NEAR ZERO D.O. ACTIVATED SLUDGE CASE HISTORY
W. A. Barkley, Research Engineer
R. W. Sackellares, Control Strategy Engineer
Weyerhaeuser Company
Tacoma, Washington 98477
J. R. Ellavsky, Water & Effluent Dt. Supervisor
R. D. Simmons, Senior Process Engineer
J. W. Yount, Senior Project Engineer
Weyerhaeuser Company
Long View, Washington 98632
INTRODUCTION
Some years ago a chemical engineering professor [1] taught his student that: "THE PROBLEM
OF INDUSTRY IS TO PRODUCE A PRODUCT TO MEET A DEMAND AT A PROFIT."
Through the simple device of asking this question on every test, he obtained a certain respect and
retention of this viewpoint. More recently an environmental engineering professor [2] noted that the
problem of a wastewater treatment plant operator was, sequentially, to: 1) keep the plant running; 2)
meet permit regulations; and 3) minimize costs. Both of these statements have the same flavor. For
many years in the wastewater treatment field, the emphasis has been on "producing a product to meet
a demand" and on "keeping the plant running and meeting the permit regulations." Relatively lesser
weight was given to making a profit or minimizing costs. This seemed logical and reasonable when
operation and quality were not routinely attainable. The purpose of this paper is to provide information on operating experiences with emphasis on the third priority-minimizing costs.
BACKGROUND
Mill/Waste Load/Effluent Treatment System
Weyerhaeuser's Longview, Washington facility is a large integrated wood products manufacturing
complex located on the Columbia River about 60 miles upriver from the mouth and 35 miles west of
the formerly picturesque Mt. St. Helens. Almost all aspects of wood products manufacturing are performed at this site including log preparation, log exporting, dimension lumber manufacturing,
plywood manufacturing, and pulp and paper manufacturing. A chloralkali plant is also located at this
facility.
The pulping and papermaking portion of this complex generate an effluent waste load of 110,000
lb of BOD per day and 240,000 lb of TSS per day at 60 million gallons per day flow. This waste load is
generated by a combined gross machine production of 1000 tons per day bleached kraft pulp, paper
and paperboard, 280 tons per day semichemical corrugating medium and 1200 tons per day thermo-
mechanical newsprint. The daily average effluent limits, which are based on this production rate, are
26,000 lb BOD per day and 44,000 lb TSS per day.
A deep tank air activated sludge system is used to treat this effluent (Figure 1). Suspended solids
are removed from one half of the effluent in a 295 ft diameter primary clarifier prior to entering the
deep tanks. The remaining effluent which contains few suspended solids enters the deep tanks
directly.
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