Influence of temperature and pH on the kinetics of the Sharon nitritation process

The SHARON (Single reactor High activity Ammonia Removal Over Nitrite) process is an innovative process that improves the sustainability of wastewater treatment, especially when combined with an Anammox process. It aims at ammonium oxidation to nitrite only, while preventing further nitrate formation. In order to optimize this process by means of modelling and simulation, parameters of the biological processes have to be assessed. Batch tests with SHARON sludge clearly showed that ammonia rather than ammonium is the actual substrate and nitrous acid rather than nitrite is the actual inhibitor of the ammonium oxidation in the SHARON process. From these batch tests the ammonia affinity constant, the nitrous acid inhibition constant and the oxygen affinity constant were determined to be 0.75 mgNH₃‐N L^?1, 2.04 mgHNO₂‐N L^?1 and 0.94 mgO₂ L^?1. The influence of pH and temperature on the oxygen uptake rate of SHARON biomass was determined, indicating the existence of a pH interval between 6.5 and 8 and a temperature interval from 35 to 45 °C where the biomass activity is maximal. The kinetic parameters of the SHARON process were determined based on batch experiments. These parameters can now be implemented in a simulation model for further optimization of the SHARON process. Copyright © 2007 Society of Chemical Industry     

Sustained nitrite accumulation in a membrane‐assisted bioreactor (MBR) for the treatment of ammonium‐rich wastewater

A membrane‐assisted bioreactor (MBR) for sustained nitrite accumulation is presented, treating a synthetic wastewater with total ammonium nitrogen (TAN) concentrations of 1 kg N m^?3 at a hydraulic retention time down to 1 day. Complete biomass retention was obtained by microfiltration with submerged hollow fibre membranes. A membrane flux up to 189.5 dm³ day^?1 m^?2 could be maintained at a suction pressure below 100 kPa. Nitrification was effectively blocked at the nitrite stage (nitritation), and nitrate concentration was less than 29 g N m^?3. The rate of aeration was reduced to obtain a mixture of ammonium and nitrite, and after adjusting this rate the TAN/NO₂‐N ratio in the reactor effluent was kept around unity, making it suitable for further treatment by anaerobic oxidation of ammonium with nitrite. After increasing again the rate of aeration, complete nitrification to nitrate recovered after 11 days. It is suggested that nitrite accumulation resulted from a combination of factors. First, the dissolved oxygen (DO) concentration in the reactor was always limited with concentrations below 0.1 g DO m^?3, thereby limiting nitrification and preventing significant nitrate formation. The latter is attributed to the fact that ammonium‐oxidising bacteria cope better with low DO concentrations than nitrite oxidisers. Second, the MBR was operated at a high ammonia concentration of 7–54 g N m^?3, resulting in ammonia inhibition of the nitrite‐oxidising microorganisms. Third, a temperature of 35 °C was reported to yield a higher maximum growth rate for ammonium‐oxidising bacteria than for nitrite‐oxidising bacteria. Nitrite oxidisers were always present in the MBR but were out‐competed under the indicated process conditions, which is reflected in low concentrations of nitrate. Oxygen limitation was shown to be the most important factor to sustain nitrite accumulation. Nevertheless, nitritation was possible at ambient temperature (22–24 °C), lower ammonia concentration (<7 g N m^?3) and when using raw nitrogenous wastewater containing some biodegradable carbon. Overall, application of the MBR for nitritation was shown to be a reliable technology. © 2003 Society of Chemical Industry     

复合生物反应器亚硝酸型同步硝化反硝化脱氮

Sequence hybrid biological reactor （SHBR） was proposed, and some key control parameters were investigated for nitrogen removal from wastewater by simultaneous nitrification and denitrification （SND） via nitrite. SND via nitrite was achieved in SHBR by controlling demand oxygen （DO） concentration. There was a programmed decrease of the DO from 2.50 mg·L^-1 to 0.30 mg·L^-1, and the average nitrite accumulation rate （NAR） was increased from 16.5% to 95.5% in 3 weeks. Subsequently, further increase in DO concentration to 1.50 mg·L^-1 did not destroy the partial nitrification to nitrite. The results showed that limited air flow rate to cause oxygen deficiency in the reactor would eventually induce only nitrification to nitrite and not further to nitrate. Nitrogen removal efficiency was increased with the increase in NAR, that is, NAR was increased from 60% to 90%, and total nitrogen removal efficiency was increased from 68% to 85%. The SHBR could tolerate high organic loading rate （OLR）, COD and ammonia-nitrogen removal efficiency were greater than 92% and 93.5%, respectively,, and it even operated under low DO concentration （0.5 mg·L^-1） and maintained high OLR （4.0 kg COD·m^-3·d^-1）. The presence of biofilm positively affected the activated sludge settling capability, and sludge volume index （SVI） of activated sludge in SHBR never hit more than 90 ml·L^-1 throughout the experiments.     

乙腈与氧原子反应的动力学研究

采用Gaussian98从头算程序包,从理论上对乙腈与氧原子反应的动力学进行了研究。在UB3LYP/6—311 G(d,p)水平下优化了反应物、产物和过渡态的几何结构,用UMP4(SDTQ)方法进行了单点能校正,并计算出它们的谐振频率和反应在温度范300-2100℃的速率常数。     

苯酚对氨氧化菌硝化和污泥性能冲击影响

以苯酚为毒性抑制剂,短程硝化污泥为对象,分析研究了不同苯酚浓度对氨氧化菌硝化过程的抑制特性和抑制动力学,以及对污泥胞外聚合物组分及呼吸速率的短期冲击影响。结果表明,55 mg·L-1苯酚的存在使硝化速率降低37%;低浓度苯酚条件下（< 80 mg·L-1）符合Monod单分子一级动力学方程,且为可逆性抑制,恢复后呼吸速率可达20～25 mg O2·L-1·h-1;且因接种污泥含大量异养菌使得抑制常数（52.871 mg·L-1）远大于纯硝化菌群系统。另外,苯酚的存在促使菌群启动自我保护机制产生更多的胞外聚合物(EPS)抵抗环境变化。苯酚浓度升至135 mg·L-1时,蛋白质和多糖分别增加87.4%和311.7%;而且EPS组分发生相应变化,蛋白质/多糖（P/C）与初始COD/氨氮（C/N）比呈负相关性,P/C从22.1降至3.80。     

Aerated membrane‐attached biofilm reactor as an effective tool for partial nitrification in pretreatment of anaerobic ammonium oxidation (ANAMMOX) process

BACKGROUND: A laboratory‐scale membrane aeration bioreactor was employed to treat synthetic ammonium‐rich wastewater to yield an appropriate NH₄⁺/NO₂^? ratio for anaerobic ammonium oxidation (ANAMMOX). The main objectives of this study were to steadily obtain 50% partial nitrification in batch experiments, to evaluate the effects of aeration and to identify the dominant bacterial community of the biofilm for partial nitrification. RESULTS: Some of the ammonium in the synthetic wastewater was partially nitrified. A suitable NH₄⁺/NO₂^? ratio (1:1 to 1:1.3) for the ANAMMOX process was obtained after 24 h. The dissolved oxygen (DO) level in the treated water was very low (below 0.6 mg L^?1). Both the appropriate NH₄⁺/NO₂^? ratio and the low DO level make this bioreactor an ideal pretreatment system for ANAMMOX. In addition, a molecular biotechnology method was applied to prove that the ammonia‐oxidizing bacteria dominated the biofilm. CONCLUSION: This system achieved surprising cost savings in the aeration process compared with traditional aeration systems. The combination of this system with the subsequent ANAMMOX process has great potential as a favorable short‐cut in the treatment of ammonium‐rich wastewater. Copyright © 2007 Society of Chemical Industry     

缺氧FNA对氨氧化菌和亚硝酸盐氧化菌的选择性抑菌效应

为了研究缺氧条件下游离亚硝酸（FNA）对氨氧化菌（AOB）和亚硝酸盐氧化菌（NOB）的选择性抑菌效应,通过批次试验考察活性污泥经缺氧FNA（0.27 mg HNO₂^--N·L^-1）处理6 h后,其氨氧化速率与亚硝酸盐氧化速率的变化及AOB和NOB活性恢复情况。结果表明：经缺氧FNA处理的活性污泥,NOB活性下降83.57%,而AOB的活性仅下降22.34%。此污泥在正常条件下运行34个周期后,NOB的活性仍未得到恢复,且硝化过程中亚硝酸盐积累率逐渐增加,最后稳定在90%以上。典型周期内氮化合物浓度变化研究表明,即使在过曝气2 h的条件下,亚硝酸盐积累并未遭到破坏。上述试验结果表明基于缺氧FNA选择性抑菌效应有望稳定实现城市污水短程硝化,为城市污水短程硝化厌氧氨氧化提供基础。     

Contribution of Microcosm and Respirometric Experiments to PAHs' Intrinsic Biodegradation in the Soil of a Former Coke Site

Microcosm and respirometric experiments were used to evaluate polycyclic aromatic hydrocarbons' (PAHs') intrinsic biodegradation in soil from a former coke site. The study was carried out in solid phase, over 12 months, at 20°C, in aerobic conditions. Microbial degradation activity in respirometry was assessed by monitoring the CO₂ production and O₂ consumption as well as by following the decrease in PAH content in the soil samples. PAHs' biodegradation patterns are very similar both in microcosm experiments and in respirometry. Respirometric experiments show CO₂ production and O₂ consumption over all biodegradation experiments, whereas no more loss of PAHs is measured after only a few weeks of experimentation. This indicates that monitoring only CO₂ production or O₂ consumption is not enough to assess PAHs' biodegradation. It seems that, after having degraded the most available PAHs, microbiota shift to other sources of carbon for their metabolism.     

限氧条件下亚硝化的稳定运行及动力学

采用高氨氮人工配水和序批式反应器,在限氧(0.2～0.3mg/L)条件下,研究了进水氨氮负荷、游离氨和游离亚硝酸对氨氮转化率、亚硝化率和亚硝氮生成速率的影响及游离氨对氨氧化菌的基质抑制动力学。结果表明,在进水氨氮负荷逐步提升过程中,由于高浓度游离氨的抑制作用及负荷冲击的影响,亚硝化效果易出现波动,且负荷越高,亚硝化性能恢复的时间越长。反应系统最终可达到的氨氮容积负荷为3.60kg/(m³·d),亚硝氮生成速率为2.98kg/(m³·d),亚硝化率始终维持在85%左右。反应体系中较高的游离氨浓度(24.4～85.8mg/L)和低浓度溶解氧是维持亚硝化工艺稳定运行的主要因素。游离氨对氨氧化菌的抑制动力学符合Haldane模型,拟合得到最大氨氧化速率为6.71gN/(gVSS·d),游离氨半饱和常数和抑制常数分别为3.2mg/L和27.8mg/L。     

Effect of oxygen mobility in solid catalyst on transient regimes of catalytic reaction of methane partial oxidation at short contact times

Mathematical modeling of the effect of the oxygen mobility in a solid oxide catalyst on the dynamics of transients of fast catalytic reactions has been carried out. The analysis was based upon the redox mechanistic scheme with a due regard for diffusion of oxygen from the bulk of catalyst to its surface. Parameters of kinetic and mathematical models were selected via fitting of the experimental data for methane selective oxidation into syngas on 1.4%Pt/Gd_0.2Ce_0.4Zr_0.4O _x catalyst. The range of the Thiele parameter (φ) where the oxygen bulk diffusion affects the most strongly reaction transients corresponds to φε [0.3 ÷ 7]. For high-surface-area oxide catalysts, the bulk oxygen diffusion coefficients corresponding to this range of the Thiele parameter are in the range of 10^–18 ÷ 10^–13cm²/s.     

Respirometric method for kinetic modeling of ammonium-oxidizing and nitrite-oxidizing bacteria in a membrane bioreactor

A respirometric method for the kinetic modeling of ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) was implemented in two membrane bioreactor (MBR_A and MBR_B) systems. These biological systems worked at mixed liquor suspended solids concentration of about 6.6 g L⁻¹. MBR_A worked at 6 hr of hydraulic retention time (HRT) and 20.7°C, while the operational conditions for MBR_B were 9.5 hr of HRT and 14.7°C. Experimental data were fitted to the kinetic model with R² values of .9320 and .9250 for MBR_A and MBR_B, respectively. Both systems showed similar performances regarding organic matter and nitrogen removal. However, MBR_B showed highest rates of carbon source degradation and net heterotrophic bacteria growth, and MBR_A had highest rates of nitrogen source degradation and net autotrophic bacteria growth. This last system was characterized by values for Y_AOB, Y_NOB, μ_m,AOB and μ_m,NOB of 1.1749 mgVSS mgN⁻¹, 0.6473 mgVSS mgN⁻¹, 0.3664 hr⁻¹ and 0.1823 hr⁻¹, respectively.     

Selection of oxygen permeation models for different mixed ionic‐electronic conducting membranes

Permeation data of several mixed ionic‐electronic conducting (MIEC) membranes were analyzed by two oxygen permeation models (i.e., Zhu's model and Xu–Thomson's model), respectively, to find a concise method to guide the choice of permeation models. We found that Zhu's model can well fit the permeation data of perovskite‐type membranes, like Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3‐δ (BSCF) and BaCe_0.05Fe_0.95O_3‐δ (BCF), and dual‐phase membranes, like 75 wt % Ce_0.85Sm_0.15O_1.925–25 wt % Sm_0.6Sr_0.4Al_0.3Fe_0.7O_3‐δ (SDC‐SSAF), whose oxygen vacancy concentrations are almost independent of the oxygen partial pressure at elevated temperatures. However, Zhu's model was not appropriate for membranes whose oxygen vacancy concentration changed obviously with oxygen partial pressure at elevated temperatures, such as La_0.6Sr_0.4Co_0.2Fe_0.8O_3‐δ (LSCF) and La_0.7Sr_0.3CoO_3‐δ (LSC). On the contrary, Xu–Thomson's model can fit the data of LSCF and LSC well, but it is inapplicable for BSCF, BCF, and SDC‐SSAF. Therefore, the dependence of oxygen vacancy concentration on oxygen partial pressure was suggested as an index for the selection of the permeation models. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4043–4053, 2017     

厌氧氨氧化生物脱氮技术的演变、机理及研究进展

厌氧氨氧化(Anammox)生物脱氨技术由于在经济面的独特优势,成为近年国内外研究的热点,是未来污水生物脱氮技术发展的主流。国内对该技术的研究与国外还存在较大的差距,尤其在Anammox机理方面。文章对Anammox生物脱氮技术的演变、机理及研究现状作了全面的论述,从而为该技术的深入研究及其在实际中的应用奠定基础,同时为该技术的进一步发展提出了具体的建议。     

Role of Al segregation and high affinity to oxygen in formation of adhesive alumina layers on FeCr alloy support

The aim of this study is to gain information necessary to propose the mechanism of the oxide layers’ formation on the FeCr alloy foil of 0.05 mm thickness as well as to obtain indications about thermal treatment resulting in the relatively uniform adhesive layers.

The surface morphology of the oxide layers formed on the foil in the course of its thermal treatment as well as layers’ thickness and element distribution along their cross sections were investigated with scanning electron microscopy and secondary ion mass spectrometry. Observed differences were ascribed to the various orientations of FeCr alloy crystallites.     

SBR工艺实现长期稳定的部分短程硝化

采用SBR工艺以实际生活污水为研究对象,通过3组预实验得出实现部分短程硝化(部分NH₄⁺-N转化为NO₂^--N)的最佳曝气量和曝气时间,启动长期运行的部分短程硝化序批式反应器(PNSBR),在好氧阶段以最佳曝气量[7.2~12L·(h·L)^-1]和曝气时间(2~3h)曝气,持续运行110多天(450多个周期)。结果显示,出水亚硝态氮积累率稳定维持在94%~100%,表明了长期稳定的短程硝化效果;出水NO₂^--N与NH₄⁺-N的比值大部分集中在2~4之间。进一步的分析得出,在PNSBR长期运行中,一方面通过控制曝气量和曝气时间使得好氧阶段溶解氧较低,更利于AOB的生长代谢而抑制NOB的活性;另一方面排水后剩余的亚硝态氮通过利用进水中的碳源反硝化去除(本周期的内源反硝化和下周期的外源反硝化),避免了为NOB提供底物的可能,从而实现了稳定的部分短程硝化。同步厌氧氨氧化和反硝化(SAD)工艺广泛存在,PNSBR反应器作为SAD的前置反应器,可提供满足SAD运行的进水,因此部分短程硝化是一项有潜力的工艺。     

调节pH抑制亚硝酸盐对碘量法测定溶解氧干扰的抑制作用

为进一步提高碘量法测定溶解氧(DO)对亚硝酸盐存在的上限,提出在滴定前调节溶液pH在4～5,以抑制亚硝酸盐的干扰。实验表明此法适用于亚硝酸盐质量浓度在5～300 mg/L的水样溶解氧测定,在较高浓度亚硝酸盐存在的条件下,此法对DO质量浓度在2～10 mg/L的水样均具有较高的准确度。     

分子氧氧化环己烷制环己酮催化剂的研究进展

综述了分子氧氧化环己烷制取环己酮的催化剂的研究进展,重点介绍了光催化剂、纳米催化剂、仿生催化剂、分子筛催化剂和复合催化剂在环己烷催化氧化方面的应用,其中,负载在分子筛上的纳米金催化剂具有较高的催化活性、选择性及稳定性。     

Autotrophic nitrification and denitrification characteristics of an upflow biological aerated filter

Wastewater nitrification was carried out using a laboratory‐scale upflow biological aerated filter (BAF) packed with a polyurethane‐based porous medium. The filtration medium has macro‐pores which provide a greater surface area for the development of biofilms. The macro‐pores have both aerobic and anaerobic zones, depending on the depth of oxygen penetration in the medium. Wastewater ammonium was oxidized at a maximum rate of 1.8 kg NH₄⁺m^?3d^?1 and showed more than 90% nitrification efficiency in the BAF. During the biological nitrification of wastewater, considerable nitrogen loss was observed in the BAF under oxygen‐limited conditions when organic carbons were not provided for denitrification. Most probably, the lost nitrogen was converted to gaseous nitrogen compounds including dinitrogen by autotrophic dentrification and anaerobic ammonium oxidation. © 2001 Society of Chemical Industry     

Comparison of various solvents for determination of intrinsic viscosity and viscometric constants for cellulose

Different solvents used to determine the intrinsic viscosity and the viscometic constants, a and K, published in the literature for cellulose, were compared. The various parameters affecting the viscometric constants were also evaluated. The main conclusions obtained from the experimental data available in the literature are that (1) the intrinsic viscosities in various solvents are ordered as follows: [η]_LiCl/DMAc > [η]_NH3/NH4SCN ≥ [η]_FeTNa > [η]_CED > [η]_Cadoxen > [η]_Cuoxam; (2) the reported intrinsic viscosities and molecular weights for cellulose are lower than the true value due to degradation of cellulose in the solvents; (3) the rate of degradation was the smallest in LiCl/DMAc and NH₃/NH₄SCN, moderate in cadoexn and FeTNa, and the highest in CED and cuoxam; (4) the plot of log K versus exponent a was linear and inversely related; (5) the curve was used for estimation of the constant K for cellulose in a solvent (NH3/NH4SCN) with a known exponent a; and (6) among various reported solvents, LiCl/DMAc and NH₃/NH₄SCN are advantageous over other solvents because of a complete dissolution of the polymer with a negligible reduction in its intrinsic viscosity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2189–2193, 2002