Reaeration and oxygen dissipation into a circular hydraulic channel: experimental and dimensionless approach

Abstract

Dissolved oxygen (DO) is a key parameter in water quality. The DO concentration in a water body can be changed by interfacial phenomena such as reaeration and oxygen dissipation, which can be represented by the coefficients K2 and KD, respectively. Few studies have jointly correlated K2 and KD with physical and hydraulic parameters of the channel. The present work investigated the behavior of these coefficients over a range of hydraulic conditions, and developed semi-empirical equations capable of relating both coefficients. Reaeration and DO dissipation tests were conducted in a circular hydraulic channel with flow velocity ranging from 0.20 to 0.79 m.s-1 and depth ranging from 0.09 to 0.15 m. Estimates of K2 and KD were performed using the non-linear regression method. Semi-empirical equations were obtained based on classical dimensional analysis and multiple regression analysis. The comparison between measured and estimated coefficients yielded R2 for reaeration and dissipation of 0.940 and 0.844, respectively. KD was higher than K2 for all turbulence levels applied at the hydraulic channel. An estimate obtained by the relation between the semi-empirical equations indicates that the transfer of oxygen in the water-air direction (dissipation) is approximately twice as fast as the transfer in the air-water direction (reaeration).

Bactericidal efficiency and photochemical mechanisms of micro/nano bubble–enhanced visible light photocatalytic water disinfection

“…This agreed with the previous finding that the higher DO level could benefit the treatment. Nevertheless, the supersaturated system is unstable, because of the high vibrational energy of dissolved oxygen molecules and the low entropy (Harano et al, 2018). Once bubble addition was stopped, the oversaturated O2 is quickly released or consumed and the solution returns to a saturated and stable state (Hirakawa et al, 2007).…”

Evaluation of dissolved oxygen sinks in water-stirring setups used in reaeration experiments

“…Using an oscillating grid tank, Silva et al (2020) showed that humic substances reduce K 2 , regardless of the air-water interface's turbulence. Additionally, several other studies performed reaeration experiments using WSSs (Gonçalves et al 2017;Harano et al 2018;Lee 2020).…”

Humic substances reduce the oxygen mass transfer in the air–water interface

“…The parameters that control the oxygen mass transfer in water have been intensively investigated since the middle of the last century 1‐9 . In general, this interest is because the oxygen mass transfer (or reaeration) is the main source for the restoration of dissolved oxygen concentration in polluted water 6 .…”