Removal of phthalate esters in soil column inoculated with microorganisms.

Abstract

The removal of phthalate esters, such as di-2-ethyl hexyl phthalate (DEHP) was efficiently effected by inoculating and retaining viable cells of Nocardia erythropolis, a bacterium known capable of rapidly degrading phthalate esters, in soil column. When an influent containing 3000 ppm of DEHP was passed through a column inoculated with Nocardia erythropolis, the eluent from the column was gas-chromatographically free of DEHP after 1 day. Residual DEHP on the support after 32 days in the column inoculated with Nocardia erythropolis was only 0.14% against the total amount of DEHP fed, whereas it was 5.2% in the uninoculated column. Microorganisms capable of utilizing DEHP were isolated from the inoculated and uninoculated columns after 32 days operation and identified. The DEHP utilizing microorganisms in the inoculated column were found to belong to Nocardia erythropolis, Nocardia restricta and Pseudomonas putida (Biotype B), and those in the uninoculated column to Nocardia erythropolis, Pseudomonas putida (Biotype A and B) and Pseudomonas acidovorans. In particular, strain I-1 of Nocardia erythropolis isolated from the inoculated column was morphologically and biochemically identical with the inoculated Nocardia erythropolis S-1. Ratio of all Nocardia erythropolis to total cells recovered increased from 10.8% immediately after inoculation to 27.2% after 32 days in inoculated column.