Cost-effective development of urban wastewater systems for Water Framework Directive compliance – the CD4WC EU project

This paper will introduce the CD4WC project and its first results after approximately 1.5 years from its beginning. The project CD4WC deals with optimising the efficiency of the urban wastewater system. Various optimisation measures are investigated with regard to ecological consequences in natural water bodies and in regard with investment and operational costs. The variety of possible systems approaches, operating strategies and management options will increase due to the implementation of the European Water Framework Directive. CD4WC aims to systematically identify ecological and economic synergy potential by making use of the degrees of freedom offered by the WFD philosophy. The various options investigated to induce potential benefits are: • extensions and development of the sewer system; • systems choice and possible extensions of the WWTP; • measures in the receiving water to enhance morphology and self purification; • source control measures; • optimisation of the operation of present and of developed systems e.g. by RTC; • systems integration considering and optimising the interactions between the subsystems; • application of management tools including the evaluation of economic driving forces. CD4WC further aims to evaluate the resulting cost savings and to put them into relation with additional costs originating from management and monitoring requirements required by the WFD, in order to achieve realistic cost estimation. The main expected results of the project are: • a list of options to extend the wastewater system and improve its performance; • an evaluation of these options with regard to ecological consequences and investment/operation costs; • quantification of cost savings due to increased degrees of freedom induced by the WFD approach; e.g. application of effective control measures as opposed to structural system extensions. The project group is put together of four university research teams (TU Dresden, Ghent University, Innsbruck University, Panteion University of Athens) and of four companies operating wastewater systems (Ruhrverband, Aquafin, TIWAG, PVK Prague), supporting the project with their experience, their data and serve as “on-line users and testers” of the findings. CD4WC is part of the CityNet project cluster. Introduction The project CD4WC deals with optimising the efficiency of the urban wastewater system with regard to ecological consequences in natural water bodies and with regard to investment and operation costs. The need to solve this problem is a direct consequence of the European Water Framework Directive (WFD) which requests to achieve good quality for ground and surface waters on a river-basin scale. With this new water-quality based approach, the design of the systems is by far less predetermined and the options to meet the goals become much more widespread. CD4WC will give guidance and support for this optimisation to operators, inasmuch the potential to improve the systems performance is identified while the cost-benefit ratio ought to be increased. In CD4WC the benefits for the development of the urban wastewater system resulting from the WFD approach will be identified and quantified with regard to its ecological and economic consequences. Criteria to assess the ecological consequences are – besides the water quality – also secondary resources inputs such as energy, materials and chemicals. Various options and strategies to develop the wastewater system are evaluated. Main emphasis is put on the dynamic interactions between the subsystems sewer system, WWTP and receiving water as well as on the possibilities of taking measures in the receiving water and at the sources. The methods applied are analysis of river basin managers data to gain insight in experience, the performance of measurement campaigns to close information gaps, numerical modelling to assess systems changes and extensions, and economic balancing to evaluate alternative pollution control instruments, such as permits, fees and pollution trading. Overview of the project The problem The European Water Framework Directive (WFD) requests to achieve good quality for ground and surface waters by organising water management on a river-basin scale and – with regard to impacts on natural water bodies originating from wastewater release – applying a combined emission and water-quality based approach. Managers and operators of wastewater systems on a regional scale claim that the approach requested by WFD will require additional authorities, management structures to be reorganised, and an improved performance of the wastewater system such that enormous investments will be necessary to meet the goals. So far, it was not yet evaluated and quantified what potential benefits could result from the WFD approach, which is setting water-quality goals in the natural water bodies instead of prescribing the design of urban wastewater systems. With this new water-quality based approach, the design of the systems is by far less predetermined and the options to meet the goals become much more widespread. Also, interactions between the subsystems sewer system, wastewater treatment plant (WWTP) and receiving water as well as between different measures, such as source control or increase of the WWTP loading during wet-weather conditions, may result in synergy effects. The economic benefit from these synergy effects must be balanced against the additional costs resulting from the implementation of the WFD (as claimed by river-basin managers) in order to be able to quantify the consequences reliably. Expected results In the project, knowledge will be gained that serves both the scientific community as well as the water managers in Europe. The following results can be expected: • a list of options to extend the wastewater system and improve its performance, among others namely the options resulting from integrated system operation; • an evaluation of these options with regard to ecological consequences in order to found a basis for comparing various options; • evaluation and comparison of the options with regard to investment and operation costs; • quantification of cost savings due to increased degrees of freedom induced by the WFD approach of setting the goals in the receiving waters as opposed to the system extension that would conventionally be implemented by strictly following design guidelines. Scientific knowledge is gained with regard to: • the coupling of models of the subsystems sewer system, WWTP and receiving water as well as the description of the interfaces and the interactions across these interfaces; • the quantification of loads to the receiving water caused by the various options of systems development; these loads are interpreted as indicators for ecological impacts. The practice of European water management will profit from the results of the project CD4WC in the sense that: • a basis for decision making is provided to improve the wastewater management; • the efficiency of urban-water quality management can be improved and the associated cost/benefit ratio can be enhanced; • not only technical aspects are evaluated but also the potential of economic tools to influence the system and the water management; • a guidance on how to efficiently develop the wastewater system will be provided on a CD. The innovation potential of the CD4WC project is to be seen against the background of the Water Framework Directive (WFD) and the problem of operators on how to develop and extend wastewater systems with an average lifetime expectancy of roughly 30 years (WWTP) to 80 years (sewer system). The innovative approach of the project is: • to link the WFD approach with the needs of operators; • to give guidance to develop the wastewater system from an integrated viewpoint; • to assess the benefits of a wide range of extension strategies with regard to ecological and economic criteria; • to link economic driving instruments with development scenarios. Present estimations of the costs caused by the implementation of the WFD suffer from the assumptions that the new aspects and increased requirements introduced by WFD are added on top of the present activities of the operators and do hardly induce a positive feed back. While the additional costs have been already relatively well estimated it was hardly discussed so far whether the new approach to set the goals – that is to aim at maintaining good water quality in the natural compartments instead of installing the wastewater systems according to the characteristics of the urban catchment – may also result in cost savings. Following the new approach, the possible options of measures to reach a certain goal or to improve the water quality, respectively, are numerous indeed, whereas they are much more restricted when the system is extended according to conventional guidelines. CD4WC aims to systematically identify ecological and economic synergy potential by making use of the degrees of freedom offered by the WFD philosophy, and evaluate the resulting cost savings and to put them into relation with additional costs originating from management and monitoring requirements required by the WFD, in order to achieve a realistic cost estimation. For the evaluation of the development strategies, it is crucial to recognise that measures required by today’s guidelines are replaced by the investigated options and are therefore not causing costs any more, e.g. by increasing the combined water flow to the WWTP the increase of combined water retention volume is not necessary any more. Identifying cost savings in the CD4WC project means to counterbalance the capitalised investment and operation costs of the new options, which become possible due to the openness of the WFD, against the costs of the “classical approach”. This outcome will support decision making of wastewater system operators and river basin managers. They are provided with various options to reach good water quality, evaluated with regard to ecological and economic consequences in view of an optimal development. The project group is put together of four university research teams from middle and southern Europe and of four companies operating wastewater systems on a city or on a regional scale situated in middle and central (eastern) Europe. The latter are end users on the one hand, but are actively contributing to the project with their experience, their data and as “on-line users and testers” of the findings on the other hand. It is of vital importance to analyse existing data available from operating companies and to continuously include their feedback into the project development.