Affiliation:
1. Environmental Sciences Center, Monsanto Company, St. Louis, Missouri 63167.
Abstract
Microbiological analyses of activated sludge reactors after repeated exposure to 100 mg of p-nitrophenol (PNP) per liter resulted in the isolation of three Pseudomonas species able to utilize PNP as a sole source of carbon and energy. Cell suspensions of the three Pseudomonas sp., designated PNP1, PNP2, and PNP3, mineralized 70, 60, and 45% of a 70-mg/liter dose of PNP in 24, 48, and 96 h, respectively. Mass-balance analyses of PNP residues for all three cultures showed that undegraded PNP was less than 1% (less than 50 micrograms); volatile metabolites, less than 1%; cell residues, 8.4 to 14.9%; and water-soluble metabolites, 1.2 to 6.7%. A mixed culture of all three PNP-degrading Pseudomonas sp. was immobilized by adsorption onto diatomaceous earth biocarrier in a 1.75-liter Plexiglas column. The column was aerated and exposed to a synthetic waste stream containing 629 to 2,513 mg of PNP per liter at flow rates of 2 to 15 ml/min. Chemical loading studies showed that the threshold concentration for acute toxicity of PNP to the immobilized bacteria was 2,100 to 2,500 mg/liter. Further studies at PNP concentrations of 1,200 to 1,800 mg/liter showed that greater than 99 and 91 to 99% removal of PNP was achieved by immobilized bacteria at flow rates of 10 and 12 ml/min, respectively. These values represent hydraulic retention times of 48 to 58 min and PNP removal rates of 0.99 to 1.1 mg/h per g of biocarrier at 25 degrees C under optimal conditions. This study shows the successful use of immobilized bacteria technology to remove high concentrations of PNP from aqueous waste streams.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
91 articles.
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