Manganese oxidation induced by water table fluctuations in a sand column

On-off cycles of production wells, especially in bank filtration settings, cause oscillations in the local water table, which can deliver significant amounts of dissolved oxygen (DO) to the shallow groundwater. The potential for DO introduced in this manner to oxidize manganese(II) (Mn(II)), mediated by the obligate aerobe Pseudomonas putida GB-1, was tested in a column of quartz sand fed with anoxic influent solution and subject to 1.3 m water table changes every 30-50 h. After a period of filter ripening, 100 μM Mn was rapidly removed during periods of low water table and high dissolved oxygen concentrations. The accumulation of Mn in the column was confirmed by XRF analysis of the sand at the conclusion of the study, and both measured net oxidation rates and XAS analysis suggest microbial oxidation as the dominant process. The addition of Zn, which inhibited GB-1 Mn oxidation but not its growth, interrupted the Mn removal process, but Mn oxidation recovered within one water table fluctuation. Thus transient DO conditions could support microbially mediated Mn oxidation, and this process could be more relevant in shallow groundwater than previously thought.     

Designing hypolimnetic aeration and oxygenation systems--a review

When properly designed, hypolimnetic aeration and oxygenation systems can replenish dissolved oxygen in water bodies while preserving stratification. The three primary devices are the airlift aerator, Speece Cone, and bubble-plume diffuser. In each device, gas bubbles in contact with water facilitate interfacial transfer of oxygen, nitrogen, and other soluble gases. However, early design procedures for airlift aerators were empirical, while most bubble-plume models did not account for stratification or gas transfer. Using fundamental principles, a discrete-bubble model was first developed to predict plume dynamics and gas transfer for a circular bubble-plume diffuser. The discrete-bubble approach has subsequently been validated using oxygen transfer tests in a large vertical tank and applied successfully at full-scale to an airlift aerator as well as to both circular and linear bubble-plume diffusers. The performance of each of the four completely different full-scale systems (on a scale of 10 m or more) was predicted based on the behavior of individual bubbles (on a scale of about 1 mm). The combined results suggest thatthe models can be used with some confidence to predict system performance based on applied air or oxygen flow rate, initial bubble size, and, in the case of bubble plume diffusers, near-field boundary conditions. The discrete-bubble approach has also been extended to the Speece Cone, but the model has not yet been validated due to a lack of suitable data. The unified suite of models, all based on simple discrete-bubble dynamics, represents the current state-of-the-art for designing systems to add oxygen to stratified lakes and reservoirs.     

Partial nitrification of ammonium-rich wastewater as pretreatment for anaerobic ammonium oxidation (Anammox) using membrane aeration bioreactor

A lab-scale membrane aeration bioreactor (MBR) system was developed for treating synthetic ammonium-rich wastewater to yield an appropriate NO(2)(-)/NH(4)(+) mixture as a pretreatment for anaerobic ammonium oxidation (Anammox). The effluent with a suitable NO(2)(-)/NH(4)(+) ratio (1:1 to 1:1.3) was obtained in 24 h using the developed MBR system under suitable conditions. Additionally, the control of bulk dissolved oxygen (DO) level under a desired condition (anoxic condition) was easier and more economical than traditional aeration systems. An optimal initial alkalinity of 1500 mg CaCO(3)l(-1) was necessary for achieving 50% partial nitrification of wastewater with an initial ammonium concentration of 510 mg NH(4)-N l(-1) within 24 h. Furthermore, there is no need for pH adjustment by adding a base or an acid throughout the reaction if the initial alkalinity is appropriately controlled. Both the appropriate NO(2)(-)/NH(4)(+) ratio and the low DO level make this MBR system an ideal system for Anammox.     

裂褶菌液态深层培养条件的研究

研究了裂褶菌液态深层培养过程中通风量以及控制溶氧浓度(DO)对裂褶菌丝体生长和胞外多糖产量的影响。通过在发酵过程中的不同时期改变通风量和将溶氧浓度维持在20%以上,均能有效地控制罐内氧传递速率,增加菌体对碳源的利用率,且还原糖消耗速率和菌体得率明显提高。当在发酵过程中的不同时期改变通风量时,菌丝体得率和胞外多糖产量分别为14.83g/L和2.12g/L。当溶氧浓度维持在20%以上时,菌体得率为15.56g/L,但是多糖产量仅有1.00g/L,说明高溶氧不利于多糖的生产。     

Dynamic dissolved oxygen concentration control for enhancing the formation rate of torpedo-stage embryos in carrot somatic embryo culture

In utilizing somatic embryogenesis for transplant production, torpedo-stage embryos are harvested. In order to enhance the formation rate of torpedo-stage embryos to total embryos of all developmental stages in the culture at the time of harvest, a dynamic dissolved oxygen concentration (DO) control algorithm is proposed. The algorithm is based on the difference in developmental response of somatic embryogenesis to DO level depending on developmental stages, and the culture period was divided into three phases of different DO levels. The timing of the phase change was determined based on the formation rate of the embryos in each developmental stage in the suspension assessed by noninvasive monitoring of the culture. The induction of carrot (Daucus carroa L.) somatic embryogenesis resulted in doubled formation rate of torpedo-stage embryos by dynamic DO control compared to the 20% oxygen gas aeration, and 1.4 times higher formation rate compared to 6% oxygen gas aeration, while the total number of embryos did not differ among DO treatments. Plant conversion rate of torpedo-stage embryos cultured by the dynamic DO control was 70%, and was approximately the same as that in the control cultures. The relations between variations of medium pH and somatic embryogenesis were also analyzed.     

Effects of dissolved oxygen level on cell growth and total lipid accumulation in the cultivation of Rhodotorula glutinis

The total amount of lipids produced in Rhodotorula glutinis is a subject which has attracted increasing attention due to the potential biodiesel conversion from these microbial oils. The effects of the dissolved oxygen (DO) level in lipid accumulation were examined in this study. Variations of different medium volumes (30, 40 and 50ml) and shaking speed (60, 150 and 210rpm) in the flask trials were adopted to explore the DO effects on lipid production. All of the results revealed that a low DO could retard cell growth, while enhancing lipid accumulation. The 5l-fermentor results also confirm that a low DO (25 ± 10%) batch could have higher lipid content than that of high DO batch (60 ± 10%). Nevertheless, the DO level would not obviously affect the lipid composition profile. Oleic acid (C18:1) was the primary fatty acid in both batches. Due to the slow biomass growth rate resulting from the low DO, a two-stage DO controlled strategy (consisting of a high DO stage and following a low DO stage) was performed to improve the cell growth and lipid accumulation simultaneously. However, the strategy was not successful on the enhancement of total lipid production as compared to other batches. Conclusively, even a low DO could retard cell growth; the total production of lipids in the batch with low DO was higher that of the high DO batch due to the enhancement of lipid accumulation. Therefore, the batch operation of R. glutinis at the low DO was suggested for the purpose of lipid production.     

High rate nitrogen removal in an alum sludge-based intermittent aeration constructed wetland

A new development on treatment wetland technology for the purpose of achieving high rate nitrogen removal from high strength wastewater has been made in this study. The laboratory scale alum sludge-based intermittent aeration constructed wetland (AlS-IACW) was integrated with predenitrification, intermittent aeration, and step-feeding strategies. Results obtained from 280 days of operation have demonstrated extraordinary nitrogen removal performance with mean total nitrogen (TN) removal efficiency of 90% under high N loading rate (NLR) of 46.7 g N m(-2) d(-1). This performance was a substantial improvement compared to the reported TN removal performance in literature. Most significantly, partial nitrification and simultaneous nitrification denitrification (SND) via nitrite was found to be the main nitrogen conversion pathways in the AlS-IACW system under high dissolved oxygen concentrations (3-6 mg L(-1)) without specific control. SND under high dissolved oxygen (DO) brings high nitrogen conversion rates. Partial nitrification and SND via nitrite can significantly reduce the demand for organic carbon compared with full nitrification and denitrification via nitrate (up to 40%). Overall, these mechanisms allow the system to maintaining efficient and high rate TN removal even under carbon limiting conditions.     

Biogeochemical controls on Diel cycling of stable isotopes of dissolved O2 and dissolved inorganic carbon in the Big Hole River, Montana

Rivers with high biological productivity typically show substantial increases in pH and dissolved oxygen (DO) concentration during the day and decreases at night, in response to changes in the relative rates of aquatic photosynthesis and respiration. These changes, coupled with temperature variations, may impart diel (24-h) fluctuations in the concentration of trace metals, nutrients, and other chemical species. A better understanding of diel processes in rivers is needed and will lead to improved methods of data collection for both monitoring and research purposes. Previous studies have used stable isotopes of dissolved oxygen (DO) and dissolved inorganic carbon (DIC) as tracers of geochemical and biological processes in streams, lakes, and marine systems. Although seasonal variation in 6180 of DO in rivers and lakes has been documented, no study has investigated diel changes in this parameter. Here, we demonstrate large (up to 13%o) cycles in delta18O-DO for two late summer sampling periods in the Big Hole River of southwest Montana and illustrate that these changes are correlated to variations in the DO concentration, the C-isotopic composition of DIC, and the primary productivity of the system. The magnitude of the diel cycle in delta18O-DO was greater in August versus September because of the longer photoperiod and warmer water temperatures. This study provides another biogeochemical tool for investigating the O2 and C budgets in rivers and may also be applicable to lake and groundwater systems.     

Significant increase in recombinant protein production of a virus-infected Sf-9 insect cell culture of low MOI under low dissolved oxygen conditions

Spodoptera frugiperda Sf-9 insect cells were infected with recombinant Autographa californica nuclear polyhedrosis virus at a low multiplicity of infection (MOI) (0.1), and the effect of dissolved oxygen (DO) on the production of a polyhedrin promoter-driven recombinant protein (beta-galactosidase), intrinsic proteases (carboxyl and cysteine proteases), and the virus was determined. The DO concentrations used in the present study were 45%, 25%, 5%, and 1.3% of air saturation. At 5% DO the cell growth following viral infection was greatest and beta-galactosidase was about 5-fold increased in volumetric yield compared to that at 45% and 25% DO, whereas the growth at 1.3% DO was extremely poor. The virus titer in the medium at 4-8 d post-infection (dpi) was also highest at 5% DO, but the titer was significantly decreased by further increasing the culture time. This was in part attributed to the fact that baculovirus is susceptible to oxidative inactivation under aerobic conditions. The DO dependency of the specific oxygen consumption rate of virus-infected and uninfected Sf-9 cells was expressed by a Monod-type equation. A critical DO, above which the rate of oxygen utilization is not limited by DO, was estimated to be 3.5% of air saturation for virus-infected Sf-9 cells. These results indicated that for a baculovirus-infected Sf-9 insect cell culture of low MOI, the optimal DO was likely to be approximately 5% of air saturation, which is above the critical DO for the infected Sf-9 cells but sufficiently low to reduce the possibility of the oxidative inactivation of virus. For the production of carboxyl and cysteine proteases, the accumulation behavior and concentrations did not significantly vary with DO, except that a peak of cysteine protease activity was observed intracellularly only at 5% DO, coinciding with beta-galactosidase production.     

离子特性及贮藏条件对强酸性电生功能水理化性质的影响

在相同条件下对离子配比不同以及阳离子不同的电解液分别电解,测定生成水样的理化指标。研究发现,当氯离子浓度不变时,钠离子浓度成倍数增加会导致强酸性电生功能水(AEW)中有效氯浓度成倍数增加;当同时电解Cl-为35mmol/L的溶液时,KCl、MgCl2、NaCl和CaCl2四种电解质产生水样的有效氯浓度分别为90.1、74.8、56.8和48.2mg/L。另外,本文还将有效氯浓度为50mg/L左右的强酸性电生功能水在不同条件下贮藏了21d,定期测定有效氯浓度(ACC)、pH、氧化还原电位(ORP)、电导率(EC)以及溶解氧浓度(DO)在贮藏过程中的变化。结果表明,大容量器、玻璃容器和低温贮藏有利于酸性电生功能水有效氯和溶解氧的保存,密闭有利于氧化还原电位值的保持;酸性电生功能水贮藏不宜超过1周,最好在5d以内;不同电解质制备水样的贮藏稳定性由高到低依次为MgCl2、CaCl2、NaCl和KCl。     

Enhancement and inhibition of denitrification by fluid-flow and dissolved oxygen flux to stream sediments

Microscale measurements of nitrate (NO3-) and dissolved oxygen (DO) concentrations in sediments were made in a laboratory channel under turbulent fluid-flow conditions to examine the effects of DO flux on denitrification rates. DO concentrations and flux within sediments increased with increasing velocity in the surface water. Under low fluid-flow conditions (shear stress velocity, u* < 0.23 cm s(-1)), increasing velocity increased NO3- loss from the bulk flow. For high fluid-flow conditions (u* > 0.39 cm s(-1)), increasing velocity inhibited NO3-loss. Sediment cores were collected and sliced to measure the depth distribution of denitrifying biomass in sediments. Quantities of nirK and nirS genes were higher within the surface layer and decreased with depth in the sediments. Microscale concentration profiles of DO and NO3- revealed that denitrification occurs within a thin region just below the oxic-anoxic interface in sediments. The interplay of mass transfer and DO flux generated threshold conditions for NO3- loss by denitrification. These results suggest that for a given sediment and environmental conditions (chemical, physical, microbiological), there exists an optimal range in velocities for enhancing denitrification in aquatic systems.     

Spatially complex distribution of dissolved manganese in a fjord as revealed by high-resolution in situ sensing using the autonomous underwater vehicle Autosub

Loch Etive is a fjordic system on the west coast of Scotland. The deep waters of the upper basin are periodically isolated, and during these periods oxygen is lost through benthic respiration and concentrations of dissolved manganese increase. In April 2000 the autonomous underwater vehicle (AUV) Autosub was fitted with an in situ dissolved manganese analyzer and was used to study the spatial variability of this element together with oxygen, salinity, and temperature throughout the basin. Six along-loch transects were completed at either constant height above the seafloor or at constant depth below the surface. The ca. 4000 in situ 10-s-average dissolved Mn (Mnd) data points obtained provide a new quasi-synoptic and highly detailed view of the distribution of manganese in this fjordic environment not possible using conventional (water bottle) sampling. There is substantial variability in concentrations (<25 to >600 nM) and distributions of Mnd. Surface waters are characteristically low in Mnd reflecting mixing of riverine and marine end-member waters, both of which are low in Mnd. The deeper waters are enriched in Mnd, and as the water column always contains some oxygen, this must reflect primarily benthic inputs of reduced dissolved Mn. However, this enrichment of Mnd is spatially very variable, presumably as a result of variability in release of Mn coupled with mixing of water in the loch and removal processes. This work demonstrates how AUVs coupled with chemical sensors can reveal substantial small-scale variability of distributions of chemical species in coastal environments that would not be resolved by conventional sampling approaches. Such information is essential if we are to improve our understanding of the nature and significance of the underlying processes leading to this variability.     

Heterogeneous oxidation of Fe(II) on ferric oxide at neutral pH and a low partial pressure of O2

The objective of this study was to identify the rate and mechanism of abiotic oxidation of ferrous iron at the water-ferric oxide interface (heterogeneous oxidation) at neutral pH. Oxidation was conducted at a low partial pressure of O2 to slow the reactions and to represent very low dissolved oxygen (DO) conditions that can occur at oxic/anoxic fronts. Hydrous ferric oxide (HFO) was partially converted to goethite after 24 h of anoxic contact with Fe(II), consistent with previous results. This resulted in a significant decrease in sorption of Fe(II). No conversion to goethite was observed after 25 min of anoxic contact between HFO and Fe(II). O2 was then introduced into the chamber and sparged (transfer half-time of 1.6 min) into the previously anoxic suspension, and the rate of oxidation of Fe(II) and the distribution between sorbed and dissolved Fe(II) were measured with time. The concentration of sorbed Fe(II) remained steady during each experiment, despite removal of all measurable dissolved Fe(II) in some experiments. The rate of oxidation of Fe(II) was proportional to the concentration of DO and both sorbed and dissolved Fe(II) up to a surface density of 0.02 mol Fe(II) per mol Fe(III), i.e., approximately 0.2 Fe(II) per nm2 of ferric oxide surface area. This result differs from previous studies of heterogeneous oxidation, which found that the rate was proportional to sorbed Fe(II) and DO but did not find a dependence on dissolved Fe(II). Most previous experiments were autocatalytic; i.e., the initial concentration of ferric oxide was low or none, and sorbed Fe(II) was not measured. The results were consistentwith an anode/cathode mechanism, with O2 reduced at electron-deficient sites with strongly sorbed Fe(II) and Fe(II) oxidized at electron-rich sites without sorbed Fe(II). The pseudo-first-order rate constants for oxidation of dissolved Fe(II) were about 10 times faster than those previously predicted for heterogeneous oxidation of Fe(II).     

组合生化池曝气器坏损的原因及解决方法

食品饮料行业废水处理工艺系统中组合生化池常见的问题是 ,由于曝气器的坏损导致接触氧化池中曝气不均 ,甚至出现局部曝气而大面积不曝气现象 .经分析 ,其根本原因是管道内的积水所致 ;应用文丘里管原理并通过理论计算 ,设计了一种排出管道内积水以解决曝气器坏损问题的具体方案 ,并应用于实际 ,获得了较好的实践效果 .     

Measure the Dissolved Oxygen Consumed by Red Wines in Aging Tanks

The techniques of accelerated wine aging imply the addition of wood pieces of oak to the wine and the use of small doses of oxygen (micro-oxygenation). The dosage of extremely small amounts needs the knowledge of the dissolved oxygen (DO) at every moment in order to assure its correct assimilation. This work presents the first results of a study about the evolution of the dissolved oxygen content in red wines during alternative accelerated aging. Samples were treated in stainless steel vessels with wood pieces and low micro-oxygenation levels. French oak was applied with different toasting levels: light, medium, and high. Quality parameters of the wine were monitored. The knowledge of wine DO levels allowed developing a controlled micro-dosage in the different phases during the accelerated aging. The wine was able to use the whole amount of oxygen provided throughout the process.     

干红葡萄酒生产和瓶储过程中溶解氧变化规律的研究

本文通过对干红葡萄酒生产过程中溶解氧的跟踪检测,找出了酿造过程中每种工艺处理溶解氧的变化规律,发现葡萄酒中的溶氧量与葡萄酒生产工艺、游离二氧化硫、温度等密切相关,其中冷冻工艺、灌装工艺以及成品酒仓储阶段是溶解氧波动较大的环节。因此,掌握生产过程中各工艺环节溶解氧变化规律是解决溶解氧技术问题的前提。     

溶解氧控制对枯草芽孢杆菌发酵生产腺苷的影响

在50 L的生物反应器中,通过控制溶解氧水平为5%、10%、20%、30%四个水平考察枯草芽孢杆菌发酵生产腺苷的影响,发现该菌株生长的溶解氧浓度在10%～20%。并通过发酵过程中菌株的生长情况、菌体摄氧率和发酵产苷进行相关分析。结果表明,在发酵过程中DO水平控制在10%～20%时腺苷积累量高,发酵液中DO水平为5%和30%均不利于发酵液中的腺苷积累。通过对发酵终点丙酮酸的检测,发现枯草芽孢杆菌在低溶氧状态下比高溶氧状态下积累更多的丙酮酸。在此基础上,提出两阶段DO控制策略,最终腺苷积累量达到20.1 g/L。     

pH及溶氧对重组大肠杆菌发酵生产5-氨基乙酰丙酸的影响

以重组大肠杆菌DALA为实验菌株,研究了该菌株在机械搅拌通风发酵罐发酵过程中pH以及溶解氧对5-氨基乙酰丙酸（ALA）积累的影响。结果发现,发酵前期（0～27 h）pH保持为6.5;稳定期后期（28～48 h）,pH为6.0时有利于5-ALA的积累。其次,通过控制转速与通气量调节发酵液中的溶氧,发现发酵前期转速为500 r/min,通气量为2 vvm;稳定期后期,转速降低至250 r/min,通气量减少为1 vvm,有利于重组菌DALA发酵生产5-ALA,在此条件下发酵5-ALA的产量可达到3.46 g/L。     

Trichloroethylene transformation by natural mineral pyrite: the deciding role of oxygen

The transformation of trichloroethylene (TCE) in natural mineral iron disulfide (pyrite) aqueous suspension under different oxygen conditions was investigated in laboratory batch experiments. TCE transformation was pursued by monitoring its disappearance and products released with time. The effect of oxygen was studied by varying the initial dissolved oxygen concentration (DO(i)) inside each reactor. Transformation rates depended strongly on DO(i) in the system. In anaerobic pyrite suspension, TCE did not transform as it did under aerobic conditions. The transformation rate increased with an increase in DO(i). The TCE transformation kinetics was fitted to a pseudo-first-order reaction with a rate constant k (h(-1)) varying from 0.004 to 0.013 for closed systems with DO(i) varying from 0.017 to 0.268 mmol/L under the experimental conditions. In the aerobic systems, TCE transformed to several organic acids including dichloroacetic acid, glyoxylic acid, oxalic acid, formic acid, and finally to CO2 and chloride ion. Dichloroacetic acid was the only chlorinated intermediate found. Both TCE and the pyrite surface were oxidized in the presence of O2. Oxygen consumption profiles showed O2 was the common oxidant in both TCE and pyrite oxidation reactions. Ferric ion cannot be used as an alternative oxidant to oxygen for TCE transformation.     

SOME EFFECTS OF AERATION ON THE GROWTH AND METABOLISM OF SACCHAROMYCES CEREVISIAE IN CONTINUOUS CULTURE

In continuous fermentation of a complex, synthetic medium by Saccharomyces cerevisiae, a steady state was maintained for prolonged periods in the absence of oxygen. Growth reached a maximum at a low rate of aeration and under these conditions ester formation was markedly inhibited. At higher levels of aeration growth was reduced, the cells formed chains and aggregated, the rate of fermentation decreased and large quantities of acetoin and acetaldehyde were produced. Under fully aerobic conditions, ethanol production continued to account for the major part of the glucose consumed. The amount of diacetyl produced was insignificant at all rates of aeration. The extent of growth and the nitrogen content of the yeast were inversely related.