Application of the Ozonation Pre-treatment for Biodegradation of Aqueous Solutions of Methyltert-Butyl Ether

Abstract

The effectiveness of ozone treatment for improving the biodegradability of recalcitrant pollutants has been proved by investigating the ozonation reaction of Methyl tert-butyl ether (MTBE) a bioresistant gasoline oxygenate. Laboratory scale experiments have been carried out, at room temperature, by bubbling, for 120 min, ozonated air (3.4 ppm min^-1 ) into 3 liter of an alkaline (pH=11.5) aqueous solution (100 mg L^-1) of MTBE. The experimental results indicated that during the ozonation, complete MTBE degradation occurs in 100 min and after this time, ozone consumption goes on very slowly. At the end of the ozonation, after 100 min, the initial value of COD (256 mg O₂ L^-1) is 98 and correspond to a relative removal of about 62%.As for MTBE solution biodegradability expressed as (BOD5)/(COD) ratio, during the first 90 min its value regularly increases from lowest (0.01) up to a maximum of 0.68 that corresponds to an ozone consumption of 1.25 mg per each mg of COD initially present in the solution.The experimental results for determining the rate of MTBE removal due to stripping showed that about 14% of MTBE strips out after an hour of sparging with oxygen gas. The fraction of MTBE oxidized and/or striped increases to about 28% (in pH=7) and 70% (in pH=11.5) with ozonation over the same time period.