Scholarly record
FRAMEWORK FOR EVALUATING SEWAGE OVERFLOWS IN URBAN ENVIRONMENTS
Abstract
Modern requirements for limiting the frequency of overflows in water bodies increasingly require an emphasis on increased control over sewer overflows and their operation. The requirements in the new Directive (EU) 2024/3019 of the European Parliament and of the Council of 27 November 2024 on urban wastewater treatment. One of the main requirements is to limit pollution from wastewater overflow during rainfall. This overflow should not be more than 2% of the annual load of individual parameters, accounting for biological pollution, calculated in dry weather. The study analyzed the available information on the population coverage by the sewerage network, population density, water supply , sewerage rates, and the degree and type of coverage of the surface of the territory. The proposed methodology provides a framework for a preliminary assessment of the existing situation of the sewage network of urbanized residential areas and the frequency of overflows into water bodies. In one case, the degree of dilution at the overflow should be sought, which would correspond to a given frequency of overflow, as well as the necessary runoff coefficient in the case of a highly congested territory. In the second task, with available data on the operation of the sewer overflow with confirmed data on the runoff coefficient, an estimate of the equivalent precipitation is given that corresponds to the dry runoff formed by the population in the studied territory. This analysis will provide an estimate of the real frequency of overflow, relative to the climatic characteristics of the site area. Calculations have been made for several Bulgarian cities.
Publication details
References16
Directive (EU) 2024/3019 of the European Parliament and of the Council of 27 November 2024 on urban wastewater treatment (recast), Official Journal of the European Union, L series, 12 December 2024.
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