2-Methylisoborneol and geosmin uptake by organic sludge derived from a recirculating aquaculture system

In a previous study on a recirculating fish culture system, levels of geosmin and 2-methylisoborneol were found to decrease when culture water was recirculated through the anaerobic sludge digestion treatment stage of the system. This finding led us to the present study in which the geosmin and 2-methylisoborneol removal capacity of the sludge derived from this treatment stage was examined in vitro. It was found that reduction of off-flavor compounds by the sludge was mediated by both chemical/physical sorption and biological degradation. At geosmin and 2-methylisoborneol concentrations within the range of those experienced in fish culture systems, chemical/physical sorption by the sludge was found to account for a 93% reduction in geosmin and a 79% reduction in 2-methylisoborneol from the overlying water within 48 h of incubation. Combined with the biological degradation taking place in the sludge, a complete removal of these compounds from the water phase occurred within 9 days of incubation. By means of repeated washing of the geosmin and 2-methylisoborneol contaminate sludge with clean water, relatively small amounts of these compounds were released from the sludge, a possible indication for the fact that absorption, rather than adsorption, underlies the chemical/physical removal process.     

垃圾处理场与污水池的防水处理

针对污水处理池防水处理的特殊性,介绍了其防水设计方案、选用主要材料的性能特点和施工方案,并就施工中要注意的几个问题加以阐述.     

Mathematical model for analysis of recirculating vertical flow constructed wetlands

The recirculating vertical flow constructed wetland (RVFCW) was developed for the treatment of domestic wastewater (DWW). In this system, DWW is applied to a vertical flow bed through which it trickles into a reservoir located beneath the bed. It is then recirculated back to the root zone of the bed. In this study, a compartmental model was developed to simulate the RVFCW. The model, which addresses transport and removal kinetics of total suspended solids, 5-day biological oxygen demand and nitrogen, was fitted to kinetical results obtained from pilot field setups and a local sensitivity analysis was performed on the model parameters and operational conditions. This analysis showed that after 5 h of treatment water quality is affected more by stochastic events than by the model parameter values, emphasizing the stability of the RVFCW system to large variations in operational conditions. Effluent quality after 1 h of treatment, when the sensitivity analysis showed the parameter impacts to be largest, was compared to model predictions. The removal rate was found to be dependent on the recirculation rate. The predictions correlated well with experimental observations, leading to the conclusion that the proposed model is a satisfactory tool for studying RVFCWs.     

层流病房的净化空调设计

简要介绍了层流病房的概念,结合层流病房净化空调要求,论述了层流病房净化空调的两种设计方法,并以具体工程为例深入阐述了自循环净化机组的设计方法,指出两种设计方法各有利弊,应根据实际情况合理选用。     

A simple simulation method for river self-purification studies

A simple simulation system is described for the study of river self-purification processes. A linear relationship between the organic load and the critical deficit on the sag curve was obtained for each temperature, corresponding to 36–52 per cent assimilation. The rate is not constant, and the monomolecular theory is not suitable to describe the results. Two distinct phases are observed. Nitrification appears as a second and distinct sag in the oxygen curve. It is limited by oxygen transfer and equilibrates at an O₂ tension of 0·6–1·05 mg 1⁻¹.     

A pneumatic dosing apparatus for flow-through bioassays

A multichannel pneumatic injector, when used with an equal-volume diluter, possesses several advantages over the mechanical approach to toxicant dosing. The system is reliable and highly versatile, capable of maintaining an unlimited range of toxicant levels in flow-through bioassays. Use of a single toxicant concentration eliminates the necessity of preparing several stock solutions. Automatic reloading of the injector syringes reduces maintenance.     

A computer program for randomizing toxicity bioassays

A short program, written in Applesoft (tm) BASIC, is presented which randomly assigns concentrations of toxic substance to containers prior to performing a toxicity bioassay. The program also calculates the amount of stock solution to add to each container, in a static bioassay, in order to obtain the desired test concentration. The program will run unaltered on Apple II computers and should be easily modified to run on most other microcomputers using a similar version of BASIC.     

A sensitivity analysis method for water distribution system tank siting for energy savings

Energy savings in water distribution system (WDS) pumping can save the municipality money and reduce the amount of greenhouse gas emissions. A straightforward method is introduced here that allows any WDS manager to determine source-tank location and connectivity that minimizes pumping energy usage. The method is demonstrated on twelve diverse WDSs to investigate whether less pumping energy is used by having the tank at four key locations. It was found that the new method worked well and identified that having the tank near to the system and connected directly to the source saves pumping energy in all of the WDSs analyzed. If the initial cost of relocating the tank for existing systems or locating the tank near to the source in new systems is less than the cost of energy savings over the lifetime of the tank, then having the tank near to the source is financially worth it.     

A simple omnidirectional sensor for wind-tunnel studies of pedestrian-level winds

A new sensor for measuring pedestrian-level winds in wind-tunnel models is described. It is axisymmetric about a vertical axis and outputs a pressure difference that is related to the wind speed at a chosen reference height just above the surface. Because of its axisymmetry it requires no alignment with the flow direction. Its calibration is described and it is compared with simultaneously measured hot-wire data in conditions representative of the pedestrian environment. It is found that it can be used to measure both the mean wind speed and the lower-frequency fluctuations in pedestrian wind-studies. Because of its simplicity, it can be installed in large numbers on a model and is well suited for use with automated Scanivalve equipment. The sensor may also be used as an omnidirectional skin friction meter if so desired.     

辐流沉淀池混凝剂投加参照曲线的绘制及应用

根据辐流沉淀池近三年的单池负荷、原水浊度以及混凝剂投加量数据,绘制了混凝剂投加量与浊度、单池负荷之间的曲线关系图,并介绍了混凝剂投加曲线的应用,以期对现实生产起指导作用。     

液化石油气储罐被动防火系统

为什么说仅有主动的系统是不够的 ,我们在确保被动防火系统火灾前耐久性方面能做些什么。最新的研究成果显示了 :在发生火灾时 ,仅靠安装在液化石油气储罐上的雨淋灭火系统不能很好地完成灭火。雨淋灭火系统被设计成能够用一个稳定的冷却水流完全灌润着火设备。为了使该系统能适当地运行 ,系统必须迅速浇灌着火储罐的外壳 ,保持整个外表面湿润 ,直到消防队能够到达扑灭火灾。在此危急时刻 ,任何一个干燥的储罐外表面都有可能被高温融化和发生破裂。因为储罐外表面温度在 5 min内就能迅速飙升到 2 0 0 0 。根据诸多报道 ,雨淋灭火系统工作过…     

某黑色金属熔炼炉循环冷却水系统设计

介绍了某特殊行业废旧污染黑色金属熔炼处理中心的中频无心感应熔炼炉循环冷却水系统设计,针对工程所在地的气候条件及水质等确定循环冷却水系统的工艺流程、运行控制方式,并结合现场实际运行情况对运行及处理效果进行了评价和分析,得出了一些有参考价值的结论。     

A simple continuous-flow toxicant delivery system

This paper describes a simple continuous-flow toxicant delivery system for use in testing toxicity of dissolved or suspended compounds to aquatic organisms. Its advantages are simplicty, ease of construction, and capacity for high flow rates. The system consists of a glass headbox and diluter box, a toxicant pump, a framework for support, and a system of tubes to deliver a series of toxicant concentrations to the test aquaria. Methods are given for construction and for calibration of the system.     

雨淋喷水灭火系统设置屋顶水箱的探讨

本文叙述了雨淋喷水灭火系统的组成及规范中对设置消防水箱所存在的问题,通过实际应用说明了应合理选择增压设施.     

一种双水箱太阳能热水系统

本文主要阐述了一种双水箱太阳能热水系统,该系统中包含冷、热两个水箱,冷水箱既能作为补水箱又能存储生活用水,为农村市场定时供水或为无自来水的用户提供了用水解决方案。     

太阳能热水系统用水箱的多种形式

太阳能热水系统水箱为与大气相通的开式贮水设备,作为贮存热水装置广泛应用于太阳能热水工程中。     

A simple manifold flow injection analysis for determining phosphorus in the presence of arsenate

A simple manifold flow injection analysis (FIA) for determining phosphorus in the presence of arsenate in water, by the on-line reduction of As(V) to As(III) using sodium sulfite. The FIA method is applicable for the determination of phosphorus in water samples containing less than 0.37 μg·mL^?1 of AsO₄ ^3?. A solution obtained by mixing 6.30 g of Na₂ SO₃ (1 M), 5.0 ml H₂SO₄ 18 M completed up to 50 ml with deionized distilled water was used to reduce on line As(V) to As(III), using a reactor of 0.30 m. The limit of detection is 0.05584 ± 0.00167 μg·mL^?1 P-PO₄ ^3? and sampling frequency is 45 samples per hour. It is a simple and low cost methodology, easily applicable in the determination of phosphorus in samples of water contaminated with arsenate.     

A comparison of microbial bioassays for the detection of aquatic toxicants

The toxicity of 35 test chemicals was analyzed using two microbial bioassay systems. The commercially available Microtox Toxicity Analyzer System™ and the two-organism procedure of Tchan were used to determine the concentration of test chemicals resulting in a 50% reduction in response (EC₅₀). Both of the tests employed a luminescent bacterium while the procedure of Tchan also utilized an alga. Results from the two microbial tests were compared with available data obtained with fish toxicity bioassays and with each other. The Microtox™ procedure was somewhat more sensitive than the Tchan bioassay in detecting most of the test chemicals and fish bioassays were generally more sensitive than either of the microbial tests. As a notable exception, photosynthesis-inhibiting herbicides were detected at remarkably lower concentrations with the procedure of Tchan than any of the other bioassays. Potential applications for these tests are discussed.     

A case study of ground source direct cooling system integrated with water storage tank system

Energy consumption for the commercial buildings has increasingly gained attentions, due to the significant electricity consumption and peak power demand. To solve this problem, this paper focuses on performance on the Ground Source Direct Cooling (GSDC) system integrated with a Water Storage Tank System (WSTS) in the summer, which directly utilizes the low-grade energy to supply high temperature water for the radiant floor cooling system and make full use of the electric rate difference between on-peak and off-peak periods. In summer, the indoor air temperature is controlled between 23 and 26 °C, resulting in a comfortable thermal environment. The total cooling capacities in 2014 and 2015 were 32.6 kWh/m² and 30.7 kWh/m², respectively. The annual energy consumptions for Electricity Unit Intensity (EUI) in 2014 and 2015 were 33.0 kWh/(m²·yr) and 32.1 kWh/(m²·yr), and the cooling energy consumptions only consumed 4.19 kWh/(m²·yr) and 4.55 kWh /(m²·yr), respectively. The annual operating cost of this cooling system only reaches 9 yuan/(m²·yr) through the analysis of 5 years’ operation. Compared to a conventional air cooled heat pump system, this cooling system has a larger initial cost, but its recovery period is less than 4.3 years, due to the extremely low operating cost. Overall, this GSDC system integrated with WSTS in the summer has remarkable advantages in thermal comfort and energy efficiency.     

Sedimentary microbial oxygen demand for laminar flow over a sediment bed of finite length

Dead organic material accumulated on the bed of a lake, reservoir or wetland often provides the substrate for substantial microbial activity as well as chemical processes that withdraw dissolved oxygen (DO) from the water column. A model to estimate the actual DO profile and the "sedimentary oxygen demand (SOD)" must specify the rate of microbial or chemical activity in the sediment as well as the diffusive supply of DO from the water column through the diffusive boundary layer into the sediment. Most previous experimental and field studies have considered this problem with the assumptions that the diffusive boundary layer is (a) turbulent and (b) fully developed. These assumptions require that (a) the flow velocity above the sediment bed is fast enough to produce turbulent mixing in the boundary layer, and (b) the sediment bed is long. In this paper a model for laminar flow and SOD over a sediment bed of finite length is presented and the results are compared with those for turbulent flow. Laminar flow near a sediment bed is encountered in quiescent water bodies such as lakes, reservoirs, river backwaters, wetlands and ponds under calm wind conditions. The diffusive oxygen transfer through the laminar diffusive boundary layer above the sediment surface can restrict the microbial or chemical oxygen uptake inside the sediment significantly. The developing laminar diffusive boundary layer above the sediment/water interface is modeled based on the analogy with heat transfer, and DO uptake inside the sediment is modeled by Michaelis-Menten microbial growth kinetics. The model predicts that the rate of SOD at the beginning of the reactive sediment bed is solely dependent on microbial density in the sediment regardless of flow velocity and type. The rate of SOD, and the DO penetration depth into the sediment decrease in stream-wise direction over the length of the sediment bed, as the diffusive boundary layer above the sediment/water interface thickens. With increasing length of the sediment bed both SOD rate and DO penetration depth into the sediment tend towards zero if the flow is laminar, but tend towards a finite value if the flow is turbulent. That value can be determined as a function of both flow velocity and microbial density. The effect of the developing laminar boundary layer on SOD is strongest at the very lowest flow velocity and/or highest microbial density inside the sediment. Under quiescent conditions, the effective SOD exerted by a reactive sediment bed of a lake or wetland approaches zero, i.e. no or very little oxygen demand is exerted on the overlying water column, except at the leading edge.