Electrokinetically enhanced transport of organic and inorganic phosphorus in a low permeability soil

Abstract

The transport of P sources (organic and inorganic phosphorus) using electrokinetic process through a low-permeability soils was investigated. A series of batch experiments was conducted to construct the adsorption isotherms of KH₂PO₄ and triethyl phosphate (TEP) on kaolin soils. Approximately 60.3% of phosphorus from KH₂PO₄ was adsorbed within 24 hours, and the maximum adsorption (73%) was attained at 6 days after adsorption. In contrast, TEP showed no P adsorption in 7 days, thus suggesting an alternative P source that may maintain a favorable proportion of C∶N∶P through the effective delivery duringin situ bioremediation in low permeability soils. Experiments using electrokinetic process were carried out with electrokinetic reactor having a hydraulic conductivity of 1.99×10⁻⁷ cm s⁻¹ for a 0.01 M NaCl aqueous solution. TEP and KH₂PO₄ were used as organic P source and inorganic P source, respectively, and introduced individually into a chamber near the platinum anode and near the platinum cathode, respectively. Potassium dihydrogen phosphate was not distributed uniformly along the soil column and most of transported phosphorus was changed to water-insoluble aluminum phosphate after 12 days of treatment, indicating the decrease of bioavailability of the phosphorus. In case of TEP, the advancing P front progressed with time, resulting in uniform P distribution through the kaolin column. In terms of transport, organic phosphorus, TEP, would be a more effective P source than inorganic phosphorus, KH₂PO₄, in electrokinetic enhanced bioremediation.