Phosphate Removal from Sewage Water by Soil Columns1
- J. C. Lance2
Phosphate (PO4-P) removal from secondary sewage effluent by calcareous sand columns was proportional to the infiltration rate. Phosphate concentrations in drainage from columns, packed with a mixture of sand from recharge basins and sand never previously exposed to sewage water, were below 1 ppm for over 200 days, increased, and finally leveled off at different concentrations, depending upon the infiltration rate. The equilibrium PO4-P concentration could be increased or decreased by increasing or decreasing the infiltration rate. Evidently, PO4-P was initially adsorbed by a reaction independent of flow velocity or retention time and, when this adsorption capacity was reached, PO4-P was removed by a time-dependent adsorption or precipitation reaction. The rapid response to either increases or decreases in infiltration rate suggested a precipitation reaction. The PO4-P removal continued after application of 250 m of sewage water and 60,000 kg/ha PO4-P during 7 years of flooding. Removal of 75–80% of the PO4-P applied in secondary sewage effluent continued when the infiltration rate was maintained below 15 cm/day. Bermudagrass (Cynodon dactylon) greatly increased PO4-P concentrations in column effluent samples.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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