Pollution status of the Indus River,Pakistan, through heavy metal and macronutrient contents of fish,sediment and water

Concentrations of Ag, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn and Hg, together with Na, K, Ca and Mg in 19 species of fish captured from the Indus River, Pakistan, are estimated by the atomic absorption method. Corresponding data for sediment and water from 11 sites along the down-stream route of the river are also reported. Mercury and arsenic concentrations were high (3.920 and 3.072 μg/g, respectively) in the muscle of fish from Guddu barrage as compared with those from other sites. Hetroptirus fossilus showed maximum concentrations of Ag, Cu and Pb in its muscle as compared with other fish. Labeo calbasu from Guddu barrage showed highest As concentration at 3.072 μg/g. Mystus vitatus from Chashma barrage contained maximum cadmium concentration at 0.990 μg/g. Several other fish exhibited elevated levels of metals along the downstream route of the river, a trend exhibited also by the elevated metal contents of sediment and water at Guddu and Lloyd barrages. The study indicated a gross pollution of the sediment and water at various locations of the river, e.g. As (7.452 μg/g) in sediment from Lloyd barrage, Hg (5.710 μg/g) in sediment from Jinnah barrage, Pb (2.709 μg/g) in sediment from Guddu barrage and Mn (0.038 μg/g) in water from Lloyd barrage. The macronutrients showed an inverse relationship with trace metals. Hetroptirus fossilus could be used as indicator species for Ag, Cu and Pb.     

Predicting oxygen transfer of fine bubble diffused aeration systems--model issued from dimensional analysis

The standard oxygenation performances of fine bubble diffused aeration systems in clean water, measured in 12 cylindrical tanks (water depth from 2.4 to 6.1m), were analysed using dimensional analysis. A relationship was established to estimate the scale-up factor for oxygen transfer, the transfer number (N(T)) The transfer number, which is written as a function of the oxygen transfer coefficient (k(L)a(20)), the gas superficial velocity (U(G)), the kinematic viscosity of water (nu) and the acceleration due to gravity (g), has the same physical meaning as the specific oxygen transfer efficiency. N(T) only depends on the geometry of the tank/aeration system [the total surface of the perforated membrane (S(p)), the surface of the tank (S) or its diameter (D), the total surface of the zones covered by the diffusers ("aerated area", S(a)) and the submergence of the diffusers (h)]. This analysis allowed to better describe the mass transfer in cylindrical tanks. Within the range of the parameters considered, the oxygen transfer coefficient (k(L)a(20)) is an increasing linear function of the air flow rate. For a given air flow rate and a given tank surface area, k(L)a(20) decreases with the water depth (submergence of the diffusers). For a given water depth, k(L)a(20) increases with the number of diffusers, and, for an equal number of diffusers, with the total area of the zones covered by the diffusers. The latter result evidences the superiority of the total floor coverage over an arrangement whereby the diffusers are placed on separate grids. The specific standard oxygen transfer efficiency is independent of the air flow rate and the water depth, the drop in the k(L)a(20) being offset by the increase of the saturation concentration. For a given tank area, the impact of the total surface of the perforated membrane (S(p)) and of the aerated area (S(a)) is the same as on the oxygen transfer coefficient.     

The Wansbeck Barrage Scheme: Twenty-One Years of Environmental Impact

The Wansbeck barrage (in Northumberland), which was completed in 1975, was envisaged as a means of removing unsightly saltmarsh and creating an amenity lake and country park. This study examines the effect of the scheme on the estuarine environment and focuses on (a) the nature of the habitat, (b) the rate of sedimentation, (c) the control on water quality within the impoundment, and (d) amenity use.     

Effect of hypolimnetic oxygenation on oxygen depletion rates in two water-supply reservoirs

Oxygenation systems, such as bubble-plume diffusers, are used to improve water quality by replenishing dissolved oxygen (DO) in the hypolimnia of water-supply reservoirs. The diffusers induce circulation and mixing, which helps distribute DO throughout the hypolimnion. Mixing, however, has also been observed to increase hypolimnetic oxygen demand (HOD) during system operation, thus accelerating oxygen depletion. Two water-supply reservoirs (Spring Hollow Reservoir (SHR) and Carvins Cove Reservoir (CCR)) that employ linear bubble-plume diffusers were studied to quantify diffuser effects on HOD. A recently validated plume model was used to predict oxygen addition rates. The results were used together with observed oxygen accumulation rates to evaluate HOD over a wide range of applied gas flow rates. Plume-induced mixing correlated well with applied gas flow rate and was observed to increase HOD. Linear relationships between applied gas flow rate and HOD were found for both SHR and CCR. HOD was also observed to be independent of bulk hypolimnion oxygen concentration, indicating that HOD is controlled by induced mixing. Despite transient increases in HOD, oxygenation caused an overall decrease in background HOD, as well as a decrease in induced HOD during diffuser operation, over several years. This suggests that the residual or background oxygen demand decreases from one year to the next. Despite diffuser-induced increases in HOD, hypolimnetic oxygenation remains a viable method for replenishing DO in thermally-stratified water-supply reservoirs such as SHR and CCR.     

Barrage Developments in the Welsh Region: The Role of the National Rivers Authority in Protecting the Aquatic Environment

During recent years, barrages and marina developments have increasingly been viewed as a means of improving the aesthetic and recreational qualities of degraded urban areas, thereby encouraging inward investment. However, barrage schemes can have major implications for the National Rivers Authority's statutory responsibility for flood defence, fisheries, recreation, water quality and conservation.
The experiences gained by the National Rivers Authority's Welsh Region in its negotiations with promoters of the Tawe, Cardiff Bay and Usk barrages are presented. The paper describes the environmental safeguards secured for the Tawe barrage, together with some initial assessments of its impact on the aquatic environment following its completion in 1992. The experience gained with the Tawe barrage has contributed to a more rigorous approach being applied by the National Rivers Authority to the Cardiff Bay and Usk schemes.     

Energy saving in activated sludge plants by the use of more efficient fine bubble diffusers

Many activated sludge plants (ASP) use fine bubble diffused air as their source of oxygen. Blowers are attached to air pipework, which distributes air to a network of diffusers installed on the floor of the ASP tank. Modern diffusers are made from a rubber membrane which flexes to allow fine bubbles of air to pass through holes in the diffusers which then pass into the mixed liquors in the tank. The diffusers come as circular discs, tubes and more recently mats or panels. Yorkshire Water is in the process of building new ASP at some of their biggest sewage treatment works to meet new final effluent consent standards associated with the freshwater fisheries directive (FFD). These new works will treat sewage from a combined population of over two million people in the Yorkshire area. Black & Veatch is involved in some of the first works to have a new type of fine bubble diffuser installed in the ASP basins. These diffusers resemble a mat or panel and are fixed to the floor of the tank as opposed to circular and tubular diffusers which as fixed above the floor. Oxygen transfer testing has been carried out to show the efficiency of these aeration systems, which may offer significant savings in operating costs to water operators. This paper examines the results from the tests and compares them with other tests carried out in the United States and tests that have been carried out on other types of diffusers. The paper will discuss the results of the oxygen transfer tests and present capital and net present costs (NPC) for various diffuser installations.     

变风量风口的安装调试与运行维护

本文根据国外常用的变风量风口的使用情况，介绍了变风量风口的结构特点，安装调试方法及风量平衡步骤，并对使用过程中的常见故障提供了解决方法，为我国的施工和运行维护人员提供参考，以推进变风量空调系统在我国的使用。     

Floor-supply displacement ventilation for workshops

This paper reported the investigation of the performance of floor-supply displacement ventilation with swirl diffusers or perforated panels under a high cooling load (nearly 90 W/m²). The experiment was carried out in a full-scale environmental chamber to obtain reliable data on the floor-supply displacement ventilation for the validation of a computational-fluid-dynamics (CFD) program. Numerical simulations using CFD program were to evaluate the performance of the system for a large workshop. The impacts of several parameters, such as the air change rate, number of diffusers, diffuser location, occupant location, furniture arrangement, partition location, and arrangement of exhausts, on the indoor environment were investigated based on the thermal comfort level and indoor air quality. This study ranked the impacts of these parameters on indoor environment.     

富华国际会议及展览中心空调设计

结合高大空间特点,介绍了各展厅空调系统设计,包括气流组织的确定、系统的划分及机房的设置。第一展厅外区采用下送下回方式、双层百叶风口,内区采用上送下回方式、旋流风口;第二、三展厅均为内区,采用上送下回方式、旋流风口;共享大厅采用侧送下回方式、球型喷口。水系统采用变水量、两管制系统。介绍了通风、自控设计。     

低温送风条件下风口结露实验研究

对3种普通风口在低温送风条件下的结露特性进行了实验研究,针对实验现象分析了各种风口的结露机理,为普通风口在低温送风条件下的使用制定了软启动控制策略,认为若无软启动措施,低温送风系统宜采用专用风口。     

置换通风的热压驱动增益模式可行性研究

通过对传统下置置换通风系统特点的研究,提出了一种新的下置置换通风空调系统——由太阳能烟囱为新系统中送风提供热压动力,使送风具有传统下置置换通风系统的送风特点,室内工作区具有良好的空气品质。同时通过数值模拟的方法分析并比较了传统下置置换通风系统与新系统。结果表明:该系统能解决传统置换通风不舒适的吹风感和竖直温差大的问题;相对于传统下置置换通风,新系统还具备节能和环保特性;烟囱具有良好的自我调节性能。     

Geometry of transitional diffusers

Practical transitional diffuser geometries with and without varying cross-sectional shape are studied. Transitional diffusers between rectangular and rectangular, circular and rectangular, circular and equilateral triangular, and between rectangular and rectangular with offset centre-lines are investigated. The analysis presented is based on straight-line generators along the transitional diffusers in all cases.The analysis shows that the amount of area variation depends on the aspect ratio of the rectangular section. For straight transitional diffusers between rectangular and rectangular and between circular and rectangular or triangular, the area variation is of parabolic form with either a relative reduction or a relative increase of area at the midpoint. Transitional diffusers, which provide uniform area distributions, may also be obtained.The area variation becomes more complicated when the area perpendicular to the transition centre-line is considered, in transitions with the inlet and outlet duct centre-lines offset. Here, for a rectangular-to-rectangular transitional diffuser, the variation depends on both the aspect ratios and the angles of offset.     

Gas transfer from air diffusers

The bubble and surface volumetric mass transfer coefficients for oxygen, k(L)a(b) and k(L)a(s), are separately determined for 179 aeration tests, with diffuser depths ranging from 2.25 to 32 m, using the DeMoyer et al. 12003. Impact of bubble and free surface oxygen transfer on diffused aeration systems. Water Res 37, 1890-1904] mass transfer model. Two empirical characterization equations are developed for k(L)a(b) and k(L)a(s), correlating the coefficients to air flow, Qa, diffuser depth, hd, cross-sectional area, Acs, and volume, V. The characterization equations indicate that the bubble transfer coefficient, k(L)a(b), increases with increasing gas flow rate and depth, and decreases with increasing water volume. For fine bubble diffusers, k(L)a(b) is approximately six times greater than k(L)a(b) for coarse bubble diffusers. The surface transfer coefficient, k(L)A(s), increases with increasing gas flow rate and diffuser depth. The characterization equations make it possible to predict the gas transfer that will occur across bubble interfaces and across the free surface with a bubble plume at depths up to 32 m and with variable air discharge in deep tanks and reservoirs.     

Inverse design of the thermal environment in an airplane cockpit using the adjoint method with the momentum method

Currently, the thermal environment in airplane cockpits is unsatisfactory and pilots often complain about a strong draft sensation in the cockpit. It is caused by the unreasonable air supply diffusers design. One of the best approaches to design a better cockpit environment is the adjoint method. The method can simultaneously and efficiently identify the number, size, location, and shape of air supply inlets, and the air supply parameters. However, the real air diffuser needed to design often have grilles, especially in the airplane cockpit, and the current method can only design the inlet as an opening. This study combined the adjoint method with the momentum method to directly identify the optimal air supply diffusers with grilles to create optimal thermal environment in an airplane cockpit (1) under ideal conditions and (2) with realistic constraints. Under the ideal conditions, the resulting design provides an optimal thermal environment for the cockpit, but it might not be feasible in practice. The design with realistic constraints provides acceptable thermal comfort in the cockpit, but it is not optimal. Thus, there is an engineering trade-off between design feasibility and optimization. All in all, the adjoint method with the momentum method can be effectively used to identify real air supply diffusers.     

Das Schiffshebewerk am Drei‐Schluchten‐Staudamm,China – Bau des größten Fahrstuhls der Welt

The ship lift at the Three‐Gorges‐Dam in China – Construction of the world's largest elevator With a total height of 169 m, a maximal lifting height of 113 m and moved masses of approx. 33 000 t, the ship lift at the Three‐Gorges‐Dam in China will be the largest of its kind worldwide. The entire structure is nearing completion. Operational testing started in 2015. Located parallel to the existing fully operating five stage ship lock at the 2,3 km long barrage, the ship‐lift consists of four RC towers. A steely, water filled ship chamber with 132 m length, 23 m width and 10,5 m height will lift ships with a max. water displacement of 3 000 t. The construction gains its flexibility from an innovative combination of structural and mechanical parts. Since 2008 the ship lift structure was erected by climbing formwork. Due to the tolerances demanded by the embedded parts of the mechanical drive system, a special procedure of 1st and 2nd stage concrete and grouting had to be developed. The article describes the structural aspects of the project with focus on the execution.     

Development of ventilation design strategy for effective removal of pollutant in the isolation room of a hospital

This paper investigates the airflow and pollutant distribution patterns in a “negative pressure” isolation room by means of objective measurement and computational fluid dynamics (CFD) modeling based on three ventilation strategies. An effective ventilation system is crucial to protect doctors, nurses and other health-care workers from patients with infectious disease. In the preliminary study with Strategy 1, the isolation room has two air supply diffusers and two extract grilles mounted on the ceiling. Strategy 2 retains the air supply diffusers in Strategy 1 but relocates the two extract grilles to the wall behind the bed at 0.3 m above the floor level. Strategy 3 has the same layout as Strategy 2 except the ceiling diffusers are replaced by supply grilles and relocated closer to the wall behind the bed.     

Environmental effects in a karstic aquifer due to seepage from an in-river reservoir

The paper estimates the anticipated changes in the seepage conditions towards the karstic aquifer, the recharge of the aquifer from the combined rainfall, seepage and exploitation as well as the potential alteration in the quality of the aquifer due to the creation of a nearby reservoir. It is shown that despite the somewhat increased seepage of polluted river water towards the aquifer, the quality of the groundwater in the karstic aquifer is not expected to degrade appreciably. However, since the water of the aquifer is used for the supply of neighbouring communities, it is proposed that in the areas where the thickness of the intervening semi-permeable alluvia is small, artificial sealing is installed using either compacted clay or plastic membranes.

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Conséquences sur l'environnement des fuites d'un réser voir de barrage vers un aquifère karstique

Résumé L'article traite le problème des fuites du réservoir d'un barrage qui pourraient se produire vers un aquifère karstique proche et les modifications du régime des eaux souterraines qui en résulteraient, tout en tenant compte des conditions d'alimentation et d'exploitation de cet aquifère. L'analyse montre que malgré l'augmentation des fuites des eaux du fleuve, les quantités concernées ne peuvent aggraver la qualité des eaux souterraines d'une manière notable. Néanmoins, comme les eaux sont utilisées en même temps pour les adductions d'eau potable, il est proposé, dans certains secteurs, où l'épaisseur des alluvions interposées est faible, d'imperméabiliser les berges.

     

Exploitation piscicole du barrage Guenitra (Oum Toub,Skikda, Algérie)

The breeding of the carp Cyprinus carpio L. in the Guenitra dam (Oum, Toub, Skikda, Algeria) began in 1989 with 800 larvae imported from Hungary. This pilot project in carp breeding aimed to provide a stock of protein resource at low cost, with the purpose of extending the scheme to other water bodies in the area. Studies of the dam and its fauna took place between 1995 and 1999. It was determined that the Guenitra dam is favourable to carp breeding. The experiment can be replicated with success in similar water bodies.

L’élevage de la carpe Cyprinus carpio L. dans le barrage Guenitra (Skikda, Algérie) a vu le jour en 1989 avec l’ensemencement de 800 alevins importés de la Hongrie. Ce projet pilote de carpiculture avait pour objectif la mise en place d’une ressource protéique à moindre coÛt avec l’ambition de sa généralisation à d’autres plans d’eau de la région. Pour cela, nous avons étudié entre 1995 et 1999, l’hydrobiologie du barrage et les réactions biotope‐biocénose‐ichthyofaune en estimant le stock de pêche s’évaluant entre : Carpe grosse tête Ctenopharyngodon idella Val., Carpe herbivore Aristichthys nobilis R et Carpe argentée Hypophtalmichthys molitrix Val. Les résultats obtenus, durant ces trois campagnes (1996/97, 97/98 et 98/99) englobent les paramètres climatologiques, les analyses physico‐chimiques in situ des sels minéraux et en laboratoire et enfin, l’âge et la biométrie des trois espèces de Carpes. Cette étude diagnostic préliminaire montre que le barrage Guenitra est un écosystème tout à fait favorable à la mise en place et l’exploitation d’une activité carpicole. D’autre part, elle permet de consolider l’idée de transfert de ce type d’élevage dans d’autres retenues d’eau ayant un environnement similaire.     

Optimization of ventilation system design and operation in office environment,Part I: Methodology

Ventilation principles that integrate flexible and responsive elements have grown in popularity in office buildings due to increasing concerns about the impact of indoor environment quality on office workers' well-being and productivity, as well as concerns over the rising energy costs for space heating and cooling in the office building sector. Such advanced elements as underfloor air distribution (UFAD), passive swirl diffusers, and demand controlled ventilation have posed challenges to system design and operation. This paper is concerned with the development and implementation of a practical and robust optimization scheme, aiming to assist office building designers and operators to enhance thermal comfort and indoor air quality (IAQ) without sacrificing energy costs of ventilation. The objective function was constructed in a way attempting to aggregate and weight indices (for thermal comfort, IAQ, and ventilation energy usage assessment) into one indicator. The path taken was a simulation-based optimization approach by using computational fluid dynamics (CFD) techniques in conjunction with genetic algorithm (GA), with the integration of an artificial neural network (ANN) for response surface approximation (RSA) and for speeding up fitness evaluations inside GA loop.     

风口上置置换通风的实验研究

对风口上置置换通风系统进行实验研究,得出此种通风方式下送风口的速度分布,室内的温度分布,O.1m处的风速等实验数据.通过分析实验数据得出,风口上置置换通风在满足室内热舒适性的前提下,能够提高房间的负荷承担能力,与混合通风相比能够得出较高的通风效率;另外,阶梯形的风口较普通的送风口能较少的卷吸上区品质差的空气,能更好地满足上置置换通风的风口特性要求.