Performance of Wet Weather Treatment Facility for Control of Combined Sewer Overflows: Case Study in Cincinnati, Ohio

Efforts aimed at reducing pollutant loads from combined sewer overflows (CSOs) on the Muddy Creek receiving waters in Cincinnati, Ohio have been underway in recent years. This includes an investigation of the treatment performance of a flow-through wet weather treatment facility (WWTF) using off-line sedimentation tanks, fine screening and chemical disinfection (disinfection was inactive during this study). Calculations using hydrographs and water quality samples collected at the WWTF during rain events established the mass of biochemical oxygen demand (BOD)5, chemical oxygen demand, and total suspended solids (TSS) removed. Ten storm events sampled from January to September 2002 helped characterize pollutant removal efficiencies for flow-through treatment. Pollutant removal was classified into four components: flow to the wastewater treatment plant (WWTP), sedimentation, storage, and screening. Most pollutant removal was achieved through settling and storage in the treatment tanks, with removal efficiencies of 20–50% for BOD5 and 25–70% for TSS commonly observed. Owing to the high pollutant load in the early portion of the CSO hydrograph, first-flush containment, or capturing and conveying the early portion of the runoff event to the WWTP, was the most efficient treatment method for every storm investigated.     

Pilot Scale Demonstration of Cross-Flow Ceramic Membrane Microfiltration for Treatment of Combined and Sanitary Sewer Overflows

A pilot scale investigation was undertaken at the Allegheny County Sanitary Authority (ALCOSAN) for approximately 12 months to evaluate the feasibility of using cross-flow microfiltration for the treatment of primary sewage effluent simulating combined and sanitary sewer overflows. Ceramic membranes of various pores sizes (0.05–1.4?μm) were tested to understand the impact of cross-flow velocity, transmembrane pressure, and feed suspended solids on permeate water quality and permeate flux rate. A 0.2?μm membrane operated with a 1.8?m/s cross-flow velocity, a transmembrane pressure below 2.1 bar and a backpulse frequency of 60 s showed the best performance among the conditions evaluated in this study. The 0.2?μm membrane consistently met water quality objectives for fecal coliforms, E Coli, enterococci, BOD5, and suspended solids independent of the feed concentration, suggesting that direct discharge to surface water may be feasible. Feed suspended solids concentration and temperature influenced membrane permeate flux. Membrane cleaning with alkaline sodium hypochlorite solution is recommended as the first step followed by nitric acid cleaning if needed.     

Real-Time Detection of Sanitary Sewer Overflows Using Neural Networks and Time Series Analysis

Sanitary sewer overflows (SSOs) are becoming of increasing concern as a health risk. Utilities and regulators have taken preventive measures but many overflows still occur and are not identifiable, especially in access-challenged locations. Several mathematical approaches are presented for detecting if a disruption in the system is impending or occurring based on measurements at one or more locations in the system. Time series analysis and neural networks are used as prediction tools for expected depths and flows for single measurement locations and a neural network is developed for a multiple monitor system. Control limit theory is applied in all cases for identifying significant deviations of measured values from the expected values that suggest a SSO is occurring. Data from Pima County Wastewater Management’s monitoring system are used in two case studies.     

Parsimonious Model for Combined Sewer Overflow Pollution

The reservoir concept for flow modeling has been generalized for the purpose of the parsimonious modeling of combined sewer overflow pollution. Conceptual models have been used for the buildup and washoff of pollutants on the paved surfaces, and the transport of these pollutants in the sewer system (advection, dispersion, sedimentation, and resuspension). For the parsimonious modeling of the water quality of the sewage in the effluent of the combined sewer system, the conceptual submodels of these different processes were lumped into one single model equation. When ancillary structures such as a storage sedimentation tank are present at the combined sewer overflow, the additional effect of advection, dispersion, storage, and sedimentation is considered in a similar parsimonious conceptual way. Such a parsimonious model aims to reduce the model complexity, and therefore the number of calibration parameters. In most practical cases of urban drainage modeling, water quality data are extremely limited and consequently only a small number of parameter values can be identified from the data. The proposed model is tested on the basis of 10-min and hourly concentration measurements for total suspended solids, settleable solids, biochemical oxygen demand, and ammonia at the outlet of the combined sewer system of the village of Dessel (Belgium), which were available in this case only for six overflow events.     

Settling Velocity Grading of Particle Bound PAHs: Case of Wet Weather Flows within Combined Sewer Systems

The elaboration, management, and design of the sedimentation devices require an improved knowledge not only on the suspended solids (SS) settling velocity but also on the distributions of these particulate pollutants by category of SS settling velocity. Nevertheless, there is currently a lack of available data regarding the settling velocity grading of particle bound pollutants. As a consequence, this study investigating the settling velocity grading of particle bound polycyclic aromatic hydrocarbons (PAHs) in wet weather flows within combined sewers was launched. The pursed objectives were to compare the SS and PAH settling velocity grading curves and hence to assess whether or not PAHs were associated with a specific settling velocity category. Investigations were carried out for three storms at two sampling sites within the Parisian combined sewer. Results indicate that most of PAHs seem to be preferentially associated with particles with a settling velocity >0.3?mm?s?1.     

Drop in Combined Sewer Manhole for Supercritical Flow

Manholes often contain small drops for various reasons, the most important being submergence. While this may be appropriate for subcritical flow, its effect was considered doubtful for supercritical flow. This note aims at investigating the effect of a manhole drop on the hydraulics of sewer flow. Based on systematic experimental observations, the flow pattern associated with a manhole drop was established. A distinction was also made between small and intermediate drops. Then, the main wave features were analyzed to result in expressions that contain both the upstream filling ratio and the Froude number of the approach flow. In addition, the discharge capacity was also investigated, and selected photographs show typical drop flow in combined sewer manholes. The result of the present study is evident, based on these observations, and recommendations towards future design of combined sewer manholes are also made.     

Bottom Slot Discharge Outlet for Combined Sewer Diversion Structure

The concept of a bottom slot outlet was developed to serve as a combined sewer overflow diversion structure to convey flow to deep tunnel storage under free discharge conditions and pass the remaining volume once storage capacity is exceeded with minimum backwater effects. In order to test the concept, a 1:19.5 scale model was constructed and tested over a range of discharges in order to determine the required slot length to pass a certain discharge. Different bottom slopes and slot widths were tested. For subcritical approach flow, the flow in the structure passed through critical depth at the upstream end of the slot, eliminating the possibility of backwater effects. The results were found to be nearly independent of the bottom slope for typical small slopes in sewer systems, and a simple dimensionless relation was developed to relate the slot length to other parameters. A mathematical model combining continuity and energy relations for the remaining flow in the structure with an orifice relation for flow through the slot was capable of reproducing the observed experimental results.     

Application of Cross-Flow Microfiltration for the Treatment of Combined Sewer Overflow Wastewater

Application of cross-flow microfiltration with and without backpulsing is evaluated for the treatment of dilute primary sewage effluent simulating combined sewer overflow wastewater. Four alpha alumina ceramic membranes of various pores sizes (0.2–5.0?μm) were tested to understand the impact of cross-flow velocity and transmembrane pressure on the permeate water quality and flux rate. The 0.2 and 0.8?μm membranes produced a permeate water quality that is likely to be suitable for surface water discharge. The combination of permeate chemical and biological water quality and long-term flux rates suggest that a 0.2?μm membrane would be the most appropriate membrane for the treatment of combined sewer overflow wastewater within sewersheds.     

开关站实现微机监控后负序电流保护是否保留及如何实现

研究了开关站现有和新增负荷情况,分析了负序电流的保护作用,研究了实现微机监控后负序电流保护是否可以保留及如何实现,以保证可靠供电。     

CFD Modeling of Solid Separation in Three Combined Sewer Overflow Chambers

The knowledge of solid behavior in combined sewer overflow (CSO) chambers is a great challenge for the protection of receiving watercourses. Moreover, great attention must be given to the occurrence of deposits on the bed of the chamber because they may lead to operation problems. In this paper, we investigate the capability of a particle tracking approach to determine the solid separation in CSO chambers. This is done by comparing simulations and experimental data collected in three small-scale models, as reported by Kehrwiller 1995. The trap, reflect, and bed shear stress (BSS) boundary conditions are compared. We propose to use the Shields relationship for evaluating the critical BSS. Finally, we propose a methodology for predicting the solid separation in CSO chambers using computational fluid dynamics.     

Single- and Multievent Optimization in Combined Sewer Flow and Water Quality Model Calibration

Over the last three decades, storm-water quality modeling has been used increasingly commonly to describe the general system behavior and assess the pollution loads transferred in and spilled out of combined sewer systems. The calibration of quality models is, in most cases, based on conventionally obtained calibration data, e.g., by automated sampling. Long-term high-resolution online measurement data are available for the Graz West catchment (Graz, Austria), allowing an assessment of the full dynamics of discharge and pollution concentrations. This paper focuses on the application and comparison of single-event and two different multievent optimization schemes for sewer-water quality model calibration. While both single- and multievent optimization lead to satisfying results for the calibration events in discharge calibration, it is shown that validation events are better reproduced by using multievent calibration. Single- and multievent autocalibration of pollution concentration is based on the best dataset obtained from the discharge calibration. As for discharge, the pollutographs are reproduced satisfactorily, and multievent calibration is more stable. In all cases, the two multievent approaches performed equally well.     

海拉尔一次强雷暴天气的多普勒雷达图象分析

利用常规天气资料和多普勒雷达资料产品,分析了2008年7月21日海拉尔周遍地区的强雷暴天气.结果表明,强雷暴天气一般产生在低层要有切变线等触发机制的不稳定能量大气环境中.当多普勒雷达图象上出现窄带回波即出流边界时,在其后部易产生强雷暴天气.     

铅烟气治理工程检测控制系统的研制开发

介绍了铅烟气治理工程检测控制系统计算机控制网络技术方案的形成过程,叙述了采用现场总线设备构成系统的先进性和大规模控制网络的技术问题。     

Algorithms for Automated Monitoring and Control of Fall Hazards

Most lethal accidents in construction are caused by falling from heights. Researchers point out the importance of safety control, carried out systematically and based on real-time data collection, as the most important element of accident prevention. An automated model to monitor and control fall hazard was developed. The model identifies the activities associated with risk of fall from heights and the areas where these activities are scheduled to be performed and plans the protective measures—guardrails in the present case. The model is designed to follow up the existing guardrails and constantly compare their locations and lengths to the planned ones. Based on this comparison, the model issues warnings whenever guardrails are missing, or temporarily removed. The model provides reports and warnings—the reports are used for planning the materials, or workers, needed to erect the protective measures. Warnings are given when a dangerous activity is performed without appropriate protective measures, or when the latter were removed before the dangerous activity was completed. The model’s main algorithms—dangerous activities and areas identification—were implemented and evaluated on site. Whereas the proposed model was developed to improve safety during the construction stage, it can be used as a useful tool during the design stage too. Including safety in the design stage, typically absent, can meaningfully improve safety during the actual construction.     

Ferrous Salt Demand for Sulfide Control in Rising Main Sewers: Tests on a Laboratory-Scale Sewer System

The addition of ferrous salts is a commonly used strategy for sulfide control in sewer networks. The Fe2+ dosing requirement in rising main sewers which takes into account of the effect of anaerobic sewer biofilms on the dosing demand is investigated. A laboratory-scale rising main sewer, consisting of four biofilm reactors in series and fed with real sewage, was operated for over 12 months, during which FeCl2 was dosed at several locations and at various dosing rates. The experimental results consistently revealed that approximately 0.7 mol of Fe2+ was required to precipitate sulfide formed from the reduction of 1 mol of sulfate by anaerobic sewer biofilms. This ratio is significantly lower than the ratio expected from reaction stoichiometry (molar ratio of 1:1), and also the Fe2+ to sulfide ratio (1.07–1.10 mol:1 mol) observed in batch tests conducted with real wastewater in the absence of sewer biofilms. Biofilms adapted to Fe2+ addition were found to contain a substantially higher amount of elemental sulfur than biofilms not receiving Fe2+ dosage. This suggests Fe2+ addition might have altered the final product of sulfate reduction by anaerobic sewer biofilms. The study also showed that the addition of ferrous salts at the inlet of a rising main sewer can effectively control sulfide throughout the whole system despite of the presence of competing anions in wastewater. Phosphate precipitation with ferrous iron in anaerobic rising main sewers is negligible.     

工业锅炉水位微机测控系统

设计了一种数字式锅炉液位测控系统,并给出了硬件原理图和软件流程图。该控制系统是用MCS-51系列单片机及其相关硬件来实现,利用传感器测量液位数据、温度数据,并显示温度或者水位值及LED指示加水状态和报警情况。当锅炉液位低于用户设定的值时,系统自动打开泵上水,当水位到达设定值时,系统自动关闭水泵。     

井下通风机远程监测与控制装置的研制

研制一种基于 PLC 控制的远程监测与控制装置,涉及智能处理单元、数据显示单元、保护单元、报警单元及数据传输单元。此装置可在地表远程监测井下通风机的运行状态,具有良好的稳定性,有效解决了跳闸不及时判断、巷道偏远、无法实时监测、维护不便、不易操作控制等问题 ;减少了人员投入,提高了工作效率,达到降本增效的目的。     

雷达式固体料位计在料位监测中的应用

雷达式固体料位计因不受粉尘、噪声的干扰而在物位测量中得到广泛应用。文章从VEGA雷达式固体料位计的工作原理出发,详细叙述其结构性能特点、仪表调试,探讨影响测量的干扰因素及日常故障处理方法等,为相关工程技术人员更好使用和维护雷达式固体料位计提供一定参考。     

Propagation of Waves and Dissolved Compounds in Sewer

The phenomenon of the surface wave propagating faster than the fluid that induced it is studied experimentally and numerically. The study focuses on the importance of the wave phenomenon for the urban hydrology system, where it can determine the impact of combined sewer overflows on the environment and the operation of a novel urine (anthropogenic nutrient solution) separation system. Urine would be stored decentrally and released during the night hours so that a wave would form in the sewer. The full-scale experiments were carried out in a 2-km section of a main sewer. The wave was induced with the aid of fire hydrant water traced by salt. Five measurements and sampling stations were operated downstream through which the transport of both fluid and compounds were analyzed. Numerical simulations of the results are discussed focusing on the reliability of friction approaches and dispersion prediction. Although difficult to model with commercial tools, it was shown that the wave phenomenon has no adverse effects on the practicability of the urine separation system, but can lead to the release of undiluted wastewater during a rain event.