The real issues with in-ground SUDS in Scotland

The aim of this research was to produce enhanced detailing and improved operation of in-ground SUDS. Data from on-site monitoring at three filter drain and three infiltration trench systems were analysed and the results were combined with information gathered from 40 assessments of in-situ systems in Eastern Scotland. Current findings showed that almost 50% of all systems were found to be unsatisfactory and more than half of these were rated as having failed. 36% provided fair and 16%, good performance. Only one system was considered to be performing excellently. Several reasons were identified for the poor performance. The principal cause of problems was runoff from unstabilised areas or construction runoff, which was found to be affecting the systems’ longevity. Almost 30% of all sites were affected by construction runoff. Another major problem was related to system maintenance since maintenance programs were generally not in place. This study has shown that regular maintenance is vital for the longevity of in-ground SUDS

An assessment of the cost effectiveness of vegetation harvesting as a means of removing nutrient and metals from ponds

This paper reports on an investigation to quantify the mass of pollutants removed from a stormwater retention pond by routine vegetation harvesting. The amount of plants can increase the costs of ponds, and the increased costs of plant maintenance may not be justified by enhanced pollutant removal. This study provides some of the basic information, previously lacking, which is needed to come to such decisions. The study facility was La Costa pond, a retention pond in California used to treat highway runoff. Water quality monitoring data indicate that the pond removed 43 percent of the total nitrogen entering the facility, with 5 to 7 percent directly attributable to harvesting the vegetation – in this case cattails (Typha). The data also indicate that 48 percent of the total annual phosphorus was removed from the runoff, with the harvested vegetation responsible for between 3 and 8 percent. Metal uptake by the vegetation was substantially less than nutrients. Total removal of copper, lead and zinc by the pond varied between 57 and 93 percent, with the harvested vegetation accounting for less than 2 percent of removal. Issues addressed in the paper include the cost implications of harvesting and ways of improving vegetative pollutant removal

The social impacts of stormwater management techniques

This paper presents the results of research into the social impacts of stormwater management techniques applied within urban environments. The main aim of the study was to compare public and professional attitudes of stormwater management practices such as Sustainable Urban Drainage Systems (SUDS) and river management techniques. Any new and innovative technology used in residential areas, besides being economically and environmentally acceptable, must also be accepted by the residents. There has been considerable interest in the assessment of the public perception of SUDS in the UK by consultants, developers, the Environment Agency of England and Wales as well as by the Scottish Environment Protection Agency (SEPA). This research was undertaken to inform such interest and also to obtain a more holistic view of the perception by professionals of SUDS. A comparative study of the perceptions of river management in three densely populated European cities facing similar storm water management problems was carried out. The selected cities were Glasgow in Scotland – U. K., an area in west London, England - U.K., and part of Athens – Greece. All sites were located within flood-prone suburban areas, and different river management techniques have been proposed or adopted

A water vision for Johnstone

The Water Vision is based on ideas from The Netherlands which promote communication with the public on key water related issues in a local authority area. A Water Vision for Johnstone was developed in Renfrewshire, Scotland where serious flooding has occurred in the past and new, predominantly non-structural approaches to surface water management were demanded. The paper outlines the development of a ‘Water Vision for Johnstone’ which became a key outcome of the Interreg III B project ‘Urban Water’.The Water Toets (Assessments) are statutory procedures in the Netherlands which come into play from the concept stage of developments onwards to full implementation. They are undertaken jointly on behalf of the spatial planning authority and the water authorities to evaluate the impact of development on the water network. In contrast, the Water Vision is a less well-defined process to identify community needs and aspirations but in many areas the vision is essential to support the Water Toets. The Water Vision is initiated by planning officers from the municipalities asking very basic questions of their communities about what they required of the water network. It was felt that adopting such a proactive approach where virtually any question about water bodies and drainage infrastructure could be asked, would not be practicable in the UK and it was decided to assemble information about water issues in the area, the agencies involved and potential ways forward, before approaching the public.Johnstone was selected as a test area as it was felt that this locality included many of the water related problems that can be found throughout Renfrewshire. Key water issues were identified and a range of possible solutions provided. Problems, solutions and organisations responsible for different aspects of the water network are described in the document, using images and plans to facilitate the public awareness. Normally the man in the street would not be expected to be as familiar with the nature of water-related problems as the general public in the Netherlands. The Water Vision is yet to go to public consultation as it is currently primarily a planning tool in which council processes are embedded. However, it is planned that workshops including all key stakeholders involved in water management will be held. Those bodies currently responsible for water management will then be encouraged to discuss the various options and opportunities available in a creative and integrated manner. By working together as a team in addressing water related issues it will be possible to develop a vision for the future that better assists the public in moving forward together

Session:management of drainage near source – disconnection/minimise surface water entering public drainage

Many combined sewer networks are currently constrained due to lack of capacity. Surface water entering the network may have an impact on the local environment by causing additional spills from Combined Sewer Overflows (CSOs) and flooding events. With the increasing number of developments taking place in Scotland, more and more demands are being placed upon the existing wastewater assets and infrastructure of the drainage utility, Scottish Water. The principal way of preventing these CSO spills/flooding event s is to reduce the number of surface water connections to the combined sewer network and promote more surface water discharges to nearby watercourses.The problem is being addressed by examining all development applications as they are considered by a drainage planning officer in the water authority. The research reported in this paper is investigating the conditions under which it is reasonable and practical for Scottish Water to accept surface water flows into its combined sewer network . This paper presents a summary of the initial findings of the research to date by examining a sample of the sites examined. The objective of the work is to develop a methodology to support a rigorous stance on the acceptance of surface water flows into the combined sewer network. The results have not as yet been obtained

The SWITCH transition manual

This study evaluated the potential for efficient treatment of domestic wastewater, while satisfying energy efficiency requirements. Various treatment systems and the influences of their physical configurations and operational characteristics on wastewater treatment and energy efficiency were initially considered and evaluated. Review of literature identified high rate anaerobic systems as viable low energy systems for domestic wastewater treatment, with reported high removal of influent chemical oxygen demand (COD) and high net energy balance for the anaerobic baffled reactor (ABR). Low energy recovery is reported in literature as a limitation of anaerobic domestic wastewater treatment, and anaerobic domestic wastewater treatment systems have failed to meet effluent discharge standards, and post-treatment using aerobic processes have been recommended in order to ensure high effluent quality. Therefore, the ABR was selected as a feasible option that can be developed as the first stage of an anaerobic-aerobic low energy domestic wastewater treatment system. The literature review also identified the net energy consumption per cubic metre (m3) of treated wastewater during the treatment process as an energy efficiency evaluation criterion.Energy efficiency for domestic wastewater treatment facilities should be achieved if efficient treatment performance can be sustained at ambient temperature, instead of the fixed mesophilic temperature that is commonly adopted in anaerobic treatment processes. To identify an energy efficient design of the ABR in terms of hydraulic retention time and operational temperature, the performance efficiencies of ABR bench models were monitored at ambient temperature and 37oC at hydraulic retention times (HRT) of 48, 36, 24, 12 and 6 hours, which corresponded to organic loading rates (OLR) of 1.25, 1.67, 2.5, 5.0 and 10.0 kg COD/m3 day. 88.43, 90.00, 84.03, 77.01 and 59.35% of the influent COD (mean = 2479.50 mg/L) were removed at 48, 36, 24, 12 and 6 hour HRTs, respectively, in the 37oC bench reactor, while 70.16, 70.36 and 74.99% of the influent COD were removed at 48, 36 and 24 hour HRTs, respectively, in the ambient temperature bench reactor. Steady state performance, in the form of stable pH values, was not observed in the ambient temperature reactor at 12 hours HRT before the end of the bench experiments. Retention of influent total solids was observed to correlate to hydraulic retention time, with increase retention of total solids corresponding to increase in hydraulic retention time. Furthermore, observed total solids retention in the ambient temperature reactor were less than the total solids retention in the 37oC reactor.Anaerobic reduction of domestic wastewater sludge and the corresponding methane production were also evaluated using bio-chemical methane potential (BMP) batch assays at ambient temperature and compared to a fixed mesophilic temperature of 37oC. Low reduction of volatile solids was observed in the BMP assays, with 40% at ambient temperature compared to 56% at 37oC for primary sludge, and 22% at ambient temperature compared to 38% at 37oC for secondary sludge. Critical limitations of the anaerobic stage at ambient temperature were determined to be the biological reduction and conversion of the organic contaminants to soluble COD and volatile fatty acids (VFA). Also, achieving and maintaining steady state performance required a longer time period at ambient temperature than at 37oC, potentially due to the slow growth of the anaerobic microorganisms at ambient temperature. These limitations indicate the need for long (≥ 24 hours) retention periods for efficient operation at ambient temperature. The ABR bench models were evaluated for energy efficiency with the identified energy efficiency criteria, and the operational condition with the highest energy efficiency was determined to be 12 hours HRT at 37oC. Finally, design criteria for the anaerobic stage of the anaerobic-aerobic system were proproposed, along with a process model as a preliminary step for future process research

SUDS treatment train assessment tool

This paper outlines a rationale and scoring system for the stormwater treatment train assessment tool (STTAT) which is a proposed regulatory tool for Sustainable Urban Drainage Systems (SUDS). STTAT provides guidance and regulatory consistency for developers about the requirements of planners and the Scottish Environment Protection Agency (SEPA). The tool balances the risks of pollution to the receiving water-body with the treatment provided in a treatment train. It encourages developers to take SUDS into account early, avoiding any misunderstanding of SUDS requirements at the planning stage of a development. A pessimistic view on pollution risks has been adopted since there may be a change of land use on the development in the future. A realistic view has also been taken of maintenance issues and the ‘survivability’ of a SUDS component. The rationale for STTAT as a response to the requirements of the Water Framework Directive is explored and the individual scores are given in tabular format for receiving water and catchment risks. Treatment scores are proposed for single SUDS components as well as multiple components within treatment trains. STTAT has been tested on a range of sites, predominantly in Scotland where both development and receiving water information was known. The operational tool in use by SEPA is presented

Sustainable Urban Drainage Systems (SUDS) treatment train assessment tool

This paper outlines a rationale and scoring system for the stormwater treatment train assessment tool (STTAT) which is a proposed regulatory tool for Sustainable Urban Drainage Systems (SUDS). STTAT provides guidance and regulatory consistency for developers about the requirements of planners and the Scottish Environment Protection Agency (SEPA). The tool balances the risks of pollution to the receiving water body with the treatment provided in a treatment train. It encourages developers to take SUDS into account early, avoiding any misunderstanding of SUDS requirements at the planning stage of a development. A pessimistic view on pollution risks has been adopted since there may be a change of land use on the development in the future. A realistic view has also been taken of maintenance issues and the ‘survivability’ of a SUDS component. The development of STTAT as a response to the requirements of the Water Framework Directive is explored, the individual scores being given in tabular format for receiving water and catchment risks. Treatment scores are proposed for single SUDS components as well as multiple components within treatment trains. STTAT has been tested on a range of sites, predominantly in Scotland where both development and receiving water information was known. The operational tool in use by SEPA is presented

Size distribution and diffuse pollution impacts of PAHs in street dust in urban streams in the Yangtze River Delta

Particles of dust washed off streets by stormwater are an important pathway of polyaromatic hydrocarbons (PAHs) into urban streams. This article presented a comprehensive assessment of the size distribution of PAHs in street dust particles, the potential risks of the particles in urban streams, and the sources and sinks of PAHs in the stream network. This assessment was based on measurements of 16 PAHs from the USEPA priority list in street dust particles and river sediments in Xincheng, China. The content of total PAHs ranged from 1629 to 8986 μg/kg in street dust particles, where smaller particles have a higher concentrations. Approximately 55% of the total PAHs were associated with particles less than 250 μm which accounted for 40% of the total mass of street dust. The PAH quantities increased from 2.41 to 46.86 μg/m2 in the sequence of new residential, rising through main roads, old town residential, commercial and industrial areas. The sediments in stream reaches in town were found to be sinks for street dust particle PAHs. The research findings suggested that particle size, land use and the hydrological conditions in the stream network were the factors which most influenced the total loads of PAH in the receiving water bodies.<br/