Experimental investigation of enhanced NaCl removal using porous broad crested weirs with different alumina-limestone configurations

Abstract

An innovative experimental approach was developed to enhance NaCl removal using porous broad-crested weirs with different alumina-limestone configurations in an open-channel flow under controlled hydraulic conditions. Eight experimental cases were systematically evaluated, examining pure limestone, pure alumina, and mixed arrangements (Al-Ls-Al, Ls-Al-Ls) under two flow rates over 240 minutes. Results demonstrate that pure alumina achieved superior performance with 5.88% average removal efficiency, significantly outperforming pure limestone (2.01-4.27%) and mixed configurations (4.41-5.01%). Limestone exhibited significant hydraulic dependency, with removal efficiency increasing by 112% when flow rate increased from through flow to through flow limit conditions, while alumina demonstrated consistent performance across both flow regimes. All configurations showed initial rapid removal followed by a gradual approach toward equilibrium efficiency, with the most significant removal occurring within the first 10 minutes. Mixed material configurations (Al-Ls-Al and Ls-Al-Ls) achieved removal efficiencies that fell between those of pure materials, indicating no enhancement beyond the individual material properties. The study reveals that while alumina provides optimal NaCl removal, limestone under enhanced flow rates offers economically viable alternatives, achieving 71% of alumina’s performance. Porous broad-crested weirs represent promising technology for sustainable water treatment applications.