A case study of urban water balancing in the partly sewered city of Nablus-East (Palestine) to study wastewater pollution loads and groundwater pollution

Untreated sewage can contribute a significant proportion of urban groundwater recharge, via on-site sanitation facilities and sewer exfiltration. In the West Bank of the Palestinian Territories 94% of sewage is discharged untreated to the ground or surface waters. This has contributed to increasing nitrate concentrations in groundwater, which is the critical water source. In this case study of a drainage catchment from the city of Nablus, a water balance indicates that sewage as a source of groundwater recharge is as much as 50% of total recharge from precipitation, and nitrogen pollutant loads by area are up to 60% as much as those from agriculture. Results suggest that 22% of total wastewater flow directly infiltrates the ground via cesspits and sewer exfiltration.     

Impacts of Sewers on Groundwater Quality

This paper summarizes the findings of a recent research project on groundwater contamination from leaking sewers, which was completed for the Construction Industry Research and Information Association. Fifty-four incidents were identified in England and Wales from a combined questionnaire survey and literature review. In addition to recorded incidents, the poor quality of many urban groundwaters suggests some effects from leaking sewers. Age is considered to be the most significant characteristic governing leakage from sewers; ground conditions (predominantly aquifer vulnerability) and usage (private versus public ownership) are also important factors relating to the likelihood of groundwater pollution from leaking sewers. Recommended strategies for reducing groundwater contamination include (a) modification of existing criteria for the service performance grading of existing sewers, (b) improved construction of new sewers in appropriate areas, (c) increased groundwater monitoring, and (d) risk assessments for new groundwater sources.     

Excluding Groundwater Infiltration into New Sewers

Much attention has been focused on the need for sewer renovation and rehabilitation of old sewerage systems, but age is not always the reason for sewer failure. Serious problems of performance have also been encountered on sewerage schemes less than 10 years old. This paper considers the problems of groundwater infiltration into new foul sewers, and suggests that deficiencies might exist in some aspects of modern sewer design and construction.
Infiltration is most frequently observed at sewer joints. Results are presented of laboratory tests which show the ability of flexible fixed-ring joints on clay sewers to withstand both internal and external pressures. Damaged polyester fairings on the spigots of these pipes can act as one-way valves, and massive infiltration may result. The standard site water test is shown to be inadequate in detecting some of these types of defect which may result from damaged pipes or poor workmanship.     

Integrated Monitoring and Modelling of Odours in Sewerage Systems

The parameters of sewage that affect the production and resulting concentration of hydrogen sulphide in both liquid and gas phases have been monitored in a sewerage system. The data have been used to develop a model of the chemical and physical processes leading to sulphide production in sewers, so that the sources and causes of the problem can be identified. This model has been adapted to predict the concentrations of hydrogen sulphide that can be expected in the sewage and sewer atmosphere, following the construction of a major interceptor tunnel.     

Towards the determination of an optimal scale for stormwater quality management: Micropollutants in a small residential catchment

Stormwater and atmospheric deposits were collected on a small residential urban catchment (0.8 ha) near Paris in order to determine the levels of certain micropollutants (using a preliminary scan of 69 contaminants, followed by a more detailed quantification of PAHs, PCBs, alkylphenols and metals). Atmospheric inputs accounted for only 10%–38% of the stormwater contamination (except for PCBs), thus indicating substantial release within the catchment. On this small upstream catchment however, stormwater contamination is significantly lower than that observed downstream in storm sewers on larger adjacent urban catchments with similar land uses. These results likely stem from cross-contamination activity during transfers inside the sewer system and underscore the advantages of runoff management strategies at the source for controlling stormwater pollutant loads. Moreover, it has been shown that both contamination levels and contaminant speciation evolve with the scale of the catchment, in correlation with a large fraction of dissolved contaminants in upstream runoff, which differs from what has been traditionally assumed for stormwater. Consequently, the choice of treatment device/protocol must be adapted to the management scale as well as to the targeted type of contaminant.     

山区排水管道的设计流速探讨

我国《室外排水设计规范》规定室外金属排水管道最大设计流速为10m／s，非金属管道为5m／s，然而在实际工程中可以找到一些超过这个规定并且运行良好的工程实例，为此对该规定进行了探讨，并在调研分析的基础上建议提高室外排水管道最大设计流速。     

TOXICITY TESTING OF GROUNDWATER QUALITY

Groundwater is an important resource in the UK, with 45% of public water supplies in the Thames Water region derived from subterranean sources. In urban areas, groundwater has been affected by anthropogenic activities over a long period of time and from a multitude of sources. At present, groundwater quality is assessed using a range of chemical species to determine the extent of contamination. However, analysing a complex mixture of chemicals is time-consuming and expensive, whereas the use of an ecotoxicity test provides information on (a) the degree of pollution present in the groundwater and (b) the potential effect of that pollution. Microtox^TM, Eclox^TM and Daphnia magna microtests were used in conjunction with standard chemical protocols to assess the contamination of groundwaters from sites throughout the London Borough of Hounslow and nearby Heathrow Airport. Because of their precision, range of responses and ease of use, Daphnia magna and Microtox^TM tests are the bioassays that appear to be most effective for assessing groundwater toxicity. However, neither test is ideal because it is also essential to monitor water hardness. Eclox^TM does not appear to be suitable for use in groundwater-quality assessment in this area, because it is adversely affected by high total dissolved solids and electrical conductivity.     

FCKW als Tracer für die Ausbreitung von Altablagerungsemissionen im Grundwasser

Emissions from abandoned waste disposal sites into groundwater are difficult to trace further downstream because of their complexity. Typical tracers, for example, like chloride, boron and sulphate are likely to be influenced by several factors like saline waters, emissions from seepage pits and leaky sewers. These types of components are therefore not suitable to characterise groundwater contamination caused by abandoned waste disposal sites; they will thus not be further discussed in this paper. However, due to their special geochemical properties like negligible absorption and degradation rates, chlorinated fluorocarbons, especially difluoro-dichloromethane (F12), which are frequently emitted from abandoned waste disposal sites, are particularly suitable for the detection of maximum contaminant emissions to groundwater. These elements are crucial for the assessment of groundwater contamination and the employment of natural attenuation as a remediation measure.     

从余姚市排水规划的编制谈规划的可操作性

介绍了余姚市城区污水收集系统规划的编制情况，提出在规划编制过程中应充分考虑排水现状、城市规划情况、道路及管道建设时序等，以使规划做到近、远期结合，具有较强的可操作性。     

Methane formation in sewer systems

Methane formation and emission in sewer systems has not received as much attention as hydrogen sulphide formation. Through field measurements from two rising mains, with an average sewage temperature of 28.4 and 26.6 degrees C, respectively, at the time of sampling, this study shows that a significant amount of methane can be produced in sewer systems, and that this production is positively correlated with the hydraulic retention time of wastewater in these systems. The experimental results from a laboratory-scale sewer system fed with real sewage with a temperature of approximately 21 degrees C confirmed these field observations and further revealed that methanogenesis and sulphate reduction occur simultaneously in sewers, with methane production contributing considerably more to the loss of soluble COD in sewers than sulphate reduction. The production of methane in sewers at levels revealed by this study is a serious environmental concern as it potentially results in greenhouse emissions that is comparable to that caused by the energy consumption for the treatment of the same wastewater. Further, methane production in sewers influences sulphide production and its management due to the competition between methanogens and sulphate-reducing bacteria for potentially the same electron donors. The potential interactions between sulphate-reducing and methanogenic bacteria in sewer networks are discussed.     

Xenobiotics in groundwater and surface water of the city of Leipzig

Xenobiotics are increasingly being considered as ecotoxicologically relevant for the aquatic environment and human health. Their behaviour and the effects on the environment have not yet been comprehensively investigated and, therefore, are currently the subject of the project WASSER Leipzig initiated by the UFZ. The results of this article are based on groundwater and surface water analyses of a watershed within the town of Leipzig. Here the industrial chemicals bisphenol-A and t-nonylphenol, the polycyclic fragrances galaxolide and tonalide, the antiepileptic drug carbamacepine and caffeine where investigated. Xenobiotics showed ubiquitous occurrence in the rivers, which were contaminated from treated and untreated sewage, as well as in groundwater, contaminated by leaky sewers. Mean concentrations up to several hundred ng/l were found in the rivers, while groundwater concentrations, except for bisphenol-A, tended to be lower. Applying the statistical factor analysis on the hydrochemical measurements, a differentiation of the xenobiotics with regard to their hydrochemical behaviour in groundwater was performed.     

Microbial contamination of two urban sandstone aquifers in the UK

Development of urban groundwater has historically been constrained by concerns about its quality. Rising urban water tables and overabstraction from rural aquifers in the UK have led to a renewed interest in urban groundwater, particularly the possibility of finding water of acceptable quality at depth. This study assessed the microbial quality of groundwater collected from depth-specific intervals over a 15-month period within the Permo-Triassic Sherwood Sandstone aquifers underlying the cities of Nottingham and Birmingham. Sewage-derived bacteria (thermotolerant coliforms, faecal streptococci and sulphite-reducing clostridia) and viruses (enteroviruses, Norwalk-like viruses, coliphage) were regularly detected to depths of 60 m in the unconfined sandstone and to a depth of 91 m in the confined sandstone. Microbial concentrations varied temporally and spatially but increased frequency of contamination with depth coincided with geological heterogeneities such as fissures and mudstone bands. Significantly, detection of Norwalk-like viruses and Coxsackievirus B4 in groundwater corresponded with seasonal variations in virus discharge to the sewer system. The observation of low levels of sewage-derived microbial contaminants at depth in the Triassic Sandstone aquifer is explained by the movement of infinitesimal proportions of bulk (macroscopic) groundwater flow along preferential pathways (e.g., fissures, bedding planes). The existence of very high microbial populations at source (raw sewage) and their extremely low detection limits at the receptor (multilevel piezometer) enable these statistically extreme (microscopic) flows to be traced. Rapid penetration of microbial contaminants into sandstone aquifers, not previously reported, highlights the vulnerability of sandstone aquifers to microbial contamination.     

Exfiltration in sanitary sewer systems in the US

Many municipalities throughout the US have sewer systems (separate and combined) that may experience exfiltration of untreated wastewater. A study was conducted by the US Environmental Protection Agency (USEPA) to focus on estimating the magnitude of leakage of sanitary and industrial wastewater from sewer pipes on a national basis. The method for estimating exfiltration amounts utilized groundwater table information to identify areas of the country where the hydraulic gradients of the wastewater are typically positive, i.e. the wastewater flow surface (within pipelines) is above the groundwater table. An examination of groundwater table elevations on a national basis reveals that the contiguous US comprises groundwater regions (established by the US Geological Survey) that are markedly different. Many parts of the northeastern, southeastern, and midwestern US have groundwater tables that are higher than the wastewater flow surface, resulting in inflow or infiltration. Conversely, the combination of a relatively low groundwater table and shallow sewer systems creates the potential for widespread exfiltration, a situation more commonly found in communities located in the western US.     

Additional Pollutants and Deposition Potential from Garbage Disposers

The objectives of this study were to (a) characterise the quantity and quality of crude sewage, as might be influenced by the use of domestic garbage disposers, and (b) examine the deposition potential of wastewater solids in gravitational sewerage systems.
Ground particles of organic origin require relatively low self-cleansing velocities, and therefore conform with the usual design recommendations of gravitational sewers, with no expected deposition problems. However, 'heavy'particles which are characterised by specific densities exceeding 2 and with sizes >1 mm, might cause deposition and associated problems. Where sewers are manufactured from smooth material, calculations indicate that higher scouring velocities than those recommended in the literature are required. Minimising the size of ground material by regulating the particle-size distribution produced by approved garbage disposers should mitigate the problem which is caused by deposition.     

A Gradual Rehabilitation Programme for Combined Sewerage Systems

The Kannai-Yamashita district, which is Yokohama's administrative and economic heart, was the first part of the city to be installed with a modern sewerage system. This district is served by combined sewers, many of which have extensive pipe deterioration, shallow covering, and insufficient capacity. Whilst rehabilitation of these sewers has therefore been an urgent priority, flood alleviation has been given even greater precedence.
It was consequently decided (a) to construct supplementary storm trunk sewers and a stormwater pumping station to mitigate flooding, and (b) to implement a systematic rehabilitation of the sewers on a gradual basis. Studies of branch sewer rehabilitation also used a surcharge model in the interest of achieving an economical and efficient design.     

太湖流域城镇污水规划对策研究——以浙江省长兴县为例

通过对太湖流域城镇特点和长兴县污水规划实例的剖析,重点分析了现状污水系统中存在的主要问题,对污水规划预测指标、老城区合流污水的截留管道建设、污水厂的建设原则、污水回用和运行管理模式等问题提出了规划建议。     

上海市旧住宅小区雨污分流改造效果评价

以上海市两个典型旧住宅区为研究对象,通过对已实施和未实施分流改造小区雨水管道的混接率和旱流水质监测结果的对比,评价了实施小区内部雨、污水管道清理和分流改造措施的效果,为提高城区面源污染控制决策水平提供了依据.     

A new development in locating leaks in sanitary sewers

A new method called focused electrode leak location system (FELL-41) was developed in Europe for identifying potential leaks in sanitary sewers (mainline and service connections at the mainline). The chief advantages of the FELL-41 technology include: (1) identifying leaking joints on mainline during dry weather; (2) prioritising leak repairs by intensity of leaks; (3) determining leaks in service lateral mainline connections; (4) an alternative to air-pressure testing for acceptance of new and rehabilitated sanitary sewers. The FELL-41 method measures electrical current flow between a probe that travels in the pipe and a surface electrode. Pipe defects that allow liquids to flow into or out of the pipe cause a spike in the electrical signal, thereby locating the sources of infiltration or exfiltration. The intensity of the measured current can be correlated to the magnitude of the leaks. The purpose of this paper is to discuss this technology as well as its limitations. The results of the FELL-41 technology will be validated through several case studies.     

下水道中不明水的调查及防治对策

城市下水道中的实际污水量往往超过汇入的污水与雨水量之和，在地下水位高的地区或雨水充沛的汛期这种现象尤为突出。超出的部分在日本被称为不明水量，其主要来源于地下水和雨水的渗入。不明水不仅会造成检查井溢水，还增加了污水处理厂的负荷和运行成本。通过对日本某市下水道的实地调查，就合流制管道中来源不明的水进行了定量分析，并提出了相应的防治对策。     

Estimation of sewer leakage to urban groundwater using depth-specific hydrochemistry

The contribution of sewer leakage to urban groundwater recharge remains poorly characterised. There has been a tendency to focus on estimating leakage from pipe network characteristics rather than its impact on the receiving environment. Indeed, pipeline leakage simulation models are frequently used to analyse sewage systems and optimise maintenance efforts. Here a mass balance approach employing groundwater geochemistry is presented to estimate sewer leakage rates; this is done using depth-specific groundwater quality measurements from multilevel monitoring piezometers, specially installed in the Sherwood Sandstone aquifer underlying Doncaster (UK). The results show that leakage rates from the foul sewage system are up to 10% of flow per annum (30–40% of urban recharge) and highlight the utility of groundwater quality monitoring (in particular depth-specific sampling) as an alternative means to assess sewage ingress to urban groundwater.