Removal of Phosphorus from Waste Water by Soil Under Aerobic and Anaerobic Conditions1
- D. E. Hill and
- B. L. Sawhney2
Studies of the movement of fertilizer-P and P added to soils in waste water have shown that P movement is extremely slow. But in cultivated soils with tile drains it has also been observed that reducing conditions caused by flooding can increase P mobility.
To determine the movement of P under aerobic and anaerobic conditions, a simulated waste water containing 12 µg/ml P was added to an isolated soil block two-three times a week for 2.5 years in a field experiment. The fine sandy loam soil was underlain by bedrock at 72 cm and had a water table fluctuating between the 25- and 75-cm depths during the experiment. Analyses of the effluent from the weep holes at different depths suggests that the waste water moved along preferred pathways in heterogeneous soil and produced breakthrough of P to ground water before all sorption sites were fully saturated with P. Also, anaerobic conditions produced during periods of high water table enhanced the mobility of P, thus increasing the transport of P to ground water in soils used for continued waste-water treatment. Renovation of waste water over long periods of time reduces the P sorption capacity of a soil, while periodic resting regenerates sorption sites and increases the potential for additional P sorption.
Estimates of P retention based upon its concentration in influent and effluent solutions and bulk density of the soil show a reasonably good agreement with laboratory determination of P retained following waste-water renovation. Data also show that most of the P retained is transformed into unavailable forms.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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