Determination of Reaeration Coefficient of Bedadung Hilir River Oxygen Deficit Change Method (Case Study in Balung District, Jember

Dissolved Oxygen (DO) is one of the most important parameters reflecting the ecological health of the river. DO supply must be maintained to support the life of aquatic organisms. DO supply obtained by oxygen transfer from the atmosphere to water. This research aimed to determine reaeration (continuous addition of oxygen) coefficients (KR) of Bedadung Downstream using the exchange of DO deficit. This approach uses the rate of mass transfer of oxygen from the air to the river water. The raw data was obtained by measuring stream-flow, temperature, and DO at three observed stations segment Balung district, Jember. The result showed the values of the reaeration coefficient (3 stations) were 36,084, 47,397, and 83,114 /day sequentially and tended to line up. The amount of KR obtained from the oxygen deficit and travel time of river water. The average KR was 55.532/day. High KR values indicate the ability of rivers that can supply oxygen naturally.

The effect of SDS surfactant on surface reaeration coefficient: a laboratory scale approach

Surface reaeration coefficient (K2), which represents the transfer of oxygen at the air-water interface, is an important variable in aquatic ecosystems. K2 is influenced by several factors, including surfactants; furthermore, this coefficient is used in water-quality models, which requires its correct estimation. This study evaluated the effects of the surfactant Sodium Dodecyl Sulfate (SDS) on K2 in two different experimental systems. In a cylindrical reactor with a turbine-type mechanical stirrer, 15 reaeration experiments were carried out with SDS concentrations of 0.0; 0.25; 0.5; 1.0 and 1.5 mMol L-1 and stirrer rotation velocities of 25, 50 and 100 rpm. In a circular hydraulic channel, 8 reaeration experiments were carried out, in triplicate, with SDS concentrations of 0 and 1.5 mMol L-1 and agitation levels of Reynolds 4,500, 37,500; 49,200 and 54,000. In the reactor, regardless of the rotation velocity, the surfactant reduced K2 by 20%, due to a superficial film formation at the interface that made oxygen transfer difficult, due to a phenomenon known as “barrier effect”. In the channel, an approximate K2 reduction of 15% occurred at higher levels of water agitation. In the presence of surfactants, and at low levels of agitation, phenomena that increase K2 (i.e., Marangoni effect) may coexist with those that reduce K2 (i.e., barrier effect). We concluded that the presence of SDS in aquatic environments should be considered when estimating the surface reaeration coefficient, because this surfactant can contribute to uncertain K2 estimation.