Simulation and visualization of material flows in sanitation systems for streamlined sustainability assessment

New and alternative sanitation systems are increasingly discussed and find their way into implementation. However, discussions on sanitation concepts often are held in a rather emotional way. Furthermore, not all the available sanitation concepts might be known to the decision maker. The work presented here attempts to contribute to a good discussion and decision making process by compiling available technologies, by defining easy-to-implement criteria for a sustainability assessment method and by integrating these results into a simulation tool which allows to visualize the related resource fluxes (e.g. those on nutrients, such as N, P and K) and to analyse different sanitation options with regard to their capital and operational costs and with regard to environmental impact criteria such as greenhouse gas emissions. Whilst the calculations are to be considered as being approximate in their nature (due to uncertainties or lack of suitable input data), this tool allows the planners, with sometimes little modelling experience, to consider the characteristics of sanitation systems. Whilst starting from earlier work, such as Eawag's Sanitation Compendium and work on material flow analysis, work described in this contribution merges resource flux modelling, easy-to-use simulation and visualization and methods of life cycle assessment and life cycle costing. The simulation tool is freely available on https://www.ifak.eu/en/products/sampsons.

Integrated modelling as an analytical and optimisation tool for urban watershed management

In recent years numerical modelling has become a standard procedure to optimise urban wastewater systems design and operation. Since the models were developed for the subsystems independently, they did not support an integrated view to the operation of the sewer system, the wastewater treatment plant (WWTP) and the receiving water. After pointing out the benefits of an integrated approach and the possible synergy effects that may arise from analysing the interactions across the interfaces, three examples of modelling case studies carried out in Germany are introduced. With these examples we intend to demonstrate the potential of integrated models, though their development cannot be considered completed. They are set up with different combinations of self-developed and commercially available software. The aim is to analyse fluxes through the total wastewater system or 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. Furthermore the interface between the sewer and the WWTP can be optimised by predictive simulations such that the combined water flow can be maximised according to the time- and dynamics-dependent state of the treatment processes.

Measures and costs of integrated river basin management--the Wupper example

The implementation of the European Water Framework Directive entails additional costs in the areas of management, monitoring and water quality. As a first estimate, an attempt is made to assess the effects of implementation on the development of costs in a sub-basin, taking the Wupperverband as an example. The work and measures required are presented and the costs are assessed. On this basis, a cost estimate for the maximum time required for the implementation of the WFD is made. This takes into account all the relevant tasks in the area of the association with respect to rivers.

Simulation of a nitrification control concept considering influent ammonium load

Buchenhofen wastewater treatment plant of Wupperverband (650,000 p.e.) is currently being expanded for targeted nitrogen elimination. In view of the limited space available for extension, an optimized control concept is to be used in order to minimize the number of additional tanks required. This concept was investigated by dynamic simulation based on Activated Sludge Model No. 1. The investigations included a pure feedback control configuration and a configuration combining feedback und feedforward control, considering the influent ammonium load, for aeration. The results show that combined feedforward/feedback control has significant advantages over pure feedback control. In particular, this configuration allows a reduction in the effluent NH4-N peaks, which is especially important because of the low NH4-N limit of 5 mg NH4-N/L in a grab sample.

Modern management instruments--control of a water resources management association by means of an agreement on targets (balanced scorecard)

Since the matter of water supply and sewage disposal is safeguarded in Germany, public concern would no longer appear to be directed at questions of disposal reliability, but almost exclusively to economic efficiency. The requirements with respect to sewage disposal are dominated not only by growing environmental regulations and technical challenges, but also to a major extent by a discussion on the costs arising. In order to ensure a viable and at the same time economic water supply and sewage disposal despite this, it is necessary to have a holistic corporate control system. As a counterpart to the river basin management approach adopted at the Wupperverband there is, on the business management side, the agreement on targets (balanced scorecard) as a management and controlling approach. This incorporates purely financial variables as well as non-financial variables in the economic valuation of corporate success. The starting point is the formulation of strategic goals, while including customer-oriented, in-company and forward-looking perspectives, taking into account at the same time the interactions between them. A major perspective of such balanced scorecards is customer satisfaction. By means of an intensive dialogue with members, licensing and supervisory authorities of the Wupperverband within the framework of a holistic corporate control, it has been possible not only to improve corporate success, but also, and more importantly, to achieve an appreciable increase in confidence.

Provision of data for on-line simulation

A crucial factor for the quality and results of the on-line simulation of a municipal sewage treatment system is the provision of the requisite data in adequate quality and density. Since the measured data cannot be incorporated in a simulation model without prior processing, it should be prepared in such a way that it can be converted to the model-related input quantities. If individual input measuring signals fail, substitute value concepts must be developed which are based on the remaining information. With this it is possible to ensure the continuous provision of data. Various approaches are possible in seeking a solution to this problem. At the Wupperverband a detailed programme of investigation on the subject area of the processing of inflow data is being implemented as a component of future on-line simulation at Wuppertal-Buchenhofen STP.