Specific features of hydraulic mode simulation for combined sewers

Summary

Hydraulic simulation of sewerage networks in big cities in practice involves input of large quantities of data on all the network sections including the yard ones. This complicates significantly and extends the time required for fulfilling the task. Therefore developing express-method of hydraulic simulation of transporting facilities of sewers will provide for reducing the amount of input information without reducing the accuracy of the calculation results. In order to substantiate the method experimental studies in one of the sanitation districts of Saint-Petersburg were carried out. By experiment it was stated that the use of simplified hydraulic simulation with account of only street networks (without the yard ones) resulted in 20% overestimation of the calculated flows. Herewith the express-method of calculating wastewater flows in combined sewers depending on the rainfall intensity that allows the use of hydraulic simulation with account of only street networks where virtual tanks are simulated with a capacity equal to the capacity of the yard networks connected to them has been experimentally substantiated. The method error is 2–5%.

Key words

sewerage pumping station , capacity , combined sewer , flow regulating unit , stochastic method , unsteady random flow

The use of stochastic methods in determining the required capacity of regulating units in combined sewers

Summary

The flows of wastewater removed by the combined sewers are characterized by high irregularity caused by the random nature of rainfall and snow melting. One of the ways of improving the reliability of these systems is the introduction of flow regulating units. They have been designed to diverse wastewater between the sanitation districts in case of emergency or in case of the actual wastewater inflow in one of them, e. g. because of over-estimated rainfall, exceeding the actual capacity of the regulating units. The method of determining the required capacity of the flow regulating units with the use of stochastic methods was developed. By the example of the wastewater disposal system of Saint-Petersburg it was stated that the required supply of the sewage pumping station (SPS No. 6) functioning as a regulating unit between the left-bank and right-bank sanitation districts was of random nature and was distributed according to the exponential law with the increasing probability of using the modes with lower supply.

Key words

sewerage pumping station , capacity , combined sewer , flow regulating unit , stochastic method , unsteady random flow