No abstract

The polluting effects of storm water runoff on the receiving waterbodies represent an increasingly relevant problem in developing urban areas. In combined sewer pipes, transiting flood waves cause the alternation of sediment erosion and deposition of the solid material transported by the flow. Combined sewer deposit, mainly generated as an effect of such phenomena during the dry weather period between two rain events, is generally a mix of sand and highly polluting materials. Accumulation of sediments along a combined sewer network is often the cause of dysfunctions in the drainage system itself and negative impacts on the quality of receiving waters, due to the resuspension and overflow of pollutants. Both aspects have been investigated for the combined sewer of Rome thanks to an experimental catchment of about 2800 ha in the Cesarina -S. Basilio area. Based on the simulations conducted, structural solutions were proposed and evaluated, aimed at reducing the operational and environmental problems related to sewer sediment. The results show noticeable margins for the optimisation of the whole sewer system and for the reduction of its environmental impact.

Increasing urbanisation and intensification of human activities are common trends all over the world. The higher portion of impermeable urban surfaces often leads to well known effects on storm water runoff and its polluting potential for receiving waters. Despite the variety of structural solutions and management practices proposed to mitigate the operational and environmental impact of urban runoff, their application on existing drainage systems can often be either ineffective at a metropolitan scale or unfeasible for a densely urbanised territory. Among all the proposed alternatives, the real time control (RTC) of drainage systems is proving more and more promising to dynamically regulate the system capacity in response to intense rainfall. The combined sewer network of Rome, historically built with high-capacity pipes to collect storm water from both urban and natural catchments, holds significant potential for RTC of online storage and combined sewer overflows, to optimise the global drainage capacity and reduce the impact of discharges on local river quality. To assess the real benefits, the potential limits and the feasibility of such a system for the city sewers, a pilot study has been conducted on a 3,000 hectare sub-catchment. It involved the development of a fast-response hydrodynamic simulation tool for the sewer network, the definition and evaluation of RTC strategies and the implementation of an environmental integrated telemetry system. As described here, the study has highlighted significant margins for the optimisation of the global network capacity without any major interventions on the physical assets, as well as some critical issues to solve for a fully operational RTC application.

The management of water supply systems is based on fundamental principles, set by international and national legislations; the general target for water utilities is to offer a reliable and effective service following efficiency criteria. In this context, losses in distribution networks are one of the main problems to tackle: their reduction implies a general decrease in operational costs and in the need for a limited resource such as water. Numerous solutions have been proposed to reduce non revenue water, from simple leak detection to structural interventions on distribution systems, based on new design criteria which favour district-based networks over redundant ones. The present work proposes a new procedure to restructure a water supply network starting from its hydraulic model, comparing different types of intervention and evaluating their feasibility, limits and effectiveness in terms of the global system efficiency, as measured by the infrastructure leakage index (ILI). The possibility to use excessive pressure in specific parts of a network for the production of electricity is also examined, as it offers an additional resource to improve the system performance. The procedure has been tested for the water network in the municipalities of Tarcento and Magnano in Riviera, near Udine in Italy. Thanks to a specific hydraulic model, simulations were performed to identify the optimal interventions on the system aimed at reducing water losses and improving performances and efficiency.