Proposals of a procedure to asses Pollutographs. Application to Murcia's Combined Sewer Overflows (CSOs).

Resumo

Directives 91/271/EEC and 93/481/EEC set norms regarding the management of Combined SewerOverflows. European Commission monitors the implementation status and implementation programmes. Infact, during the year 2019 all the utilities should be able to quantify the pollution spilled during storm events.And afterwards, plans have to be developed in order to reduce the impact of such events. In this paper, weproposed a method to estimate the transported pollution during events as well as to serve as a tool fordeveloping plans to lessen the corresponding pollution.The procedure is divided into three steps:A. Periodical measurements of all relevant pollutants, e.g. total suspended solids and chemical oxygendemand, in wet and dry weather. Such pollutant “concentrations” are correlated with the turbidity, updatingthe relation among them [1].B. Continuous measures of the turbidity. Turbidity is continously register in the sewer areas near overflowspillways. Turbidimeters are a very convenient equipment for this purpose [2]. Actually, it is reliable, itsmeasures are very correlated with the total suspended solid concentration and its maintenance is easy. In thisway, combining A. and B. turbidity measures provide us a real-time estimation of the pollutant concentration.on real time.C. Assesment of each catchment hydrograph. Depending on the available data, this step could be based on adesign, a measured or a simulated hydrograph. In order to apply this methodology to Murcia’s CombinedSewer System, we have used simulated hydrographs based on real measured rainfall. Murcia’s utility hasdeveloped a calibrated SWMM model, and therefore, using the rainfall data, it is possible to estimatehydrographs for all the relevant points of the system.D. Estimation of each catchment pollutograph. Combining the pollutant concentration, estimated in theprevious steps, with the hydrographs, we can asses how the mass of pollutants are transported. Thisinformation allows us to comply with EU Directives, but it will also be useful to design Murcia’s strategy tominimize environmental impacts.