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Tests to determine the tightness of wastewater pipes can in some cases produce results that are worthy of discussion. Therefore, testing procedures for real-scale sewage pipes used for house connections were evaluated and data were statistically analysed. The results of the investigation showed that leaky pipes are detected with a very high degree of reliability by all leak test methods. The test methods are also robust against errors by expert testers and deviations from the test specifications. In contrast, tight pipelines can also be incorrectly classified as ‘leaking’ (test failed) to a significant extent during leak tests. Even for the more reliable test methods, i.e. air overpressure, air underpressure and water with low test pressure, a tight pipe is incorrectly classified as leaking (false positive) in one out of 10 cases (10%). The highest false-positive rate was 20% for water with high test pressure. In addition to the leak test methods, the quality of the visual inspection was also analysed. Here it was found that visual inspection is not sufficiently reliable for determining the tightness of pipelines above the groundwater level. Error rates of approximately 50% were found for the detection of tight and leaky pipelines. HIGHLIGHTS Investigation of the quality of leak tests and visual inspection for sewage pipes on a real scale.; Determination of error rates for the different test methods (visual inspection, air overpressure, air underpressure and water pressure).; Evaluation of the different test methods for the determination of tightness.; Development of recommendations for action to increase the reliability of the test results.

Water and sewerage companies (WaSC) in the UK are under increasing pressures to improve customer satisfaction. The biggest cause for customer dissatisfaction in the wastewater sector is a service failure caused by a blockage. There is therefore a need to understand the factors which influence blockage processes in order to prevent them. This work demonstrates how preceding rainfall impacts the sewer system of two highly populated regions within South Wales that have differing gradients. The total rainfall, number of dry days and consecutive number of dry days prior to a blockage were investigated using statistical analysis in order to determine the impact that rainfall has on blockages. The results obtained demonstrate the importance that dry weather has on blockage rates in both steep and flat catchments. Future work will incorporate predicted rainfall impact into a proactive maintenance scheduling model.

Urban hydrology was created in order to improve methods of managing the runoff of precipitation in towns and protect them from flooding while also protecting public health and environment. The essence of a future solution consists in finding an acceptable compromise of an alternative solution for draining rainwater from a territory. The content of this work is a study focused on resolving the percolation of water from surface runoff and the confrontation between a field test, laboratory analysis, and numerical analysis. By confronting and subsequently proposing conditions for percolation, documents will be created for making urban drainage better and more efficient. The reason for the origin of the subject work follows from the insufficient information on infiltration systems in Slovak technical standards and, likewise, the lack of support for the percolation of water from surface runoff. This work points out the approaches, principles, and fundamentals of a proposal for percolation. The aim of the work is distribution of scientific knowledge in the field of research and solutions for the percolation of water from surface runoff, with emphasis placed on the retention capacity of the selected territory and the intensity of precipitation. A geological study (orientational, detailed or supplementary) must always be conducted with any decision on rainwater percolation in a certain locality. Its range is dependent on the difficulty and type of construction. The preliminary study of areal condition should be focused on detailed engineering-geological and hydrological information. After this work, it is concluded that the percolation of rainwater in urban areas with suitable hydrogeological condition is an effective rainwater management technology as well as protection to congestion of sewer systems.

Vortex separators still draw attention from specialists investigating the process of removing particles suspended in liquids. The devices are locally applied for waste water treatment in different systems – from storm waste water sewerage to water circulation in fish ponds. However, the methods for separator design presented in the literature are questionable. The paper presents two simple and functional criteria that were employed to construct a laboratory test stand. The test results gave positive feedback on the efficiency of vortex separators.

Currently, unprecedented levels of damage arising from major weather events have been experienced in a number of major cities worldwide. Furthermore, the frequency and the scale of these disasters appear to be increasing and this is viewed by some as tangible proof of climate change. In the urbanized areas sewer overflows and resulting inundation are attributed to the conversion of previous surfaces into impervious surfaces, resulting in increased volumes of runoff which exceed the capacity of sewer systems and in particular combined sewer systems. In this study, the characteristics of sewer overflows and inundation have been analyzed in a repeatedly flooded zone in the city of Cheongju in Korea. This included an assessment of inundation in a 50-year storm event with total rainfall of 165 mm. A detailed XP-SWMM 2D model was assembled and run to simulate the interaction of the sewerage system overflows and surface inundation to determine if inundation is due to hydraulic capacity limitations in the sewers or limitations in surface inlet capacities or a combination of both. Calibration was undertaken using observation at three locations (PT #1, PT #2, PT #3) within the study area. In the case of the subsurface flow calibration, R2 value of 0.91 and 0.78 respectively were achieved at PT #1 and PT #2. Extremely good agreement between observed and predicted surface flow depths was achieved also at PT #1 and PT #2. However, at PT #3 the predicted flow depth was 4 cm lower than the observed depth, which was attributed to the impact of buildings on the local flow distribution. Areas subject to flooding were classified as either Type A (due to insufficient hydraulic capacity of a sewer), Type B (which is an area without flooding notwithstanding insufficient hydraulic capacity of a sewer) or Type C (due to inlet limitations, i.e. there is hydraulic capacity in a sewer which is not utilized). In the total flooded zone, 24% was classified as Type A (10.2 ha) and 25% was classified as Type C (2.61 ha). It was concluded that greater attention should be paid to the area classified as Type B, which covers 50.5% (5.15 ha) of the total flooded zone.

Onsite greywater reuse (GWR) and installation of water-efficient toilets (WETs) reduce urban freshwater demand and thus enhance urban water use sustainability. Research on GWR and WETs has generally overlooked their potential effects on municipal sewer systems: GWR and WETs affect the flow regime in sewers, and consequently also influence gross solids transport. To asses these impacts, a gross solids transport model was developed. The model is based on approaches found in the literature. Hydrodynamic calculations of sewage flow were performed using the SIMBA6 simulator and then used for the gross solid movement models. Flow characteristics in the up- and downstream sections of the sewer network differ. Therefore different approaches were used to model solids movement in each of these two parts. Each model determines whether a solid moves as a result of a momentary sewage flow, and if it moves, calculation of its velocity is possible. The paper shows the adoption and implementation of two gross solids transport models using SIMBA6 and depicts the results of the effects of various GWR and WET scenarios on gross solids movement in sewers for a real case study in Israel.

Sludge management is one of the critical issues facing modern society due to the fast increase in its production as a result of extended sewerage, new work installations and up-grading of existing facilities. In order to (i) properly perform the utilization and disposal operations, (ii) correctly fulfil the legal requirements and (iii) build stakeholder and public confidence, it will be necessary to establish defined outlet procedures/routes and guarantee a good sludge quality. Therefore, characterization to evaluate sludge chemical, biological and physical properties is a necessary tool in sludge management. However, characterization procedures often specify different methodologies, materials and accessories; so results obtained in different places may not be fully reliable. Also comparison of the results can be problematic because they have not been obtained under standardized conditions. Consequently, the development of standardized validated characterization methods and procedures becomes necessary too. Further, the development of standardized characterization methods and procedures should be supported by the preparation of ‘guidelines’ of good practice for the different options of sludge use and disposal in order to give guidance to producers/users on how to meet legislation requirements and perform sustainable operations. In this paper the main parameters for sludge characterization are discussed and developments in European standardization outlined.

Prolonged drought which has occurred everywhere around the world has caused water shortages, leading many countries to consider more sustainable practices, which are called source management practices (SMPs) to ensure water availability for the future. SMPs include the practices of water use reduction, potable water substitution and wastewater volume reduction such as water demand management, rainwater harvesting, greywater recycling and sewer mining. Besides the well known advantages from SMPs, they also contribute to the alteration of wastewater characteristics which finally affect the process in downstream infrastructure such as sewerage networks. Several studies have shown that the implementation of SMPs decreases the wastewater flow, whilst increasing its strength. High-strength wastewater can cause sewer problems such as sewer blockage, odour and corrosion. Yet, not all SMPs and their impact on existing sewer networks have been investigated. Therefore, this study reviews some examples of four common SMPs, the wastewater characteristics and the physical and biochemical transformation processes in sewers and the problems that might caused by them, and finally the potential impacts of those SMPs on wastewater characteristics and sewer networks are discussed. This paper provides sewer system managers with an overview of potential impacts on the sewer network due to the implementation of some SMPs. Potential research opportunities for the impact of SMPs on existing sewers are also identified.

The Ganges River, one of the most heavily populated and urbanized river basins in Asia, is polluted by increasing wastewater influent and water-borne diseases are caused in the metropolitan area. This study focused on the Yamuna River, a major tributary of the Ganges. We determined the pollutant load per unit of urban area classified by the income of the residents to help design an appropriate sewerage system. In addition, a simple method of estimating runoff pollutant load was examined using data on pollutant load per unit and runoff coefficient.

Sewer systems are closely interlinked with groundwater and surface water. Due to leaks and regular openings in the sewer system (e.g. combined sewer overflow structures with sometimes reverse pressure conditions), groundwater infiltration and surface water inflow as well as exfiltration of sewage take place and cannot be avoided. In the paper a new hydrodynamic sewer network modelling approach will be presented, which includes – besides precipitation – hydrographs of groundwater and surface water as essential boundary conditions. The concept of the modelling approach and the models to describe the infiltration, inflow and exfiltration fluxes are described. The model application to the sewerage system of the City of Dresden during a flood event with complex conditions shows that the processes of infiltration, exfiltration and surface water inflows can be described with a higher reliability and accuracy, showing that surface water inflow causes a pronounced system reaction. Further, according to the simulation results, a high sensitivity of exfiltration rates on the in-sewer water levels and a relatively low influence of the dynamic conditions on the infiltration rates were found.

WSP technology has been used in Ceará, Northeast Brazil, since middle 1970s. There are presently 96 ponds plants and most of them are comprised by single cells (40%) and series of 3 ponds (35%). They were under loaded due to incomplete house connections to the sewerage network and low per capita wastewater contributions. Highest removal rates of organic material, ammonia and faecal coliform were found in 3 pond series. Faecal coliform removal was in accordance with the literature and series of ponds reached numbers ≤105 cells/100 ml. In series with 4 and 5 ponds FC was below 103 cells/100 ml. Ammonia removal varied from 30 to 80% and total phosphorus the removal was not significant. An increase in the number of maturation ponds enhances nutrient and coliform removal. Up-grading schemes should be investigated as well as effluent reuse potential.

Urban sanitation issues should be tackled strategically, and may be addressed effectively when sewerage development is pursued in conjunction with complementary sanitation measures. Five sanitation improvement scenarios employing sewerage, night-soil collection-and-treatment (NSCT) system, and/or septic-tank improvement by annual desludging were analyzed from the perspective of COD loads, total nitrogen loads, and cost under the conditions found in Hanoi, Vietnam. Compared to the development of sewerage alone, the scenario of developing NSCT systems in a complementary manner with sewerage development was estimated to be the most effective for a rapid decrease of both COD and total nitrogen loads. However, it may be difficult in some cases to replace ordinary water-flush toilets by the micro-flush toilets that are used in NSCT systems. In this case, the scenario employing septic-tank improvement in conjunction with sewerage development may be effective for a rapid decrease of COD in locations where septic tanks are widely used under poor maintenance conditions and nitrogen pollution is not serious compared to COD. It was calculated that the two scenarios above would respectively require cost increases of 16 and 22% over the sewerage development scenario.

The bulk and retail water companies of the greater Melbourne area are developing the 2009 Metropolitan Sewerage Strategy to provide sustainable sewerage services to 2060. The objective of the strategy is to establish long term principles and near term actions to produce a robust sewage management system for Melbourne. Melbourne's existing sewerage system is largely centralised and discharges to two major treatment plants. Several small satellite treatment plants service local urban areas generally more distant from the centralised system. Decentralised and on-site wastewater systems are options for future sewage management and could play a role in local recycling. A portfolio of 18 on-site and decentralised concept designs was developed, applicable to the full range of urban development types in Melbourne. The concepts can be used in evaluation of metropolitan system configurations as part of future integrated water cycle planning. The options included secondary and tertiary treatment systems incorporating re-use of water for non potable uses, urine separation, black and greywater separation and composting toilets. On-site and cluster treatment systems were analysed. Each option is described by its indicative capital and operating costs, energy use and water and nutrient balances. This paper summarises and compares the portfolio mix of decentralized and on-site options in Melbourne's context.

A generic model is introduced that represents the combined sewer infrastructure of a settlement quantitatively. A catchment area module first calculates the length and size distribution of the required sewer pipes on the basis of rain patterns, housing densities and area size. These results are fed into the sewer-cost module in order to estimate the combined sewer costs of the entire catchment area. A detailed analysis of the relevant input parameters for Swiss settlements is used to identify the influence of size on costs. The simulation results confirm that an economy of scale exists for combined sewer systems. This is the result of two main opposing cost factors: (i) increased construction costs for larger sewer systems due to larger pipes and increased rain runoff in larger settlements, and (ii) lower costs due to higher population and building densities in larger towns. In Switzerland, the more or less organically grown settlement structures and limited land availability emphasise the second factor to show an apparent economy of scale. This modelling approach proved to be a powerful tool for understanding the underlying factors affecting the cost structure for water infrastructures.

At present, the potential generation of methane in wastewater collection systems is ignored under international greenhouse gas (GHG) accounting protocols, despite recent reports of substantial dissolved methane formation in sewers. This suggests that the current national GHG inventories for wastewater handling systems are likely to be underestimated for some situations. This study presents a new catalogue of field data on methane formation in rising main sewerage systems and proposes an empirically-fitted, theoretical model to predict dissolved methane concentrations, based upon the independent variables of pipeline geometry (i.e. surface area to volume ratio, A/V) and hydraulic retention time (HRT). Systems with longer HRT and/or larger A/V ratios are shown to have higher dissolved methane concentrations. This simple predictive model provides a means for water authorities to estimate the methane emissions from other pressurised sewerage systems of similar characteristics.

Using the example of raw water quality this paper examines the relationship between different spatial characteristics (geographical and physical properties) of Water and Sewerage Companies (WaSCs) supply and sewage areas and response to the Water Framework Directive. Results were obtained from thematic analysis and content analysis of 14 interviews with WaSCs representatives. Principal component analysis and cluster analysis of 51 WaSCs business function characteristics was employed to derive groups of similar WaSCs. Results indicate that there is difference in how WaSCs approach raw water quality issues. It appears that small WaSCs with relatively large agricultural areas in their supply catchments are more likely to seek managerial solutions to raw water quality problems.

This text reports research which was undertaken to assess the failure consequences associated with sewerage systems. In an effort to move away from considering only flood volume, depth or extent, the text will focus on how a survey of public opinion was used to inform the development of a consequence scoring methodology. The failure consequences considered range from internal flooding of properties, to road closure, environmental damage and odour problems. The text reports the extent to which experience of flooding influences perceptions of failure consequence and sewerage system management. It is also outlined how this data was used, along with other data sources, to construct an objective scoring process that can be used to evaluate failure consequence and readily prioritise sewerage maintenance.

Exfiltration of waste water in sewer networks represents a potential danger for the soil and the aquifer. Various modelling approaches have been proposed to quantify sewerage exfiltration and its spatial and temporal variation. Common models are based on the law of Darcy, extended by a more or less detailed consideration of the expansion of leaks, the characteristics of the soil and the colmation layer. In the paper investigations are introduced, which are focused on the actual water content of the soil and its influence on exfiltration rates. Modelling results with HYDRUS 1D show, that under unsaturated conditions initial exfiltration rates are increased compared to saturated conditions. In experiments it was found, that the matrix potential increases the tightness of the colmation layer. Further a colmation model was deduced, which allows the calculation of the thickness and conductivity of the colmation layer.

Many European countries tend to shift from constructing combined sewer systems to separate ones, in order to optimise wastewater treatment efficiency and reduce CSO impact on surface waters. An economic design minimises maintenance requirements by aiming at self-cleansing pipes. However, providing the necessary slopes for self-cleansing sanitary sewer pipes often is unfeasible in flat regions, resulting in an increased risk of loss of hydraulic capacity or blocking. To reduce these risks, flushing tanks can be installed in the sewer system. Where most other researchers contribute to a better understanding of the hydraulics of flushing, this paper rather tries to formulate a methodology to design and test flushing devices in sanitary sewer systems using standards and hydrodynamic simulations. Therefore, several aspects that require consideration when incorporating flushing devices into a sanitary sewer system are discussed. For instance, when flushing sanitary sewers the increase in discharge has to be explicitly considered. A Belgian case study is used to investigate the suitability of the developed methodology. Although the pipe slopes in the methodology are derived assuming uniform flow, the simulation results comply with it. Furthermore, pressurisation of the conduits due to multiple flushing waves remains within acceptable limits.

The development and implementation of alternative wastewater servicing approaches in rural communities in Australia appears more feasible than in larger urban developments as many rural centres rely on septic tanks and surface discharge of greywater. This method of disposal creates many environmental, social and economic issues and is seen to limit potential for growth in many towns. This paper describes a generic methodology for the selection of innovative sewerage options for six regional towns in Victoria, Australia. The method includes consultation with stakeholders, multi-criteria assessment and concept design of the most favourable option. Despite the broad range of initial wastewater servicing options presented which included cluster-scale systems, upgrade of existing systems, greywater reuse and alternative collection, the outcome for five of the six towns was a modified centralised collection system as the preferred option. Lack of robust and reliable data on the human health risks and environmental impacts of alternative systems were identified as the primary data gaps in the sustainability assessment. In addition, biases in the assessment method due to stakeholder perceptions were found to be an additional issue.

Many parts of Japan have experienced rapid urbanization and industrialization over the past 50 years. This trend resulted in severe water pollution in many urban areas. To address the pollution problems, several measures such as construction of sewerage systems and enactment of laws and regulations have been undertaken. Because of these measures, the water quality has been improved to some extent. However, many water quality concerns still remain and are attributed in part to diffuse pollution. In this paper, historical progress, present situation and future aspects of diffuse pollution problems in Japan are reviewed. It is noted that solving diffuse pollution problems will require a combination of several measures including application of conventional treatment technologies and natural purification systems, implementation of appropriate policy measures, and promotion of citizen participation.

Rapid population growth and urbanization are exerting excessive pressure on soil and water resources. To address these problems this paper proposes a cheap and sustainable alternative sanitation system, which accelerates nutrient recycling (“closing the loop”): ecological sanitation (ecosan) is a potential alternative to conventional sanitation systems that replenishes the organic matter and nutrients of the soil that are taken off as the crop harvest. A comparison is made of the environmental and the operation and maintenance costs between a modern wastewater treatment plant and on-site sanitation. An elevated double box urine diverting toilet (“ecotoilet”) is proposed and its advantages and disadvantages over a system with a centrally controlled modern WWTP are discussed. Bagmati Area Sewerage Project in Kathmandu is taken as an example of modern WWTP and ecosan being practiced in a village in Nepal is taken as an example of ecotoilet for the comparison.

In the Netherlands, wastewater is collected in municipal areas and transported to centralised WWTPs by an extensive system of pressure mains. Over the last decades these pressure mains did not receive much attention in terms of monitoring of performance or maintenance. A recent inventory showed that half of the pressure mains show an increased pressure loss for no directly obvious reason. One of the many causes that account for the reduction of the flow capacity is the occurrence of free gas in the pipeline. During dry weather periods with low flow velocities, gas may accumulate at high points in the system. Once the velocity increases during storm weather flow, the air pockets may be broken down and transported to the end of the system. A research study is started focussing on the description of the gas-water phenomena in wastewater pressure mains with respect to transportation of gas. An experimental facility is constructed for the study of multi-phase flow. This paper describes the preliminary results of experiments on breakdown rates of gas pockets as a function of inclination angle and water flow rate. The results show an increasing breakdown rate with increasing inclination angle.

The Greater Moncton Sewerage Commission has developed, in concert with National Defence Canada, an environmentally sustainable and cost effective biosolids management and land reclamation programme at the Canadian Forces Base (CFB) Gagetown, New Brunswick, Canada (the second largest land based Military Training Facility in the British Commonwealth). The use of composted biosolids to re-vegetate military training lands is thought to be a unique application for the beneficial use of biosolids. Results and practical experience gained from this approach to successfully re-vegetate initial sections of extremely large and vast tracts of these lands are described. The paper also overviews the Commission's modern 115 000 m3.d−1 advanced, chemically assisted primary wastewater treatment facility and associated alkaline (lime) sludge stabilisation process. Planning strategies, security aspects, special and unique challenges in operating adjacent to an active military training facility, costs, spreading techniques, monitoring, next steps and conclusions are also presented.

New guidelines have been developed and trialled in Australia to assist urban stormwater managers to assess options for projects that aim to improve urban waterway health. These guidelines help users to examine the financial, ecological and social dimensions of projects (i.e. the so-called “triple-bottom-line”). Features of the assessment process described in the guidelines include use of multi criteria analysis, input from technical experts as well as non-technical stakeholders, and provision of three alternative levels of assessment to suit stormwater managers with differing needs and resources. This paper firstly provides a background to the new guidelines and triple-bottom-line assessment. The assessment methodology promoted in the new guidelines is then briefly summarised. This methodology is compared and contrasted with European guidelines from the “SWARD” project that have been primarily developed for assessing the relative sustainability of options involving urban water supply and sewerage assets. Finally, the paper discusses how assessment methodologies that evaluate the financial, ecological and social dimensions of projects can, under some circumstances, be used to evaluate the relative progress of options for urban water management on a journey towards the widely pursued, but vaguely defined goal of “sustainable development”.

Existing inadequate sewerage systems and direct disposal of household waste into water courses has tremendously increased water pollution. Dry toilets are feasible in rural and peri-urban areas to reduce the consumption of costlier water that is required for flushing. As conventional treatment technologies require high investment, and operation and maintenance costs, dry toilets are the only suitable option left for sanitation in the 21st century when working with limited financial resources. To reduce environmental degradation and overcome this problem, the dry toilet is only the realistic option in Nepal. Two reactors, one exposed to sunrays and the other without sunrays, were constructed. In the model with sunrays, it was found that in 48 days of observation faecal coliform presence depleted to 610 cells per gm from the initial value of 7×1010 and volatile organic matter came down from 98.09% to 70.18%. Similarly, in the other model, the destruction of faecal coliform in 65 days was found to be 920 cells/gm while the destruction of organic matter took 75 days. Also, observing from 313 people in a cluster on the pilot project, the annually recovered value of N, P and K was found to be 1565kg, 125kg, 344kg, respectively. This paper deals with the different types of dry ecological toilet, their performance and feasibility study in Nepal, with the full involvement of local people, based on complete laboratory analysis and regular monitoring. Using dry toilets will save 14 LPCD, which is equivalent to 14 MLD and the resulting demand will become only 80 MLD for the urban area of Kathmandu. The result advocates the implementation of ecological dry toilets to save valuable water wasted in flushing, as well as saving the resources needed to treat the waste.

Since the 1970s, we have known about real-time control of urban drainage systems. However, global real-time control strategies still show a lack of implementation for large drainage systems of high complexity. In Berlin, Germany, a city of 3.5 million inhabitants covering an area of around 900km2, the demand for enhanced protection of the environment and growing economic pressure have led to an increasing application of control assets and concepts within the sewage system. In the framework of the project “Integrated Sewage Management”, the possibilities of a global and integrated control strategy for the Berlin system are examined. The paper is focused on the historical concept and design of the sewerage and the further improvement towards an environment-oriented system that builds the basis for today's considerations. The operational method and functionality of local regulators that have already been implemented are described. Further-more, the model-based methodology for the analysis of the system and the development of global control concepts, as well as the results of system analysis, are stated. On the basis of model simulations, it is shown that a global coordination of pump stations can lead to a reduction of sewer overflows, and consequently to an enhanced water protection.

Thirty-nine municipalities in the Netherlands conducted a pilot study to develop and try out a methodology to compare the quality of their sewerage management. The participants chose a multidimensional benchmarking with an emphasis on the aim of improving the working processes within sewerage management. A second goal was accountability to the stakeholders. The benchmarking methodology was based as well on analysing data within a “balanced-score-card” system as on intensive exchange of knowledge and experiences. The pilot resulted in a state of the art overview of the quality of sewerage management in the Netherlands. However, above all, it resulted in the shocking fact that the work is carried out in many different ways which cannot be explained by technical reasons or local circumstances. To pinpoint best practices and actually implement these improvements the learning process must continue after the analysis and presentation of the data. A start has been made to form regional specialist networks for further discussion and exchange of experiences.

Today's planning standards deal with the individual urban drainage components (sewer system, wastewater treatment plant and receiving water) separately, i.e. they are often designed and operated as single components. As opposed to this, an integral handling considers the drainage components jointly. This novel approach allows a holistic and more sustainable planning of urban drainage systems. This paper presents an integrated modelling concept. The aim is to analyse fluxes through the total wastewater system and to integrate pollution-based control in the upstream direction, that is, e.g., managing the combined water retention tanks as a function of state variables in the WWTP or the receiving water. All models of the different subsystems are based on the Activated Sludge Model (ASM) concept of IWA, including River Water Quality Model No. 1 (RWQM). Simulations can be done in truly parallel mode using the simulation environment SIMBA. The integrated modelling concept is applied to the river Dhuenn and the urban wastewater system of the municipality of Odenthal (Germany). An optimised operation of the system using RTC proves to be a very effective measure.

A special arrangement of combined sewer overflow tanks is the in-line storage sewer with downstream discharge (ISS-down). This layout has the advantage that, besides the sewer system, no other structures are required for stormwater treatment. The verification of the efficiency with respect to the processes of sedimentation and remobilization of sediment within the in-line storage sewer with downstream discharge is carried out in a combination of a field and a pilot plant study. The model study was carried out using a pilot plant model scaled 1:13. The following is intended to present some results of the pilot plant study and the mathematical empirical modelling of the sedimentation and remobilization process.

Assessments of sewer performance are usually based on a single computation of CSO (combined sewer overflow) volumes using a time series of rainfall as system loads. A shortcoming of this method is that uncertainties in knowledge of sewer system dimensions are not taken into account. Moreover, sewer models are rarely calibrated. This paper presents the impacts of database errors and model calibration on return periods of calculated CSO volumes. The impact of uncertainties is illustrated with two examples. Variability of calculated CSO volumes is estimated using Monte Carlo simulations. The results show that calculated CSO volumes vary considerably due to database errors, especially uncertain dimensions of the catchment area. Furthermore, event-based calibration of a sewer model does not result in more reliable predictions because the calibrated parameters have low portability. However, it enables removal of database errors harmonising model predictions and ‘reality’.

The objective of the present study is the estimation of the potential benefits of sewer pipe rehabilitation for the performance of the drainage system and the wastewater treatment plant (WWTP) as well as for the receiving water quality. The relation of sewer system status and the infiltration rate is assessed based on statistical analysis of 470 km of CCTV (Closed Circuit Television) inspected sewers of the city of Dresden. The potential reduction of infiltration rates and the consequent performance improvements of the urban wastewater system are simulated as a function of rehabilitation activities in the network. The integrated model is applied to an artificial system with input from a real sewer network. In this paper, the general design of the integrated model and its data requirements are presented. For an exemplary study, the consequences of the simulations are discussed with respect to the prioritisation of rehabilitation activities in the network.

In recent years numerical modelling became a standard procedure to optimise urban wastewater systems design and operation by integration. For dynamic control of the wastewater teatment plant (WWTP) inflow, a model-based predictive concept is introduced aiming at improving the receiving water quality. An on-line simulator running parallel to the real WWTP operation reflects the actual state of operation and provides this model information to a prognosis tool which determines the best option for the WWTP inflow. The investigations showed that it is possible to reduce the NH4-N peak concentrations in the receiving water by dynamic WWTP inflow control based on predictive scenario analysis.

Engineering infrastructure is provided at high cost and is expected to have a useful operational life of decades. However, it is clear that the future is uncertain. Traditional approaches to designing and operating urban storm drainage assets have relied on past performance of natural systems and the ability to extrapolate this performance, together with that of the assets across the usable lifetime. Whether or not climate change is going to significantly alter future weather patterns in Europe, it is clear that it is now incumbent on designers and operators of storm drainage systems to prepare for greater uncertainty in the effectiveness of storm drainage systems. A recent UK Government study considered the potential effects of climate and socio-economic change in the UK in terms of four future scenarios and what the implications are for the performance of existing storm drainage facilities. In this paper the modelling that was undertaken to try to quantify the changes in risk, together with the effectiveness of responses in managing that risk, are described. It shows that flood risks may increase by a factor of almost 30 times and that traditional engineering measures alone are unlikely to be able to provide protection.

This paper describes a modelling approach for evaluating the efficiency of different non-structural best management practices for stormwater management. A scenario with a set of source reduction practices was simulated using the substance flow model SEWSYS for an urban catchment in the city of Göteborg, Sweden. The scenario is based on a hypothetical control program that includes prevention, education and regulations. The simulation shows relatively high reductions of copper and PAH, 77% and 50%, respectively. The reduction in copper is mainly due to less copper roof corrosion and brake wear, while reduced road wear has the greatest effect for PAH. An important result from this study is that the non-structural BMPs applied did not give a sufficient reduction in pollution to meet the desirable environmental quality criteria. To meet these criteria, additional BMPs must be implemented, preferably a combination of both non-structural and structural measures.

When looking at acute receiving water impacts due to combined sewer overflows the characteristics of the background diurnal sewage flux variation may influence the peak loads from combined sewer overflows (CSO) and wastewater treatment plant (WWTP) effluent significantly. In this paper, effects on the dynamic compounds transported in the sewer, on CSO discharges and WWTP loading are evaluated by means of hydrodynamic simulations. The simulations are based on different scenarios for diurnal dry-weather flow variations induced by different infiltration rates.

Integrated real-time control (RTC) concepts, which are trying to operate drainage systems and WWTPs depending on the current capacities of both systems, are becoming more and more important. While almost all publications in this field have been concentrating on continuous flow systems, this paper will present a project which has been initiated to realise an integrated RTC strategy for a Sequencing Batch Reactor (SBR) plant in simulation as well as in full-scale. The results of the simulation are that SBR plants can handle high hydraulic loads. The cost–benefit analysis shows that an integrated operation is reasonable concerning environmental and economic aspects. In order to verify the simulation results, full-scale operation has been started in January 2004. The first results seem to confirm the results of the simulation study.

Monitoring of carbamazepine concentrations in wastewater and groundwater enables us to identify and quantify sewer exfiltration. The antiepileptic drug carbamazepine is hardly removed in wastewater treatment plants and not or just slightly attenuated during bank infiltration and subsoil flow. Concentrations in wastewater are generally 1,000 times higher than the limit of quantification. In contrast to many other wastewater tracers carbamazepine is discharged to the environment only via domestic wastewater. The results from this study carried out in Linz, Austria indicate an average exfiltration rate of 1%, expressed as percentage of the dry weather flow that is lost to the groundwater on the city-wide scale. This rate is lower than sewage losses reported in most other studies which attempted to quantify exfiltration on the basis of groundwater pollution. However, it was also possible to identify one area with significantly higher sewage losses. This method seems to be very suitable for the verification of leakage models used to assess sewer exfiltration on a regional scale.

In the framework of a German field and numerical study the possibilities of an optimal cleaning by flushing of a combined sewer with storage capacity and bottom-end overflow were investigated. The objective of this combined investigation was to find out the boundaries for the flushing operation to prevent wave reflections and impoundages at the throttle by guaranteeing the necessary shear stress for remobilization.

In The Netherlands, wastewater is collected in municipal areas and transported to large centralised WWTPs by means of an extensive system of pressure mains. Over the past decades these pressure mains did not receive much attention in terms of monitoring of performance or maintenance. For that reason, in practice their state of functioning is often not known. Failure of operation is only noticed when the capacity of the system proves to be insufficient to fulfil the minimum design capacity demand. A recent inventory showed that half of the pressure mains show an increased pressure loss for no directly obvious reason. Many causes may account for the reduction of the system's nominal capacity like an increased wall roughness, scaling or occurrence of free gas in the pipeline. The occurrence of free gas may be caused by degassing of dissolved (bio) gas or by air entrained at the pumps' inlet or at air valves. A research study is started that will focus on three main issues:• The description of the gas-water phenomena in wastewater pressure mains with respect totransportation and dynamic hydraulic behaviour,• A method to diagnose gas problems, and• To overcome future problems by either applying remedial measures or improving the design ofwastewater pressure systems.For this study, two experimental facilities are constructed, a small circuit for the study of multi-phase flow and a second, larger one for the research into diagnostic methods. This paper describes the preliminary results of the experiments in the multi-phase circuit.

The main concern of this paper was to predict the sludge quantities generated from 18 wastewater treatment plants, which were stated to be established in the “Istanbul Water Supply, Sewerage and Drainage, Sewage Treatment and Disposal Master Plan”, 10 of which are in operation at present. Besides this, obtaining the required data to compare various treatment schemes was another goal of the study. Especially, the estimation of the sludge quantity in the case of enhanced primary sedimentation was of importance. Wastewater sludge management strategies were discussed in order to develop suggestions for Istanbul Metropolitan city. Within this context, the wastewater treatment facilities, mentioned in the Master Plan that had been completed by 2000, were evaluated in terms of sludge production rates, locations and technical and management aspects. Disposal alternatives of the wastewater treatment sludge were also evaluated in this study. Using of the dewatered sludge as a landfill cover material seems the best alternative usage. Up to the year of 2040, the requirement of cover material for landfills in İstanbul will be met by the dewatered sludge originated from wastewater treatment plants in the region.

Small communities that are sewered by either package sewage treatment plants or on-site sewerage facilities are finding that the ground and surface waters are being contaminated. Nitrogen, which typically is not removed in these conventional systems, is a major concern. This project evaluated the capability of four sewage treatment technologies to reduce the amount of nitrogen being discharged in the effluent to the receiving environment. The four sewage treatment processes evaluated include a recirculating sand filter, biofilter, slow sand filter and constructed subsurface flow wetland. These processes were evaluated for their capability to reduce nitrogen, phosphorus, BOD5 and TSS. The primary objective of the project was to evaluate the capability of these treatment processes to reduce nitrogen using biological processes nitrification and denitrification. This paper reports on the performance of these processes to reduce nitrogen. The study demonstrated that the biofilter was capable of removing from a primary treated influent 40% of the total nitrogen. For the same quality influent the recirculating sand filter was capable of removing 35% of the total nitrogen. Secondary treated effluent was fed to the slow sand filter and the subsurface flow wetland. There was a 52% reduction in total nitrogen through the wetland however there was virtually no reduction in total nitrogen through the slow sand filter.

Exfiltration from sewers is widespread and emerging legislation may require water service providers to identify, and rectify, its sources in sewerage systems. This paper describes exfiltration test apparatus and a series of experiments undertaken using sewage to gain a better understanding of the influence of sewage solids and sediments on leakage rates. An overview of the results obtained is given, which demonstrates that most previous estimates of exfiltration leakage rates were too high due to a lack of appreciation of the “self-repairing” action of sewage and sewage associated solids. Exfiltration rates of 0.1% of the sewer flow or 0.001 l/s have been recorded for defects up to 6 mm wide.

Since January 2000, the sewerage network of a very urbanised catchment area in the Greater Nancy Urban Community has been operated according to the alarms generated in real time by a storm alert system using weather radar data. This alert system is based on an automatic identification of intense rain cells in the radar images. This paper presents the characteristics of this alert system and synthesises the main results of two complementary studies realised in 2002 in order to estimate the relevance and the operational effectiveness of the alert system. The first study consisted in an off-line analysis of almost 50,000 intense rain cells detected in four years of historical radar data. The second study was an analysis of the experience feedback after two years of operational use of this alert system. The results of these studies are discussed in function of the initial operational objectives.

Severn Trent Water have been using constructed wetlands since 1991 as part of a flowsheet in which 6 DWF (Dry Weather Flow) is treated by rotating biological contactors (RBCs), and constructed reed beds used to provide both tertiary treatment and stormwater treatment. The company now has over 50 such sites using this flowsheet. Dimensioning and effluent quality achievable is reported and data presented showing the performance of reed beds treating stormwater alone or in admixture with RBC effluent. After 8-10 years of operation the condition of a number of storm reed beds was assessed to determine the remaining asset life. The majority seem likely to achieve at least another five years of operation before further review is needed.

In Finland the question of appropriate wastewater treatment in rural areas has become very prominent during the last years. The new Environmental Protection Act stipulates that wastewaters must be treated to the extent that they cannot have a negative impact on nature. The Ministry of the Environment is currently preparing a decree specifying the requirements. The draft of the decree proposes that on-site treatment units should decrease the BOD load by 90, total phosphorus load by 85 and total nitrogen load by 40 per cent. To meet the new requirements, the old systems that include septic tanks only need more efficient wastewater treatment methods. Whatever technical solution is selected, the house owner must pay for it. At the moment, even the septic tanks are emptied and maintained irregularly. More sophisticated wastewater treatment methods definitely need more maintenance, which cannot be made the sole duty of the house owners. One potential organisational alternative for managing wastewater treatment in rural areas is the co-operative. Finland has one such pioneering co-operative formed for on-site sanitation. Varsinais-Suomi Water Services Co-operative provides the house owner with professional assistance in wastewater treatment at a reasonable cost. Suvisaari Water Services Co-operative is another new organisation selling sewerage services to its members. But its technology is different: this co-operative operates an LPS-sewerage system instead of on-site treatment.

LC/MS analysis with improved SPE preparation was applied to determine trace amounts of LAS in river waters. By using this procedure, the distribution of LAS was investigated and compared with the previous concentration level measured by HPLC in the Akashi River flowing through urbanized coastal areas in Hyogo Prefecture, western Japan. Detected LAS were in the range of 0.6-11 μg/L and considerably lower than those in 1985. This indicated that LAS concentration levels reduced to 1/10 and below during the past 18 years. From the model analysis, major factors contributing to the reduction of their concentrations were estimated to be the sewerage development and the decrease of consumption of anionic surfactants. Statistical analysis of MBAS monitoring data suggested that over 90% of sewerage diffusion rate was needed in order to reduce LAS to the concentration level of the order of 10 μg/L in river waters.

Wastewater Treatment plants can cause odour emissions that may lead to significant odour annoyance in their vicinity. Thus, over the past 20 years, several measurements were taken of the odour emissions that occur at WWTPs of different sizes, treatment technology, plant design and under different operating conditions. The specific aspects of odour sampling and measurement have to be considered. I presented some of the results of my odour emission measurements 11 years ago. However, it is now necessary to update the figures by evaluating newer measurement results obtained from measurements taken from 1994 to 2003. These are presented in this paper. Also, the paper highlights the odour emission capacity (OEC) measurement technique which characterises liquids and can be used to assess the results achieved by different types of treatment in the liquid phase, e.g. in a sewerage system. In addition, the OEC is a suitable parameter to set standards for the odorant content of industrial wastewaters that are discharged into the publicly owned sewerage system.

The Greater Moncton Sewerage Commission's 115,000 m3/d advanced, chemically assisted primary wastewater treatment facility located in New Brunswick, Canada, has developed an integrated, long term, sustainable, cost effective programme for the management and beneficial utilization of biosolids from lime stabilized raw sludge. The paper overviews biosolids production, lime stabilization, conveyance, and odour control followed by an indepth discussion of the wastewater sludge as a resource programme, namely: composting, mine site reclamation, landfill cover, land application for agricultural use, tree farming, sod farm base as a soil enrichment, topsoil manufacturing. The paper also addresses the issues of metals, pathogens, organic compounds, the quality control program along with the regulatory requirements. Biosolids capital and operating costs are presented. Research results on removal of metals from primary sludge using a unique biological process known as BIOSOL as developed by the University of Toronto, Canada to remove metals and destroy pathogens are presented. The paper also discusses an ongoing cooperative research project with the Université de Moncton where various mixtures of plant biosolids are composted with low quality soil. Integration, approach to sustainability and “cumulative effects” as part of the overall biosolids management strategy are also discussed.