PERFORMANCE OF AN ANAEROBIC FILTER
TREATING SOLUBLE CARBOHYDRATE WASTE
Frederick J. Siino, Environmental Engineer
Mass Transfer Systems, Inc.
Fall River, Massachusetts 02722
Frederic C. Blanc, Professor
James C. O'Shaughnessy, Associate Professor
Department of Civil Engineering
Northeastern University
Boston, Massachusetts 02115
INTRODUCTION
A large portion of the energy consumed during wastewater treatment is from the biological stabilization of organic matter. Biological processes are used to treat a variety of industrial wastes as
well as domestic wastewaters. Aerobic systems are the most widely used system for the biological
treatment of wastewaters. Aerobic systems (particularly suspended growth systems) are the largest
consumer of energy in a wastewater treatment plant. It is for this very reason that industry continues
to investigate alternate, more energy efficient biological treatment systems. Extensive research has
been expended on anaerobic systems for treatment of industrial wastewaters.
Young and McCarty [1] developed the anaerobic filter process for the treatment of soluble wastewaters. Research since its introduction has shown that the anaerobic filter offers several desirable
features in comparison to other biological treatment systems [2]. These include: 1) efficient treatment
of soluble organic waste streams at high loadings, while recovering energy in the form of methane;
2) very low biological solids production which allows long periods of operation with no sludge wasting; 3) ability to retain solids within the reactor which promotes long SRT and allows system to handle
organic shock loads; and 4) ability for intermittent operation of the process makes it attractive to
industry.
This study is concerned with evaluating the ability of the anaerobic filter to treat a synthetic
soluble carbohydrate waste. Fructose corn syrup was used as the carbon source to simulate the sweet-
ner used by a typical soft drink bottling company. Soft drink bottling waste characteristics are typically very low in suspended solids with soluble COD concentrations ranging from 1,000 to 6,000
mg/1 [3].
The objectives of this study were to determine performance of the anaerobic filter with respect
to influent waste strength, hydraulic retention time (HRT), and organic loading. Observations were
also made with respect to the distribution of solids within the reactor.
ANAEROBIC FILTER PROCESS
The anaerobic filter process (Figure 1) consists of a reactor containing a fixed media matrix. Flow
is upward through the media so that the filter is totally submerged. Microorganisms either accumulate
in the interstitial pore volume or are loosely attached to the media. The ability of the anaerobic filter
to retain microorganisms allows the influent waste to come in contact with a large active biological
population as it passes upward through the reactor.
Loading rates have been found to range from approximately 60-600 lbs COD/1,000 ft'/day (1-
10 kg/m'/d) of total reactor volume at soluble COD removal efficiency of 80%-95% [4]. Hydraulic
retention times (HRT) investigated have been between 4.5 hours and 72 hours [2]. HRT and media
type have been shown to be two very significant parameters that control process performance [5].
These two parameters affect the contact time between the influent waste stream and active biomass.
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