixing conditions in the UASB. Maintaining a sufficient mixing condition in the UASB is important for achieving effective sulfate reduction. For a typical Hong Kong wastewater composition 80% of COD can be removed through sulfate reduction. A minimum sulfide sulfur to nitrate nitrogen ratio of 1.6 in the influent of the anoxic filter is necessary for achieving over 90% nitrate removal through autotrophic denitrifiers which forms the major contribution to the total nitrogen removal in the SANI system. Sulfur balance analyses confirmed that accumulation of elementary sulfur and loss of hydrogen sulfide in the system were negligible.     

Heterotroph anoxic yield in anoxic aerobic activated sludge systems treating municipal wastewater

As input to the steady state design and kinetic simulation models for the activated sludge system, the correct value for the heterotroph anoxic yield is essential to provide reliable estimates for the system denitrification potential. This paper examines activated sludge anoxic yield values in the literature, and presents experimental data quantifying the value. In the literature, in terms of the structure of ASM1 and similar models, theoretically it has been shown that the anoxic yield should be reduced to approximately 0.79 the value of the aerobic yield. This theoretical value is validated with data from corresponding aerobic OUR and anoxic nitrate time profiles in a batch fed laboratory scale long sludge age activated sludge system treating municipal wastewater. The value also is in close agreement with values in the literature measured with both artificial substrates and municipal wastewater. Thus, it is concluded that, in ASM1 and similar models, for an aerobic yield of 0.67mg COD/mg COD, the anoxic yield should be about 0.53 mg COD/mg COD. Including such a lower anoxic yield in ASM1 and similar models will result in a significant increase in denitrification potential, due to increased denitrification with wastewater RBCOD as substrate. In terms of the structure of ASM3, for the proposed substrate storage yields and the aerobic yield of 0.63 mg COD/mg COD, experimental data indicate that the corresponding anoxic yield should be about 0.42 mg COD/mg COD. This is significantly lower than the proposed value of 0.54 mg COD/mg COD, and requires further investigation.     

Organic removal by denitritation and methanogenesis and nitrogen removal by nitritation from landfill leachate

A system consisting of a two-stage UASB and anoxic-oxic reactor was used to enhance COD and nitrogen removal from landfill leachate. To improve denitrification efficiency, the raw leachate with recycled final effluent was pumped into the first-stage UASB (UASB1) to carry out simultaneous denitrification and methanogenesis. The results over 180 d show that the maximum organic removal rate in UASB1 and UASB2 was 12.5 and 8.5 kgCODm(-3)d(-1) in the oxic zone of the A/O reactor, respectively. The COD and biochemical oxygen demand (BOD5) removal efficiency of the system was 80-92% and about 99%, respectively. Without controlling temperature (17-30 degrees C) and dissolved oxygen (0.5-4.0 mgL(-1)), the maximum NH4+-N removal rate was 0.68 kg NH4+-Nm(-3)d(-1), and about 99% of NH4+-N removal was obtained by nearly complete nitritation. The 81-93% total nitrogen removal was obtained by complete denitrification in the UASB1 and in the anoxic zone of the A/O reactor. Fluorescence in situ hybridization (FISH) analysis of the sludge samples from A/O reactor showed that ammonia oxidizing bacteria (AOB) consisted 4% of the eubacterium, while nitrite oxidizing bacteria (NOB) counted less than 0.2% of that. The study shows that the main factors achieving and maintaining nitritation are a proper range of free ammonia concentration obtained by dilution recycled final effluent that inhibits NOB but not AOB; effective control on aeration time by indication of "ammonia valley" on pH profile; and highly efficient denitrification and its reproducing alkalinity to result in pH above 8.5.     

Steady-state model-based evaluation of sulfate reduction, autotrophic denitrification and nitrification integrated (SANI) process

Recently we developed a process for wastewater treatment in places where part of the fresh water usage is replaced by seawater usage. The treatment of this saline sewage consists of sulfate reduction, autotrophic denitrification and nitrification integrated (SANI) process. The process consists of an up-flow anaerobic sludge bed (UASB) for sulfate reduction, an anoxic filter for autotrophic denitrification using dissolved sulfide produced in the UASB and an aerobic filter for nitrification. The system was operated for 500 days with 97% COD removal and 74% total nitrogen removal without withdrawal of sludge. To verify these results and to understand this novel process, a steady-state model was developed from the COD, nitrogen and sulfur mass and charge balances based on the stoichiometries of the sulfate reduction, the autotrophic denitrification and the autotrophic nitrification. The model predictions agreed well with measured data on COD, nitrate and sulfate removal, sulfide production, effluent TSS, and mass balances of COD, sulfur and nitrogen in the three reactors. The model explains why withdrawal of sludge from the SANI system is not needed through comparisons of the predictions and measurements of effluent TSS and phosphorus concentrations.     

Simultaneous removal of phenol and ammonia by an activated sludge process with cross-flow filtration

Attempts were made for removing ammonia from synthetic wastewater under the presence of phenol, which is inhibitory to nitrification, by using a single-stage activated sludge process with cross-flow filtration. Activated sludge biomass which had been acclimated with phenol for over 15 years was used for the inoculum, and synthetic wastewater was continuously supplied to the process retaining biomass at 8000 mg VSS l(-1). Phenol was completely removed, and ammonia was simultaneously nitrified to nitrate; nitrification rate reached 200 mg N l(-1) d(-1) when phenol was removed at a rate up to 300 mg l(-1) d(-1). It was observed that 0-13% of the ammonia was removed via denitrification. Intermittent aeration enhanced the denitrification rate to 160 mg N l(-1) d(-1) by utilizing phenol. and approximately 24% of the denitrified nitrogen was recovered as nitrous oxide. Methanol, which is the most commonly used electron donor in conventional nitrogen removal processes, did not enhance the denitrification rate of the phenol-acclimated activated sludge used in this study, however phenol did. The results suggest that this process potentially works as a space- and energy-saving nitrogen removal process by utilizing substances inhibitory to nitrifiers as electron donors for denitrification.     

The effect of operational parameters of the process of sludge ozonation on the solubilisation of organic and nitrogenous compounds

An evaluation of various operational parameters on the process of sludge ozonation was carried out based on semi-batch experiments. Particular reference has been given to examine the main parameters affecting the solubilisation of organic matter and nitrogenous compounds. Various sets of experiments were undertaken using real sewage sludge to feed a semi-industrial ozonation plant. Applying ozone dosages between 25 and 35 mg O(3)/gTSS, the organic matter solubilisation obtained through ozonation increases proportionally to ozone dosage until a maximum value of 430 mg COD/L. Concerning the nitrogenous compounds, no variation in nitrite concentration and a low increase in nitrate concentration were attained, regardless of the applied ozone dosage. Little increase in ammonia concentration was achieved for low ozone dosages, whilst applying dosages higher than 20 mg O(3)/gTSS, the variation of ammonia increased proportionally with ozone dosage. Experiments using hydraulic retention time (HRT) between 10 and 60 min resulted in a similar COD solubilisation, confirming a rapid rate of cell lysis during ozonation of sludge.     

Kinetics of denitrification reactions in single sludge systems

This paper reports denitrification studies performed using the anoxic reactor of a laboratory scale anoxic-aerobic plant as a batch reactor of variable volume. This was achieved by adding to the anoxic reactor a supplementary flow of nitrate after the shut down of the recirculation line and the interruption of the hydraulic connection to the aerobic reactor. By operating in this way, in a relatively short time, it is possible to get a number of experimental data sufficient to describe the biological process kinetics. The system is extremely flexible and gives kinetic data in short times for different experimental conditions. In fact, it is possible to operate at different COD/NO₃-N ratios simply by changing the influent wastewater flowrate to the anoxic reactor. Two series of tests were performed: in the first series (use of endogenous carbon) a supplementary flow of nitrate was fed to the anoxic reactor while the wastewater influent flow was interrupted; in the second series (use of internal carbon) the influent wastewater flow was fed during the addition of nitrate. The importance of the carbonaceous substrate nature on the denitrification rate was also verified. Data analysis was performed by utilizing the integral method procedure and a zero order kinetics referring to both the substrates COD and nitrate nitrogen was considered. A satisfactory agreement between predicted and experimental data was found. Values obtained for k_D range from 0.07 mg NO₃-N/mg VSS·d, at which the carbon source is mostly endogenous, to 0.25 mg NO₃-N/mg VSS·d, at which the carbon source consists mainly of readily biodegradable COD. Intermediate values occur when the readily biodegradable COD is limiting and denitrification takes place by utilizing the slowly biodegradable one.     

利用储碳活性污泥强化反硝化脱氮研究

为提高脱氮效果,在SBR进水的缺氧操作结束后取出部分储碳污泥并加以保存,待好氧末返投储碳污泥作为碳源来强化缺氧反硝化反应.结果表明:对TN的去除率可达98%左右,远高于以缺氧/好氧方式运行的SBR;在好氧段的污泥浓度约为3 000 mg/L的情况下,选择缺氧搅拌段的污泥浓度为5 000 mg/L左右能使TN基本全部被去除.SBR经改造后,能有效实现取、返储碳污泥,提高了脱氮效果.     

一体化A/O生物膜反应器处理生活污水

根据缺氧 好氧 (Anoxic Oxic ,A O)工艺原理设计了升流式一体化A O生物膜反应器 ,并就反应器对生活污水的处理效果和运行参数进行了试验。结果表明 ,当缺氧区HRT为 5h、好氧区HRT为 3h时对COD的去除率 >80 % (大部分接近 90 % ) ,对SS去除率 >95 % ;维持反应器内适宜的碱度可获得良好而稳定的脱氮效果 ;剩余污泥少 ,无需频繁排泥。     

Application of a membrane bioreactor for treating explosives process wastewater

A bench-scale anoxic membrane bioreactor (MBR) system, consisting of a bioreactor coupled to a ceramic cross-flow ultrafiltration module, was evaluated to treat a synthetic wastewater containing alkaline hydrolysis byproducts (hydrolysates) of RDX. The wastewater was formulated the same as hydrolysis wastewater and consisted of acetate, formate and formaldehyde as carbon sources and nitrite and nitrate electron acceptors. The MBR system removed 80-90% of the carbon sources, and approximately 90% of the stoichiometric amount of nitrate, 60% of nitrite. The reactor was also operated over a range of transmembrane pressure, temperature, suspended solids concentration, and organic loading rate to maximize treatment efficiency and permeate flux. Increasing the transmembrane pressure and temperature did not improve flux significantly. Increasing mixed liquor volatile suspended solids (MLVSS) concentration in the bioreactor decreased the permeate flux significantly. The maximum volumetric organic loading rate was 0.72 kg COD/m3/day. The maximum food-to-mass ratio was 0.50 kg N/kg MLVSS/day and 1.82 kg COD/kg MLVSS/day. Membrane permeate was clear and essentially free of bacteria, as indicated by heterotrophic plate count. Permeate flux ranged between 0.15 and 2.0 m3/m2 day and was maintained by routine backwashing every three days. Backwashing with tap water containing chlorine bleach every fourth or fifth backwashing was able to restore membrane flux to its original value.     

Removal of ammonia from contaminated air in a biotrickling filter - denitrifying bioreactor combination system

The removal of gaseous ammonia in a system consisting of a biotrickling filter, a denitrification reactor and a polishing bioreactor for the trickling liquid was investigated. The system allowed sustained treatment of ammonia while preventing biological inhibition by accumulating nitrate and nitrite and avoiding generation of contaminated water. All bioreactors were packed with cattle bone composite ceramics, a porous support with a large interfacial area. Excellent removal of ammonia gas was obtained. The critical loading ranged from 60 to 120 gm(-3)h(-1) depending on the conditions, and loadings below 56 gm(-3)h(-1) resulted in essentially complete removal of ammonia. In addition, concentrations of ammonia, nitrite, nitrate and COD in the recycle liquid of the inlet and outlet of each reactor were measured to determine the fate of nitrogen in the reactor, close nitrogen balances and calculate nitrogen to COD ratios. Ammonia absorption and nitrification occurred in the biotrickling filter; nitrate and nitrite were biologically removed in the denitrification reactor and excess dissolved COD and ammonia were treated in the polishing bioreactor. Overall, ammonia gas was very successfully removed in the bioreactor system and steady state operation with respect to nitrogen species was achieved.     

Combined aerobic heterotrophic oxidation, nitrification and denitrification in a permeable-support biofilm

A biofilm reactor, termed the permeable-support biofilm (PSB), was developed in which oxygen was supplied to the interior of the biofilm through a permeable membrane. The reactor was tested on filtered sewage supplemented with nutrient broth; the bulk solution was anoxic and the interior of the biofilm was supplied with pure oxygen. All tests were performed on a non-steady state biofilm with a depth of 1 mm. Mass balances on total organic carbon, ammonia, organic nitrogen and nitrate showed that combined heterotrophic oxidation of organics, denitrification and nitrification occurred simultaneously within the biofilm. The advantages of such a reactor are discussed.