Water-Saving Study of Urban Domestic Water Based on the Flow Pipe Optimization

The waste of domestic water causes the waste of water resource and the increasing sanitary sewage generated. To make the necessary reductions in the volumes of water used and wastewater generated, the water-saving study of urban domestic water based on the optimization design of flow pipe was performed at laboratory scale. Dynamics of the two-dimensional flow in siphonic water closets (WC), such as the flow regimes, velocity field and pressure field in the flow pipe, was investigated using a computational fluid dynamics (CFD) model and particle image velocimetry (PIV). The pressure and velocity in the shrinking nozzle of pipe were compared by CFD under different pipe shape. Result indicated that the pressure in pipe in the full-siphon stage and the siphon-generated time are of the most importance for the performance of WC. It was confirmed that the redesign of the shrinking nozzle of the pipe led to the reduction of water consumption. These numerical analyses and analog simulations presented the optimal shape design of flow pipe, which reduced the water consumption from 6 L to 4.5 L. The decrease of the water used in WC reduced the sanitary sewage generated. All the results and the research methods are expected to offer some reference for improving the sustainability of water based sanitation systems and developing a friendly sustainable domestic-water-saving technology. The method reported in this paper has profound environmental effect.