Sedimentation, Mineralization and Resuspension of Sludge in a Sewerage System: A Case Study
Quantitative information was obtained on the processes of sedimentation, mineralization and resuspension of organic matter in a combined sewerage system by means of statistical analysis of dry and wet weather data on sewage flows. The effects of temperature and length of intermittent dry weather periods on daily pollutant loads were also evaluated. For the sewerage system investigated it was found that in summer 5-26% of the BOD produced is mineralized in the system before reaching the sewage treatment plant. Due to sedimentation under dry weather conditions up to 12% of the daily organic load produced may be present in the sewers as resuspendable deposits; in winter this percentage may even amount to 20-30% because of slow mineralization.