合流制管道溢流污染的特征与控制研究进展

综述了国内外合流制管道溢流污染特征与控制的研究进展,总结了合流制管道溢流废水的污染物来源、水质水量关系和水环境影响特征,分析了影响合流制管道溢流污染特征的影响因素、常用合流制管道溢流污染控制措施,以及旋流分离、沉淀等末端控制技术的研究进展;指出管道沉积物的沉积、冲刷、污染释放监测与管道、截流井和排口净化技术的工艺组合,是控制我国合流制管道溢流污染的关键技术节点。     

雨污兼合的排水系统体制探讨

城市排水系统体制的选择,无论对于城市新区建设还是对于旧城改造,都是个现实问题。分析了雨污分流实施的困难、问题和原因,探索了雨污兼合系统。结合实际情况、当地自然条件、受纳水体环境要求和现有设施情况、资金因素、管理水平、动态发展等因素,实事求是,科学地确定无锡市排水体制。雨污兼合系统是防洪与排水相结合、市政排水与建筑排水相衔接、污水与雨水有机统一的较经济、现实的排水系统。     

The performance of a novel combined sewer overflow with perforated conical screen

Increasing concern over the discharge of sewer solids from combined sewer overflows (CSOs) has encouraged the introduction of installations which incorporate either mesh or bar screen arrangements, or both. Gross solids create visual and aesthetic pollution if they reach watercourses. An entirely new arrangement for a CSO with a perforated screen of 6 mm diameter apertures is described in the paper. The arrangement is circular, with tangential flow across the screen to facilitate its cleaning. High velocities across the screen holes ensure that solids which have been prevented from discharging are swept clear from the screen. As a result, a sufficient screen area remains free from trapped solids to permit discharge of flow. The device has been designed to meet all anticipated performance criteria for the removal of solids, and to require a minimum of maintenance.A thorough testing programme in different conditions is described. Laboratory testing utilised a wide range of gross solids and flows to determine efficiencies of solids removal under all anticipated operating conditions. The performance of the CSO in a sewer environment was evaluated at a sewage treatment works with flows up to 1801/s using both raw and treated sewage to simulate storm sewage of different strengths. Both the device and its testing are described, together with the results of the testing programme.     

Numerical simulation of domestic wastewater sewer performance

The hydraulics of municipal sewers were considered with respect to flow rate fluctuations that sometimes cause accumulation and sometimes cause scouring of the sediments. The minimal slopes that would ensure self‐cleaning conditions once a day and the required capacity for the yearly maximum peak flows were calculated. The range of fluctuations in shear stresses along the sewer walls and in the wastewater table were observed and compared for sewers of different diameters. From these computations a simple design rule for predicting minimal slopes was developed.     

银川市某高密度城区合流制溢流污染特性研究

针对合流制管网系统溢流污染严重且易造成受纳水体出现黑臭现象等问题,以银川市第一污水处理厂片区为例,基于雨洪管理模型(SWMM),在短历时设计降雨和典型年长历时降雨条件下,模拟分析了研究区域溢流排口溢流量及溢流污染物负荷对不同降雨条件的响应关系及其对受纳水体水质的影响。结果表明：雨天合流制管网系统的溢流量及溢流污染负荷量较大,且无论是短历时还是长历时降雨条件下,均具有随着降雨量的增加而增大的特点;厂前溢流污染浓度大,超过受纳水体自净能力,短期内水体水质处于黑臭状态。本研究对银川市黑臭水体治理及溢流污染防治方案的制订具有重要的参考价值。     

A software-based sensor for combined sewer overflows

A new methodology for online estimation of excess flow from combined sewer overflow (CSO) structures based on simulation models is presented. If sufficient flow and water level data from the sewer system is available, no rainfall data are needed to run the model. An inverse rainfall-runoff model was developed to simulate net rainfall based on flow and water level data. Excess flow at all CSO structures in a catchment can then be simulated with a rainfall-runoff model. The method is applied to a case study and results show that the inverse rainfall-runoff model can be used instead of missing rain gauges. Online operation is ensured by software providing an interface to the SCADA-system of the operator and controlling the model. A water quality model could be included to simulate also pollutant concentrations in the excess flow.     

Solids separation efficiency of combined sewer overflows.

The removal of sewer solids at combined sewer overflow locations depends on the flow patterns inside the overflow structure on the one hand and on the sediment characteristics on the other hand. Flow conditions can be described by the residence time distribution; sewer sediments can be characterised by their settling velocity distribution. The combination of both distributions leads to a dimensionless efficiency curve, which gives the removal efficiency as a function of the Hazen number. For field conditions this efficiency curve is mainly influenced by the settling velocity distribution of the sewer sediments and, as a consequence, nearly identical efficiency curves are found for different types of prototype CSO structure. For design purposes, a methodology using return frequency analysis is proposed.     

合流制溢流控制指标与标准制定研究

合流制溢流(combined sewer overflow,CSO)控制是城市水环境质量改善的关键一环,相关指标及标准制定尚显薄弱.基于技术的排放控制指标主要包括溢流频次、溢流体积控制率、污染物排放浓度限值、CSO效率及稀释度等,因这些指标缺乏对CSO水质水量控制效果的综合评价,进而提出雨季CSO污染负荷占比的指标;基...     

Advanced real time control of a combined sewer system

The research project ‘Real Time Control of a Combined Sewer System by Radar estimates of Precipitation’ seeks to improve the water quality of a stream by reducing quantitative and qualitative discharges of combined sewage overflow (CSO). The complex monitoring and simulation system that has been set up for control purposes is described. Two advanced real time control (ARTC) strategies have been developed. First a pollution based real time control (PBRTC) strategy, and second a water quality based real time control (WQBRTC) strategy. The PBRTC strategy is already implemented, the WQBRTC strategy will be implemented during the course of the project. For the PBRTC an off-line analysis is presented to show the effectiveness of the strategy.     

Hydraulic performance of sewer pipes with deposited sediments.

This paper investigates in-sewer sediment deposit behaviour and its influence on the hydraulic performance of sewer pipes. This evaluation is based on experimental results regarding the mobility of non-cohesive and partly cohesive deposits in a partially full circular pipe. The focus of these tests is on the development of bed forms and friction characteristics. In particular, it is investigated to what extent the bed forms from the non-cohesive and (partly) cohesive sediments affect a sewer's discharge capacity. Based on the laboratory study results and on the existing criteria for sewer design, a generic assessment of a sewer's hydraulic performance is made. The relative discharge factor for a pipe with sediment deposit is analysed in terms of the thickness and roughness of the deposit.     

合流制溢流污染控制系统决策

合流制溢流(CSO)污染控制以削减溢流进入受纳水体的污染物总量为目标。由于合流制排水系统的复杂性以及污染物传输、溢流过程的随机性和多变性,CSO污染控制涉及一系列错综复杂的理论与工程实际问题,因而需要进行科学的系统决策,以降低投资、提高效益。首先分析我国城市CSO污染控制存在的主要问题;再从解析合流制及其溢流污染控制系统的组成关系入手,从宏观、系统的角度分析CSO污染的产生与传输过程,构建CSO污染控制系统,并对几个主要子系统进行分析;最后提出CSO污染的系统控制原理,探讨子系统的合理衔接、匹配和控制方案的优化选择问题,为我国城市CSO污染控制提供一个清晰的思路。     

污水管道中检查井通风特性模拟研究

检查井内跌水对污水管道中气体流动具有显著的促进作用。利用CFD对检查井跌水进行计算,将等效通风机特性曲线与管道阻力曲线联立,评价污水管道内的通风状况。研究表明,目前常见井盖开孔比较小,增加开启孔开口面积能显著增加下游管道安全长度,但是如果大到一定程度,继续增加开孔比对控制管道内甲烷气体浓度的效果并不显著。对于跌水高度为0.9m、井盖开孔比为0.125%和0.5%检查井,当污水管道管径为DN600时,由跌水通风确保的下游污水管道安全长度分别为164m和465m;当污水管道管径为DN800时,分别为246m和626m;当污水管道管径为DN1 000时,分别为327m和810m。     

Evaluation of total emissions from treatment plants and combined sewer overflows

Based upon the connection of a simulation program for combined sewer systems with the IAWQ-Activated Sludge Model No.l the new simulation tool GEMINI was developed, which allows the calculation of sewer and sewage treatment plant as a unit. Some obtained results are presented in an example. They suggest, that for every treatment plant a rate of inflow is determinable, which leads to a minimum of total emissions out of sewer and treatment plant. The optimal value of sewage treatment plant inflow in the example is distinctly greater than the design flow rate fixed in German design rules. So it is recognizable that a rigid flow management for sewer and treatment plant does not always fulfil the aim of minimization of total emissions.     

截流式合流制排水管网设计新思路

提出了一种以溢流井为分界线,将截流式合流制排水管网分解为一系列小型完全合流制排水管网的设计新思路,并以管网关联矩阵和节点连接特性矩阵为基础,以节点平衡原理和节点递归算法为核心,实现完全合流制排水管网的流量计算和水力计算.该方法能有效减小管网计算模型的规模,降低程序设计难度,提高程序的实用性.     

A new database on urban runoff pollution: comparison of separate and combined sewer systems.

For a long time people have questioned what the "best" sewer system is for limiting the pollution load released into the receiving waters. In this paper the traditional separate and combined sewer systems are compared using a pollution load balance. The investigation is based on measured concentration data for a range of pollutant parameters in the sewer from the new database "ATV-DVWK Datenpool 2001". The approach also accounted for the wastewater treatment plant outflow which contributes to the total pollutant load considerably. In spite of a number of neglected effects, the results show that the separate system is superior to the combined for some parameters only, such as nutrients, whereas for other parameters, e.g. heavy metals and COD, the combined system yields less total loads. Any uncritical preference of the separate system as a particularly advantageous solution is thus questionable. Individual investigations case by case are recommended.     

Probabilistic modelling of combined sewer overflow using the First Order Reliability Method.

This paper presents a new and alternative method (in the context of urban drainage) for probabilistic hydrodynamical analysis of drainage systems in general and especially prediction of combined sewer overflow. Using a probabilistic shell it is possible to implement both input and parameter uncertainties on an application of the commercial urban drainage model MOUSE combined with the probabilistic First Order Reliability Method (FORM). Applying statistical characteristics on several years of rainfall, it is possible to derive a parameterization of the rainfall input and the failure probability and return period of combined sewer overflow to receiving waters can be found.     

An elutriation apparatus for assessing settleability of combined sewer overflows (CSOs).

An elutriation apparatus was proposed for testing the settleability of combined sewer outflows (CSOs) and applied to 12 CSO samples. In this apparatus, solids settling is measured under dynamic conditions created by flow through a series of settling chambers of varying diameters and upward flow velocities. Such a procedure reproduces better turbulent settling in CSO tanks than the conventional settling columns, and facilitates testing coagulant additions under dynamic conditions. Among the limitations, one could name the relatively large size of the apparatus and samples (60 L), and inadequate handling of floatables. Settleability results obtained for the elutriation apparatus and a conventional settling column indicate large inter-event variation in CSO settleability. Under such circumstances, settling tanks need to be designed for "average" conditions and, within some limits, the differences in test results produced by various settleability testing apparatuses and procedures may be acceptable. Further development of the elutriation apparatus is under way, focusing on reducing flow velocities in the tubing connecting settling chambers and reducing the number of settling chambers employed. The first measure would reduce the risk of floc breakage in the connecting tubing and the second one would reduce the required sample size.     

Size fractionation of COD in urban wastewater from a combined sewer system.

The objective of this work was to determine the partitioning of the pollutant load in urban wastewater in order to improve the conventional sewage treatment. In addition to settling tests, physical fractionation of COD in the degritted influent of Roma-Nord sewage treatment plant was performed via sequential filtration through sieves and membrane filters of the following pore size: 150-100-50-25-1-0.2 microm, and 100 kD (about 0.02 microm). Biodegradability studies were also performed on the different size fractions. Size fractionation showed that COD in Roma-Nord sewage is predominantly associated with settleable and supracolloidal (> 1 microm) particles, each size range including about 40% of total COD. Biodegradability tests indicated that the large fraction of COD associated with supracolloidal particles, which are not removed in the primary treatment, is characterised by slow degradability. This suggests that removal of these particles prior to biological treatment may greatly improve the overall treatment scheme. Preliminary pilot plant coagulation tests with lime at pH 9 showed that lime-enhanced primary treatment may increase COD removal efficiencies from typical 30-35% up to 65-70%, by inducing almost complete removal of the COD fraction associated with supracolloidal particles.     

Possibility of sewage and combined sewer overflow reuse with biological aerated filters.

The secondary effluent from municipal plants in Korea generally represents higher BOD with lower SS. Therefore, more soluble forms of organics and NH4-N need to be removed to improve its effluent for reuse. In this study reuse possibility of secondary effluent and CSO (combined sewer overflow) using BAF (biological aerated filter) was evaluated. The tertiary application with 1.2 h EBCT, SS, BOD and COD showed stable concentrations less than 1.3, 1.3 and 6.2 mg/L, respectively. Nitrogen could be nitrified even at 7 degrees suggesting BAF can be used for a water reuse method as well as an effective add-on facility in cold regions. However, BAF was not stable with CSO application at increased flow rates suggesting CSO must be equalised prior to application. Disinfection was necessary even during normal weather conditions.