Abstract
Aeration is one of the most cost intensive steps in water and wastewater treatment due to the large energy requirement for the creation of large surfaces for sufficient gas exchange as well as for providing efficient liquid transport in order to exchange saturated liquid elements at the surface with unsaturated ones from the bulk. In this work we show that geometrically constrained vortices in a hyperbolic funnel are a promising aeration technique as they meet these criteria and allow oxygen transfer coefficients up to 50 h−1, a number significantly higher than that of comparable methods like air jets or impellers (<10 h−1).
Highlights
Dissolving oxygen in water is one of the most energy intensive steps in water and wastewater treatment plants (WWTPs)
In the present work we investigate whether the mass transfer can be further enhanced when swirling flows with liquid–gas interfaces are constrained in a hyperbolic funnel
It has been reported that utilizing a free-surface vortex in a shower head might result in ≈14% lower water consumption while maintaining the shower comfort, higher amounts of oxygen dissolved, and a favourable change in pH if a hyperbolically shaped funnel is used [9]. In this type of funnel, which was first suggested by Schauberger [10], the liquid–gas interface can extend from the top of the funnel all the way to the outlet, resembling a helix or standing wave pattern
Summary
Dissolving oxygen in water (aeration) is one of the most energy intensive steps in water and wastewater treatment plants (WWTPs). It has been reported that utilizing a free-surface vortex in a shower head might result in ≈14% lower water consumption while maintaining the shower comfort, higher amounts of oxygen dissolved, and a favourable change in pH if a hyperbolically shaped funnel is used [9]. In this type of funnel, which was first suggested by Schauberger [10], the liquid–gas interface can extend from the top of the funnel all the way to the outlet, resembling a helix or standing wave pattern. These aeration systems are well defined, highly controllable and extremely efficient aeration systems, with the potential to supersede currently commercially available technologies
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