The design of vegetative constructed wetlands for the treatment of highway runoff.

The Environment Agency for England and Wales are responsible for assessing the effects of highway runoff and for monitoring the treatment systems/procedures which have been introduced for the reduction of deleterious effects. The Agency is looking into the improvement of surface water management in terms of best management practices and plans to work in partnership with the Highways Agency to achieve this aim. Among the treatment options being considered are constructed wetlands. Draft Guidelines have been developed to provide information on their design. This paper describes procedures for carrying out an Environmental Sensitivity Analysis to determine whether treatment by a constructed wetland is appropriate. Information on water quality and quantity is required as well as the sensitivity of the receiving environment. The legislative position, particularly in relation to the discharge quality of the water and the conservation status of the receiving environment, needs also to be considered. The factors that will determine the most appropriate wetland design criteria include traffic loadings, road drainage area, land availability, cost and the size/extent and type of the receiving water body. The following structures are recommended for incorporation in the overall design; oil separator and silt trap, spillage containment, settlement pond, vegetative wetland and final settlement tank. The operation and maintenance procedures and the monitoring requirements for a functioning wetland are described.     

Monitoring pollutants in highway runoff

Highway surface runoff discharges may contain pollutants that have accumulated on the carriageway, particularly following periods of dry weather. The Highways Agency, in association with the Environment Agency, commissioned a 5‐year study in 1997 to collect data to improve the understanding of pollutants in highway runoff and the treatment efficiency of drainage systems. The study involved the monitoring of nonurban highway drainage at six sites, each for a minimum of 1 year. The results have been used to identify ranges of pollutant concentrations in highway runoff, relationships between runoff concentrations/loads and both highway and environmental factors, drainage system treatment efficiencies, and impacts on receiving waters. This paper describes the methods used for runoff monitoring, the results obtained to characterise pollutants in highway runoff, and the measured pollutant removal efficiency of a number of drainage system types.     

Research and Development in Methods of Soakaway Design

Soakaways have been a traditional method of disposal of stormwater for decades, and their usage has mainly been determined by the absence of a convenient watercourse, drain, or sewer into which to discharge runoff arising from roofs and paved surfaces. Today, soakaways are still being installed at a rate of tens of thousands per annum, despite the extensive storm-sewer systems in the UK. It is therefore surprising that little systematic research and development has been undertaken into their design and performance, or into the appropriate forms of maintenance to be conducted to extend operational life.
The paper briefly describes the recent research into, and design approaches for, the sizing of soakaways. An example is given of the use of Building Research Establishment Digest 365 to review alternative soakaway designs and to assess the cost implications. Some field data are reported which (a) illustrate the seasonal variability and difficulties of determination of the soil infiltration rate, and (b) provide some insight into the pollution issues from the use of soakaways.     

Modelling of recharge and pollutant fluxes to urban groundwaters

Urban groundwater resources are of considerable importance to the long-term viability of many cities world-wide, yet prediction of the quantity and quality of recharge is only rarely attempted at anything other than a very basic level. This paper describes the development of UGIf, a simple model written within a GIS, designed to provide estimates of spatially distributed recharge and recharge water quality in unconfined but covered aquifers. The following processes (with their calculation method indicated) are included: runoff and interception (curve number method); evapotranspiration (Penman-Grindley); interflow (empirical index approach); volatilization (Henry's law); sorption (distribution coefficient); and degradation (first order decay). The input data required are: meteorological data, landuse/cover map with event mean concentration attributes, geological maps with hydraulic and geochemical attributes, and topographic and water table elevation data in grid form. Standard outputs include distributions of: surface runoff, infiltration, potential recharge, ground level slope, interflow, actual recharge, pollutant fluxes in surface runoff, travel times of each pollutant through the unsaturated zone, and the pollutant fluxes and concentrations at the water table. The process of validation has commenced with a study of the Triassic Sandstone aquifer underlying Birmingham, UK. UGIf predicts a similar average recharge rate for the aquifer as previous groundwater flow modelling studies, but with significantly more spatial detail: in particular the results indicate that recharge through paved areas may be more important than previously thought. The results also highlight the need for more knowledge/data on the following: runoff estimation; interflow (including the effects of lateral flow and channelling on flow times and therefore chemistry); evapotranspiration in paved areas; the nature of unsaturated zone flow below paved areas; and the role of the pipe network. Although considerably more verification is needed, UGIf shows promise for use: in providing input for regional groundwater solute transport models; in identifying gaps in knowledge and data; in determining which processes are the most important influences on urban groundwater quantity and quality; in evaluating existing recharge models; in planning, for example in investigation of the effects of landuse or climate change; and in assessing groundwater vulnerability.     

Urban and semi‐urban planning in developing countries from a water and waste water treatment point of view

Several appropriate technology alternatives are suggested for water and wastewatei treatment in less developed countries. Large‐scale water supply systems employing conventional water treatment methods should be replaced by several small‐scale water treatment units utilizing appropriate water treatment methods.

Conventional sewerage systems should be replaced by low cost on‐site sanitation systems and several other low‐cost wastewater treatment methods such as oxidation ponds, aerated lagoons and anaerobic lagoons. Wastewater renovation and re‐use should be actively encouraged in view of dwindling water resources in these countries.     

Evaluation of a first‐flush capture and detention tank receiving runoff from an asphalt‐paved road

In this article, we propose and examine a first‐flush capture and detention tank (FCDT) working as a first flush capture device and pretreatment unit receiving stormwater runoff from an asphalt‐paved road. We design the FCDT to completely capture all the stormwater including a first flush generated by an initial 5 mm effective rainfall depth, and to bypass the exceeding part. According to our analysis based on the data from field monitoring and SWMM simulation for 27 events from April to June, 2015, the tank captured 35% of total runoff, which resulted in catching 74% of the TSS load. The TSS mass detention attained in this study by capturing the first 35% of the total runoff is close to the typical definition of a first flush, and also justifies the need for a first‐flush friendly treatment.     

In Situ Performance Monitoring of an Infiltration Drainage System and Field Testing of Current Design Procedures

Sustainable urban drainage systems offer a sustainable option for the disposal of stormwater runoff - reducing the risks of flooding and pollution of receiving watercourses. However, the adoption of such systems has been slow, with a lack of performance data identified as being one barrier. This paper presents in situ performance data from a perforated concrete ring soakaway which was installed to collect stormwater runoff from a school roof and paved area. Data on rainfall at the site and water depth in the soakaway were collected for a period of twenty months, and a number of rain events were studied in detail. Data from the soakaway were used to test the most recent design procedures for infiltration drainage systems, and it was found that the design equations gave reasonable predictions of system response to rainfall - especially when the observed runoff coefficients were taken into account.     

Characteristics of washed-off pollutants and dynamic EMCs in parking lots and bridges during a storm

Given the importance of water quality in drinking water sources, the Korean Ministry of Environment is designing and instigating the total maximum daily load (TMDL) program for major large rivers. For the successful implementation of this program, nonpoint pollutants resulting from various land uses should be controlled. Especially, paved areas such as parking lots and bridges are stormwater intensive land uses because of their high imperviousness and high pollutant mass emissions from vehicular activity. Vehicle emissions from these paved areas include various pollutants such as heavy metals, oil, grease and particulates. This research was conducted to investigate the magnitude and nature of the stormwater emissions with the goal of quantifying stormwater pollutant concentrations and mass emission rates from a parking lot and a bridge. Two monitoring sites in Kongju city were equipped with an automatic rainfall gauge and an automatic flow meter for measuring rainfall, water quality and runoff flow. This study presents the concentration changes during storm occurrence and event mean concentrations (EMCs) in the parking lot and bridge. The first flush criteria, a new concept explaining the relationship between EMC and the first flush effect, is also suggested using dynamic EMCs.     

Constructed wetlands for stormwater management in the UK: a concise review

The use of constructed wetlands (CWs) for stormwater management is growing due to the need for sustainable water use and to prevent damage to local watercourses caused by the pollutants collected and transported by runoff. However, despite their increased use around the world, there is a lack of information regarding the use of CWs for stormwater management in the UK. This study reviews the application of CW systems for stormwater management in the UK by examining the design, treatment performance and challenges associated with their use, while drawing comparisons with the rest of the world. The review indicates that although CWs have the potential for cost-effective and efficient stormwater management in the UK, there are several challenges that must be overcome to allow their widespread implementation. These include (i) a lack of design codes and unified guidelines; (ii) ambiguities regarding drainage responsibilities and land use issues and (iii) land availability.     

城市快速干道雨水收集处理系统设计

以1989年-2004年上海浦东地区的降雨资料和雨水径流特点为基础，参考国外高速公路雨水径流污染处理设施的设计，提出了采用弃流-沉淀-人工湿地组合工艺处理城市快速干道收集的雨水，将处理后的出水储存于清水池，用于道路浇洒和绿化灌溉。对沉淀池、人工湿地、清水池的设计方法和设计参数进行了讨论，使其在满足工程条件下，保证雨水的处理效果和可利用的水量。     

Modelling the fate of organic micropollutants in stormwater ponds

Urban water managers need to estimate the potential removal of organic micropollutants (MP) in stormwater treatment systems to support MP pollution control strategies. This study documents how the potential removal of organic MP in stormwater treatment systems can be quantified by using multimedia models. The fate of four different MP in a stormwater retention pond was simulated by applying two steady-state multimedia fate models (EPI Suite and SimpleBox) commonly applied in chemical risk assessment and a dynamic multimedia fate model (Stormwater Treatment Unit Model for Micro Pollutants — STUMP). The four simulated organic stormwater MP (iodopropynyl butylcarbamate — IPBC, benzene, glyphosate and pyrene) were selected according to their different urban sources and environmental fate. This ensures that the results can be extended to other relevant stormwater pollutants. All three models use substance inherent properties to calculate MP fate but differ in their ability to represent the small physical scale and high temporal variability of stormwater treatment systems. Therefore the three models generate different results. A Global Sensitivity Analysis (GSA) highlighted that settling/resuspension of particulate matter was the most sensitive process for the dynamic model. The uncertainty of the estimated MP fluxes can be reduced by calibrating the dynamic model against total suspended solids data. This reduction in uncertainty was more significant for the substances with strong tendency to sorb, i.e. glyphosate and pyrene and less significant for substances with a smaller tendency to sorb, i.e. IPBC and benzene. The results provide support to the elaboration of MP pollution control strategies by limiting the need for extensive and complex monitoring campaigns targeting the wide range of specific organic MP found in stormwater runoff.     

Flow cytometry and adenosine tri-phosphate analysis: alternative possibilities to evaluate major bacteriological changes in drinking water treatment and distribution systems

An ever-growing need exists for rapid, quantitative and meaningful methods to quantify and characterize the effect of different treatment steps on the microbiological processes and events that occur during drinking water treatment and distribution. Here we compared cultivation-independent flow cytometry (FCM) and adenosine tri-phosphate (ATP) analysis with conventional cultivation-based microbiological methods, on water samples from two full-scale treatment and distribution systems. The two systems consist of nearly identical treatment trains, but their raw water quality and pre-treatment differed significantly. All of the drinking water treatment processes affected the microbiological content of the water considerably, but once treated, the finished water remained remarkably stable throughout the distribution system. Both the FCM and ATP data were able to describe the microbiology of the systems accurately, providing meaningful process data when combined with other parameters such as dissolved organic carbon analysis. Importantly, the results highlighted a complimentary value of the two independent methods: while similar trends were mostly observed, variations in ATP-per-cell values between water samples were adequately explained by differences in the FCM fingerprints of the samples. This work demonstrates the value of alternative microbial methods for process/system control, optimization and routine monitoring of the general microbial quality of water during treatment and distribution.     

软基处理监测信息系统设计与实现

在软基处理施工中必须要做现场监测,内容包括淤泥表面沉降、分层沉降、水位计和孔隙水压力监测等。所获得的数据量大,提交的报告多。针对软基处理监测的实际情况,在深圳-香港西部通道填海及地基处理工程中开发了基于GIS的软基处理监测信息系统。该系统采用三层体系结构,主要功能包括GIS空间数据管理、统计成图和报告的自动生成,满足了现场监测工作的实际需要,具有较高的推广和实用价值。     

Aeromonads in Drinking-Water Supplies: Their Occurrence and Significance

Traditionally, bacteriological monitoring of drinking-water supplies has focused on the detection of Escherichia coli and related coliform bacteria. However, attention has recently been given to the occurrence of biofilms and associated organisms which occur in distribution systems. One group of bacteria which have been isolated from water supply systems are the Aeromonads. This group is gaining increased recognition as they have been implicated as causal agents of gastro-enteritis in humans and are indicators of regrowth potential. In order to obtain a better insight into these organisms and their relationship with other parameters, a number of laboratory and field-based studies were undertaken. These included (a) comparison of isolation media, (b) examination of biofilms, (c) temperature growth studies, (d) toxicity testing, and (e) sampling and analysis at treatment works and in distribution systems.     

Flood Generation Modelling

This paper summarizes recent research and development of a particular process-based runoff generation model, the Institute of Hydrology Distributed Model. Surface and subsurface flow equations are linked in a hydrologically appropriate system to allow simulation of catchment runoff processes. Predictions can be made of channel flow, surface runoff and subsurface flow, pressure potentials and water contents. The structure and methods of the model are described and its data and computing requirements are outlined. Field and systematic applications are discussed, together with the work carried out on providing guidelines for use for the wider hydrological community.     

Understanding data requirements for trihalomethane formation modelling in water supply systems

Tighter regulatory standards for trihalomethanes in drinking water have been introduced in many countries in response to improved epidemiological evidence. This has led to the need to model better the THM concentrations in water distribution systems in order to manage efficiently economic, chemical and microbiological factors. THM modelling is a challenging process given the complex chemistry and dependence on river catchment, water treatment works and distribution system characteristics. It is demonstrated that a good understanding of the system from raw water to tap is needed if cost effective models of appropriate fidelity are to be produced. For appropriate systems models can incorporate, through empirical relationships, raw water quality variations based on river flow predictions, aspects of unit process management decision making variables as well as distribution system characteristics. In many systems model fidelity and hence efficient management is constrained by a lack of knowledge of system response.     

Setting Effluent Consent Standards

The paper outlines how consent standards are normally calculated in Scotland for both river systems and tidal waters. A background is given to the reason why a more statistical approach has been adopted in England and Wales where the use of combining distribution methods is more widespread. Comparison of the two approaches is made, particularly with regard to their potential impact on resources required for treatment plants, and also the problems of taking enforcement action. The setting of standards under the EC urban waste water treatment Directive is considered where, in addition to the implications of primary, secondary and more stringent treatment, consideration is given to storm-sewage overflows and industrial discharges.     

Pollution loads in urban runoff and sanitary wastewater

While more attention has been paid in recent years to urban point source pollution control through the establishment of wastewater treatment plants in many developing countries, no considerable planning nor any serious measures have been taken to control urban non-point source pollution (urban stormwater runoff). The present study is a screening analysis to investigate the pollution loads in urban runoff compared to point source loads as a first prerequisite for planning and management of receiving water quality. To compare pollutant loads from point and non-point urban sources, the pollutant load is expressed as the weight of pollutant per hectare area per year (kg/ha.year). Unit loads were estimated in stormwater runoff, raw sanitary wastewater and secondary treatment effluents in Isfahan, Iran. Results indicate that the annual pollution load in urban runoff is lower than the annual pollution load in sanitary wastewater in areas with low precipitation but it is higher in areas with high precipitation. Two options, namely, advanced treatment (in lieu of secondary treatment) of sanitary wastewater and urban runoff quality control systems (such as detention ponds) were investigated as controlling systems for pollution discharges into receiving waters. The results revealed that for Isfahan, as a low precipitation urban area, advanced treatment is a more suitable option, but for high precipitation urban areas, urban surface runoff quality control installations were more effective for suspended solids and oxygen-demanding matter controls, and that advanced treatment is the more effective option for nutrient control.     

Diffuse and point pollution impacts on the pathogen indicator organism level in the Geum River, Korea

The pathogens originating from diffuse pollution have raised much concern recently. In many countries, pathogen levels are monitored in surface water by measuring the pathogen indicator organism level, which indicates the concentration of pathogen associated microorganisms to determine contamination. Among indicator organisms, total coliform, fecal coliform, and Escherichia coli were selected for study, and their concentration as well as their flow rate were monitored at monitoring stations from October, 2001 to April, 2003. Monitoring stations include six sampling stations in the Geum River, two small watersheds used for forestry and agricultural land, one large wastewater treatment plant, one separate sewer overflow site, and one separate sewer overflow site in the Geum River basin. The coliform concentration of the combined sewer overflow was the highest, followed by the runoff from agricultural land use, the separate sewer overflow, and the runoff from forestry land use. The Pearson correlation coefficient for flow rate against total coliform concentration was 0.71 and was significant at 0.01 level, while the Pearson coefficient for other water quality constituents showed weak correlation (-0.36 to +0.37) against flow rate. Coliform concentration showed higher correlation against suspended solid concentration or flow rate during storm flow condition than during low flow condition. Two different relationship lines could explain the relationships between the flow rate and coliform loadings. Load duration curve technique was presented to assess the relative contributions of diffuse and point source pollution to the pathogen level at monitoring sites in the Geum River.