The practical performance of decentralized waste water treatment technologies in Dutch urban areas

Abstract

Over the last few years, the approach of waste water management is shifting from the conventional centralized treatment system to a modern decentralized treatment system including the separation of domestic waste water streams. The treatment of separated domestic waste water streams on local scale is considered to be beneficial for the treatment efficiency, the mitigation of local water shortages and the recovery of valuable resources. The concept of the decentralized waste water system is increasingly taken into consideration in the Netherlands. The implementation of decentralized waste water systems on neighborhood scale is more frequently put on the agenda. In fact, the system design phase has already started in multiple Dutch cities. Yet, the selection of the most suitable treatment technology for a decentralized waste water system is not a clear-cut decision. Firstly, this challenge is caused by the variation among the available technologies. Each treatment technology has a specific set of theoretical benefits and limitations (product specifications). Secondly, the performance of a technology in actual practice is dependent on contextual influences from the specific location of application. Thus, no ‘one-size-fits-all’ solutions exists for the selection of a decentralized waste water treatment technology. In order to contribute to the selection of the most suitable treatment technologies for the implementation in Dutch urban areas, this study aimed to evaluate on how the product specifications will manifest in practice. Therefore, product specifications and the actual performance of the vertical subsurface flowing constructed wetland and the DESAH system were analyzed. The product specifications and the actual performance were analyzed on 11 distinctive aspects divided over the environmental, functional, economic and sociocultural dimension. The results of this study show that for the vertical subsurface flowing constructed wetland and the DESAH system the actual performance of the assessed technologies partly comply with the product specifications. This report presents in detail whether the actual performance complies with the product specifications on each technology aspect. What theoretical benefits will manifest in practice, and what actual challenges should be taken into account during the design of a waste water system?