Analisi degli aspetti di qualità nella gestione dei sistemi di drenaggio urbano attraverso modellazione numerica e indagini di campo
Creators: name: Casadio, Andrea <1977>
Publisher: name: Alma Mater Studiorum - Università di Bologna
Year: 2008
Subjects: ICAR/02 Costruzioni idrauliche e marittime e idrologia

description: In order to protect river water quality, highly affected in urban areas by continuos as
intermittent immissions, it is necessary to adopt measures to intercept and treat these
polluted flows.
In particular during rain events, river water quality is affected by CSOs activation. Built
in order to protect the sewer system and the WWTP by increased flows due to heavy
rains, CSOs divert excess flows to the receiving water body.
On the basis of several scientific papers, and of direct evidences as well, that
demonstrate the detrimental effect of CSOs discharges, also the legislative framework
moved towards a stream standard point of view.
The WFD (EU/69/2000) sets new goals for receiving water quality, and groundwater as
well, through an integrated immission/emissions phylosophy, in which emission limits
are associated with effluent standards, based on the receiving water characteristics and
their specific use.
For surface waters the objective is that of a “good” ecological and chemical quality
status. A surface water is defined as of good ecological quality if there is only slight
departure from the biological community that would be expected in conditions of
minimal anthropogenic impact. Each Member State authority is responsible for
preparing and implementing a River Basin Management Plan to achieve the good
ecological quality, and comply with WFD requirements.
In order to cope with WFD targets, and thus to improve urban receiving water quality, a
CSOs control strategy need to be implemented. Temporarily storing the overflow (or at
least part of it) into tanks and treating it in the WWTP, after the end of the storm,
showed good results in reducing total pollutant mass spilled into the receiving river.
Italian State Authority, in order to comply with WFD statements, sets general
framework, and each Region has to adopt a Water Remediation Plan (PTA, Piano
Tutela Acque), setting goals, methods, and terms, to improve river water quality. Emilia
Romagna PTA sets 25% reduction up to 2008, and 50% reduction up to 2015 fo total
pollutants masses delivered by CSOs spills.
In order to plan remediation actions, a deep insight into spills dynamics is thus of great
importance.
The present thesis tries to understand spills dynamics through a numerical and an
experimental approach. A four months monitoring and sampling campaign was set on
the Bologna sewer network, and on the Navile Channel, that is the WWTP receiving
water , and that receives flows from up to 28 CSOs during rain events. On the other
hand, the full model of the sewer network, was build with the commercial software
InfoWorks CS.
The model was either calibrated with the data from the monitoring and sampling
campaign. Through further model simulations interdependencies among masses spilled,
rain characteristics and basin characteristics are looked for.
The thesis can be seen as a basis for further insighs and for planning remediation
actions.