污水短程硝化影响因素的对比分析

短程硝化的实现与维持,将会推动基于短程硝化发展起来的工艺得以工程化应用。对不同研究者就此不一致的结论进行了阐述,并对各影响因素促进短程硝化的可行性进行了对比分析。要实现短程硝化,同时控制中温条件、游离氨、污泥龄是最容易的,其次是同时控制中温条件和污泥龄,另外还可同时控制中温条件和游离氨或溶解氧在生物膜污泥中实现短程硝化。常温条件下,仅仅依靠较低的溶解氧浓度无法维持短程硝化的稳定,必须配合其他因素的控制。各因素按可行性的高低及稳定性的好坏综合排序依次分别为中温条件、游离氨、污泥龄、溶解氧、间歇曝气、游离亚硝酸、pH值。     

短程反硝化工艺的研究进展与展望

厌氧氨氧化技术利用NO_=2^--N氧化NH_4^+-N,实现污水中氮素的高效去除,其中NO_=2^--N的产生是实现厌氧氨氧化应用的难点。短程硝化是获取NO_=2^--N的重要途径之一,但目前在实际工程中通过短程硝化难以实现长期稳定的亚硝酸盐积累。短程反硝化工艺将反硝化过程控制在硝酸盐还原的第一步来积累NO_=2^--N,可实现从反硝化途径获得NO_=2^--N为厌氧氨氧化反应提供底物,去除污水中的氮素污染物。简要介绍了短程反硝化工艺的发展背景、研究进展、启动及控制策略等,并对短程反硝化过程亚硝酸盐积累机制及其与厌氧氨氧化工艺耦合方式进行了总结,最后对其未来的研究方向进行了展望。     

SBBR系统短程硝化处理低碳城市污水研究

采用序批式生物膜反应器(SBBR),应用短程硝化技术处理南方地区的低碳城市污水。在进水TN为25.6～32.1 mg/L、COD为50～100 mg/L、pH值为7.1～7.6、温度为24～29℃的条件下,进行曝气量对氨氧化速率及短程硝化效果的影响研究,同时考察了SBBR反应器的生物膜特性。结果表明:在曝气量为100～200 L/h范围内,氨氧化速率随着曝气量的增加而增大;在曝气量为100～120 L/h条件下能够实现NO2--N的稳定积累和高效短程硝化,且有较明显的同步硝化反硝化(SND)过程,对TN的去除率在48.1%～60.1%之间。同时,由于生物膜复杂的食物链结构,还实现了系统的污泥减量。     

短程硝化反硝化工艺简析

指出短程硝化反硝化工艺是目前国内外生物脱氮技术研究应用的热点,通过介绍短程硝化反硝化工艺原理,分析了不同工艺稳定亚硝态氮积累实现短程硝化的工艺控制措施,对短程硝化反硝化工艺今后的研究和应用进行了展望。     

自养脱氮ANITA~(TM) Mox MBBR与IFAS运行启动经验

自养脱氮工艺ANITA~(TM) Mox MBBR利用移动填料的生物膜发生短程硝化和厌氧氨氧化反应进行脱氮。通过工程实例运行数据发现,ANITA~(TM) Mox MBBR工艺脱氮负荷为1.2 kg N/(m3·d),其脱氮负荷与生物膜内基质的传输有关,如生物膜密度、厚度、温度、基质浓度。为改善基质传输速率,提高脱氮的效率,威立雅研发了由悬浮活性污泥和固定生物膜相结合的ANITATM Mox IFAS工艺,其将短程硝化和厌氧氨氧化反应从同一生物膜中分离,大部分氨氧化菌(AOB)集中在活性污泥中,提高了溶解氧的利用率;而厌氧氨氧化菌An AOB集中在填料生物膜上,改善了基质的传递速率。ANITA~(TM) Mox IFAS工艺运行时所需溶解氧浓度低,仅为0.2~0.5 mg/L。但实际运行数据(50 m~3ANITA~(TM) Mox IFAS反应器)显示,其脱氮负荷是ANITA~(TM) Mox MBBR工艺的2~3倍。     

附着生长系统中短程反硝化试验研究

结合现有的关于短程反硝化的理论,通过膜法A/O工艺试验,探讨了在附着生长系统中实现短程反硝化的可能性。     

水力停留时间对海绵填料CANON反应器性能的影响

以片状海绵作为CANON反应器的填料,通过接种CANON污泥,采用人工配制高氨氮废水为进水,研究了水力停留时间(HRT)对生物膜CANON反应器去除TN及短程硝化的影响。控制反应器的HRT分别为5、7、9 h,研究发现:当HRT=5 h时系统的短程硝化稳定性能较佳,但对TN的去除率、去除负荷分别只有32.02%、0.689 kg/(m3·d);当HRT=7 h时,反应器的短程硝化稳定性能较佳,且对TN的去除率、去除负荷分别可达58.05%、0.863 kg/(m3·d);当HRT=9 h时,反应器对TN的去除率、去除负荷分别为73.96%、0.854 kg/(m3·d),但短程硝化稳定性能不佳。对于片状海绵填料反应器而言,HRT越短则短程硝化效果越稳定。     

温度对不同水质条件下生活污水短程硝化的影响

采用SBR工艺研究了温度对不含海水的城市生活污水和含30%海水的城市生活污水短程硝化的影响.试验结果表明:对于不含海水的城市生活污水,提高温度有利于实现短程硝化,当温度升至32℃时,可以实现短程硝化;生活污水中海水比例为30%时中温条件下可以实现短程硝化.     

城市污水短程硝化的实现途径

探讨了影响废水中亚硝酸盐积累的三大主要因素：溶解氧、温度和pH。针对常温低氨氮城市污水,从理论上分析了以活性污泥法和生物膜法的形式进行亚硝化的启动方法和运行策略,为短程硝化／厌氧氨氧化工艺在城市污水处理中的应用提供了可借鉴的研究基础。     

活性污泥快速实现短程硝化及稳定高效运行

为了实现快速有效的短程硝化控制和高硝化速率,采用A2O工艺的活性污泥,利用CSTR反应器,分别控制游离氨和溶解氧浓度,对硝化活性污泥快速实现短程硝化及稳定高效运行进行研究。在低游离氨浓度控制体系中,对硝态氮的产生不具有很好的控制作用,短程硝化难以启动;在高游离氨浓度控制体系中,实现了5 d快速启动短程硝化,亚硝态氮积累率稳定在90%以上;提高短程硝化过程的溶解氧浓度,硝化性能从26 mg/(L·h)增长到54 mg/(L·h),亚硝态氮积累率仍稳定维持在90%以上,达到高效稳定运行的目的;另外,从AOB生长动力学分析可知,提高游离氨浓度对提高AOB生长速率具有非常重要的意义。因此,通过控制高游离氨浓度、提高溶解氧可以快速实现短程硝化并稳定高效运行。     

不同控制模式下SBR的短程硝化反硝化

以实际豆制品生产废水为处理对象，研究了传统固定时间控制和实时控制两种模式下SBR反应器的短程硝化反硝化效果。结果显示，实时控制下的硝化速率和反硝化速率分别为按固定时间控制时的1．40倍和1．86倍，硝化和反硝化时间则比传统运行方式分别缩短了60min和25min。因此，可采用DRP和pH值实时控制SBR法的短程硝化反硝化过程，它不仅可以合理分配曝气和搅拌时间，而且还能提高硝化速率并缩短反应时间，达到了降低运行成本的目的。     

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.     

Macroscale and microscale analyses of nitrification and denitrification in biofilms attached on membrane aerated biofilm reactors

A membrane aerated biofilm reactor (MABR), in which O(2) was supplied from the bottom of the biofilm and NH(4)(+) and organic carbon were supplied from the biofilm surface, was operated at different organic carbon loading rates and intra-membrane air pressures to investigate the occurrence of simultaneous chemical oxygen demand (COD) removal, nitrification and denitrification. The spatial distribution of nitrification and denitrification zones in the biofilms was measured with microelectrodes for O(2), NH(4)(+), NO(2)(-), NO(3)(-) and pH. When the MABR was operated at approximately 1.0 g-COD/m(2)/day of COD loading rate, simultaneous COD removal, nitrification and denitrification could be achieved. The COD loading rates and the intra-membrane air pressures applied in this study had no effect on the start-up and the maximum rates of NH(4)(+) oxidation in the MABRs. Microelectrode measurements showed that O(2) was supplied from the bottom of the MABR biofilm and penetrated the whole biofilm. Because the biofilm thickness increased during the operations, an anoxic layer developed in the upper parts of the mature biofilms while an oxic layer was restricted to the deeper parts of the biofilms. The development of the anoxic zones in the biofilms coincided with increase in the denitrification rates. Nitrification occurred in the zones from membrane surface to a point of ca. 60microm. Denitrification mainly occurred just above the nitrification zones. The COD loading rates and the intra-membrane air pressures applied in this study had no effect on location of the nitrification and denitrification zones.     

Coupled BAS and anoxic USB system to remove urea and formaldehyde from wastewater

Wastewater containing formaldehyde and urea was treated using a coupled system consisting of a biofilm airlift suspension (BAS) reactor and an anoxic upflow sludge blanket (USB) reactor. The anoxic USB reactor was used to carry out denitrification and urea hydrolysis, while the BAS reactor was used to carry out nitrification. In a first step, individual experiments were carried out to investigate the effects of both compounds on the nitrifying and denitrifying biomass. The BAS reactor was fed with a synthetic medium containing 500 mg N-NH4(+)l(-1) and 100mg N-urea l(-1), that were added continuously to this medium. Neither urea hydrolysis nor inhibition of nitrification was observed. Nitrification efficiency decreased when formaldehyde was fed during shocks at concentrations of 40, 80 and 120 mg C-formaldehyde l(-1). The anoxic USB reactor was fed with a synthetic medium containing nitrate, formaldehyde and urea. Concentrations of formaldehyde in the reactor of 100-120 mg C-formaldehyde l(-1) caused a decrease in the denitrification and urea hydrolysis rates. In a second step, the coupled system was operated at recycling ratios (R) of 3 and 9. Fed C/N ratios of 0.58, 1.0 and 1.5 g C-formaldehyde g(-1) N-NH4(+) were used for every recycling ratio. The maximum nitrogen removal percentages were achieved at a C/N ratio of 1.0 g C-formaldehyde g(-1) N-NH4(+) for both recycling ratios. A fed C/N ratio of 1.5 g C-formaldehyde g(-1) N-NH4(+) caused a decrease in the efficiency of the system with respect to nitrogen removal, due to the presence of formaldehyde in the BAS reactor, which decreased the nitrification. Formaldehyde was completely removed in the BAS reactor and a heterotrophic layer formed around the nitrifying biofilm.     

Nitrifying and heterotrophic population dynamics in biofilm reactors: effects of hydraulic retention time and the presence of organic carbon

Two biofilm reactors operated with hydraulic retention times of 0.8 and 5.0 h were used to study the links between population dynamics and reactor operation performance during a shift in process operation from pure nitrification to combined nitrification and organic carbon removal. The ammonium and the organic carbon loads were identical for both reactors. The composition and dynamics of the microbial consortia were quantified by fluorescence in situ hybridization (FISH) with rRNA-targeted oligonucleotide probes combined with confocal laser scanning microscopy, and digital image analysis. In contrast to past research, after addition of acetate as organic carbon nitrification performance decreased more drastically in the reactor with longer hydraulic retention time. FISH analysis showed that this effect was caused by the unexpected formation of a heterotrophic microorganism layer on top of the nitrifying biofilm that limited nitrifiers oxygen supply. Our results demonstrate that extension of the hydraulic retention time might be insufficient to improve combined nitrification and organic carbon removal in biofilm reactors.     

A simple biofilm model of bacterial competition for attached surface

A simple biofilm model of competition in bacterial growth for an attached surface is developed. Competition for the attached surface is expressed with the crowded and detachment effects. The developed model is verified by comparing simulated results with data obtained in the experiments of batch culture of nitrifier and continuous treatment of actual sewage with biofilm reactor. This model can favorably simulate the growth competition between autotrophic and heterotrophic bacteria for the attached surface. Then some parameters for nitrification process are discussed with this model. It is clarified that the effective removal of organic matter before nitrification tank is required for effective nitrification in the biofilm reactor.     

Distribution of Nitrosomonas europaea and Nitrobacter winogradskyi in an autotrophic nitrifying biofilm reactor as depicted by molecular analyses and mathematical modelling

The autotrophic two-species biofilm from the packed bed reactor of a life-support system, containing Nitrosomonas europaea ATCC 19718 and Nitrobacter winogradskyi ATCC 25391, was analysed after 4.8 years of continuous operation performing complete nitrification. Real-time quantitative polymerase chain reaction (Q-PCR) was used to quantify N. europaea and N. winogradskyi along the vertical axis of the reactor, revealing a spatial segregation of N. europaea and N. winogradskyi. The main parameters influencing the spatial segregation of both nitrifiers along the bed were assessed through a multi-species one-dimensional biofilm model generated with AQUASIM software. The factor that contributed the most to this distribution profile was a small deviation from the flow pattern of a perfectly mixed tank towards plug-flow. The results indicate that the model can estimate the impact of specific biofilm parameters and predict the nitrification efficiency and population dynamics of a multispecies biofilm.     

固定化氨氧化菌短程硝化的启动研究

采用亲水性玻璃态单体,应用辐射技术制备生物相容性高分子共聚物载体,使用固定化细胞增殖技术对氨氧化菌进行固定化,并以流化床为生物反应器,采用SBR运行方式对人工配水进行短程硝化的启动研究.结果表明:当进水氨氮浓度为100、75、50和25mg/L时,对氨氮的的去除率分别为98.6%、99.1%、98.8%和99.8% ,亚硝化率分别为 98.6%、94,5%、95.2%和94.7%:对氨氮的去除速率由开始时的10.6mg/(L·d)提高到25.7mg/(L·d),耗氧速率(OUR)则由0.37mg/(L·d)提高到1.12mg/(L·d).可见,该方法具有启动速度快、亚硝化程度高、容易控制等优点.     

Evaluation of the impact of bioaugmentation and biostimulation by in situ hybridization and microelectrode

Three rotating disk biofilm reactors were operated to evaluate whether bioaugmentation and biostimulation can be used to improve the start-up of microbial nitrification. The first reactor was bioaugmented during start-up period with an enrichment culture of nitrifying bacteria, the second reactor received a synthetic medium containing NH(4)(+) and NO(2)(-) to facilitate concomitant proliferation of ammonia- and nitrite-oxidizing bacteria, and the third reactor was used as a control. To evaluate the effectiveness of bioaugmentation and biostimulation approaches, time-dependent developments of nitrifying bacterial community and in situ nitrifying activity in biofilms were monitored by fluorescence in situ hybridization (FISH) technique and microelectrode measurements of NH(4)(+), NO(2)(-), NO(3)(-), and O(2). In situ hybridization results revealed that addition of the enrichment culture of nitrifying bacteria significantly facilitated development of dense nitrifying bacterial populations in the biofilm shortly after, which led to a rapid start-up and enhancement of in situ nitrification activity. The inoculated bacteria could proliferate and/or survive in the biofilm. In addition, the addition of nitrifying bacteria increased the abundance of nitrifying bacteria in the surface of the biofilm, resulting in the higher nitrification rate. On the other hand, the addition of 2.1mM NO(2)(-) did not stimulate the growth of nitrite-oxidizing bacteria and did inhibit the proliferation of ammonia-oxidizing bacteria instead. Thus, the start-up of NO(2)(-) oxidation was unchanged, and the start-up of NH(4)(+) oxidation was delayed. In all the three biofilm reactors, data sets of time series analyses on population dynamics of nitrifying bacteria determined by FISH, in situ nitrifying activities determined by microelectrode measurements, and the reactor performances revealed an approximate agreement between the appearance of nitrifying bacteria and the initiation of nitrification activity, suggesting that the combination of these techniques was a very powerful monitoring tool to evaluate the effectiveness of bioaugmentation and biostimulation strategies.     

Influence of detachment on substrate removal and microbial ecology in a heterotrophic/autotrophic biofilm

Competition between heterotrophic bacteria oxidizing organic substrate and autotrophic nitrifying bacteria in a biofilm was evaluated. The biofilm was grown in a tubular reactor under different shear and organic substrate loading conditions. The reactor was initially operated without organic substrate in the influent until stable ammonia oxidation rates of 2.1 g N/(m² d) were achieved. A rapid increase of fluid shear in the tubular reactor on day 156 resulted in biofilm sloughing, reducing the biofilm thickness from 330 to 190 μm. This sloughing event did not have a significant effect on ammonia oxidation rates. The addition of acetate to the influent of the reactor resulted in decreased ammonia oxidation rates (1.8 g N/(m² d)) for low influent acetate concentrations (17 mg COD/L) and the breakdown of nitrification at high influent acetate concentrations (55 mg COD/L). Rapidly increasing fluid shear triggered biofilm sloughing in some cases—but maintaining constant shear did not prevent sloughing events from occurring. With the addition of acetate to the influent of the reactor, the biofilm thickness increased up to 1350 μm and individual sloughing events removed up to 50% of the biofilm. Biofilm sloughing had no significant influence on organic substrate removal or ammonia oxidation. During 325 days of reactor operation, ammonia was oxidized only to nitrite; no nitrate production was observed. This lack of nitrite oxidation was confirmed by fluorescent in situ hybridization (FISH) analysis, which detected betaproteobacterial ammonia oxidizers but not nitrite oxidizers. Mathematical modeling correctly predicted breakdown of nitrification at high influent acetate concentrations. Model predictions deviated systematically from experimental results, however, for the case of low influent acetate concentrations.