Section 13: PHYSICAL/BIOLOGICAL SYSTEMS
ORGANIC PARTICULATE REMOVAL WITH
THE ANAEROBIC ATTACHED-FILM EXPANDED-BED PROCESS
James W. Morris, Research Assistant
William J. Jewell, Professor
Department of Agricultural Engineering
Cornell University
Ithaca, New York 14853
The anaerobic attached-film expanded-bed process (AAFEB) has been shown to successfully treat a variety of wastestreams including primary settled domestic wastewater at 20 C
and hydraulic retention periods shorter than 30 minutes, producing an effluent containing
less than 40 mg/1 total COD and 5 mg/1 SS [ 1,2]. This process has for the first time demonstrated the feasibility of utilizing an anaerobic methane fermentation for the treatment of
dilute organic wastewaters at low temperatures while producing energy and only small
amounts of excess biological solids. The process exhibits remarkable resiliency, uncommon
to conventional anaerobic treatment systems, when subjected to large instantaneous changes
of temperature, flow rate and substrate concentration [3]. The AAFEB appears to have significant potential to become an attractive alternative wastewater treatment technology.
Previous studies in the development of process understanding have mostly concentrated
on soluble substrates [1-6]. Since many, if not most, biologically treated wastestreams
contain appreciable amounts of organic particulate or colloidial material, a two-year study
has been conducted to better understand their impact on the AAFEB. This paper reports the
initial findings of a larger effort to better define the overall process capabilities and investigate the relationship of the biological community responsible for the destruction of particulate organic solids, such as pure cellulose, within the AAFEB at 30 C.
OBJECTIVES
1. define the capability for organic particulate removal using cellulose as well as a variety
of more complex organic particulate substrates, and
2. identify the relationship of organic particulates within the system to the biologically
active reactor phases.
MATERIALS AND METHODS
This study began immediately after the variability study by Jewell and Morris as reported
earlier [1,3]. The basic procedures followed, the equipment, and apparatus configurations
are similar to those used in earlier studies. Media with mature attached microbial films which
developed during these studies were continued in use for this study [4,5].
The reactor configuration used for all three of the AAFEB units is shown schematically
in Figure 1. The hydraulic retention times and volumetric loading rates were based on the
empty reactor volume occupied by the biologically active expanded bed in each unit. By
basing these parameters on the reactor empty volume, it is possible to compare the AAFEB
to other processes that do not contain inert biosupport material. The total reactor empty
volume for each unit was 1 liter, including the recycle lines.
Bed expansion was accomplished hydraulically using a multi-channel Cole-Parmer Master-
flex variable speed pump. The recycle rate was adjusted (to a small degree) to accommodate
changing biomass and entrapped particulate matter in the reactor while maintaining the bed
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