Oxygen Transfer at High Solids Concentrations

Oxygen transfer relationships have not been well defined for mixed liquors with high solids concentrations. This study evaluated the ability of a cage rotor to transfer oxygen in an operating oxidation ditch located at the Agricultural Waste Management Laboratory, Cornell University, Ithaca, N.Y. Data were collected over a 13-month period. Solids were maintained at predetermined equilibrium levels by controlling the water flow into the ditch. Solids concentrations ranged from 1% to 4.5% and temperatures ranged from 8.5°C to 25.5°C. A reduction in oxygen transfer occurred when the solids concentration exceeded 2%. The reduction was related to the increased viscosity of the mixed liquor at the high solids concentration. Mixed liquor temperature variations had no effect on oxygen transfer by the rotor. Relationships between alpha, viscosity, and solids concentration were obtained. The results were summarized to indicate the amount of oxygen necessary to stabilize poultry wastes.