Impact of urban drainage and sewerage systems on the quality of water bodies and mitigation strategies

Pollution due to anthropogenic activities is a significant factor in compromising receiving water quality status. Rural areas accumulate plant protection products and other pollutants which are eventually washed off by irrigation channels or during rainfall events towards nearby water bodies. To assess water quality of rivers and water bodies over time, long-term monitoring activities which usually consist in collecting few samples over the year for laboratory analysis, are done. However, being these activities expensive, time consuming and staff intensive, the frequency of sampling in many cases is limited both in time and space, making the assessment of physical and chemical processes derived from several factors, such as rural activities and urban areas, a challenging task. To overcome limitations related to the possibility of collecting only a certain amount of samples in time and space, models that consider both water quantity and quality aspects, have been developed to interpret data collected, predict future quality status and suggest possible actions to mitigate or eliminate pollution sources. To manage problems generated as a consequence of the increase of urbanization and of changes in climatic forces, Sustainable Urban Drainage Systems, have being proposed. Among others, permeable pavements can be easily retrofitted in the urban environment and have proved to be highly effective at managing stormwater. However, these systems are subjected to clogging, the accumulation of particles on the porous surface and in the permeable layers. Thus concerns related to the long term performance of this solution as well as the optimal configuration to be adopted to reduce the evolution of clogging in time and allow for effective maintenance have prompted many researchers to test these solutions through both laboratory scale, real scale experiments and modelling. This research aims at providing insights on the impact of urban areas as well as rural activities on rivers water quality both during normal conditions and rainfall events and at assessing the efficiency of permeable pavements as stormwater control facilities. For the first research topic, the city of Treviso has been selected as case study. A monitoring system has been designed and developed consisting of 6 stations equipped with radar sensors to obtain discharge data. Results from the analysis of data collected show advantages and limitations of the selected instruments, the evolution in time and space of several water quality parameters and suggest the main sources of pollutants upstream and downstream the downtown. A hydrodynamic model was also developed considering the river-channel network and tested using data collected by the radar sensors. For the second reseach topic, a large scale (6m x 2m) laboratory model of a permeable pavement has been realized. The performances of the newly constructed permeable pavement subjected to different rainfall intensities have been assessed using several sensors (3 piezometers, 6 tensiometers, 4 water content reflectometers and two tipping buckets discharge gauges). Results from the laboratory experiments have proven the efficiency of a newly constructed permeable pavement subjected to very intense rainfall events.