A novel aerator for enhancing the oxygen transfer rate and efficiency, named multistage vortex aerator (MVA), was developed. It uses vortex flow in repeated stages to increase the gas-liquid interfacial area and to decrease the thickness of the stagnant layer at the interface between the two phases. The basic characteristics of oxygen transfer using this aerator were investigated using the American Society of Civil Engineers standard procedure. The MVA could rapidly transfer oxygen to water to a concentration higher than 40 mg/L in 60 min owing to the effect of high purity oxygen, additional pressure induced by water and gas, and vortex flow dynamics. A gas transfer model was developed for describing the non-steady state operation of the aerator. This model is based on the mass and molar balances of oxygen in gas and water. It could successfully simulate the DO change inside the aerator. This study can help better understand the oxygen transfer mechanism and evaluate the performance of the new aerator at the various temperatures, pressures, and gas compositions found in diverse environmental systems.

In this work, we report the restoration of a polluted urban stream by employing the multistage vortex aerator (MVA), an in-line mixer device that improves the dissolved oxygen concentration of polluted streams and accelerates the water purification rate. It was observed during the field experiment that the dissolved oxygen was enhanced up to 7.05 mg/L and the water quality was improved to a good grade. As a result, the complex odor was successfully eliminated and reduced by up to 71.9%, while the water quality grade was also improved by more than two grades on average. Stream water quality indicators monitored for twelve months revealed high removal rates of total phosphorous (56.4%) and suspended solids (61%). The study demonstrated MVA as a promising eco-friendly technology for significant improvement in urban stream water quality. Moreover, the MVA process creates no secondary pollution and is believed to be a sustainable treatment option for odorous water bodies. Overall, the MVA process is technically feasible for implementation, and this study provides a specific reference as a basis for the treatment of polluted water bodies in urban settings.

This study investigates the impact of port construction on suspended solid concentrations and key water quality parameters in Jinhae Bay, using seventeen years of water quality data up to 2020. The study highlights the significant impact of suspended solids on marine water quality, particularly in areas affected by dredging operations at Busan New Port. Suspended solids concentrations peaked at 92 mg/L, exceeding 10 mg/L in both surface and bottom waters, with the highest levels near the port. These solids were identified as key predictors of coastal eutrophication in locations such as Jinhae Bay 01, 17, 19, where positive correlations with Chl-a suggest their role in promoting eutrophication. The highest average Chl-a levels were recorded at Jinhae Bay 01 (9.82 µg/L), while the lowest were at Jinhae Bay 14 (3.2 µg/L). The WQI, ranged from 1 to 3, with Jinhae Bay 19 showing the highest value and Jinhae Bay 14 the lowest due to low dissolved oxygen levels. Using ARIMA modeling, the study effectively analyzed the time-series dynamics of suspended solids, demonstrating their relationships with Chl-a and WQI components. These findings underscore the importance of monitoring and managing suspended solids to mitigate the risk of eutrophication and protect marine ecosystems in the context of port development.