流量对微压过滤冲洗池过滤性能的影响研究

为研究微压过滤冲洗池在不同流量下的过滤性能,开展了流量为5. 4、9. 1、12. 4、15. 4、18. 5 m3/h下的物理模型试验。结果表明:不同流量下,微压过滤冲洗池的过滤情况可分为滤网过滤、滤饼过滤和挤压过滤3个阶段;流量对微压过滤冲洗池的泥沙去除效率影响不大,均为66%左右; 0. 125 mm以上泥沙的粒级效率达到100%,符合微灌或喷灌对水质的要求;流量为5. 4 m3/h下的过滤时间和拦截的泥沙质量分别为18. 5 m3/h的3. 44倍和2. 32倍,一旦超过对应流量下的过滤时间,则需进行排污,否则易损坏滤网;流量越小,微压过滤冲洗池的过滤时间越长,滤网能拦截的泥沙越多,尤其是小于滤网孔径的细小颗粒。     

不同滤网条件的微压过滤冲洗池过滤性能研究

为探讨微压过滤冲洗池采用不锈钢和腈纶滤网作为过滤元件的过滤性能,以过滤时间、拦截泥沙质量及泥沙去除率为评价指标,在水流含沙量为0.66 kg/m³和流量为5.0 m³/h条件下分别开展了物理模型试验。试验结果表明：在水箱水深变化方面,腈纶滤网存在水深恒定、水深快速增加及水深急速增加3个过滤阶段,而不锈钢滤网没有水深急速增加阶段;两种滤网的水深恒定时间相差不大,但不锈钢滤网的过滤时间略大于腈纶滤网;腈纶滤网拦截泥沙质量大于不锈钢滤网,且腈纶滤网能拦截到更小粒径的泥沙;腈纶和不锈钢滤网的泥沙去除率分别为61.10%～83.50%和44.00%～62.05%,前者是后者的1.35～1.42倍。综合考虑各项指标认为腈纶滤网更适用于微压过滤冲洗池,试验成果可为微压过滤冲洗池的深入研究提供理论依据和技术支撑。     

离散型流道结构叠片过滤器性能试验研究

在叠片过滤器中,叠片流道的结构决定着其工作性能。为提高叠片过滤器的水力性能和过滤性能,设计了一种离散型流道新型叠片过滤器,并与直线型流道传统叠片过滤器进行对比。通过室内模型试验,研究了两种叠片过滤器的水头损失、除沙率、拦沙量、拦截泥沙粒径分布等指标。结果表明：清水条件下离散型流道新型叠片过滤器最大水头损失为2.34 m,传统叠片过滤器为3.46 m,前者比后者小32.3%～50.0%;含沙水条件下,两种叠片过滤器拦沙量与流量呈负相关关系,随着流量的增加,过滤器拦截泥沙量逐渐减少,前者平均除沙率为18.94%,后者为15.15%;离散型流道新型叠片过滤器的有效过滤周期长、水头损失峰值低,且对细粒径泥沙的拦截效果较好。综上所述,离散型流道新型叠片过滤器与直线型流道传统叠片过滤器相比,具有较好的水力性能和过滤性能。     

圆中环沉沙排沙过滤池结构特性试验研究

圆中环沉沙排沙过滤池是一种新型的浑水沉沙、排沙、过滤装置,通过新疆呼图壁城镇工业供水工程圆中环沉沙排沙过滤池的物理模型试验,模拟了在1 m3/s工况下的运行效果。试验结果表明:采用三层不同粒径的滤料,中心溢流筒加高0.4 m时,能较好的起到沉沙、排沙和过滤的作用且不被击穿,同时能满足引水量的要求,汇流槽平均流速在0.88～2.77 m/s范围内。与常规水沙分离装置相比,这种新型的装置实现了节能减排,环保性处理泥沙的目标,为水沙分离提供了另一种新的思路。     

Tertiary filtration in small wastewater treatment plants.

Tertiary filtration can be proposed in small wastewater treatment plants with impact on protected water bodies. Rotating disk filters may be adopted, in respect to conventional sand filters, when low availability of space and low investment costs are the prevailing conditions. The overall objective of this research was to evaluate the filtration efficiency of rotating disk filters; to compare effectiveness with traditional sand filters; to analyse thoroughly the importance of particle size distribution in wastewater tertiary filtration. In the experimental activity, conventional wastewater quality parameters were investigated and particle size distribution (PSD) was characterized to discuss the filter effectiveness. The effect of design and operation parameters of tertiary filters were discussed related to particle removal curves derived from particles counts. Analysis of particle size distribution can be very useful to help comprehension of filtration processes, design of filtration treatments and to decide the best measures to improve filter performance.     

Impact of organic ligands on uranium removal during anaerobic biological treatment

Anaerobic batch experiments were conducted to evaluate the reduction and precipitation of U⁶⁺+ complexed to acetate, oxalate, citrate and tiron using a pure culture of sulfate reducing bacteria (Desulfovibrio desulfuricans). These ligands were chosen to evaluate the nature of complex formation on uranium bioreduction. Experiments in which uranium was initially complexed to the ligand (>92%) indicated that bacteria reduce U⁶⁺+ to U⁴⁺+ in the presence of each ligand tested. The rate of acetate complexed uranium reduction was fastest and that of citrate complexed uranium was slowest. Precipitation of reduced uranium was evaluated by filtering the reduced complex through 0.2 μm filters. The U⁴⁺+ formed after biotransformation in acetate solutions was retained on the filter whereas U⁴⁺+ in the oxalate, citrate and tiron solutions passed through the filter. When ligand concentrations were lowered (44–50% of the uranium initially complexed) a greater amount of UO₂ precipitate from oxalate samples was collected on the filter indicating that ligand concentration can impact uranium removal via precipitation. Little or no precipitate was collected from citrate or tiron containing solutions. The preferred reaction of U⁴⁺+ appeared to be recomplexation with these ligands rather then precipitation as UO₂.     

Technical solutions for a modernized TPE-216M boiler in a highly efficient unit

A design is presented for a modernized lignite-fired TPE-216M boiler for a highly efficient 225-MW power-generating unit, which can be installed at the Kharanorskaya state area power plant (Station No. 3). The boiler has a guaranteed gross efficiency of 92.5%, and satisfies modern ecological requirements: NO_x concentration of less then 300 mg/m³ in the flue gases, owing to the high gross efficiency of the unit, which is no less than 40%, NO_x emissions computed per 1 kW · h are reduced additionally by 10%, and the same applies to CO₂ emissions. The temperature of the steam is raised from 545 to 565°C. A low-pressure water economizer, which is included in the heat diagram of the unit, is installed to lower the temperature of the exiting gases. __________ Translated from élektricheskie Stantsii, No. 6, pp. 8–13, June, 2006.     

小浪底土石坝反滤设计

阐述了小浪底土石坝反滤设计的原则，方法和成果。设计中，根据大坝防渗体的结构特点设置了多种反滤。按各个部位反滤的工作条件和重要性，将反滤分为关键性反滤和非关键性反滤。对这两类不同性质的反滤采用了不同的设计原则和方法。对于关键性反滤着重强调在防渗体发生集中漏时应不致于产生渗透破坏而危及大坝安全，而对于非关键性反滤则根据不同情况进行适当简化。根据料场砂卵石级配特点和反滤设计要求，综合利用筛分料和轧制料改     

An application of linear programming to determine optimal systems for rainwater management: An economic view

Two decision models, one for determining optimal systems for rainwater management and the other for allocating additional water supplies from managed rainfall in conjunction with irrigation water, are formulated. The application of a rainwater management model to the command and to a watercourse, decides the minimum cost activities to manage rainwater. The output from the first model is used as the input in the second model which optimally allocates water to competing crops. It has been shown that 80% of rainwater could be managed economically in rice fields and in storage underground through artificial recharge. Optimal allocation of managed rainwater in conjunction with irrigation water increases the income of the project area to the extent of 14%.List of symbols AER Total available energy kWh - B _max Maximized value of the objective function, Rs - C _W Cost of canal water, Rs/10³ m³ - C _i Cost of managing rainwater through activityi, Rs/10³/m³ - C _min Minimized cost of managing surplus rainwater, Rs - C _RF Average cost of managed rainwater through activityi, Rs/10³ m³ - E _i Energy consumption in rainwater management activityi, kWh/10³ m³ (only energy required for pumping water is considered) - FLS Available capacity for fallow land storage, 10³ m³ - FPS Total storage in lined and unlined farm ponds, 10³ m³ - GWR Runoff diversion for artificial recharge through inverted tubewells, 10³ m³ - i A suffix for management activities having values 1,2,3,..., - j Crop index having values 1,2,3,..., - k Index for crop season, 1=kharif (summer) and 2=rabi(winter) - MRF Maximum rainfall surplus (runoff) available for management. (Runoff value at a 5-year return period was adopted) - P _j Income from crop activityj, Rs/ha - RFL Storage in fallow alkali land, 10³ m³ - RFS Storage in rice fields up to various depths, 10³ m³ - RWM _i Volume of rainwater managed through activityi, 10³ m³ - VCW Volume of canal water, 10³ m³ - VGW Volume of ground water, 10³ m³ - X _j Area under cropj, ha.     

微灌系统过滤器性能的试验研究

本文以试验为依据，提出了我国已有的３类在微灌系统中使用的过滤器的过滤元件堵塞程度与局部水头损失系数的关系式，探讨了过滤元件的过不面积和过滤器的冲洗性能问题。     

Modernizing the boiler installation for unit no. 3 at the Kashirskaya GRÉS to reduce nitrogen oxide emissions

The purpose of modernizing the Pp-1050-25-545 KGZh (P-50R) boiler is to reduce the emissions of nitrogen oxides (NO_x) to levels consistent with modern requirements. The following engineering steps were taken, with liquid slag removal from the boiler, to attain NO_x levels of 700–750 mg/m³ for operation with coal and 125 mg/m³ for operation with natural gas — three-stage combustion with natural gas as the reducing fuel (∼15% thermal) burning in the recirculating gases; and — use of low-emission coal-dust burners with dust feed at high concentrations, overflow burners, and tertiary draft nozzles to lower the amount of excess air in the active combustion zone. The NO_x level was further reduced to 570 g/m³ (just for operation with coal) by using a selective noncatalytic nitrogen oxide reduction system with injection of ammonia (NH₃) vapor into the boiler in a zone with temperatures of 950°C. __________ Translated from élektricheskie Stantsii, No. 1, pp. 2–8 (2008).     

土工织物的孔洞曲线和瓶颈曲线及其应用

介绍土工织物的孔洞曲线和瓶颈曲线及其相关的概率分析 ,提出了设计中应注意的一个参数———渗径孔洞数m .这两种曲线和参数m一起 ,更加完整地反映了土工织物滤层的渗滤性能 .在理论分析的基础上 ,提出了一种新的滤层设计方法 ,并提供了可供设计使用的计算图 ,该方法同时考虑了O10 0 和m两个参数 ,解决了具有相同或相似特征孔径织物的优选问题     

黄河水滴灌系统灌水器结构-泥沙淤积-堵塞行为的相关关系研究

传统的黄河水沉淀-过滤系统存在沉沙池建设成本高、过滤器频繁反冲洗能耗高等问题,让更多的细颗粒泥沙随水流排出灌水器体外是解决黄河水滴灌系统灌水器堵塞的新思路,而摸清泥沙在黄河水滴灌系统内部的淤积特性以及灌水器结构-淤积泥沙特性-堵塞特性参数间的相关关系是探索其排沙能力的前提和基础。为此,本文在河套灌区开展了黄河水滴灌系统灌水器堵塞原位试验,系统分析了6种内镶贴片式灌水器内部细颗粒泥沙含量及粒径分布动态变化特征,探索了三者间的级联关系。结果表明：进入灌水器内部的泥沙99%以上可以排出体外,淤积在灌水器内部的泥沙以粉粒为主、砂粒次之、黏粒最少。随着灌水器堵塞加剧,内部淤积泥沙的黏粒、粉粒比例相对降低,而砂粒比例相对增加,泥沙进入灌水器后存在聚集等行为,使得灌水器内部淤积泥沙粒径明显高于毛管入口。泥沙比表面积淤积量、粉粒比例、砂粒比例、D₅₀、D₉₅对黄河水滴灌系统Dra、克里斯琴森均匀系数CU影响显著（p<0.05）,不同灌水器淤积泥沙粒径明显不同,D₅₀与灌水器结构无量纲参数（流道宽深比W/D、面积长度比A^1/2/L）及断面平均流速v显著（p<0.05）相关。本研究对引黄滴灌灌水器设计及灌溉系统过滤配置具有指导意义。     

Sediment greenhouse gases (methane and carbon dioxide) in the Lobo-Broa Reservoir, São Paulo State, Brazil: Concentrations and diffuse emission fluxes for carbon budget considerations

Carbon gases (methane, CH₄, and carbon dioxide, CO₂) were measured for the first time in sediments of the Lobo‐Broa Reservoir, near São Carlos in São Paulo State, Brazil. It is believed these are the first measurements of this kind in any of the many reservoirs located in Brazil. Even though the Lobo‐Broa Reservoir is classified as oligotrophic, the sediment gas concentrations were exceedingly high, ranging from 0.4–3 mmol L^?1 for CH₄ and 1–9 mmol L^?1 for CO₂. Both gases exceeded their in situ gas saturation values at these shallow water depths (7 m in central basin; 11 m at dam), resulting in numerous sediment bubbles. Organic matter was highly concentrated in the reservoir sediments, averaging 25.5% loss on ignition (LOI) (dam) to 26.9% LOI (central basin) for the 0–12 cm depth interval, with values as high as 29–30% LOI (12% organic carbon) in the surface 0–5 mm layer. The theoretical flux of dissolved pore water carbon gases to the sediment–water interface (SWI) averaged 3.4 mmol L^?1 m^?2 day^?1 CH₄ and 7.3 mmol L^?1 m^?2 day^?1 CO₂ for the surface 0–10 mm. From gas emission measurements at the water surface, it was calculated that 90% of CH₄ is consumed either at the SWI or in the water column, resulting in a loss of 0.31 mmol L^?1 m^?2 day^?1 of CH₄ to the atmosphere. However, only 20% of the total CO₂ gas transported across the water–atmosphere interface (36.3 mmol L^?1 m^?2 day^?1, or 1600 mg CO₂ m^?2 day^?1) was produced in the sediments. The remaining 80% of CO₂ probably comes from other carbon sources. With CH₄ oxidation in the aerobic water column, close to 30% of the carbon gas flux to the atmosphere could be accounted for by gas production of CO₂ and CH₄ in the sediments and their diffuse transport to the water column.     

The artificial recharge of groundwater: A solution by successive variations of steady states

The artificial recharge of groundwater aims at the modification of water quality, an increase of groundwater resources, and the optimization of the exploitation and recovery of contaminated aquifers. The purpose of this work is to develop a new mathematical model for the problem of an artificial recharge well, using the method of successive variations of steady states. Applying this method, one arrives at an expression of time as a double integral. This integral contains the time-dependent radius of the recharge boundary and the piezometric head of the well, calculated with the finite-element method. The new model is simple and useful, and can be applied to many practical problems, using the designed dimensionless graphs.Notations A area of the finite element (m²) - c the Euler constant (0.5772156649...) - e index of the finite element - E _i the exponential integral function - F _j nodal values of the functionF - h piezometric head, (m) - h ₀ piezometric head at timet=0 (m) - h _w piezometric head on the well contour (m) - i, j, k nodal indices of the finite element - K hydraulic contactivity (ms^–1) - N _i interpolation function - Q discharge (m³ s^–1) - r cylindrical coordinate (m) - r ₀ the action radius of the well (m) - r _w the radius of the well (m) - S the effective porosity - t the time (s) - T the transmissivity of the aquifer (m²s^–1) - V the stored water volume (m³) - x, y, dummy variables     

刚果英布鲁水电站土石坝反滤设计 与试验研究

英布鲁水电站拦河坝为土质防渗体分区坝，用太沙基设计准则对上、下游坝坡渗流出逸处进行反滤设计。由于几种筑坝材料的抗渗性能较差，对设计的反滤级配进行试验验证，结果表明，本工程的反滤层按太沙基设计准则进行设计是合理的，能满足防止大坝渗透破坏的需要。     

新疆玛纳斯河流域植被水分利用效率时空格局及影响因素研究

水分利用效率（WUE）是生态系统碳水循环的基础,是评价植被生长条件的重要生态指标。为了揭示玛纳斯河流域不同植被类型WUE的时空变化规律,分析不同植被类型WUE的差异,探讨影响WUE的驱动因子,基于MODIS数据估算了2001-2019年玛纳斯河流域水分利用效率,利用变异系数、Theil-Sen median趋势分析结合M-K显著性检验以及Hurst指数分析了研究区植被WUE时空变化的现状和未来的趋势,并利用地理探测器定量分析了WUE的影响因素。结果表明：2001-2019年玛纳斯河流域WUE在0.74～1.08 g/(mm·m²)之间,WUE多年平均值为0.88 g/(mm·m²),整体表现为波动降低趋势,降幅为6.82%。流域WUE空间差异显著,呈现中部和北部高、南部低以及中游高、上游和下游低的分布格局。研究区各植被类型中林地WUE平均值较高,其中针叶林的平均WUE最高,为1.52 g/(mm·m²);其次为阔叶林,WUE平均为1.29 g/(mm·m²)。研究区WUE主要驱动因子为CO₂、土壤湿度、温度植被干旱指数和饱和水汽压差。与单因子相比,多因子相互作用对研究区WUE的影响更明显。双因子交互探测均呈显著增强关系,解释力均在60％以上,其中CO₂与土壤湿度的交互作用解释力最高,达到90.3％。研究结果可为研究区农业高效生产、水资源优化管理及生态恢复提供科学依据。     

A water policy intercomparison model for a region with three seasons

A water policy model is proposed as a solution to the problem of obtaining maximum net benefit from providing irrigation and urban water in regions where the major source of supply is groundwater. In essence, the model introduces an innovative scheme based on two types of penalties. These intervene when either watertable elevation falls below a critical value during the operation of a system of wells or a remote source is used to partially cover the needed amount of water expected from the basic groundwater source. Another specific idea of the model is the consideration, for southern regions, of a three-season division in the climatic character of a year. The algorithm is illustrated by a numerical example in which five possible alternatives are compared. The conclusion of the study (although a function of regional economics, natural conditions, as well as specific zonal water policy constraints) reveals a compromise between limiting the amount provided from remote sources and confining the aquifer operation to critical values of the water-table elevation.Notation B benefits from water use, 10³ US$ - C sum of total costs, 10³ US$ - CMR total maintenance-repair cost, 10³ US$ - CO total cost of operation, 10³ US$ - C _HO unit cost of operation per hour, US$ hr^–1 - C _y unit average cost of a repaired pump, US$/(year × well) - d screen diameter for each well, m - H _G average groundwater elevation, m - H _{W cr} critical water elevation value in wells, m - H _{W dj} hydraulic head deficit in wells (belowH _{W cr} ), m - H _{W j} seasonal water elevation in each well, m - j current season - K average hydraulic conductivity of the aquifer, m s^–1 - NB net benefit, 10³ US$ - Ns maximum number of seasons - N _HO number of hours of operation per well and month - N _{W j} number of wells in operation over a seasonj - n _j number of months over each seasonj - P sum of total penalties, 10³ US$ - PH total penalty for pumping whenH _{W dj} >0, 10³ US$ - PQ total penalty for remote source use, 10³ US$ - P _RSj unit penalty for remote source use, 10³ US$ month^–1 - P _{W dj} unit penalty for pumping whenH _{W dj} >0, 10³ US$ month^–1 - pRM percentage of repaired and maintained pumps yearly, % - Q _iRj discharge needed for irrigation use, m³ s^–1 - Q _Nj total discharge needed by users, m³ s^–1 - Q _Pj total seasonal yield capacity of the battery, m³ s^–1 - Q _RSj discharge covered from remote sources, m³ s^–1 - Q _UWj discharge needed for urban water use, m³ s^–1 - Q _j seasonal operated pumping rate in each well, m³ s^–1 - Q _waj weighted average of pumping rate at timet _j , m³ s^–1 - S _Y average specific yield of the aquifer - S _cr critical drawdown value in wells, m - S _j seasonal drawdown in each well - T average transmissivity of the aquifer, m² s^–1 - t _OPj current duration of system operation - t _j –t _j–1 duration of each seasonj     

Trophic evolution of Lake Lugano related to external load reduction: Changes in phosphorus and nitrogen as well as oxygen balance and biological parameters

Lake Lugano is located at the border between Italy and Switzerland and is divided into three basins by two narrowings. The geomorphologic characteristics of these basins are very different. The catchment area is characterized by calcareous rock, gneiss and porphyry; the population amounts to approximately 290 000 equivalent inhabitants. The external nutrient load derives from anthropogenic (85%), industrial (10%) and agricultural (5%) sources. The limnological studies carried out by Baldi et al. (1949) and EAWAG (1964) revealed early signs of eutrophication, with a phosphorous concentration of about 30–40 mg m^–3 and an oxygen concentration of less than 4 g m^–3 in the deepest hypolimnion. Subsequently Vollenweider et al. (1964) confirmed these data and was the first to point out the presence of a meromictic layer in the hypolimnion of the northern basin. From the 1960s, as a result of an increase in the population and internal migration, the lake became strongly eutrophic with the P concentration reaching 140 mg m^–3 and the oxygen in the hypolimnion reduced to zero. Fifty‐five per cent of the P was from metabolic sources and 45% from detergents and cleaning products. In 1976, a partial diversion of waste water from the northern to the southern basin was begun, and gradually eight waste water treatment plants came into operation using mechanical, chemical and biological treatments. In 1986, Italy and Switzerland began to eliminate the P in detergents and cleaning products. Since 1995, the main sewage treatment plants have improved their efficiency by introducing P post‐precipitation, denitrification and filtration treatments. The recovery of the lake is due to be completed by the year 2005. Altogether, during the last 20 years recovery measures have reduced the external P load from about 250 to 70–80 tonnes year^–1; the goal to be reached is 40 tonnes year^–1. In‐lake phosphorous concentrations have decreased from 140 to 50–60 mg m^–3, with the target at 30 mg m^–3. Dissolved oxygen concentration is satisfactory only between the depths of 0 and 50 m, falling rapidly to zero in the deepest layers. Below a depth of 90 m, high CH₄, HS^–, NH₄⁺, Fe²⁺ and Mn²⁺ concentrations exist. Primary production has decreased from 420 to 310 g C_ass m^–2 year^–1, notwithstanding an increase in the thickness of the trophogenic layer. Structure and dynamic biomass show marked changes: phytoplankton dry weight has decreased from 16 to 7 g m^–2, while zooplankton dry weight has increased from 3 to 4.5 g m^–2. Chlorophyll concentration has fallen from 14 to 9 mg m^–3 and Secchi disk transparency has increased from 3.5 to 5.5 m. The current sources of the external load are uncollected small urban conglomerations, storm‐water overflows from outfall sewers, and the residual load from sewage treatment plants, particularly those without P post‐precipitation.     

Effects of residence time on summer nitrate uptake in mississippi river flow‐regulated backwaters

Nitrate uptake may be improved in regulated floodplain rivers by increasing hydrological connectivity to backwaters. We examined summer nitrate uptake in a series of morphologically similar backwaters on the Upper Mississippi River receiving flow‐regulated nitrate loads via gated culverts. Flows into individual backwaters were held constant over a summer period but varied in the summers of 2003 and 2004 to provide a range of hydraulic loads and residence times (τ). The objectives were to determine optimum loading and τ for maximum summer uptake. Higher flow adjustment led to increased loading but lower τ and contact time for uptake. For highest flows, τ was less than 1 day resulting in lower uptake rates (U_net < 300 mg m^?2 day^?1), low uptake efficiency (U% < 20%) and a long uptake length (S_net > 4000 m). For low flows, τ was greater than 5 days and U% approached 100%, but U_net was 200 mg m^?2 day^?1. S_net was < half the length of the backwaters under these conditions indicating that most of the load was assimilated in the upper reaches, leading to limited delivery to lower portions. U_net was maximal (384–629 mg m^?2 day^?1) for intermediate flows and τ ranging between 1 and 1.5 days. Longer S_net (2000–4000 m) and lower U% (20–40%) reflected limitation of uptake in upper reaches by contact time, leading to transport to lower reaches for additional uptake. Uptake by ～10 000 ha of reconnected backwaters along the Upper Mississippi River (13% of the total backwater surface area) at a U_net of ～630 mg m^?2 day^?1 would be the equivalent of ～40% of the summer nitrate load (155 mg day^?1) discharged from Lock and Dam 4. These results indicate that backwater nitrate uptake can play an important role in reducing nitrate loading to the Gulf of Mexico. Copyright © 2008 John Wiley & Sons, Ltd.