MBR的脱氮除磷工艺研究

采用厌氧/缺氧池/好氧MBR工艺处理模拟的城市生活污水,就系统主要的运行参数对氮磷去除的影响进行了研究.结果表明:TN、TP、NH3-N去除率分别达到80%、90%、95%以上,出水各项指标完全满足城市杂用水水质标准的要求.     

A novel wastewater treatment process: simultaneous nitrification, denitrification and phosphorus removal.

Simultaneous nitrification and denitrification (SND) via the nitrite pathway and anaerobic-anoxic enhanced biological phosphorus removal (EBPR) are two processes that can significantly reduce the COD demand for nitrogen and phosphorus removal. The combination of these two processes has the potential of achieving simultaneous nitrogen and phosphorus removal with a minimal requirement for COD. A lab-scale sequencing batch reactor (SBR) was operated in alternating anaerobic-aerobic mode with a low dissolved oxygen concentration (DO, 0.5 mg/L) during the aerobic period, and was demonstrated to accomplish nitrification, denitrification and phosphorus removal. Under anaerobic conditions, COD was taken up and converted to polyhydroxyalkanoates (PHA), accompanied with phosphorus release. In the subsequent aerobic stage, PHA was oxidized and phosphorus was taken up to less than 0.5 mg/L at the end of the cycle. Ammonia was also oxidised during the aerobic period, but without accumulation of nitrite or nitrate in the system, indicating the occurrence of simultaneous nitrification and denitrification. However, off-gas analysis found that the final denitrification product was mainly nitrous oxide (N2O) not N2. Further experimental results demonstrated that nitrogen removal was via nitrite, not nitrate. These experiments also showed that denitrifying glycogen-accumulating organisms rather than denitrifying polyphosphate-accumulating organisms were responsible for the denitrification activity.     

Biological phosphorus removal with nitrite as election acceptor.

Biological phosphorus removal was studied in a sequencing batch reactor (SBR). The results showed that nitrite could be used as electron acceptor in denitrifying phosphorus removal. Feed mode of nitrite had significant influence on denitrifying phosphorus removal. Anoxic phosphorus assimilation rate could reach 10.44 mgP/gSS.h and the percentage of anoxic phosphorus assimilation amount was more than 97% with continuous feed mode. Granular sludge with denitrifying phosphorus removal activity was found in the SBR. The effects of different operational conditions, such as COD loading, settling time, HRT etc., on the formation of granules were also studied.     

反硝化生物滤池同化除磷性能研究

针对再生水厂实际运行中出现的反硝化生物滤池对总磷(TP)有去除的现象,通过试验研究了在实际工程运行条件下反硝化生物滤池的除磷效能、除磷原理以及进水磷浓度对脱氮效能的影响.结果表明,反硝化生物滤池对溶解性总磷(SP)的去除主要由生物膜中微生物的同化作用完成,在进水SP浓度为0.1～0.5 mg/L时,其去除量与进水浓度大...     

Comparison of sequentially combined carbon with sole carbon in denitrification and biological phosphorus removal.

The sequentially combined carbon (SCC) of methanol and acetic acid was used for the biological nutrient removal (BNR). Its BNR performance was compared with methanol or acetic acid as a sole carbon substrate. Compared to the sole carbon substrate, the use of SCC demonstrated the highest overall TIN removal of 98.3% at a COD ratio of 30 mg COD/l of methanol/50 mg CDO/l of acetic acid. Furthermore, denitrification was more enhanced when methanol was used as one of the SCC, rather than as a sole carbon source. Complete phosphorus removal was accomplished with a non-detectable o-P concentration when SCC was added. This research also showed that aerobic denitrifiers appear to prefer acetic acid to methanol, and the amount of poly-beta-hydroxybutyrate (PHB) stored by P accumulating organisms (PAOs) using acetic acid in the anoxic zone could be another important factor in improving the aerobic denitrification. The SCC was a very favorable carbon source for the aerobic denitrification since acetic acid was utilized more efficiently for P-release in accordance with increase of PHB stored in the cell of PAOs by removing nitrogen first using methanol.     

Biological phosphorus and nitrogen removal with biological aerated filter using denitrifying phosphorus accumulating organism.

In order to accomplish the biological nutrient removal with a weak sewage at low temperature, a hybrid process consisted of anoxic denitrifying phosphorus accumulating organism (dPAO) and nitrifying biological aerated filter (BAF) was studied in both lab and field pilot plants with weak sewage. The biofilm BAF was used as a post-nitrification process that provided sufficient nitrate to suspended growth dPAO. The anoxic/BAF configuration could remove nitrogen and phosphorus appreciably compared to other BNR systems. The enhanced biological phosphorus removal (EBPR) was mainly occurred in anoxic zone of suspended growth reactor. It has been found that P removal efficiency of dPAO was enhanced with an addition of a short oxic zone in suspended reactors compared to that of without oxic zone. However, the degree of aerobic P uptake in oxic zone was far lower than anoxic P uptake. The operating results of field plant indicated that dPAO/BAF configuration successfully reduced the adverse temperature effects at lower than 15 degrees C.     

Comparison of linear alkylbenzene sulfonates removal in conventional activated sludge systems and membrane bioreactors.

The potential of a membrane bioreactor (MBR) and a conventional activated sludge (CAS) system to remove polar micropollutants was evaluated using linear alkylbenzene sulfonates (LAS) as model components. Removal efficiencies over 97% were achieved in both reactor systems. The appearance of biological breakdown metabolites and the respirometric response of the sludges to LAS addition indicated that LAS removal was due to biodegradation, rather than sorption phenomena. The effect of operational variables, such as hydraulic retention time, LAS composition and hydrophobicity of the membrane used in the MBR, was negligible in the range tested. A stepwise increase in LAS influent concentration resulted in higher residual effluent concentrations but did not change the procentual removal efficiency. Because an increase in LAS and SPC effluent concentration occurred to a larger extent in the CAS than in the MBR under similar operating conditions, MBRs may turn out to be be more robust with respect to biological degradation of micropollutants than CAS.     

Biological nutrient removal model No.1 (BNRM1).

This paper presents the results of the work carried out by the CALAGUA Group on Mathematical Modelling of Biological Treatment Processes: the Biological Nutrient Removal Model No.1. This model is based on a new concept for dynamic simulation of wastewater treatment plants: a unique model can be used to design, simulate and optimize the whole plant, as it includes most of the biological and physico-chemical processes taking place in all treatment operations. The physical processes included are: settling and clarification processes (flocculated settling, hindered settling and thickening), volatile fatty acids elutriation and gas-liquid transfer. The chemical interactions included comprise acid-base processes, where equilibrium conditions are assumed. The biological processes included are: organic matter, nitrogen and phosphorus removal; acidogenesis, acetogenesis and methanogenesis. Environmental conditions in each operation unit (aerobic, anoxic or anaerobic) will determine which bacterial groups can grow. Thus, only the model parameters related to bacterial groups able to grow in any of the operation units of a specific WWTP will require calibration. One of the most important advantages of this model is that no additional analysis with respect to ASM2d is required for wastewater characterization. Some applications of this model have also been briefly explained in this paper.     

Exploring the potential of membrane bioreactors to enhance metals removal from wastewater: pilot experiences.

The potential of membrane bioreactors to enhance the removal of selected metals from low loaded sewages has been explored. A 1400 litre pilot plant, equipped with an industrial submerged module of hollow fibre membranes, has been used in three different configurations: membrane bioreactor, operating in sequencing batch modality, for the treatment of real mixed municipal/industrial wastewater; membrane-assisted biosorption reactor, for the treatment of real leachate from municipal landfills; continuously fed membrane bioreactor, for the treatment of water charged with cadmium and nickel ions. The results show that: (a) in treating wastewaters with low levels of heavy metals (< one milligram per litre concentration), operating high sludge ages is not an effective strategy to significantly enhance the metals removal; (b) Hg and Cd are effectively removed already in conventional systems with gravitational final clarifiers, while Cu, Cr, Ni can rely on a additional performance in membrane bioreactors; (c) the further membrane effect is remarkable for Cu and Cr, while it is less significant for Ni. Basically, similar membrane effects recur in three different experimental applications that let us estimate the potential of membrane system to retain selected metal complexes. The future development of the research will investigate the relations between the membrane effect and the manipulable filtration parameters (i.e., permeate flux, solids content, filtration cycle).     

Fouling control in submerged membrane bioreactors.

The impact of fouling on the operation of submerged membrane bioreactors (MBRs) is discussed. The discussion proceeds through a review of the impacts of fouling and fouling speciation, with correlations of filterability against candidate foulants being provided. There follows a brief comparison of hydraulic performance of the submerged and sidestream configurations: data is presented to demonstrate the efficacy of coarse bubble aeration in the submerged MBR. The critical flux concept is then discussed and its applicability to MBRs deliberated in view of recent publications demonstrating fouling under sub-critical flux conditions. Finally, the two most commercially important MBR products are briefly reviewed with specific reference to design and operation for fouling amelioration.     

Relationship between the electric conductivity and phosphorus concentration variations in an enhanced biological nutrient removal process.

Phosphorus release and uptake in a sequencing batch reactor were monitored by the simple online measurements of electric conductivity (EC) and oxidation-reduction potential (ORP), and the result was verified by the measurement of phosphate concentration changes. The influence of nitrate ion presence on the phosphorus removal was evaluated by a jar test operated in the cyclic anaerobic (anoxic)-aerobic condition. The relationships of EC, ORP and metal species with phosphorus concentrations were investigated. Under strict anaerobic conditions, EC showed positive correlation with phosphorus concentrations, but it became negligible under anoxic conditions with nitrate present. Strong inverse correlation was found between ORP values and phosphorus concentration. The increase and decrease of magnesium and potassium ions took place in accordance with phosphorus release and uptake, and the relationship between the metal species and phosphorus changes was clearer in the anaerobic condition than anoxic condition.     

Characterization of fouled membranes from a membrane enhanced biological phosphorus removal system.

Characterization of fouled membranes is the first step towards a good understanding of membrane fouling nature and thus formulating effective engineering measures for fouling prevention and control. In this study, fouled membrane fibres collected from a pilot scale membrane enhanced biological phosphorus removal (MEBPR) process were systematically examined. Several analytical tools, including scanning electron microscopy (SEM), conventional optical microscopy (COM), energy dispersive X-ray (EDX) microanalysis, matrix assisted laser desorption/ionization--mass spectrometry (MALDI-MS) analysis, and conventional chemical analysis techniques were used. The results indicated that membrane fouling in the MEBPR process was mainly of an organic nature, and most extractable foulants were carbohydrates and humic or humic-like substances. Unlike in other wastewater treatment membrane bioreactors, microbial growth on fouled membranes was not substantial, probably due to the vigorous aeration applied and the strong hydrodynamic conditions within the membrane pore structure. After a period of sludge filtration, membrane surfaces became more hydrophobic and the resultant hydrophobic interactions between the fouled membranes and mixed liquor constituents might have accelerated the fouling process.     

市政污水生物除磷效能和功能微生物分布特征

调研了4座市政污水处理厂的除磷效能、污泥活性以及微生物分布特征。结果表明出水总磷均达到《城镇污水处理厂污染物排放标准》(GB18918—2002)一级标准,但污泥性能差异显著。活性污泥厌氧释磷率和好氧聚磷率范围分别是0.224～7.77mg/(gVSS.h)和0.386～7.9mg/(gVSS.h)。聚磷假丝酵母菌(Accumulibacter)比例较低,为3.8%～8.7%,聚糖假丝酵母菌(Competibacter)为3.2%～9.1%。进水乙酸含量和乙酸吸收率,厌氧释磷率和好氧聚磷率间都存在很好的线性相关性,表明污水中可利用碳源的数量和磷素的比例极大影响污泥除磷性能。故控制工业废水排入,适当添加碳源,或设置独立的前置反硝化池有望增加污水处理厂的除磷效能。     

Chemical denitrification for nitrogen removal from landfill leachate.

A new system that removes nitrogen from landfill leachate and other waste waters with similar properties has been proposed with nitritation (i.e. oxidation of ammonium to nitrite) of half of the influent ammonium followed by chemical denitrification with a reaction between equal amounts of ammonium and nitrite to form nitrogen gas. Chemical denitrification occurs at high concentrations and the reactions were studied in combination with a concentration step. Studied concentration methods were freezing/thawing and evaporation/drying. Chemical denitrification is well-known in inorganic chemistry and has been observed in natural systems. Studies in laboratory were focused on chemical denitrification and showed that nearly complete removal of soluble nitrogen can be obtained in evaporation/drying of water solutions or leachate with equal amounts of ammonium and nitrite. Freezing/drying was less efficient with a removal of about 50-60% at high initial concentrations. Chemical denitrification is much influenced by concentration, pH-value, temperature and some compounds in leachate have an inhibiting effect on the reaction. Factors as safety (ammonium nitrite as a salt is explosive above 60 degrees C) and possible side-reactions as formation of ammonia and nitrogen oxides must be carefully evaluated before use in full-scale. Conductivity is a suitable parameter to follow-up the chemical denitrification process.     

Microbial succession of glycogen accumulating organisms in an anaerobic-aerobic membrane bioreactor with no phosphorus removal.

The succession of glycogen accumulating organisms (GAOs) has been observed in an acetate-fed, anaerobic-aerobic sequencing membrane bioreactor (MBR) operated for 260 days without enhanced biological phosphorus removal (EBPR) activity. Semi-quantitative fluorescence in situ hybridization results showed that a gammaproteobacterial lineage GB frequently observed in EBPR processes was initially the numerically dominant species (50-66% of total cells) of the GAO in the MBR from day 1 to day 38. During this period, succession of two different subgroups of group GB was also observed. On day 85 onward, a population shift from GB group to 'Defluvicoccus'-related tetrad-forming organisms (TFO) occurred. This microbial succession was suspected to be related to the applied operating conditions (long hydraulic retention time and long solid residence time) which favored the proliferation of 'Defluvicoccus'-related TFO rather than the GB group. Application of terminal restriction fragment length polymorphism on selected samples further revealed that the microbial diversity of the seeding sludge as determined by the number of terminal restriction fragments was higher than that of sludge samples taken after day 85.     

Bio-layer management in anaerobic membrane bioreactors for wastewater treatment.

Membrane separation technology represents an alternative way to achieve biomass retention in anaerobic bioreactors for wastewater treatment. Due to high biomass concentrations of anaerobic reactors, cake formation is likely to represent a major cause of flux decline. In the presented research, experiments are performed on the effect of biomass concentration and level of gas sparging on the hydraulic capacity of a submerged anaerobic membrane bioreactor. Both parameters significantly affected the hydraulic capacity, with biomass exerting the most pronounced effect. After 50 days of continuous operation the critical flux remained virtually unchanged, despite an increase in membrane resistance, suggesting that biomass characteristics and hydraulic conditions determine the bio-layer formation rather than the membrane's fouling level. The concept of bio-layer management is introduced to describe the programmed combination of actions performed in order to control the formation of biomass layer over membranes.     

Strategies for chemical cleaning in large scale membrane bioreactors.

Systematically testing alternative cleaning agents and cleaning procedures on a large scale municipal membrane bioreactor, the Erftverband optimized the cleaning strategies and refined the original cleaning procedures for the hollow fiber membranes in use. A time-consuming, intensive ex-situ membrane cleaning twice a year was initially the regular routine. By introducing the effective means of cleaning in place in use today, which employs several acidic and oxidative/alkaline cleaning steps, intensive membrane cleaning could be delayed for years. An overview and an assessment of various cleaning strategies for large scale plants are given.     

An ecology-based analysis of irreversible biofouling in membrane bioreactors.

To provide the first step towards a microbial ecology-based understanding of irreversible membrane biofouling, four laboratory-scale membrane bioreactors (MBRs) were operated to investigate the identity of bacterial populations highly correlated with irreversible membrane biofouling. The conventional MBR was divided into two separate experimental units. Unit one consisted of four suspended-growth, activated sludge, sequencing batch bioreactors treating a synthetic paper mill wastewater. Unit two consisted of a microfiltration membrane cell. Amplified ribosomal deoxyribonucleic acid restriction analysis (ARDRA) was used to compare the predominant bacterial populations in samples of mixed liquor and irreversibly bound to the membrane surface. The results of ARDRA showed a significant difference between the planktonic and sessile bacterial communities suggesting that irreversible biofouling of microfiltration membranes may be more highly correlated to specific bacterial populations rather than the total, bulk concentration of biomass. A custom-built mini-flow cell and light microscopy were used to visualise the early formation of biofilms by two pure cultures (Escherichia coli and Acinetobacter calcoaceticus) on membrane surfaces. The results confirmed that A. calcoaceticus was able to enhance the initiation of biofilm formation on microfiltration membranes.     

Economic and environmental optimization of phosphorus removal.

Do operating costs conform to environmental impact after introduction of charges on discharge of wastewater? A study on optimization of phosphorus removal at two Danish wastewater removal plants shows that this is actually the case. By measurement of inlet and outlet concentrations and of chemicals added it was possible to determine the relationships between chemical dosing and phosphorus discharge and thus calculate the operational cost and environmental impact of different dosing/discharge levels.     

Removal of ibuprofen from wastewater: comparing biodegradation in conventional, membrane bioreactor, and biological nutrient removal treatment systems.

Pharmaceuticals are continually being introduced into the influent of municipal wastewater treatment plants (WWTPs). Developing a better understanding of pharmaceutical removal mechanisms within the different treatment processes is vital in preventing downstream contamination of our water resources. In this study, ibuprofen, a popular over-the-counter pain reliever, was monitored by taking wastewater samples throughout the City of Guelph municipal WWTP. Greater than 95% of ibuprofen was found to be removed in the aeration tank, with aerobic biodegradation being the dominant mechanism. For comparison, first-order kinetics were used to quantify ibuprofen biodegradation in a conventional WWTP aeration tank and in a membrane bioreactor (MBR) pilot plant. The rate constants, k biol, for the conventional tank and the MBR were determined to be (-6.8+/-3.3) L/g SS*d and (-8.4+/-4.0) L/g SS*d, respectively. These two rate constants were found to be statistically similar. Preliminary study of a biological nutrient removal pilot system also suggests that ibuprofen can be anaerobically degraded.