Gas transfer model for a multistage vortex aerator: A novel oxygen transfer system for dissolved oxygen improvement

Effect of aeration on oxygen transfer characteristics in integrated wastewater treatment systems utilizing mass transfer model and computation fluid dynamics methods

This paper investigates the aeration and oxygen transfer characteristics within the aeration tank of an integrated wastewater treatment system (IWTS) using Computational Fluid Dynamics coupled with Population Balance Model and oxygen transfer model. The findings suggest that increasing the air flow rate significantly enhances the oxygen transfer rate, albeit at a decreasing rate of growth. The oxygen overall mass transfer coefficient is primarily influenced by the interfacial area per unit volume and to a lesser by the oxygen mass transfer coefficient (kL). A strong positive correlation is found between turbulence intensity and kL, which, along with dissolved oxygen distribution, confirms the critical role of turbulence in the oxygen transfer process. For small-scale IWTS, an air flow rate of 30 L/min may be the optimal choice.

Using ozone nanobubbles, and microalgae to promote the removal of nutrients from aquaculture wastewater: Insights from the changes of microbiomes

Integrated aquaculture wastewater treatment systems (IAWTSs) are widely used in treating aquaculture wastewater with the aeration-microalgae unit serving as an important component. In this study, we artificially constructed an IAWTS and applied two aeration-microalgae methods: ordinary aeration or ozone nanobubbles (ONBs) with microalgae (Nannochloropsis oculata). The impact of N.oculata and ONBs on the removal performance of nutrients and the underlying micro-ecological mechanisms were investigated using 16S rRNA gene amplicon sequencing. The results demonstrated that the combined use of ONBs and N.oculata exhibited superior purification effects with 78.25%, 76.59% and 86.71% removal of CODMn, TN and TP. N.oculata played a pivotal role as the primary element in wastewater purification, while ONBs influenced nutrient dynamics by affecting both N.oculata and bacterial communities. N.oculata actively shaped bacterial communities, with a specific focus on nitrogen and phosphorus cycling in the micro-environment remodeled by ONBs. Rare bacterial communities displayed heightened activity in response to the changes in N.oculata, ONBs, and nutrient levels. These findings provide a novel approach to improve the technological processes the IAWTS, contributing to the advancement of sustainable aquaculture practices by offering valuable insights into wastewater purification efficiency and micro-ecological mechanisms.