A simple continuous-flow respirometer for comparative respiratory changes in medium-sized aquatic organisms

A continuous-flow respirometer was designed to accommodate medium-sized aquatic organisms for comparative respiratory studies. The apparatus is simple in design, easily constructed and can be adapted to various flow rates, aquatic organisms and experimental designs. The system was tested with golden shiners. Notemigonous crysoleucas Mitchill, and with the blue crab. Callinectes sapidus Rathbun, and found to be a useful tool in physiological studies.     

A titrimetric respirometer measuring the nitrifiable nitrogen in wastewater using insensor-experiment

Measurement of nitrifiable nitrogen contained in wastewater by combining the existing respirometric and titrimetric principles is reported. During an in-sensor-experiment using nitrifying activated sludge, both the dissolved oxygen (DO) and pH in the mixed liquor were measured, and the pH was controlled at a set-point through titration of base or acid. A combination of the oxygen uptake rate (OUR), which was obtained from the measured DO signal, and the titration data allowed calculation of the nitrifiable nitrogen and the short-term biological oxygen demand (BOD) of the wastewater sample that was initially added to the sludge. The calculation was based solely on stoichiometric relationships. The approach was preliminarily tested with two types of wastewaters using a prototype sensor. Good correlation was obtained.     

Mathematical analysis of oxygen and nitrate consumption in deep microbial films

The simultaneous diffusion and consumption of oxygen and nitrate into microbial films with aerobic and anaerobic layers was modeled by a system of differential equations and solved by numerical methods. Fickian diffusion was assumed. Models used Monod kinetics and zero-order kinetics, for growth limitation by oxygen and nitrate. Denitrification was assumed to be repressed by oxygen concentrations greater than a finite critical value. Both models indicate that oxygen concentration in the overlying water would have little effect on the nitrate uptake of thick films.     

酸性高锰酸钾法测定化学需氧量的方法及技巧

指出酸性高锰酸钾法测定化学需氧量是饮用水中COD测定的常用方法，就该测定的几种方法进行了对比试验和分析，结合工作经验，提出了一些操作建议，从而使得测定结果的相对误差减小。     

A simple apparatus for measuring the permeability of borehole core

The measurement of permeability forms the basis for many engineering and geological engineering investigations. Most of these investigations require that a large number of determinations be made rapidly and accurately. The permeameter discussed here is a modification of the one designed by Ohle (1951). The permeameter allows for rapid sample change and is capable of measuring the permeability of a core sample using any fluid. The permeameter has been used successfully to test permeabilities as low as 10^?5 millidarcies to permeabilities as high as 10 millidarcies at fluid pressures up to 10 MPa. The reproducibility of the tests was found to be in the order of 90%.     

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.     

A simple and inexpensive monitor for recording oxygen and temperature in lakes and reservoirs

The design, construction and operation of a simple and inexpensive monitor for the continuous recording of oxygen and temperature at multiple depths in small lakes and reservoirs is described. The system currently employs four electrodes suspended at selectable depths. Additional sensors can be readily incorporated into the system either to measure other “water quality” variables or to include a greater number of depths. Data is collected with a solid state multi-channel data logger.     

测定砂土水分特征曲线的一种简易方法

土壤水分特征曲线反映了土壤含水率与吸力之间的关系,是研究土壤水分流动和溶质运移的基础数据。对于砂性土,提出一种测定水分特征曲线的简易试验方法,即对砂柱进行逐级排水,获得排水量与自由面(潜水面)高度的关系曲线,将其转化为水分特征曲线。采用这种砂柱试验测定了地大粗砂的土壤水分特征曲线,得到了良好的"S"型曲线,能够用Van Genuchten公式进行拟合。砂柱试验结果与压力膜仪法实测的和Arya-Paris模型间接推求的土壤水分特征曲线具有一致性。与现有测定方法相比,砂柱实验具有原理简单、准确度较高、成本低的优势。     

A data framework for measuring the energy consumption of the non-domestic building stock

The transition to a low-carbon economy urgently demands better information on the drivers of energy consumption. UK government policy has prioritized energy efficiency in the built stock as a means of carbon reduction, but the sector is historically information poor, particularly the non-domestic building stock. This paper presents the results of a pilot study that investigated whether and how property and energy consumption data might be combined for non-domestic energy analysis. These data were combined in a ‘Non-Domestic Energy Efficiency Database’ to describe the location and physical attributes of each property and its energy consumption. The aim was to support the generation of a range of energy-efficiency statistics for the industrial, commercial and institutional sectors of the non-domestic building stock, and to provide robust evidence for national energy-efficiency and carbon-reduction policy development and monitoring. The work has brought together non-domestic energy data, property data and mapping in a ‘data framework’ for the first time. The results show what is possible when these data are integrated and the associated difficulties. A data framework offers the potential to inform energy-efficiency policy formation and to support its monitoring at a level of detail not previously possible.

Le passage à une économie bas carbone exige de toute urgence de meilleures informations sur les facteurs de consommation énergétique. La politique du gouvernement britannique a donné la priorité à l'efficacité énergétique du parc bâti en tant que moyen de réduction du carbone, mais ce secteur est historiquement pauvre en informations, s'agissant en particulier du parc bâti non résidentiel. Cet article présente les résultats d'une étude pilote qui a étudié si et comment les données relatives à l'immobilier et à la consommation énergétique pouvaient être combinées afin d'analyser la consommation d'énergie non résidentielle. Ces données ont été combinées en une « Base de Données de l'Efficacité Energétique Non Résidentielle », de façon à décrire l'emplacement et les attributs physiques de chaque bien immobilier et sa consommation d'énergie. Le but était d'appuyer la création d'un éventail de statistiques sur l'efficacité énergétique concernant les secteurs industriels, commerciaux et institutionnels du parc bâti non résidentiel, et de fournir des éléments probants solides pour le développement et le suivi d'une politique nationale d'efficacité énergétique et de réduction du carbone. Ces travaux ont rassemblé pour la première fois sous forme d'un « cadre de référence » des données sur l'énergie non résidentielle, des données sur l'immobilier et un mappage de ces données. Les résultats montrent ce qu'il est possible de faire lorsque ces données sont intégrées, ainsi que les difficultés qui s'y rapportent. Un cadre de référence offre la possibilité d'influer sur l'élaboration des politiques d'efficacité énergétique et d'en appuyer le suivi à un niveau de précision qui n'était pas possible auparavant.

Mots clés: parc bâti, consommation, données, base de données, statistiques énergétiques, énergie, politique fondée sur des données probantes, cadre de référence     

A continuously recording polarographic respirometer and its use in oil biodegradation studies

A continuously recording flow respirometer based on an oxygen electrode is described. It was designed to give long-term respiration measurements without loss of the carbonate-bicarbonate buffering character of sea water, and without the build up of waste products as in closed systems. An experiment on the microbial degradation of oil is described, together with investigations of a photochemical oxidation discovered fortuitously during similar experiments. The relationship between nutrient supply and bio-oxidation rate is discussed.     

An aquatic respirometer for use in sublethal studies

A computer-controlled respirometer system which permits measurement of oxygen consumption of marine and freshwater organisms at regular intervals over a period of several days is described. The system enables assessment of changes in respiration during and after exposure to sublethal concentration of pollutants.     

Ferrihydrite in water wells and bacterial enrichment cultures

The chemical and mineralogical composition of Fe(III)-precipitates formed in water wells and laboratory cultures was examined. Ferrihydrite, a poorly ordered Fe(III)-oxide of bulk formula 5Fe₂O₃ · 9H₂O, was detected by X-ray diffraction analysis in all samples. The crystallinity varied from one sample to another. Fe was the only major element detected by energy-dispersive X-ray spectrometry; several other elements were present at minor levels reflecting the chemical composition of the medium. The results suggest that the biologically-catalyzed iron encrustation of water wells begins with the initial formation of ferrihydrite.     

Chlorination of pure bacterial cultures in aqueous solution

The fate and distribution of chlorine in aqueous solutions containing four pure bacterial cultures was studied. Solutions were subjected to chlorination at different initial free chlorine concentrations. Resulting concentrations of residual chlorine were determined by both DPD/FAS titration and membrane introduction mass spectrometry (MIMS). In all cases, false-positive breakpoint chlorination curves, probably attributable to the formation of chloroorganic-N compounds, were observed by DPD/FAS titration, while little or no inorganic residual chloramine was found by MIMS. Free chlorine was observed in similar quantities by both methods after chlorine demand by bacterial cellular materials in solution was satisfied. These results indicated the residual chloramines existed in the form of organic chloramines; these compounds are generally recognized as being poor antimicrobial agents. Further investigation confirmed that the bacterial cells were the source of organic-N compounds. The kinetics of chlorination of pure bacterial suspensions was also studied. The pattern of residual chlorine decay following chlorination of the bacterial suspensions indicated rapid initial free chlorine consumption, followed by slow free chlorine consumption, with trace quantities of inorganic chloramine being formed.     

Development of cultures capable of reducing perchlorate and nitrate in high salt solutions

An ion exchange process with biological perchlorate and nitrate destruction and reuse of spent regenerant brine has been proposed as an efficient and environmentally sound method to treat perchlorate-contaminated groundwater. A culture capable of reducing perchlorate and nitrate in spent ion exchange regenerant brine containing at least 30 g/L NaCl is needed for this to be feasible. A batch culture inoculated from activated sludge failed to acclimate to more than 15 g/L NaCl whether nitrate was present or not. A mixed culture inoculated from marine sediment was capable of simultaneously reducing 100mg/L perchlorate and denitrifying 500 mg/L nitrate within 5 h in a synthetic medium in the presence of 30 g/L NaCl. The growth conditions to maintain this culture in a healthy state required the addition of trace metals, Na2S, and phosphate. A second culture capable of removing 100 mg/L perchlorate from synthetic medium containing 60 g/L NaCl within 24 h was also developed.     

Optimum temperature shift for Nitrobacter winogradskyi: Effect of dissolve oxygen and nitrate concentrations

The temperature that maximizes the rate at which Nitrobacter winogradskyi oxidizes nitrite-nitrogen (i.e. the optimum temperature) was shown to have a complicated dependence on ambient dissolved oxygen and nitrite concentrations. In general, the optimum temperature shifted to lower values as dissolved oxygen and nitrite concentrations fell. A steep, almost linear drop in optimum temperature with decreasing values of the logarithm of nitrite concentration was found at dissolved oxygen concentrations above 0.1 ppm (gm⁻³ and nitrite-nitrogen concentrations below 10 ppm. A sharp nonlinear drop in optimum temperature with decreasing values of the logarithm of dissolved oxygen concentration occurred at dissolved oxygen concentrations below 1–2 ppm. At higher dissolved oxygen concentrations, the optimum temperature asymptotically approached a maximum value that increased with nitrite concentration. The solubility of oxygen placed an upper bound on the optimum temperature. At the dissolved oxygen and nitrite concentrations usually found in natural waters and domestic wastewaters, the rate of NO₂⁻-N oxidation should have an optimum temperature below 15°C and as a result should be thermally inhibited at higher temperatures. The negative thermal sensitivity of the NO₂⁻-N oxidation rate above 15°C means that nitrite accumulation may be a side-effect of elevated temperatures in some nitrifying systems.     

Stimulating hydrogenotrophic denitrification in simulated groundwater containing high dissolved oxygen and nitrate concentrations

In agricultural areas, nitrate (NO3-) is a common groundwater pollutant as a result of extensive fertilizer application. At elevated concentrations, NO3- consumption causes methemoglobinemia in infants and has been linked to several cancers; therefore, its removal from groundwater is important. The addition of hydrogen gas (H2) via gas-permeable membranes has been shown to stimulate denitrification in a laboratory-scale reactor. This research, using large columns packed with aquifer material to which a simulated groundwater was fed, was conducted to further identify the conditions required for the use of membrane-delivered H2 in situ. In this study, we show that this novel technology was capable of treating highly contaminated (25 mg/L NO3- -N) and oxygenated (5.5mg/L dissolved oxygen) water, but that nutrient addition and gas pressure adjustment was required. Complete NO3- reduction was possible without the accumulation of either NO2- or N2O when the H2 lumen pressure was increased to 17 psi and phosphate was added to the groundwater. The total organic carbon content of the effluent, 110 cm downgradient of H2 addition, did not increase. The results from these experiments demonstrate that this technology can be optimized to provide effective NO3- removal in even challenging field applications.