A solid chemical oxygen demand (COD) method for determining biomass in waste waters

A method of biomass determination similar to volatile suspended solids (VSS) that used chemical oxygen demand (COD) as a detection method instead of gravimetric methods is described. The “solid COD” method has a strong correlation with VSS for biomass at different stages of growth on different wastewaters including municipal sewage and bleached kraft mill effluent. Soluble COD from the wastewaters did not interfere with the assay. However, non-biomass suspended solids in chemi-thermo-mechanical pulping effluent were found to have a different COD/VSS ratio and thus interfered with solid COD results. The ratio between COD and VSS for biomass was approx. 1.2–1.6 mg COD/mg VSS.     

化学需氧量测定改进方法的研究进展

综述了COD测定改进方法的发展和研究现状,在指出国标重铬酸钾法不足的基础上,阐述了现有测定方法的改进,如消解方法的改进、替代银催化剂的研究、氯离子干扰的消除等,同时介绍了几种与国标法完全不同的COD测定的新方法,从而为化学需氧量的测定提供了更准确更先进的方法。     

A safety device for use in the automated determination of chemical oxygen demand

The operation and circuit details of a safety device for use with an automated Chemical Oxygen Demand system ( and , 1969), is described.     

An automated system for the determination of chemical oxygen demand

Measured volumes of sample, mercuric sulphate and potassium dichromate/ sulphuric acid digestant are metered into a mixing pot. The mixed solution is pumped through a 40 ft length of glass coil suspended in a fluidized sand bath heated to 160°C. After cooling, the solution is passed through a colorimeter which measures the change in optical density due to the reduction in dichromate concentration and records it as a peak on a strip chart recorder. The chemical oxygen demand (COD) of samples is computed by reference to the peak heights given by known standards. A base or wash solution is automatically added between samples to separate the individual peaks and re-establish the base line. A new system designed to eliminate the use of a peristaltic pump is described. This has eliminated stoppage of the system due to failure of the pump tubing. This was previously the most frequent cause of breakdown.     

A field method for determining the chemical and biological activity of sediments

A field method for the rapid estimation of chemical and biological activities in sediments was developed. This spectrophotometric test is based on the quantitative reduction of the dye resazurin by chemically reducing substances and by dehydrogenase in microorganisms; the chemical and biological activities are differentiated by using m-cresol to inhibit the dehydrogenase. Activity is expressed as μmol resazurin reduced h^-1 g^-1 sediment (dry weight). Dry weights of the sediment samples are determined by membrane filtration and oven drying.Replicate samples from Hamilton Harbour and Bay of Quinte (Lake Ontario) and from Thunder Bay and Batchawana Bay (Lake Superior) were examined. Hamilton Harbour (heavy industry) had both low biological and low chemical activity; Bay of Quinte (eutrophic) had high chemical and biological activity. Samples from Thunder Bay showed high chemical and biological activity near an area receiving industrial wastes but moderate to low activity in an “unpolluted” area. Batchawana Bay (oligotrophic) had only low to moderate chemical and biological activity.The field method offers ease of performance, sensitivity, and stability of samples as well as good reproducibility. Comparison is made between results with this test and those with a respirometer.     

Preparation and application of TiO2 photocatalytic sensor for chemical oxygen demand determination in water research

In this work, a TiO(2) photocatalytic sensor was prepared and utilized into flow injection analysis (FIA) for chemical oxygen demand (COD) determination. With a positive bias potential of 0.4V (vs. Ag/AgCl) applied to the sensor and a 12-W quartz UV lamp illuminating it, photocurrent, due to the charge transfer at the interface of TiO(2) sensor and the passing solution, was recorded and its change (deltaI(Photo)) caused by the detected sample was calculated to characterize the COD value of the sample. Under the optimizing conditions, the sensor responded linearly to the COD of D-glucose solution in the range of 0.5-235 mg/L, with a linear correlation coefficient of 0.9998. Its application in artificial wastewater analysis has achieved results in good agreement with those from the conventional dichromate method; meanwhile, the process requires no hypertoxic reagents and less analysis time, suggesting that it would be another appropriate method for COD determination in water assessment.     

A new method for determining the water tightness of building facades

Wind-driven rain and wind pressure are two fundamental climatic parameters affecting the penetration of water through building facades. Water tightness tests attempt to reproduce exposure extremes in order to evaluate the resistance to the passage of water through a facade. However, the exposure conditions for a given return period in a real situation can vary with each location and operating condition. Therefore, standardized test conditions may not be representative of all actual exposure conditions, which prevent a precise evaluation of the facade's performance under operating conditions that differ from test settings. A key challenge for water tightness tests is creating a correlation between standard exposure parameters used in testing and any actual exposure conditions. To address this concern, a new method is proposed that determines the return period associated with the tested exposure for the operating conditions of each facade. The new method is used to assess the adequacy of standardized test exposures (specified by EN 12865:2001 for European localities) on a specific facade at a site in Spain. The method estimates more rigorously the design return period related to water tightness performance of any facade and allows for an improvement of its design using the standardized test results.

La pluie battante et la pression du vent sont deux paramètres climatiques fondamentaux affectant la pénétration de l'eau à travers les façades des bâtiments. Les tests d'étanchéité à l'eau tentent de reproduire les conditions extrêmes d'exposition afin d'évaluer la résistance au passage de l'eau à travers une façade. Cependant, les conditions d'exposition pour une période de retour donnée dans une situation réelle peuvent varier avec chaque lieu et chaque condition d'exploitation. Par conséquent, les conditions de test normalisées peuvent ne pas être représentatives de toutes les conditions d'exposition réelles, ce qui empêche une évaluation précise des performances de la façade dans des conditions d'exploitation qui diffèrent des paramètres de test. L'une des principales difficultés pour les tests d'étanchéité à l'eau est d'établir une corrélation entre les paramètres d'exposition standard utilisés pour effectuer les tests et n'importe quelles conditions d'exposition réelles. Pour faire face à cette préoccupation, il est proposé une nouvelle méthode qui détermine la période de retour associée à l'exposition testée pour les conditions d'exploitation de chaque façade. Cette nouvelle méthode est utilisée pour évaluer l'adéquation des expositions des tests normalisés (spécifiées par la norme EN 12865 : 2001 pour les localités européennes) par rapport à une façade spécifique d'un site situé en Espagne. La méthode estime de manière plus rigoureuse la période de retour de conception en lien avec les performances d'étanchéité à l'eau de n'importe quelle façade et permet d'en améliorer la conception en utilisant les résultats des tests normalisés.

Mots clés: enveloppe des bâtiments, charges climatiques, conception des façades, paramètres de test, étanchéité à l'eau     

An improved determination of chemical oxygen demand in water and wastes by a simplified acid dichromate digestion

A simplified and improved chemical oxygen demand (COD) procedure is suitable for water and waste water samples containing up to 1500 mg Cl l⁻¹. Samples are digested with sulfuric acid, potassium dichromate, silver sulfate, mercury(II) sulfate and sulfamic acid in open glass tubes for 2 h at 140 ± 2°C without boiling, and excess dichromate is determined colorimetrically at 440 nm. The use of 49-position digestion racks, a large oven and a spectrophotometer fitted with a 1-cm flow cell allow analysis of ca. 12 samples h⁻¹. A correction for chloride interference is not required in the 0–500 mg Cl l⁻¹ range. The detection limit is 3 mg l⁻¹, and the relative standard deviation at the 112 mg COD l⁻¹ level is 4.3%. Thirty-five waste water samples were analyzed by the standard dichromate reflux method and by the proposed procedure. There was no significant difference between the two sets of data (P > 0.25). Recovery data for 15 major water pollutants including benzene, toluene and pyridine are presented.     

Electrochemical treatment of chemical oxygen demand in produced water using flow‐by porous graphite electrode

Produced water is the largest wastewater stream generated in the oil and gas industries. In this study, experiments were carried out using a bench‐scale electrochemical cell using flow‐by porous graphite electrode, for oxidation of organic matter in produced water which was collected from natural gas processing field (real sample). The effect of anodic current density and influent feed flow rate on chemical oxygen demand (COD) removal efficiency, and energy consumption were investigated. The maximum removal efficiency of 66.52% was obtained for a flow rate of 50 mL/min, current density of 1.41 mA/cm² and pH of 7.3 for an influent COD of 2845 mg O₂/L. The energy consumption at these conditions was 2.12 kWh/kg_COD.     

大直径深水圆柱结构动水压力的时域算法

提出一种计算大直径深水圆柱结构所受动水力的时域算法。大直径深水圆柱结构动水压力计算中,需要考虑水体的可压缩性。基于解析方法推导了频域动水力公式,该公式在时域计算中需要进行快速傅里叶变换或者时间卷积运算,计算量巨大。采用由频域有理函数近似和时域辅助变量实现构成的时间卷积算法,将动水力的频域解析公式实现为高精度、高效率时域算法。算例表明,本文方法具有较高的计算精度和计算效率。     

生化需氧量测定中获得接种液的一种方法

指出接种稀释水质量是直接决定生化需氧量测定准确与否的关键因素,提出了直接用工业废水驯化微生物以培养适合测定生化需氧量接种液的方法,并通过实践分析了培养方法的可行性和测定结果的准确性。     

A sensitive seminested PCR method for the detection of Shigella in spiked environmental water samples

A rapid seminested polymerase chain reaction (PCR) method for the specific, sensitive detection of virulent Shigella spp. in spiked environmental water samples was developed. A set of primers specific for the invasion plasmid antigen gene (ipaH) of virulent Shigella spp. and enteroinvasive Escherichia coli produced a 620-bp fragment that was used as template for the seminested primer pair delineating a 401-bp fragment. By using agarose gel electrophoresis for detection of the seminested PCR-amplified products, a detection limit of 1.6 x 10(3) cfu S. flexneri was obtained with amplification reactions from crude bacterial lysates. The PCR procedure coupled with an enrichment culture incubated for 6 h detected as few as 1.6 S. flexneri organisms in pure culture. Treated sewage, ground, surface and drinking water samples collected from various sources were seeded with S. flexneri and incubated in GN broth for 6 h before detection by seminested PCR. A detection limit lower than 14 cfu/ml was achieved in some water samples. The results indicate that the described seminested PCR has the advantage of a rapid turnaround time and it fulfills the requirements of sensitivity and specificity for use in an environmental laboratory.     

地震作用下动孔隙水压力对边坡永久位移影响的简便计算方法

基于转动平衡理论,提出了考虑地震作用下动孔隙水压力影响的边坡永久位移简便计算方法,并通过砂土边坡（长度×宽度×高度为1.96 m×0.96 m×1.20 m）的振动台试验进行了验证。结果表明：地下水对边坡动力特性影响较大,随着地下水位的升高,边坡的自振周期呈现增加趋势,水位1.0 m时边坡的自振周期是无水时的2.88倍;地下水位越高,地下水对边坡临界加速度的影响越显著,且当水位为1.0 m时边坡的临界加速度比无水时减小了28%;随着水位的升高,边坡永久位移均表现出增加的趋势,地震峰值加速度为2.0m/s²时,水位1.0 m的永久位移是无水时的9.8倍;此外,随着地震峰值加速度的增加,边坡永久位移急剧增加,当地震峰值加速度为2.0m/s²时,永久位移是地震峰值加速度为1.0m/ s²时的6.9倍。建议的简便方法与试验测得的边坡永久位移最大偏差在10%以内,验证了建议方法的可靠性。     

A semi-analytical method for the elastic-plastic large deflection analysis of welded steel or aluminum plating under combined in-plane and lateral pressure loads

The aim of the present paper is to develop a semi-analytical method which can quickly and accurately compute the elastic–plastic large deflection response of welded steel or aluminum plating under a combination of biaxial compression/tension, biaxial in-plane bending, edge shear and lateral pressure loads, until the ultimate limit state is reached. The post-weld initial imperfections (i.e. initial deflection and residual stresses) are included in the method as parameters of influence. It is assumed that the plating is simply supported at all (four) edges which are kept straight. A unique feature of the developed method is that geometric nonlinearity associated with large deflection response of plating under combined loads is treated by analytically solving the nonlinear governing differential equations of the elastic large deflection plate theory, while material nonlinearity due to plasticity is dealt with implicitly by a numerical procedure. This approach reduces the magnitude of numerical computations, resulting in a saving of modeling effort and computing time. As another contribution, this paper investigates and discusses the ultimate strength characteristics of plating, by varying the plate properties and load combinations, based on elastic–plastic large deflection analysis using the developed method.     

Optimization of hydroxyl radical production using electro‐Fenton method for chemical oxygen demand reduction in diluted palm oil mill effluent

Palm oil mill effluent (POME) is a well‐known highly polluting wastewater due to its extremely high contents of organic matter, suspended solids and nutrients. In this study, we used electro‐Fenton method to treat POME by optimizing OH? generation from hydrogen peroxide (H₂O₂) under low voltage input (1.5–6.0 V). A set of electro‐Fenton system was set up using stainless steel as the anode and graphite as the cathode. Four parameters namely retention times, concentrations of H₂O₂ as well as FeSO₄ catalyst and applied voltages were studied. The results were reflected in the form of removal efficiency of chemical oxygen demand (COD). The optimum conditions to degrade organic matter in POME were found to be in 4 h retention time with the respective H₂O₂ and FeSO₄ catalyst concentrations of 0.05 and 0.10 M, and the power input of 1.5 V. Under such conditions, the maximum COD removal efficiency achieved 94%. The electro‐Fenton treatment was found to have higher efficiency than the conventional Fenton treatment. Without the electrolysis, the COD removal efficiency of the conventional Fenton treatment was only 48%.     

A simplified method for determining acceleration amplitude of prestressed concrete floor under individual jumping load

Modern long‐span prestressed concrete (PC) floors typically possess low damping and low natural frequency, presenting a potential vibration sensitivity problem induced by human activities. Field test and numerical analysis methods are available to study this kind of problems but would be inconvenient for design engineers. This paper proposes a simplified method to determine the acceleration amplitude of a PC floor subjected to individual jumping load, carrying out through a mix of analytical and experimental techniques. To theoretically analyze the acceleration response, the PC floor was simplified as an anisotropic rectangular plate and the mode decomposition method was used. To facilitate the calculation of the acceleration amplitude a_P, a frequency‐dependent coefficient β_J is introduced, which depends on the geometry and support condition of the PC floor and dynamic amplification factor K_J. Field tests on 7 PC floors with various boundary conditions and fundamental natural frequencies were conducted to determine β_J coefficient. Based on the test results, practical formulas for β_J coefficient is first proposed, followed by that for acceleration amplitude a_P. The proposed simplified method is easy for practical use and will yield safe and conservative structural designs.     

A stochastic approach for the water demand of residential end users

Reliable hydraulic modeling of water distribution networks requires a deep knowledge of water demand. In the past few years, technical literature has been enriched with many contributions aimed at realistically representing the residential water demand of end users. The proposed models generally represent water demand through rectangular pulses, describing demand as the sum of the requests from single domestic appliances. This paper proposes a new stochastic model - Overall Pulse (OP) - which allows the generation of the overall domestic demand as displayed at the house water meter. The proposed model allows the taking into account of the randomness of the arrivals rate and the demand persistence phenomenon. The effectiveness of the proposed model has been tested, comparing the generated data series with those measured for residences with different lifestyles. The generation of the synthetic data series has been made by means of the OP model with the Monte Carlo method.     

超深地下室大直径灌注桩抗拔承载力确定方法分析

依据福州市某超高层建筑试桩工程项目特点,通过设置长、短桩分别进行抗拔静载试验并对抗拔承载力进行扣减的方式,得到该项目大直径灌注桩在有效桩长范围内的单桩竖向抗拔承载力,经分析,此方法准确可行。