Fate of Nutrients During Aerobic Digestion

by Paul L. Bishop, (M.ASCE), Assoc. Prof. and Chmn.; Dept. of Civ. Engrg., Univ. of New Hampshire, Durham, N.H.,
Michael Farmer, (A.M.ASCE), Supervising Area Ranger; East Bay Municipal Water Utility, Oakland, Calif.,

Serial Information: Journal of the Environmental Engineering Division, 1978, Vol. 104, Issue 5, Pg. 967-979

Document Type: Journal Paper

Abstract: Laboratory scale aerobic digestion experiments were performed and nutrient balances were maintained in order to evaluate nutrient transformations during digestion of waste activated sludge. Reactors loaded at 0.03 ft³ and 0.081 lb VS/day/ft³, were operated under both batch and daily feed conditions. Significant nitrification occurred, resulting in substantial reductions in pH and alkalinity. Denitrification occurred when dissolved oxygen concentrations dropped below 1.0 mg/l. Phosphorus and nitrogen were released to the liquid in approximately a stoichiometric ratio to the volatile solids destroyed. As much as 37% of the phosphorus and 41% of the nitrogen in the feed sludge was found in the supernatant after digestion. The solid phase of aerobically digested waste activated sludge had a nitrogen content of 7% of the suspended solids and a phosphorus content of 2% of the suspended solids.

Subject Headings: Waste treatment | Solid mechanics | Nutrients | Phosphorus | Nitrogen | Activated sludge | Dissolved oxygen | Turbidity

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