Search

Disinfection is an effective microorganism inactivation method that has contributed historically to decreasing waterborne diseases. It is necessary to improve hydraulic efficiency for ensuring disinfection ability without creating disinfection by-products. However, many hydraulic efficiency indices, which are a type of black-box analyses based on residence time distribution curves, have been used to assess short-circuiting and mixing. We propose a novel index (internal short-circuiting index, ISI) and analysis approach (internal short-circuiting estimation method, ISEM) based on computational fluid dynamics (CFD) modelling for understanding the local hydrodynamics. Then, we implement ISEM to quantify the effect of the clearwell configuration with the different length-to-width and shape ratios on the hydraulic efficiency. As the hydraulic efficiency surrogated by T10/T converges to the maximum value, the ISI values at inlet and outlet reduce rapidly, and the recirculation and dead zones shrink in the channel zones. Thus, the ISI curve changes from a V shape to U shape. The ISEM demonstrates that it is applicable under various conditions and it enables engineers to design clearwells for optimizing the disinfection ability. Furthermore, the CFD model in this study can be combined with machine learning techniques in future studies to extract knowledge for reducing the computational cost.

To increase disinfection potential in a chlorine contactor, it is often recommended to increase the detention time in the contactor, that is, its hydraulic efficiency. This can be accomplished by installing inner devices such as baffle walls, diffuser walls, and intrabasins. To more accurately analyze the effect of such inner devices, it is necessary to conduct transient hydrodynamic analysis, which is computationally intensive. To reduce this computational burden, this study develops a simplified approach using steady-state dead zone analysis. In addition, this study uses the simplified approach to explain, with an indicator of dead zone volume percentage, why hydraulic efficiency changes with using different designs of length/width ratio, shape factor, diffuser walls, and intrabasins. This study suggests a relationship between dead zone volume percentage and hydraulic efficiency to replace length/width ratio. This will increase the estimation accuracy of hydraulic efficiency with various design...

Since regional water supply systems (RWSS) in Korea are all separated and are tree-shaped networks, the reliability is low and operation is not efficient in an emergency. So connecting RWSS to each other can be a good option to improve the operation efficiency. This study has been initiated to evaluate efficiency looking at a pilot case. Expected shortage has been selected as a surrogate. In this study, we developed pipe failure probability equations which are suitable in Korea by considering material, diameter, year, and length. As a pilot case, the three systems of Jeon-ju (JJ), Bu-an (BA), and Seom-jin (SJ) are selected and we consider two connections: JJ–BA and JJ–SJ. In each connection we develop three alternative plans, and we conclude that connections of JJ–BA and JJ–SJ can improve the operational efficiency as much as 5% and 4%, respectively.