Plastic Trickling Filter — Activated
Sludge Treatment of Paper Wastes
ROBERT H. FOLLETT, Development Engineer
National Council for Stream Improvement, Inc.
Northeast Research Center
Tufts University
Medford, Massachusetts
INTRODUCTION
A research study investigating methods of biological treatment of paper wastes
for a group of Ohio Paper Mills provided an ideal situation to study a combination
trickling filter-activated sludge treatment system. Construction and operating cost
of the pilot plant were financed by the Ohio Paper Mills Research Committee,
consisting of nineteen pulp and paper manufacturers located in the state of Ohio.
Operating and supervising personnel were provided by the National Council for
Stream Improvement.
PURPOSE
The purpose of this project was to determine whether a combination of a
roughing plastic media trickling filter and activated sludge process could provide
a more satisfactory method of secondary biological treatment than either of the
processes alone.
The pilot plant was operated over a two-year period, treating settled effluent
from a fine papermill, boardmill, and a papermill employing deinking, the effluent from the latter contained the discharge from both the pulp and papermills.
DESCRIPTION OF PILOT PLANT UNITS
The pilot plant units were those essentially inherent to the activated sludge
and trickling filter processes. The filter section was 10 ft in depth containing six
cu yds of PVC media providing approximately 90 per cent voids. The filter was
built above the aeration tank so that it drained into it. The aeration tank had a
capacity of 380 cu ft(2860 gals) and aeration was supplied by sparger type diffusers
of sufficient capacity so that air supply would at no time be a limiting factor.
Flow regulation was such that it could be operated reliably at from 10 to 60 gpm.
Recycle pump capacity was at the same capacity as the feed pump. Throughout
all the test work sufficient diammonium phosphate was fed to the system so that
nutrients would not be a limiting factor in the oxidation process. Mixed liquor
suspended solids were maintained in excess of 3000 mg/1 throughout the entire
test period. The final settling tank had a capacity of 6750 gals. The tank was
cleaned with a rake type collector mechanism. Evaluation of the pilot plant were
conducted at mills having primary clarification thereby eliminating the need for
presedimentation.
RESULTS AND DISCUSSION
Sludge Recirculation to Trickling Filter
Figure 1 shows the results obtained from returning activated sludge to the
-  120 -