66    COLD TEMPERATURE NITRIFICATION USING
CAPTOR® PROCESS
Padma S. Golla, Project Engineer
Ashbrook-Simon-Hartley
Houston, Texas 77222
Andy J. Lin, Project Engineer
EDI, Inc.
Columbia, Missouri 65201
INTRODUCTION
The increased demand for wastewater nitrification in the United States has resulted in the need for
an efficient nitrification system. In particular, such a system is desired for wastewater treatment
facilities in cold climates, where nitrification is not considered to be possible during winters. Two
types of treatment processes are currently in use for biological nitrification; suspended-growth systems and attached-growth systems. Attached-growth systems seem to be in favor for cold temperature
nitrification. However, operational difficulties, such as ice formation, biomass sloughing, and partial
reactor media plugging associated with cold temperature operation have been experienced with the
existing systems.1.   Inducing draft of cold air during winters has caused problems in bio-towers.
Since few biological nitrification systems are considered to nitrify at temperatures near freezing,
comparative results from extensive cold temperature operation are not available at the present time.
Gullicks and Cleasby conducted a pilot-scale trickling filter study with a wastewater temperature of
10°C.2 Haug and McCarty reported that submerged filter process was able to achieve stable nitrification at temperatures as low as 1°C.3 Oleszkiewicz et al. reported a 8g N/kg MLVSS/day (1.89#/10OO
ftVday) nitrification rate at 2°C temperature using 12 hour-cycle sequencing batch reactor.4 However,
the last two studies were done in the laboratory under controlled conditions.
Previous pilot scale studies had shown that the Captor* process was efficient for nitrification of
secondary treatment effluent at temperatures of 10° to 22°C.5'6 It was required to extend this study to
colder temperatures of 0°C to 10°C. The wastewater treatment facility of Vesper, Wisconsin, which
averaged winter temperatures in the range of 0°C to 3°C, provided an opportunity for such a study.
The facility at Vesper had two 45 day aerated lagoons in series and anticipated the need to upgrade
treatment capability to nitrify in order to meet winter limits for ammonia. As part of the studies to
evaluate treatment options for upgrading the existing lagoons, a Captor* pilot tank was installed at
Vesper in November 1988, to demonstrate winter nitrification. A schematic of the pilot tank is shown
in Figure 1.
Objectives
The objectives of this study were the following:
1. Evaluate nitrification capabilities of Captor* process at winter temperatures of 0° to
10°C;
2. Determine reductions in BOD and suspended solids; and
3. Determine the requirement of clarification after Captor* process.
Pilot Tank Description and Operation
The Captor* process utilized reticulated biological support media to retain large amounts of active
biomass in the reactor. The use of the biological support media allowed the process to sustain nitrifier
microorganisms by incorporating both attached-growth and suspended-growth.6 The biological reactor was filled with reticulated polyurethane pads having about 97% void space with internal and
external surfaces for biomass attachment and/or entrapment. The pads were of I" x 1" x 0.5"
dimension having a specific gravity of about 1.0 when filled with water.
46th Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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