ASSESSING EXFILTRATION FROM A SEWER BY SLUG DOSING OF A CHEMICAL TRACER (NACL)

In the urban areas, several water sources recharge the groundwater, transporting high concentrations of organic and inorganic pollutants too. Among these there are the leakages from untight sewer pipes that couid be a serious threat for groundwater quality because ofiarge extension of urban drainage system. The objective of sewer leakage determination at catchment-scale is the planning of the best rehabilitation strategies of untight pipes that for the most part of year are affected by exfiltrations during the dry weather, when the groundwater is below the pipe's bottom and surrounding soil is unsaturated. The urban sewer can be a threat for the shallow unconfmed aquifers and confined ones that can be connected with shallow groundwater. As matter of the fact, the transport of organic and inorganic compounds as well as pathogenic organisms ceompromise the groundwater quality and when it is used as drinking water supply advanced water treatments couid be necessary to clean it. The paper presents the tracer slug dosage method applied on an urban sewer network in a suburb area ofRome to assess exfiltration. Some preliminary results are discussed, too. Moreover thè paper highiights the importance of the preliminary knowledge about: flow rate, naturai conductivity background and some characteristics ofthe entire system (e.g.: sewer pipe, soils, etc.).