Date of Award

4-1997

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

First Advisor

Van Maltby

Abstract

This thesis estimates and compares the treatability of several internal mill process streams. This is important to the paper industry due to increasingly stringent regulations being placed on the effluent that is discharged from pulp and paper mills. The treatability of the process streams provides an indication of what processes are most effective on which process streams, identifies the major sources of COD, determines the treatability of the major sources, and will be very useful for emerging regulations regarding internal process streams. Samples from six different process streams within an integrated, bleach kraft mill employing their own wastewater treatment plant were analyzed using COD tests on both filtered and unfiltered samples and BOD tests on filtered samples. The process streams include (1) a blend of three main wastewater streams from the refiner mechanical pulp mill, (2) combined waste streams from the papermachine, coater, and color building, (3) kraft mill brownstock filtrate, (4) bleaching filtrate from kraft mill acid bleaching stages, (5) bleaching filtrate from kraft mill caustic bleaching stages, and (6) a combined influent to secondary treatment (following primary clarifiers). A combination of COD and BOD tests as well as the BOD rate constants were used to estimate the treatability of the different process streams in the mill.

The treatability was estimated by using the BOD test data obtained from the experiment to produce BOD rate constants, k-values, for each of the waste streams. The waste stream from the RMP mill exhibited the highest BOD and COD values, as well as the highest k-value. This indicated that while the RMP mill waste is high in BOD and COD loading, it is more-effectively treated by biological treatment when compared to the other waste streams. The results from this experiment also showed the unfiltered COD to be much higher than filtered COD in the paper machines/coater waste stream. Therefore, it can be deduced that the oxygen demanding materials are in a suspended form in solution and can be removed by filtration. These findings will help the mill to more effectively deal with the waste streams and meet the new environmental regulations.

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