ANALYSIS OF THE SPILL FLOW DISCHARGE IN WASTEWATER TREATMENT PLANT COMBINED SEWER SYSTEMS: A CASE STUDY AND REGIONAL REGULATIONS OF REFERENCE

Abstract

The aim of this study is to carry out, for unitary sewage systems, a quantitative analysis of volumes and flow rates directly introduced into the water body through wastewater treatment plant spillways. The study utilizes the ratio regulating the maximum runoff flow rate sent to treatment when compared to the average daily flow in dry weather. Specifically, the case study examined the sewer systems of the municipality of Remanzacco and Lauzacco in the province of Udine. EPA - SWMM (Storm Water Management Model) software was used to simulate flood hydrographs for the flows entering the wastewater treatment plant between 2009 and 2018. Concurrently, statistics were calculated on the flows both entering the different treatments and those directly spilled into the receiving water body as per the requirements set out in the Regional Water Protection Plan (PRTA) of the Friuli Venezia Giulia Region. As a complement to these simulations, research was undertaken into the regional regulations relating to urban wastewater treatment plants sizing, i.e. the ratio between the flow rates sent and the flow rates spilled directly into the receiving water body.