INFLUENCE OF VARYING TEMPERATURE, FLOWRATE AND
SUBSTRATE CONCENTRATION ON THE
ANAEROBIC ATTACHED-FILM EXPANDED-BED PROCESS
William J. Jewell, Professor
James W. Morris, Research Assistant
Department of Agricultural Engineering
Cornell University
Ithaca, New York 14853
A new anaerobic biological treatment process called the anaerobic attached-film ex-
panded-bed (AAFEB) has been shown to be effective with dilute as well as concentrated
waste streams, and efficient at temperatures as low as 10 C [1]. This process is of particular interest since the low microbial yield in anaerobic processes applied to domestic wastewater treatment has met the long sought goal of discharge standards without production of
secondary sludge. Since energy costs and secondary sludge management problems associated
with conventional aerobic processes comprise 20% or more of the total annual operations
and maintenance budgets for municipalities [2], such a process could eliminate a large
fraction of these costs.
There are three areas that need attention prior to widespread adoption of this technology
—the response of the microorganism to toxic materials, the interaction of particulates or
suspended solids with the films, and the response under "real world" variable conditions.
This study examined the response of the process to variable environmental conditions of
flow, temperature and biodegradable substrate concentration.
Studies by Parkin et al. [3] on the influence of toxic organics on anaerobic microbial
films and acclimation of anaerobic bacteria to complex and toxic organics by McCarty
et al. [4] indicate that anaerobic systems are capable of resisting influences of and recovery
from exposure  to highly toxic conditions,  perhaps as well as other biological systems.
The reaction of these sensitive microbes to variation in food supply, temperature, or
hydraulics is an immediate practical concern when these processes are considered as secondary treatment systems. The anaerobic methane fermentation process has almost always
been used under elevated and constant temperature conditions, and has been traditionally
studied under these constraints. Many who have studied the anaerobic digestion process
have had the misfortune of destroying an experiment due to temperature loss or due to
some undefined effect such as exposure to small quantities of oxygen. For example, an
accidental temperature decrease from 35 C to 20 C in a day and then return to 35 C may
cause cessation of methane production for several days in a sludge digester. This level of
sensitivity would be unacceptable for an on-line wastewater treatment process, since it is
continuously exposed to a wide range of variables.
Over the past eight years of research on the AAFEB process it was observed that the
process was exceptionally robust and resistant to the most harsh conditions. McCarty and
Young's work with the static film anaerobic filters [ 5 ] showed an exceptional ability of
the biological system to start-up quickly after being shut down for a year or more. The
experimental columns built by Young in 1964 are used annually in a course taught by
Professor Perry L. McCarty for wastewater treatability studies. Laboratory accidents in
the author's work such as pumping air through the unit and the loss of media into a collecting sump have resulted in no significant effects on the reaction rates. During Switzen-
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