OPTIMIZING EFFICIENCY OF THE COMBINED SEWER OVERFLOW CHAMBER HOBAS

Abstract

The paper deals with the design of swinging self-clean screen bars and the assessment of pressure losses in the combined sewer overflow chamber (HOBAS CSO Chamber), sold by the company HOBAS. The HOBAS CSO Chamber ensures a safe transfer of rainwater during a major rain event. The main goal of the research was to determine the pressure losses of the overflow chamber under various conditions - without self-clean screen bars; with screen bars without impurities and with screen bars partially or fully clogged with various impurities. The measurements were performed on a 1 : 5 scale physical model of CSO using 4 probes for measuring level heights. From the measured values, the coefficients of local losses were calculated, which were then entered into the currently used design table of flow capacities of the CSO HOBAC Chamber.

At the same time, the optimal shape of individual rods of swinging self-clean bars was investigated, so that the oscillation of the free ends of the rods supports the separation and self-cleaning function during their operation. The research was conducted on a 1 : 1 scale model, so that impurities present in the CSO during the overflow (i.e. textile, cosmetic handkerchiefs, feminine hygiene products, condoms and others) could be used directly in the measurement. At the end of the experiments, the variants of the rods of screen bars that were the most effective in the separation and self-cleaning function were selected. The self-cleaning effect, which occurs at the end of the rain event and ensures that the CSO
is free of impurities and ready for further use, was subsequently tested with the selected variant of the rods.