Phosphorus Sorption of Soils to be used in Wastewater Renovation

Abstract The same amount of P in 0.01M CaCl2 was repeatedly added to 12 soils to measure the P sorption of the soils. Compared with the P sorption maximum calculated from the Langmuir equation, repeated additions showed about twice as much sorption. However, the two measurements were well correlated. At low P concentration or in soils with low sorption capacity, each addition showed about the same sorption increment after the first three to four additions. Between 6 and 35% of the amount sorbed after 10 additions of P was desorbed in 10 subsequent additions of 0.01M CaCl2. The P sorption was lower at 4°C than at room temperature. The only soil parameter that significantly influenced the sorption capacity with dithionite—citrate extractable Al. The sorption capacity measured by repeated additions of a solution of the same P concentration as wastewater seems to give a better estimate of the field sorption capacity than the Langmuir sorption maximum.