ABSTRACT:

Risk reduction approaches in urban waters requires accurate field data in order to conduct a proper risk assessment. Currently, relevant field data is difficult or impossible to obtain due to lack of adequate instrumentation, and to high logistic complexity and costs. We present an innovative field methodology, and the associated instrumentation, for the accurate and cost-efficient in-situ determination of microbiological impact from localized or diffuse pollution sources. Estimating effects of urban microbiological pollution currently relies on hydrodynamic models coupled with rough estimates of source concentrations, sometimes aided by stochastic or artificial intelligence approaches. Such models can provide reasonable insight into the dynamics of a pollution event but are geographically limited and parameter-dependent. The novel methodology presented here enables accurate in-situ assessment of microbiological impacts for a wide range of pollution events. It uses novel and automated sampling and field measurement technologies that greatly simplify the complexity and reduce the cost. We present a case study applying this new methodology to monitoring both short-term response to triggered pollution events and longer-term sanitary impacts of normal-usage houseboat wastewater discharges in the Marne river upstream of Paris, France. E. coli measurements at the source and in the receiving river, as well as independently-measured dilution factors, were calculated on sample time series collected both manually and using an automated aquatic drone. Actual impact over the background bacterial levels was measured using rapid field quantification of E. coli, using both portable and in-situ automated instrumentation. Automated analyzers were installed upstream and downstream of the group of boats under study. They were operated autonomously, using battery and wireless data transmission, thus obviating the need for an actual laboratory and enabling a wide range of field studies.