14    DEVELOPMENT OF A BATCH BIOLOGICAL AERATION
AND FLOTATION SYSTEM FOR GROUNDWATER
DECONTAMINATION
Lawrence K. Wang, Vice President
Zorex Corporation
Pittsfield, Massachusetts 01201
Ping Wang, Research Assistant
Nicholas L. Clesceri, Professor
Department of Civil and Environmental Engineering
Rensselaer Polytechnic Institute
Troy, New York 12180
INTRODUCTION
A newly developed batch bioremediation system involving the use of biological oxidation, air
pressurization, and dissolved air flotation clarification for treatment of a phenol contaminated
groundwater is described. Specifically the new bioremediation system which is known as sequencing
batch flotation (SBF) accomplishes the unit processes and operations of filling, biological oxidation
reaction, powdered activated carbon adsorption, dissolved air flotation, decanting, sludge wasting,
and idling, within the confines of a single batch reactor. The new batch system is compact, simple and
thereby cost-effective. A treatment effectiveness comparison between the innovative SBF system and
a conventional sequencing batch reactor (SBR) system has been based upon experimental results.
Other innovative and modified sequencing batch systems, which utilize dissolved air flotation, activated carbon addition, or chemical addition in various combinations, were examined.
HISTORICAL DEVELOPMENTS
Conventional biological treatment processes, such as activated sludge aeration, activated sludge
oxygenation, trickling filter, rotating biological contactor, biological fluidized bed, or lagoon, can all
be applied to groundwater decontamination if a pump-and-treat approach is adopted. Unfortunately,
a groundwater decontamination project involves many unknown factors, for instance, the required
groundwater treatment period. It is understandable that a "responsible party" hesitates spending the
capital investment on a permanent and high-cost installation, such as one of the conventional biological treatment systems, for an unknown treatment period.
Accordingly, the use of conventional biological treatment processes for groundwater decontamination is technically feasible, but, in many cases, either economically unfeasible or simply unknown. On
the other hand, natural biological treatment processes, such as irrigation and aquaculture, may be
economically acceptable and technically manageable, only if environmental conditions are adequate.
Recently a batch process, known as the biological sequencing batch reactor (SBR; Figure la) has
gained popularity in treating contaminated soil and/or groundwater because of its simplicity and
transportability after terminating a site remediation project. SBRs represent a very elementary form
of biological treatment, known as "fill-and-draw." A contaminated water or slurry is physically added
to a reactor where it is biologically treated for removing undesirable contaminants, then gravitation-
ally clarified for settling the mixed liquor suspended solids —all inside the same reactor—and subsequently discharged.
A conventional SBR is a self-contained biological treatment system incorporating equalization,
biological oxidation (aeration or oxygenation), and sedimentation/clarification within the confines of
a single reactor. A modified sequencing batch reactor (PAC-SBR) is similar to a conventional SBR,
except that, during biological oxidation, powdered activated carbon (PAC) is dosed to the reactor for
adsorption, mainly of dissolved contaminants.
48th Purdue Industrial Waste Conference Proceedings, 1993 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
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