57    THE USE OF CLOTH-MEDIA FILTRATION TO
ACHIEVE PHOSPHORUS REMOVAL FOR FOOD
PROCESSING WASTEWATER
Satish Kamaraju. Process Engineer
Aqua-Aerobic Systems, Inc.
Rockford, Illinois 61130
William Davis, Environmental Manager
Terry L. Crider, Water Quality Specialist
Hudson Foods, Inc.
Berlin, Maryland 21811
INTRODUCTION
The importance of nitrogen and phosphorus in stimulating eutrophic conditions has been well
documented, and, as a result, over the last decade an increased emphasis has been placed on limiting these elements in wastewater effluents discharging into streams.'
Phosphorus in raw wastewater is found as ortho phosphate ion, polyphosphates or condensed
phosphates, and organic phosphate. Of these, ortho phosphate is easier to remove by precipitation. Lime and the salts of aluminum and iron are the most commonly used coagulants. Theories
on the mechanisms of coagulation using these chemicals can be found in the EPA manual on
phosphorus removal.2
Studies have shown superior removal of phosphorus (up to the level of less than 0.30 mg/L in
the treatment plant effluent) is essential to the improvement of the water quality. Chemical precipitation in the secondary treatment step can only decrease phosphorus level to about 1.0 mg/L.
Tertiary filtration following chemical flocculation is essential in achieving superior phosphorus
removals.3
Many factors should be considered in selecting the most economical method of phosphorus removal from domestic and industrial wastewaters. These include characteristics of the particular
waste, size, and type of basic treatment system, degree of operation and maintenance attention
available, availability and cost of chemicals, and degree of removal required.4 While various
types of granular media filters have typically been utilized for TSS removal, an innovative cloth-
media filter has proved to provide equal or better performance in side-by-side testing with sand
filters.5 Pilot and full-scale experience has shown that cloth media filters are more suitable for
removing metal hydroxide floes than the better known microstrainer types.6
This chapter discusses a Swiss-engineered technology that is now being marketed in the
United States as an alternative to granular-media filters. The chapter will include its operational
features, mechanical design, pilot- and full-scale performance.
A case study of Hudson Foods in Berlin, Maryland will be presented as it relates to the use of
the cloth-media filter to achieve phosphorus removal for chicken processing wastewater.
HISTORY
The AquaDisk automatic backwash tertiary filter, manufactured by Aqua Aerobic Systems,
Inc., is based on Swiss-engineered filter technology which has been used successfully in Europe
for more than 15 years. The disk filter was developed to improve the mechanical and operational
features of its predecessor—the drum filter. The originator of the technology lists more than 400
51st Purdue Industrial Waste Conference Proceedings, 1996. Ann Arbor Press, Inc., Chelsea. Michigan 481 IS.
Printed in U.S.A.
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