A wastewater retention canal as a sewage network and accumulation reservoir

Abstract

The paper presents an innovative retention canal for storm sewage as a competitive solution in relation to the ones currently used. The principle of operation of the retention canal, the conditions of its use in a sewage network and the basis for dimensioning were presented. To demonstrate its versatility and retention efficiency, comparative studies on the example of a drained catchment were carried out. A linear network layout composed of 12 storm canals with the retention reservoir located at the network outlet was assumed. Based on the developed algorithm, simulation tests were performed with the use of the SWMM 5.1 program. On the basis of hydrodynamic modelling it was determined: (1) the required geometry of storm canals, (2) the geometry of damming partitions and (3) the process of wastewater accumulation in the retention canal. Having the results of simulation research for rainfalls with a duration of 10 to 100 minutes, the critical rainfalls for network and retention canal dimensioning were determined. The comparison of hydrographs of sewage outflow from the examined catchment is interesting. From the value of 3.62 m3/s in the network it decreases three times to just 1.16 m3/s at the outlet of the retention canal. The retention canal with diameters identical to those established for the network, allow achieving the sewage retention capacity, which corresponds to a capacity of 1,844 m3 for a multi-chamber retention reservoir. Thus, the retention canal fully replaces the operation of a network of certain geometry and retention reservoir. The results of the research allowed the formulation of a number of important conclusions, including conclusions on cognitive significance. The critical rainfall appointed for the design of the retention canal always lasts longer than that, determined for the sewage network design. The retention canal is suitable for widespread use in the canals of new and already existing storm sewage systems and combined sewage systems.*