Variable dynamics of sewage supply to wastewater treatment plant depending on the amount of precipitation water inflowing to sewerage network

Abstract

The paper analyzes the effect of precipitation water that inflowing to sanitary sewage system as accidental water on the changes in the total amount of treated sewage. The effects of accidental water supply on the total amount of sewage inflowing to treatment plant were analyzed based on mean daily amounts from the investigated periods and mean daily amounts from incidental supplies. The study was conducted in the years 2010-2015. Six characteristic research periods were identified (one per each calendar year), when the amount of sewage in the sanitary sewage system was greater than during dry weather. The analysis of changes in the amount of sewage supplied to the sewerage system in the six investigated periods revealed that the accidental water constituted from 26.8% to 48.4% of total sewage inflowing to the wastewater treatment plant (WWTP). In exceptional situations, during intense rains, the share of precipitation water in the sewerage system would increase up to 75%. Then, the rainwater inflowing the sewerage system caused hydraulic overloading of the WWTP by exceeding its maximum design supply.