The influence of dwelling occupancy and day of the week on domestic appliance wastewater discharges

Abstract

This paper describes some of the results from a small-scale diary survey of domestic (sanitary) appliance usage. This was undertaken to study variations in the pattern of use of appliances used in the domestic environment in order to enable updating and/or improvement of drain/sewer sizing procedures. In particular, data from the survey has been analysed to establish the influence on appliance usage, and hence discharges to the drainage system, of dwelling occupancy levels and the day of the week. The survey itself has been outlined including brief details of its duration and timing, the size and make-up of the sample, ownership of appliances and the basic methodology used. The patterns of appliance usage have been compared and it is shown that the WC was the most frequently used appliance on average throughout the day and the wash basin was the most used appliance during the morning peak. The influence of dwelling occupancy has been clearly established by showing the linear relationship between frequency of appliance usage and dwelling occupancy. The variations in usage from weekday to weekday have been shown to be low for the WC, basin and sink. At the weekend, however, it was demonstrated that the pattern of usage was different, particulary relating to the timing and magnitude of usage during the morning peak. The following design recommendations were made; that appliance usage figures should be quoted per capita rather than per dwelling and that the weekday peak usage period should be retained as the most onerous design condition.