27    ANAEROBIC TRICKLING FILTERS:
A NEW TREATMENT POTENTIAL
Craig D. Adams, Graduate Student
Ross E. McKinney, Professor
Department of Civil Engineering
University of Kansas
Lawrence, Kansas 66045
INTRODUCTION
The development of high rate anaerobic bioreactors to treat industrial wastes in the past few years
has focused on retention of the bacteria within the bioreactors. Fixed media, fluidized beds, granules
and flocculated bacteria have been used in different anaerobic systems.1 All of these systems seemed
to have two phases, an attached phase and a dispersed phase.2 The bacteria easily attached to each
other as in activated sludge, but only became lightly attached to solid surfaces. A study by Canovas-
Diaz and Howell3 in 1986 indicated that a partially submerged, fixed media bioreactor gave better
treatment than the system when it was completely submerged. It appeared that an anaerobic trickling
filter might have potential in retaining the bacteria and for providing good contact between the
wastewaters and the bacteria. For these reasons a laboratory study was performed to examine the
characteristics of anaerobic trickling filters as a new type of anaerobic bioreactor for treating organic
industrial wastewaters.
MATERIALS AND METHODS
Anaerobic Trickling Filters
Three laboratory anaerobic trickling filters were constructed with different media to help evaluate
different media configurations. Each unit was constructed from a 6.1 cm internal diameter, 66 cm
long clear plastic tube. A circular, perforated, plastic plate was placed 17 cm from the bottom of the
tube to act as a support for the media. Approximately 25 holes, 0.5 cm in diameter, were drilled
through the plastic plate to allow the liquid to pass into the lower section of the tube. Three circular
deflection rings were inserted into the upper section of the tube to prevent liquid from short-circuiting
down the tube walls. The deflection rings were placed at 11 cm intervals above the perforated, media
support plate.
Three types of media were used in the anaerobic trickling filters: polypropylene Pall rings, a
lightweight volcanic rock, and a crossflow fabric media manufactured by Koch Industries. The
polypropylene Pall rings were 1.7 cm in diameter and 1.7 cm long. The lightweight volcanic rock,
scoria, was highly porous, and each piece of rock media was between 1.2 cm and 1.9 cm. The
crossflow fabric media was designed as a series of folded, plastic cloth channels placed to create a
crossflow fluid pattern. The crossflow media was 5.5 cm in diameter two sections 5 cm long and two
sections 15 cm long. By offsetting each section 90 degrees, it was possible to obtain complete fluid
distribution throughout the media. After the media were placed into the plastic tube, a circular cover
plate was glued to the top of the tube. The circular plate had one hole in the center and one hole offset
at about half the radius. A glass tee was placed through the center hole and a plastic tube was placed
through the other hole. A rubber tube and a small, plastic funnel were connected to the top of the
glass tee with a clamp acting as a valve to seal the tubing shut except during feeding. The other leg of
the glass tee was connected to rubber tubing attached to the discharge side of the recirculation pump.
The plastic tube was attached to rubber tubing that was connected to a glass tee. The center leg of the
glass tee had a gas sampling rubber septum while the outer leg was connected to rubber tubing which
was attached to a wet test gas meter to measure the gas produced by metabolism.
A 6 cm deep polypropylene funnel was attached to the lower end of the plastic reactor tube. A
rubber tube connected the end of the funnel to a glass tee which was also connected to the suction side
44th Purdue Industrial Waste Conference Proceedings, © 1990 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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