BIOREMEDIATION OF URANIUM-BEARING WASTE-WATER - BIOCHEMICAL AND CHEMICAL FACTORS INFLUENCING BIOPROCESS APPLICATION

A biotechnological process for the removal of heavy metals from aqueou s solution utilizes enzymatically liberated phosphate ligand which pre cipitates with heavy metals (M) as cell-bound MHPO(4). The enzyme, a p hosphatase, obeys Michaelis-Menten kinetics in resting and immobilized cells; an integrated form of the Michaelis-Menten equation was used t o calculate the apparent K-m (K-m app.) as operating in immobilized ce lls in flow-through columns by a ratio method based on the use of two enzyme loadings (E(o1), E(o2)) or two input substrate concentrations ( S-o1, S-o2). The calculated K-m app. (4.08 mM) was substituted into an equation to describe the removal of metals by immobilized cells. In o peration the activity of the bioreactor was in accordance with that pr edicted mathematically, within 10%. The initial tests were done al neu tral pH, whereas the pH of industrial wastewaters is often low; an inc rease in the K-m app. at low pH was found in previous studies. Immobil ized cells were challenged with acidic mine drainage wastewaters, wher e the limiting factors were chemical and not biochemical. Bioreactors initially lost activity in this water, but recovered to remove uranyl ion with more than 70% efficiency under steady-state conditions in the presence of competing cations and anions. Possible reasons for the bi oreactor recovery are chemical crystallization factors. (C) 1997 John Wiley & Sons, Inc.