Evaluation of Operating Parameters of Alumina Columns for the Selective Removal of Phosphorus from Waste-Waters and the Ultimate Disposal of Phosphorus as Calcium Phosphate

摘要

A synthetic secondary sewage effluent containing 10 to 30 mg/liter phosphate, 300 mg/liter bicarbonate, 112 mg/liter Cl and 50 mg/liter sulfate as anions and 130 mg/liter Na, 60 mg/liter Ca, 25 mg/liter each of K and Mg and 20 mg/liter ammonium as cations was used with 7.6 ml alumina columns to study the effects of various compositional changes on phosphorus removal. The phosphorus capacity was about half for the solution containing no Ca or Mg as compared to solutions containing them. Probably adsorption onto the alumina occurs partly as a calcium or magnesium phosphorus complex rather than as a simple phosphorus anion. Increasing the competing sulfate concentration in the influent solution to 4800 mg/liter showed little effect on phosphorus adsorption. Raising the pH of the synthetic sewage effluent to greater than 8.0 led to precipitation of calcium carbonate on the alumina grains which progressively lowered alumina phosphorus capacity. This problem was not encountered when using actual sewage effluent. It was found that alumina columns could be satisfactorily regenerated with NaOH. (WRSIC abstract)