Grease Removal With A Precoat Filter
A Case History
J.B. SMEDLEY, Process Engineer
Envirocon Limited
Vancouver, B.C.
HOWARD A. McLEAN, Director Environmental Engineering
Envirocon Limited
Calgary, Alberta
R. BLANK, Operations Manager
West Coast Reduction Ltd.
Vancouver, B.C.
THE PROBLEM
West Coast Reduction Limited is in the animal matter reduction industry. They are the
principal disposal outlet for slaughterhouses, butcher shops, poultry dressers, and other
processors of flesh foods in the Vancouver area. The principal products of the reduction
process are proteinaceous meals, which find primary use as poultry and livestock feeds, as
well as tallow. It was the tallow or grease which formed the basis of an effluent problem at
West Coast Reduction. Grease, discharging with the process water effluent, had to be
removed.
West Coast Reduction is located within an industrial area on the Vancouver
waterfront adjacent to residential property with limited space available for a treatment
facility. In addition, the treatment had to be continuous, fail-safe and effective from both an
environmental and a political perspective.
Existing facilities for treating the process water included a floor sump and a flotation
cell. The sump had insufficient capacity to operate as a surge tank and the flotation cell had
never properly been applied to this service.
Our studies of the plant process water revealed that extreme variations in flowrates and
characteristics existed and were generally encountered in daily operations.
Recommendations were made to "tighten up" plant operations but ultimately the problem
was formulated as follows.
Flowrates varied from zero to 50 GPM with an average of 30 GPM; grease (as hexane
extractable grease) concentrations ranged from 1,000 to 12,000 mg/1 into the sewer and as
high as 29,000 mg/1 into the existing flotation cell; effluent flowing to the sewer showed pH
ranges of 3 to 7 and temperature ranges of 85 F to 110 F. In addition, total solids and BOD
were high. Local standards of discharge to sewers allow a maximum 150 mg/1 grease and
pH within the range 5.5 to 9.5.
THE SOLUTION
A solution was found by combining a precoat filter with the existing air flotation unit.
An incline screen was added to remove coarse solids. Better than 99 percent grease removal
is being achieved. The primary asset of the facility is its efficiency combined with small size.
The treatment facility is simple both in concept and in operation. Problems
encountered to date have been minimal and of an operational nature rather than a
mechanical nature. These include foaming, and appreciable vacuum pump cooling water
consumption.
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