TREATING AERATED AND ANAEROBIC LAGOON EFFLUENTS
WITH INTERMITTENT SAND FILTRATION
Richard P. Bishop, Graduate Student
Steve S. Messinger, Graduate Student
James H. Reynolds, Assistant Professor
Department of Civil and Environmental Engineering
E. Joe Middlebrooks, Dean
College of Engineering
Utah State University
Logan, Utah 84321
INTRODUCTION
This paper represents a major condensation of two studies of intermittent sand filtration as a means of removing solids from aerated and anaerobic wastewater stabilization
lagoons [1,2].   Pilot-scale intermittent sand filters were used to evaluate performance
when receiving effluent from an aerated lagoon treating milk processing and cheese manufacturing wastewater.   Laboratory anaerobic lagoons and intermittent sand filters were
used to treat the dairy parlor wastewater.
The description and results of the two studies are presented separately according to
the type of lagoon effluent treated.
AERATED LAGOONS
Description of Problem
Waste from a medium-sized milk processing and cheese manufacturing plant, located
7 mi north of the Utah State University campus, was utilized in the aerated lagoon portion of this study.   The waste from this plant is made up of various dilutions of whole
milk, separated milk, buttermilk, whey from accidental or intentional spills and wash
water containing alkaline or other chemicals used to remove milk, as well as partially
carmelized materials from cans, bottles, tanks, vats, utensils, pipes, pumps, evaporating
coils and floors.
The dairy waste is mostly neutral but may become acidic quickly because of formation of lactic acid from milk sugar.   This occurs when the waste depletes available
oxygen.   The milk plant waste is high in dissolved organic content, with BOD5 values
as high as 1400 mg/l.   Since dairy plant wastes are high in soluble organics and neutral
in pit, they respond ideally to biological treatment methods.
Present treatment consists of an aerated lagoon system with two aeration cells in
series equipped with diffused-air aeration devices.   The second aeration cell is followed
by a facultative settling pond.   Effluent from the facultative settling pond is then chlorinated and discharged into a nearby creek.   This treatment scheme has had difficulty
meeting federal and state discharge requirements of 30 mg/l of BOD5 and suspended
solids in the effluent. This was recently exemplified by a $15,000 fine issued by the
Environmental Protection Agency to the dairy owners.   With the timetable for PL 92-500
and even stricter discharge limits fast approaching, improvements must be made in the
treatment facility.
Methods and Procedures
Intermittent sand filtration was evaluated on a pilot scale as a possible method of
upgrading this discharge.   Two pilot-scale filters with a surface area of 16 ft   and 8 ft
high were constructed of V* in. exterior plywood and lined with fiberglass and resin.
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