Modeling and Design of Innovative Small Diameter Gravity Sewerage System

Abstract

The article presents modern methods of hydraulic design of an innovative small diameter gravity sewerage system. In this system, domestic wastewater is preliminary treated in septic tanks equipped with outlet filters, thus the effluent features are similar to those of clear water. Innovative non-return valves at the outlets eliminate introduction of air to the system and thus the flows can be treated as one-phase ones. Computer codes EPANET 2 and SWMM 5.0 were applied and compared. Two flow schemes typical for the sewerage system were implemented in EPANET 2, and the third -in a slightly modified SWMM 5.0. Simulation results were validated on empirical data obtained on a laboratory physical model, consisting of four tanks of minimum volumes 600 dm 3 each, connecting PE pipelines of diameters 25 mm and 36 mm and relevant sanitary fittings. Water inflows, typical for domestic wastewater outflows from single homesteads, were provided by a pump. Water flows were measured using water meters with pulse outputs, and water levels in tanks by pressure transducers. Hydraulic characteristics of filters and non-return valves were provided. Simulation results showed good agreement with the empirical data. Ranges of values of design parameters, needed for successful application of both codes, were established and discussed.

A Case Study of a Small Diameter Gravity Sewerage System in Zolkiewka Commune, Poland

“…The initial level of wastewater in the tank was assumed to be equal to the inverted level of the outlet from the ST (0.9 m above the tank bottom). The minor loss at the effluent filter from the ST was simulated using the value of the coefficient ξ = 2.5 (obtained from previous research [22]).…”

“…In the SWMM, check valves and manholes were simulated using the storage unit. Head losses during wastewater flow through the check valve were simulated by providing the minor loss coefficient equal to ξ = 10 (obtained from previous research [22]). The presence of the check valve was simulated by setting the value of YES in the field flap gate for the connection between the manhole and the network.…”

“…In addition, due to the irregular shape of the tank in the storage curve field, the tabular values were given, and in the curve name field the name of the curve describing the change in the cross-sectional area of the tank in relation to the corresponding wastewater depth was given. wastewater flow through the check valve were simulated by providing the minor loss coefficient equal to ξ = 10 (obtained from previous research [22]). The presence of the check valve was simulated by setting the value of YES in the field flap gate for the connection between the manhole and the network.…”

“…The properties of this conduit-diameter (26 mm) and length (1.5 m)-were set in accordance with the design project and field measurements. The presence of the check valve was simulated by setting the value YES in the field flap gate and the minor loss coefficient for the emitter in the pumping station equal to 4000 was taken [22], typical for an almost closed ball valve. This head loss was also influenced by the emitter connection to the force main via a check valve.…”

“…The second objective was to examine the feasibility of applying the Storm Water Management Model (SWMM) to simulate operation of the SDGS system. In our previous works [22,41], the feasibility of applying the SWMM to simulate the emptying of a simple SDGS (four tanks without an effluent filter) system was checked in semi-technical and laboratory studies. As far we know, the SWMM has not been applied before for the simulation of such a system, and therefore its validation in a real case study seemed to be attractive.…”