53    FATE AND BIOKINETICS OF METHYL-t-BUTYL
ETHER IN ACTIVATED SLUDGE SYSTEMS AND ITS
ENGINEERING SIGNIFICANCE
P. T. Sun, Senior Staff Research Engineer
J. P. Salanitro, Senior Staff Microbiologist
W. T. Tang, Senior Research Engineer
Westhollow Technology Center
Shell Development Company
Houston, Texas 77251 -1380
INTRODUCTION
The use of methyl tertiary-butyl ether (MTBE) will increase significantly in the next few years
due to the requirements of the Reformulated Fuel Program which is mandated by the newly authorized Clean Air Act (CAA). MTBE will also be added to gasoline to replace light aliphatics
and aromatics. In addition, several MTBE production units will be installed by the chemical processing industries. These activities may pose a significant wastewater treatment problem at
MTBE manufacturing facilities, petroleum refineries, gasoline product terminals, as well as contaminated groundwater at retail facilities. Although MTBE has relatively low toxicity, it is highly
water soluble and is less volatile and less carbon adsorbable than benzene. Current wastewater
treatment practices for these wastewaters, such as air stripping and carbon adsorption, are mainly
designed for the removal of benzene and other similar compounds. They may not be the most
cost-effective choices in the event that stringent MTBE discharge limits are imposed. Biological
treatment of wastewater containing MTBE, if successfully demonstrated, may present a better
solution.
This chapter summarizes a laboratory study in evaluating the biokientics of MTBE degradation by an enrichment culture. The information gathered in this study was used in devising an engineering design procedure so that biodegradation of MTBE can be maximized.
THEORY-COMPETITION BETWEEN BIODEGRADATION AND STRIPPING
Although, MTBE is less volatile than compounds such as benzene, air stripping can remove
significant amounts because of the long retention time and high capacity aeration conditions prevailing in industrial wastewater treatment plants. The major processes for MTBE removal are air
stripping and biodegradation. The following sections describe the theoretical analysis to relate
pertinent factors which affect these two processes. Its detailed development can be found in reference 1.
Air Stripping
Equation 1 describes the air stripping process in a completely mixed activated sludge (CMAS)
system with no biodegradation;2
s
1 +
1+-
K\a-V
F-H/R-T
(1)
51st Purdue Industrial Waste Conference Proceedings, 1996, Ann Arbor Press. Inc.. Chelsea. Michigan 48118.
Printed in U.S.A.
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