36 CONTACT ANAEROBIC TREATMENT
AND SUGAR BEET WASTEWATER
Cathy B. Fuchs. Project Engineer
Infilco Degremont Inc.
Richmond, Virginia 23294
INTRODUCTION
The Analift™ is an anaerobic contact (suspended growth) system. This technology is currently
operating in chemical, pulp and paper, and agrifood industries where it allows treatment of
wastewater with high concentrations (5,000 to 50.000 mg/L total COD) of biodegradable pollution and suspended solids at a low operating cost. It is a low rate system (6-15 kg COD/m3.d)
compared to other anaerobic systems, such as the new Anaflux™ fluidized bed system (35-70 kg
COD/m3.d).
There are 26 Analift™ systems worldwide, 16 of them treating sugar beet wastewaters. This
chapter presents direct operating experience from Analift™ systems in three sugar beet plants—
two in Germany and one in the United States. Two alternative systems used to maintain the
anaerobic sludge in suspension are presented.
In theory, the carbonaceous pollution of sugar beet wastewater can be transformed to methane
(CH4 gas) by any anaerobic system. However, since sugar beet wastewater has high calcium concentration (frequently 1000 mg/L Ca2+ and higher), the contact growth system is the only anaerobic system possible for this application.
DEFINITIONS
Chemical Oxygen Demand (COD) is one of the parameters used to describe the level of organic pollution. Graphs showing tons of COD/d are expressed in long tons/d (2,200 lb/d and not
2,000 lb/d).
Total Suspended Solids (TSS) is the insoluble pollution of the wastewater. TSS consists of organic and mineral (inorganic) matter.
Volatile Suspended Solids (VSS) is the organic fraction of the suspended solids. The concentration of bacteria (biomass) in a biological reactor is approximated by the VSS concentration.
Anaerobic Processes: In the absence of oxygen (O-,), bacteria degrade organic matter, producing biogas containing methane (CH4). This biodegradation consists of two major steps: in the
first step, the organic matter (measured as, e.g., COD) is transformed into C02, H„ and Volatile
Fatty Acids (VFA) such as acetic, propionic butyric, and lactic acids. In the second step, the VFA
are transformed into methane (CH4).
THE ANAEROBIC CONTACT GROWTH SYSTEM ANALIFT™ SYSTEM
This system comprises two strictly separate stages (see Figure 1):
• an anaerobic reaction where free bacteria reduce the wastewater's organic matter
into CH4;
• a phase separation system allowing the treated wastewater to be separated from the
suspended solids, and where these suspended solids thicken.
*Trademark of Infilco Degremont Inc., Richmond, Virginia.
51st Purdue Industrial Waste Conference Proceedings, 1996. Ann Arbor Press, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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