室内游泳池水分蒸发量的实测与分析

分析了游泳池水面蒸发率的影响因素。应用常用的计算公式计算了某室内游泳馆的水面蒸发率,并进行了测试。比较了计算值与实测值,推荐了游泳池平静水面时和一般使用时水面蒸发率的计算公式。     

Genetic potential for N2O emissions from the sediment of a free water surface constructed wetland

Removal of nitrogen is a key aspect in the functioning of constructed wetlands. However, incomplete denitrification may result in the net emission of the greenhouse gas nitrous oxide (N₂O) resulting in an undesired effect of a system supposed to provide an ecosystem service. In this work we evaluated the genetic potential for N₂O emissions in relation to the presence or absence of Phragmites and Typha in a free water surface constructed wetland (FWS-CW), since vegetation, through the increase in organic matter due to litter degradation, may significantly affect the denitrification capacity in planted areas. Quantitative real-time PCR analyses of genes in the denitrification pathway indicating capacity to produce or reduce N₂O were conducted at periods of different water discharge. Genetic potential for N₂O emissions was estimated from the relative abundances of all denitrification genes and nitrous oxide reductase encoding genes (nosZ). nosZ abundance was invariably lower than the other denitrifying genes (down to 100 fold), and differences increased significantly during periods of high nitrate loads in the CW suggesting a higher genetic potential for N₂O emissions. This situation coincided with lower nitrogen removal efficiencies in the treatment cell. The presence and the type of vegetation, mainly due to changes in the sediment carbon and nitrogen content, correlated negatively to the ratio between nitrate and nitrite reducers and positively to the ratio between nitrite and nitrous oxide reducers. These results suggest that the potential for nitrous oxide emissions is higher in vegetated sediments.     

On the evaporation effect of a sprinkler water spray

A crude model for estimating the evaporation heat loss due to a sprinkler water spray in a smoke layer is reported. It is found that the evaporation heat loss lies below 11.2% of the convective loss when water travels through a hot gas layer 0.9 m thick and 160°C under normal sprinkler operating conditions. It is also found that the value may go up to 26% if the smoke layer reaches 1.5 m and 273°C.     

Experimental and numerical study on indoor temperature and humidity with free water surface

Free water surface may generate excessive moisture and heat and have adverse effects on indoor environment and energy loss. A series of experiments have been carried out to study the characteristics of indoor temperature and moisture distributions using a free water surface within a test chamber. Some parameters such as air change rates, surrounding air temperature and humidity, water temperature and water surface area, were chosen to find their influences on simultaneous moisture and heat transfer. In addition, a new method for determining the simultaneous heat and mass transfer rates from free water surface is developed. Using this method with connection of CFD simulations, the moisture-related problems due to free water surface can be predicted precisely.     

Comparative studies of methods for the enumeration of coli aerogenes bacteria and E. coli in surface water

In a comparative study of four enrichment media for the detection of bacteria of the coli aerogenes group, formate glutamate medium was found to be the best one. No significant differences were assessed between the three confirmation media used in this study.For the detection of E. coli, the use of Eijkman lactose broth, incubated in an air incubator at 44°C, was found to be better than the use of Eijkman glucose broth. When this method was applied, no significant differences could be observed between the results obtained upon immediate testing of the samples, and when the same samples were examined after 24 h storage at 4–6°C, as is often inevitable in practice.For the combined detection of E. coli and the coli aerogenes group, which may be required in practice, the formate glutamate medium proved again to be the best one. No evidence was found that use of this procedure may result in a low E. coli counts. On the contrary, this technique gave even slightly higher results than the direct Eijkman 44°C-procedure. Suitable confirmation tests on gassing tubes are required when this 37°C-procedure is used.     

Effect of fuel soaked time and fuel ratio on the flame spread rate over a porous bed wetted with liquid fuel

An experimental investigation was conducted to explore the rate of flame spread over an unconsolidated porous bed of sand wetted with 2-propanol under a range of operating conditions. Video cinematography was employed to determine the rate of flame spread and characterise the combustion behaviour of the system. The rate of flame spread strongly correlated with: (i) the ratio of fuel volume to the weight of the sand bed, referred to as FR, and (ii) the flame initiation delay, referred to as FID. The rates of flame spread associated with no initiation delay cases were found to rise with increasing FR while for cases associated with any given flame initiation delay the rate of flame spread was found to decrease with increasing FR. In addition, the rate of change in flame spread was observed to be different for beds containing finer particles in comparison to those containing coarser ones.     

Isolation of Yersinia from surface water: Comparative study of three selective media

Isolation of Yersinia was undertaken on three media from surface water of the Moselle River. Samples collected over an 8-month period were examined with Y-M agar, CAL agar and “Y” medium. Out of 48 water samples, 33.3% were positive. The isolation frequency with Y-M agar (27%) was significantly higher than with CAL agar of “Y” medium (χ² = 11.2; 0.001 < P < 0.01). Furthermore, Y-M agar exhibited a wide diversity of species; Y. enterocolitica, Y. frederiksenii, Y. kristensenii and Y. intermedia were isolated. In addition, the aerobic cold-enrichment technique without culture broth appears adequate for Yersinia isolation.     

Temporal and spatial variation of phosphate distribution in the sediment of a free water surface constructed wetland

This study was aimed at determining the spatial and temporal variation of P distribution in sediment of an artificial wetland for sewage and industrial wastewater treatment, and the fraction that is potentially involved in the P exchange processes. Influent, effluent, macrophytes and sediment at the inlet, middle and outlet areas were sampled over 24 months. The P-fractionation in sediment was performed following the EDTA method. Eichhornia crassipes and Typha domingensis removed P efficiently when cover was high, but E. crassipes caused anoxic conditions. The increase in cover of T. domingensis may contribute to attain oxic conditions and to improve P removal. When macrophytes are not present or when cover is low, sediment seems to increase removal efficiency. A significant increase in the concentration of the fraction of Fe(OOH) approximately P and mainly that of CaCO(3) approximately P can be observed at the inlet. High pH, Ca(2+) and CO(3)(-)(2) concentrations in the influent suggest that P co-precipitates together with CaCO(3). Therefore, it seems that CaCO(3) approximately P represents the main precipitating mechanism. However, mineralization of organic matter maintained the sediment at a pH range lower than the high values prevailing in the influent. CO(3)(-)(2) could undergo partial dissolution and the released i-P(diss) could be readsorbed onto the Fe(OOH) approximately P fraction. Since the environment for P retention (high pH, Fe, Ca and ionic concentrations) is largely provided by the influent, the wetland may be expected to continue retaining P as far as the composition of the influent is maintained and there are available adsorption sites in the sediment.     

Comparative studies of phytotoxicity and chemical composition of aqueous oil solutions affected by evaporation, illumination and extraction

Aqueous stock solutions of Ekofisk crude oil were prepared in darkness and under illumination, and fractions of both types of stock solutions were further treated by controlled evaporation, illumination, extraction with hexane and dichloromethane and phytoplankton cultivation. Chemical analysis of all fractions were combined with toxicity testing based on the marine diatom Skeletonema costatum.Removal of the readily water-soluble aromatic hydrocarbons did not reduce the phytotoxicity of the solutions. Illumination led to a dramatic increase in both toxicity and the total amount of dissolved material. In no case did the hydrocarbon content exceed 5% of the total dissolved material, and the traditional analytical values referred to as “total hydrocarbon content” are therefore considered highly misleading. The toxicity of these aqueous oil solutions must apparently be ascribed to a multitude of slightly polar, oxidized compounds originating from the oil.     

Comparison of methods for estimating loss from water storage by evaporation and impacts on reservoir management

Reservoirs are the key infrastructure of water resources management. A controlling variable of reservoir operation is evaporation, which in semi‐arid and arid regions may consume a large fraction of reservoir storage annually. This paper assesses the role of evaporation and the choice of evaporation methods on reservoir operation. The operation of the reservoir is calculated with the standard operation policy (SOP). Several efficiency criteria are employed to rank the evaporation‐calculation methods with the technique for the order of preference by similarity to ideal solution (TOPSIS). The method presented in this paper is illustrated by applying its application to Karkheh reservoir, the largest in Iran.     

Error correction of water evaporation loss on the unsaturated hydraulic conductivity

Water evaporation loss occurs during multistep outflow experiments from the soil surface and the outflow vessel. The main focus of this paper is to introduce an improved pressure plate instrument that can correct for the error of water evaporation loss on the unsaturated hydraulic conductivity. Experiments using silicon micropowder (SMP) and Guangxi Guiping clay (GGC) were conducted with an improved instrument. The results showed that the measured value of the water content will be overestimated and the unsaturated hydraulic conductivity will be underestimated without considering the water evaporation loss.     

地表水换热盘管换热特性的理论与试验研究

建立了地表水换热盘管的换热模型.对换热盘管在不同换热工况下的换热性能进行了测试,分析了管内外流速、管径及放热或吸热工况对换热性能的影响,分析了换热盘管换热量与盘管长度的关系,给出了不同接近温差时吸热量与盘管长度的关系曲线图.     

Influence of practical curing methods on evaporation of water from freshly placed concrete in hot climates

The effectiveness of different curing methods on the evaporation of water from freshly placed concrete is presented. The curing methods employed within the current experimental programme comprised plastic sheeting and burlap and were compared to the evaporation of water from an uncovered concrete surface. Samples were exposed to an ambient temperature of 40°C and a relative humidity of approximately 30% for a period of 72 h. The effectiveness of each curing method was quantified in terms of both the cumulative water loss and rate of evaporation from the concrete surface. When compared to the uncovered surface, both curing systems resulted in a reduction in both the total amount of water loss and rate of evaporation, particularly over the initial 6 h after mixing. A local maximum in the rate of evaporation coincided with the maximum in internal temperature occurring within the concrete, the latter being due to setting of the cement binder.     

Removal of nitrate from effluent following discharge on surface water

The loss of nitrate nitrogen over a 800-m long reach of canal was studied in a field experiment during a 20-days period. The nitrate originated mainly from sewage effluent. Fifty-six percent of the nitrate had disappeared during its flow through the 800-m long reach, where the average retention time was 1.7 days. The average rate of nitrate disappearance during the 20-day period was 913 mg NO₃⁻-N m⁻² day⁻¹. Laboratory experiments with undisturbed water-sediment profiles from the canal showed that the disappearance of nitrate was caused mainly by denitrification in the sediment. Increased knowledge of this phenomenon may lead to an effective and cheap means in inducing denitrification.     

Functional variability of dissolved organic matter from the surface water of a productive lake

Functional variability of dissolved organic matter (DOM) from the surface water of Esthwaite Water (N. England) was investigated using a series of 12 standardised assays, which provide quantitative information on light absorption, fluorescence, photochemical fading, pH buffering, copper binding, benzo(a)pyrene binding, hydrophilicity, and adsorption to alumina. Ten lakewater samples were collected at different times of year during 2003-2005, and DOM concentrates obtained by low-temperature rotary evaporation. Suwannee River Fulvic Acid was used as a quality control standard. For nine of the assays, variability among DOM samples was significantly (p<0.01) greater than could be explained by analytical error. Seasonal trends observed for six of the assays could be explained by a simple mixing model in which the two end-members were DOM from the catchment (allochthonous) and DOM produced within the lake (autochthonous). The fraction of autochthonous DOM predicted by the model is significantly correlated (p<0.01) with chlorophyll concentration, consistent with production from phytoplankton. Autochthonous DOM is less light-absorbing, less fluorescent, more hydrophilic, and possesses fewer proton-dissociating groups, than allochthonous material.     

Estimating the effect of water quality on surface water supplies

River quality models derived by regression analysis are often quick and cheap to produce. They can be used as a basis for forecasting river quality and to calculate the effects of water quality constraints on the operation of water supplies drawn from rivers and impoundments. Results for nitrate show that to operate intakes according to river quality is a poor method of controlling quality in impoundments.     

水冷却和汽化冷却以及空气冷却探析

介绍了水冷却、汽化冷却和空气冷却的过程，指出在实际应用中，可以采用汽化冷却同水冷却配合使用，空气冷却同水冷却配合使用，可取得良好的节水效果和经济效益。     

建筑排水水封蒸发初步实验研究

水封是建筑排水系统的重要组成部分,水封损失将会严重影响排水系统正常运行和产生不良的后果。而蒸发现象是引起水封损失和破坏的因素之一,如何提高水封可靠性问题越来越受行业的关注,也是当今行业研究的课题。本次实验历时3个多月对不同水封容量、不同水封高度、不同水封比的水封,在不同温度、不同湿度、不同遮盖情况下,对水封静态蒸发损失情况进行测量与分析,有助于提高人们对水封静态蒸发损失的认识。