Flow Variation and Flowrate

The flowrate of municipal wastewater varies according to the season of year, weather conditions, day of the week, and time of the day. Under dry weather conditions, the daily flow shows a diurnal pattern.

Figure 2 illustrates daily variations of flow in sewer. The rated capacity of waste water treatment plants is normally based on the average annual daily flowrate at design year. As a practical matter, however, primary clarifier has to be designed to meet peek hourly flowrate and minimum daily flowrate.