Biotransformation of estrogens in nitrifying activated sludge under aerobic and alternating anoxic/aerobic conditions.

Natural and synthetic estrogens present in municipal wastewater can be biodegraded during treatment, particularly in activated sludge. The objective was to assess the extent of transformation of 17-beta-estradiol (E2) and 17-alpha-ethinylestradiol (EE2) by nitrifying activated sludge and evaluate potential relationships between availability of oxygen, nitrification rate, and estrogen removal. For each batch experiment, two reactors were set up--aerobic and alternating anoxic/aerobic-which were then amended with E2 and EE2 from methanolic stock solutions. The EE2 was persistent under anoxic conditions; under aerobic conditions, the observed level of its removal was 22%. The E2 was readily converted to estrone (El)--faster under aerobic (nitrifying) than anoxic (denitrifying) conditions. During the initial anoxic conditions, a metabolite consistent with 17-alpha-estradiol transiently accumulated and was subsequently removed when the reactor was aerated. Higher removal rates of estrogens were associated with higher nitrification rates, which supports the contention that the nitrifying biomass was responsible for their removal.     

Factors affecting the growth rates of ammonium and nitrite oxidizing bacteria

The maximum specific growth rates of both ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) were investigated under varying aerobic solids retention time (SRT_a) and in the presence/absence of anoxic (alternating) conditions. Two bench SBRs, reactor R1 and R2, were run in parallel for 150 d. Reactor R1 was operated in aerobic conditions while R2 operated in alternating anoxic/aerobic conditions. The feed (synthetic wastewater), temperature, hydraulic retention time and mixing were identical in both reactors. The SRT_a in both reactors was, sequentially, set at four values: 5, 4, 3 and 2 d.Kinetic tests with the biomasses from both reactors were carried out to estimate the maximum specific growth rates (μ_max) at each tested SRT_a and decay rates, in both aerobic and anoxic conditions. The kinetic parameters of nitrifier were estimated through the calibration of a two step nitrification-denitrification activated sludge model.The results point to a slightly higher μ_max,AOB and μ_max,NOB in alternating conditions, while both μ_max,AOB and μ_max,NOB were shown not to vary in the tested range of SRT_a (from 2 to 5 d) at 20 °C. They were relatively high when compared to literature data: 1.05 d⁻¹ < μ_max,AOB < 1.4 d⁻¹ and 0.91 d⁻¹ < μ_max,NOB < 1.31 d⁻¹. The decay coefficients of both AOB and NOB were much higher in aerobic (from 0.22 d⁻¹ to 0.28 d⁻¹) than in anoxic (0.04 d⁻¹ to 0.16 d⁻¹) conditions both in R1 and R2, which explained the higher nitrification rates observed in the alternating reactor.     

Influence of operating conditions on nitrous oxide formation during nitritation and nitrification

Nitrous oxide (N₂O), a strong greenhouse gas, can be produced by ammonium-oxidizing bacteria (AOB) as a by-product of ammonium oxidation and can potentially be formed in all types of nitrification processes. However, partial nitritation has been reported to cause significantly higher N₂O emissions than complete nitrification. In the study presented here, the mechanisms and factors that drive N₂O formation by AOB were investigated with respect to different operational strategies to achieve nitrite accumulation base on combined evaluation of oxygen uptake rate (OUR) and N₂O formation rate. On the one hand, N₂O formation during partial nitritation and nitrification in a continuously stirred tank reactor (CSTR) with continuous aerobic conditions was observed. On the other hand, the effect of intermittent aeration on N₂O formation during nitrification was investigated. The presence of nitrite, the extend of sludge-specific ammonium loading, low oxygen concentration, and transition from aerobic to anoxic conditions significantly increased N₂O formation in this reactor independently from each other, indicating that different formation pathways, supposedly via nitrite or hydroxylamine, were active.     

间歇曝气潜流人工湿地的污水脱氮效果

采用间歇曝气运行方式,提升潜流人工湿地生活污水处理系统中的溶解氧浓度,强化脱氮效果。结果表明,间歇曝气运行方式有效提高了湿地内部溶解氧水平,曝气时溶解氧浓度可达6~9 mg/L,停止曝气后,溶解氧浓度迅速下降至0.5 mg/L以下,在湿地内部营造了一种交替的好氧和缺氧环境,分别促进好氧硝化和缺氧反硝化作用。在水力停留时间为3 d的情况下,间歇曝气潜流人工湿地系统对氨氮、总氮和COD的去除率分别可达到98.0%、87.6%和96.3%,较常规潜流人工湿地系统分别提高了74.1%、56.4%和18.1%,实现了氨氮、总氮和COD的同步高效去除。     

Synthetic dairy wash-water treatment by using an alternating pumped sequencing batch biofilm reactor

The performance of an alternating pumped sequencing batch biofilm reactor process in synthetic diary wash-water treatment was studied. The system comprises two reactors with two identical plastic biofilm modules. Two centrifugal pumps, one connected to each reactor, alternately move the water from one reactor to the other one, resulting in aeration. At three loading rates (336, 501 and 1080 g COD/(m³ d)), total COD and total nitrogen were removed by 91-94% and 46-80%, respectively. Nitrogen was removed from wastewater by denitrification in the anoxic phase and Simultaneous Nitrification and Denitrification (SND) in the aerobic phase.     

Effect of dissolved oxygen concentration on nitrite accumulation in nitrifying sequencing batch reactor.

A mathematical model based on Activated Sludge Model No. 3 (International Water Association, London) and laboratory-scale experiments were used to investigate ammonia conversion by nitrification in a sequencing batch reactor (SBR). The purpose of the study was to assess the effect of dissolved oxygen concentration on nitrite accumulation in the SBR. As the dissolved oxygen concentration in the SBR depends on the balance between oxygen consumption and oxygen transfer rates, ammonium conversion was measured for different air flowrate values to obtain different dissolved oxygen concentration profiles during the cycle. The ammonia concentration in the feeding medium was 500 mg ammonium as nitrogen (N-NH4(+))/L, and the maximum nitrite concentration achieved during a cycle was approximately 50 mg nitrite as nitrogen (N-NO2)/L. The air flow supplied to the reactor was identified as a suitable parameter to control nitrite accumulation in the SBR. This identification was carried out based on experimental results and simulation with a calibrated model. At a low value of the volumetric mass-transfer coefficient (kLa), the maximum nitrite concentration achieved during a cycle depends strongly on k(L)a, whereas, at a high value of k(L)a, the maximum nitrite concentration was practically independent of kL(a).     

Development of a continuously stirred flow cell for investigating sorption mass transfer

This paper introduces a new reversible-flow design for a continuously stirred reactor used to study sorption mass transfer in soil and solvent systems. The stirred reactor has potential advantages over conventional packed column or batch reactors because it isolates intraparticle sorption rate limitations from advective-dispersive transport, yet allows changes to flux through the reactor for analysis of sorption kinetics under dynamic conditions. Previously, stirred reactors have often failed due to clogging of sediment on the effluent frit. The reverse-flow backwashing design allows longer life and higher confidence in maintaining mixed conditions than previous designs. Mass transfer 'rate coefficients estimated from stirred and column experiments are compared; both techniques produced results consistent with a published correlation. The data also show that fitted sorption mass transfer coefficients can be strongly dependent on the choice of equilibrium partition coefficient (i.e. batch or first-moment derived values), and that the conventional two-site sorption kinetics model fails to accurately predict sorption mass transfer in the presence of changing solvent velocity through the reactor.     

Comparison of nitrification rates in conventional and membrane-assisted biological nutrient removal processes

A membrane-assisted and a conventional activated sludge system, both operated in an enhanced biological phosphorus removal (EBPR) mode and under identical operating conditions, were studied to investigate the effect of the membrane solids-liquid separation on nitrification activity. Both the membrane EBPR (MEBPR) and conventional EBPR (CEBPR) processes achieved stable and complete removal of ammonium-nitrogen from the influent wastewater. However, when the intrinsic nitrification activity was assessed in offline batch tests, the CEBPR mixed liquor exhibited 15 to 75% greater nitrification potential than the MEBPR counterpart. These results were further validated by monitoring nitrification rates of conventional mixed liquor as it evolved toward a membrane mixed liquor. It was also demonstrated that the larger aerobic mass fraction of the MEBPR system could not be the only factor influencing the reduced intrinsic nitrification rate. The present study strongly suggests that the presence of a membrane solids-liquid separation per se may be sufficient to alter the nitrification kinetics of an EBPR mixed liquor and that this possibility should be considered in arriving at an appropriate process design.     

污水低氧脱氮机制及其应用研究进展

阐述了污水低氧脱氮的基本原理,即抑制或去除亚硝酸盐氧化菌(NOB),同时保留氨氧化菌(AOB),并保持其活性;探讨了污水低氧脱氮实现途径;详细介绍了几种典型的污水低氧脱氮工艺(短程硝化(SHARON)工艺、厌氧氨氧化(ANAMMOX)工艺、好氧反氨化(DEMON)工艺、低氧自养硝化反硝化(OLAND)工艺、甲烷营养型硝化反硝化工艺和亚硝酸盐型完全自养脱氮(CANNON)工艺)的应用研究进展;最后对污水低氧脱氮处理工艺的工程运用进行了展望.     

Aerobic sludge digestion under low dissolved oxygen concentrations.

Low dissolved oxygen (DO) concentrations occur commonly in aerobic digesters treating thickened sludge, with benefits of smaller digester size, much reduced aeration cost, and higher digestion temperature (especially important for plants in colder areas). The effects of low DO concentrations on digestion kinetics were studied using the sludge from municipal wastewater treatment plants in Akron, Ohio, and Los Lunas, New Mexico. The experiments were conducted in both batch digestion and a mixed mode of continuous, fed-batch, and batch operations. The low DO condition was clearly advantageous in eliminating the need for pH control because of the simultaneous occurrence of nitrification and denitrification. However, when compared with fully aerobic (high DO) systems under constant pH control (rare in full-scale plants), low DO concentrations and a higher solids loading had a negative effect on the specific volatile solids (VS) digestion kinetics. Nonetheless, the overall (volumetric) digestion performance depends not only on the specific digestion kinetics, but also the solids concentration, pH, and digester temperature. All of the latter factors favor the low DO digestion of thickened sludge. The significant effect of temperature on low DO digestion was confirmed in the mixed-mode study with the Akron sludge. When compared with the well-known empirical correlation between VS reduction and the product (temperature x solids retention time), the experimental data followed the same trend, but were lower than the correlation predictions. The latter was attributed to the lower digestible VS in the Akron sludge, the slower digestion at low DO concentrations, or both. Through model simulation, the first-order decay constant (kd) was estimated as 0.004 h(-1) in the mixed-mode operations, much lower than those (0.011 to 0.029 h(-1)) obtained in batch digestion. The findings suggested that the interactions among sludges with different treatment ages may have a substantially negative effect on digestion kinetics. The use of multistage digesters, especially with small front-end reactors, may be advantageous in both "process" kinetics and "biological reaction" kinetics for sludge digestion.     

生物膜反应器中低氨氮浓度废水的亚硝化

在连续流生物膜反应器中通过控制DO、pH和HRT,对低氨氮浓度废水进行了亚硝化的实验研究。结果表明,在进水氨氮浓度为35～45 mg/L,温度为34℃的情况下,当DO=1.4～1.5 mg/L,pH=8.3,HRT=6 h时,氨氮的去除率与亚硝态氮的积累率均可达到80%左右,实现了较好的氨氮降解及稳定的亚硝态氮的积累。     

高浓度氨氮废水同步硝化反硝化性能研究

利用序批式反应器研究了溶解氧浓度和进水碳氮比对高浓度氨氮废水脱氮性能的影响.结果表明,溶解氧浓度降低实现了短程同步硝化反硝化,并提高了反应器脱氮效率.反应器运行经历了外部碳源的摄取、PHB储存、PHB有氧氧化和同步硝化反硝化作用,PHB作为同步硝化反硝化过程中反硝化的电子供体.     

MnO2对海底沉积物ANAMMOX菌的富集培养影响

采用上流式固定床反应器，在常温下连续运行，考察MnO2对海洋性ANAMMOX菌富集培养的影响，其中接种的海洋海底沉积物采自大连市附近海域。结果表明，在反应器运行近150d中，加入MnO2的R1反应器的最大总氮去除速率为137．82gN／（m3·d），比没有加人MnO2的R2反应器高出近20gN／（m3·d）。在低温环境（10～15℃）运行时，R1反应器的氨氮和亚硝氮去除率比R2反应器均高出10％，且Rl反应器对温度变化的适应性和运行稳定性都好于R2反应器。这表明MnO2的加入确实在一定程度上促进了海洋性ANAMMOX细菌的富集，并增强了ANAMMOX反应器对温度变化的适应性，使其能够在较宽的温度范围下运行。     

好氧-缺氧-闲置运行模式处理生活污水

在3个序批式反应器中,利用好氧-缺氧-闲置的运行模式处理实际生活污水,比较了不同曝气时间（2、3和4h）条件下的处理效果,结果表明,在R2（2 h）反应器中成功实现了单级好氧除磷和内聚物驱动的短程硝化反硝化。采用此反应器运行模式,对实际生活污水进行长期处理,反应器的COD、TN和TP的平均去除率分别为85.29%、74.09%和87.97%。本研究表明,在好氧-缺氧-闲置的运行模式下处理生活污水,能成功地实现单级好氧除磷与内聚物驱动的短程硝化反硝化的结合,并且在长期运行的过程中,能稳定地取得较好的脱氮、除磷效率。     

Production of polyhydroxyalkanoate during treatment of low-phosphorus-content wastewater.

To evaluate whether poly-beta-hydroxyalkanoate (PHA) production and wastewater treatment could be combined in a single biological process, a bench-scale sequencing batch reactor was operated with sequential anaerobic and aerobic stages and removal of excess sludge at different stages of treatment. The reactor treated synthetic wastewater with a high organic and low nutrient content, simulating industrial wastewater. Chemical oxygen demand removal efficiency was more than 90% in all cases. Poly-beta-hydroxyalkanoate accumulation was significant, although it did not appear to be induced by oxygen limitations during the anaerobic stage. Sphaerotilus natans was apparently the dominant PHA-accumulating organism at the end of each reactor run and corresponded to a PHA accumulation of 16 to 20% of the total dry cell mass. Before S. natans dominated the reactors, PHA accumulation was approximately 17% when biomass was removed at the end of the aerobic stage and 6.6% when sludge removal also occurred during the anaerobic stage.     

Occurrence of carbon monoxide during organic waste degradation

The concentrations of carbon monoxide (CO) and other gases were measured in the emissions from solid waste degradation under aerobic and anaerobic conditions during laboratory and field investigations. The emissions were measured as room temperature headspace gas concentrations in reactors of 1, 30, and 150 L, as well as sucked gas concentrations from windrow composting piles and a biocell, under field conditions. The aerobic composting laboratory experiments consisted of treatments with and without lime. The CO concentrations measured during anaerobic conditions varied from 0 to 3000 ppm, the average being 23 ppm, increasing to 133 ppm when methane (CH4) concentrations were low. The mean/maximum CO concentrations during the aerobic degradation in the 2-L reactor were 101/194 ppm without lime, 486/2022 ppm with lime, and 275/980 ppm in the 150-L reactors. The presence of CO during the aerobic composting followed a rapid decline in O2 concentrations Significantly higher CO concentrations were obtained when the aerobic degradation was amended with lime, probably because of a more extreme depletion of oxygen. The mean/maximum CO concentrations under field conditions during aerobic composting were 95/1000 ppm. The CO concentrations from the anaerobic biocell varied from 20 to 160 ppm. The hydrogen sulfide concentrations reached almost 1200 ppm during the anaerobic degradation and 67 ppm during the composting experiments.     

实时荧光定量PCR对A2/O短程硝化系统内氨氧化菌的定量分析

通过控制好氧区低DO浓度以及缩短好氧实际水力停留时间(actual hydraulic retention time,AHRT),在处理低C/N比实际生活污水的A2/O工艺中,成功启动并维持了短程硝化反硝化;系统亚硝酸盐积累率稳定维持在90%左右,氨氮去除率在95%以上。通过提取富集氨氧化菌(ammonia oxidizing bacteria,AOB)的基因组DNA,经两次常规PCR扩增和琼脂糖凝胶电泳,以纯化回收的DNA扩增片段作为实时荧光定量PCR检测AOB数量的DNA标准品,建立了检测AOB数量的实时荧光定量PCR标准曲线。利用实时荧光定量PCR技术比较了A2/O系统在不同运行条件及亚硝酸盐积累率情况下AOB菌群数量。结果表明,随着系统亚硝酸盐积累率的上升,系统内AOB菌群数量也大幅上升。全程硝化和短程硝化时,系统内的AOB菌群数量分别为5.28×109cells/g MLVSS和3.95×1010cells/g MLVSS。此外,亚硝酸盐积累率的下降相对于AOB菌群数量的下降有一定的滞后性。     

Degradation of acid orange 7 in an aerobic biofilm.

A stable microbial biofilm community capable of completely mineralizing the azo dye acid orange 7 (AO7) was established in a laboratory scale rotating drum bioreactor (RDBR) using waste liquor from a sewage treatment plant. A broad range of environmental conditions including pH (5.8-8.2), nitrification (0.0-4.0 mM nitrite), and aeration (0.2-6.2 mg O2 l(-1)) were evaluated for their effects on the biodegradation of AO7. Furthermore the biofilm maintained its biodegradative ability for over a year while the effects of these environmental conditions were evaluated. Reduction of the azo bond followed by degradation of the resulting aromatic amine appears to be the mechanism by which this dye is biodegraded. Complete loss of color, sulfanilic acid, and chemical oxygen demand (COD) indicate that AO7 is mineralized. To our knowledge this is the first reported occurrence of a sulfonated phenylazonaphthol dye being completely mineralized under aerobic conditions. Two bacterial strains (ICX and SAD4i) originally isolated from the RDBR were able to mineralize, in co-culture, up to 90% of added AO7. During mineralization of AO7, strain ICX reduces the azo bond under aerobic conditions and consumes the resulting cleavage product 1-amino-2-naphthol. Strain SAD4i consumes the other cleavage product, sulfanilic acid. The ability of the RDBR biofilm to aerobically mineralize an azo dye without exogenous carbon and nitrogen sources suggests that this approach could be used to remediate industrial wastewater contaminated with spent dye.     

Measuring biomass specific ammonium, nitrite and phosphate uptake rates in aerobic granular sludge

Aerobic granular sludge (AGS) technology offers the possibility to remove organic carbon, nitrogen and phosphorus in a single reactor system. The granular structure is stratified in such a way that both aerobic and anaerobic/anoxic layers are present. Since most of the biological processes in AGS systems occur simultaneously, the measurement and estimation of the capacity of specific conversions is complicated compared to suspended biomass. The determination of the activities of different functional groups in aerobic granular sludge allows for identification of the potential metabolic capacity of the sludge and aids to analyze bioreactor performance. It allows for comparison of different sludges and enables improved understanding of the interaction and competition between different metabolic groups of microorganisms. The most appropriate experimental conditions and methods to determine specific ammonium, nitrite and phosphate uptake rates under normal operation of AGS reactors were evaluated and described in this study. Extra biomass characterization experiments determining the maximum uptake rate of these compounds on optimized conditions were performed as well to see how much spare capacity was available. The methodologies proposed may serve as an experimental frame of reference for investigating the metabolic capacities of microbial functional groups in biofilm processes.     

间歇曝气SBR工艺脱氮除磷试验研究

采用间歇曝气序批式反应器(SBR)工艺,通过曝气时间、交替次数的调整对该系统的脱氮除磷效果进行了研究,最终将工艺确定为厌氧1.5 h、好氧1.0 h、缺氧1.0 h、好氧20 min、缺氧1.0 h、好氧20 min.同时进行批式试验,对不同阶段的反硝化除磷菌(DPAOs)占除磷菌(PAOs)的比例进行了计算.结果表明:该系统与最初的厌氧/好氧SBR相比节省了44%的曝气量,且对COD、总氮、氨氮和磷的去除率分别达88%、89%、100%和100%,系统中DPAOs所占比例为39%.