FIELD STUDY OF THE USE OF ALUMINUM WATER TREATMENT RESIDUALS IN A PERMEABLE REACTIVE BARRIER SYSTEM TO REDUCE SOLUBLE PHOSPHORUS MOVEMENT IN GROUNDWATER

High phosphorus (P) loading in Lake Okeechobee during past decades has resulted in advanced eutrophication with corresponding impacts on the lake’s ecosystem. A large portion of this P loading is a result of agricultural and livestock operations in the Northern Lake Okeechobee Basin (NLOB). A major source of P is from cow manure originating from intense livestock operations or from land applications as fertilizer. In many types of soils this P is bound within the soil however the Spodosols of South Florida lack the capacity to retain much P and a large percentage of the soluble P is leached through the soil and transported via groundwater to the surface water drainage network, eventually making its way into Lake Okeechobee.

This study involves the use of aluminum water treatment residuals (Al-WTRs) as a permeable reactive barrier (PRB) installed in a trench perpendicular to groundwater flow which is intended to inhibit the movement of the soluble P. The chemical attributes of Al-WTRs are such that the P will readily adsorb to the aluminum oxides and will remain stable over long periods of time. These Al-WTRs are available locally and cost effectively making this an attractive method for P removal.

Two field sites were chosen for PRB implementation and studies over a two year period showed a high percentage of P removal from GW as well as highlighting important characteristics for future PRB design.