Calculation for non-pressure sewage systems taking into account the irregularity of wastewater inflow from subscribers

Abstract

Sewerage systems are calculated according to the conditions of their operation in the mode of steady uniform wastewater flow. However, this mode is only likely to occur when the wastewater received from subscribers has a constant flow rate during the day. This, in turn, is possible if each subscriber has a regulating tank that ensures an average flow rate. Unfortunately, the established standards do not provide for such containers and, obviously, they are very expensive. Therefore, the wastewater nonuniformly enters the sewerage and nonuniformly flows through pipelines and gravity sewers. The presented work aims to model such modes of flow motion based on the particle method. The particle method is based on a graphical solution of the continuity equation (matter conservation) and the momentum conservation equation (motion). Numerical experiments performed using the particle method showed that flow rate, speed, and depth vary as wastewater moves, and they have a wave character. Knowledge of such modes is important to effectively organize the operation of gravity sewers, receiver tanks of pumping stations and treatment plants. Based on the proposed models, one can study the transfer of suspended solids and changes in the biochemical composition of wastewater. Moreover, the models can be used to calculate the storage capacity of gravity sewers.