Oxygen Transfer in Full Lift Hypolimnetic Aeration Systems

by Kenneth I. Ashley, Ministry of Environment, Vancouver, Canada,
Donald S. Mavinic, Ministry of Environment, Vancouver, Canada,
Kenneth J. Hall, Ministry of Environment, Vancouver, Canada,



Document Type: Proceeding Paper

Part of: Water Quality Issues at Fossil Fuel Plants

Abstract:

A series of experiments were conducted to examine the effect of diffuser depth, diffuser orifice diameter and separator box surface area on oxygen transfer (mg/L), daily oxygen load (kg O₂/day), transfer efficiency (E_o, %), energy efficiency (E_p, kg O₂/kW-hr) and water velocity (m/sec) in a small full lift hypolimnetic aerator (tube dia. = 0.76 m). A large hypolimnetic aerator (tube dia. = 1.5 m) was then retrofitted with 140 ? fine pore diffusers to test the pilot scale observations. The experiments demonstrated that oxygen transfer and water velocity increased with the depth of air release. This in turn increased daily oxygen load, E_o and E_p. The orifice size experiments indicated that the 140 ? diameter fine pore diffuser significantly increased oxygen transfer, daily oxygen load, E_o and E_p, however, the differences in bubble size generated by the 794 ? to 3175 ? coarse bubble diffusers were too small to have any significant effect on the aforementioned parameters. A reduction in surface area of the separator box had no effect on the oxygenation capacity of the aeration system. Retrofitting a large hypolimnetic aerator with 140 ? diffusers markedly increased its oxygenation capacity.

Subject Headings: Oxygen transfer | Aeration | Diffusion | Water treatment | Load factors | Lakes | Diffusion (porous media)

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