Assessment of Spatio-Temporal Variability of Faecal Pollution along Coastal Waters during and after Rainfall Events

More than 80% of wastewaters are discharged into rivers or seas, with a negative impact onwater quality along the coast due to the presence of potential pathogens of faecal origin. Escherichiacoli and enterococci are important indicators to assess, monitor, and predict microbial water qualityin natural ecosystems. During rainfall events, the amount of wastewater delivered to rivers andcoastal systems is increased dramatically. This study implements measures capable of monitoring thepathways of wastewater discharge to rivers and the transport of faecal bacteria to the coastal areaduring and following extreme rainfall events. Spatio-temporal variability of faecal microorganismsand their relationship with environmental variables and sewage outflow in an area located in thewestern Adriatic coast (Fano, Italy) was monitored. The daily monitoring during the rainy eventswas carried out for two summer seasons, for a total of five sampling periods. These results highlightthat faecal microbial contaminations were related to rainy events with a high flow of wastewater,with recovery times for the microbiological indicators varying between 24 and 72 h and influenced bya dynamic dispersion. The positive correlation between ammonium and faecal bacteria at the ArzillaRiver and the consequences in seawater can provide a theoretical basis for controlling ammoniumlevels in rivers as a proxy to monitor the potential risk of bathing waters pathogen pollution