Date of Award

4-1994

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

First Advisor

Paul Wiegand

Abstract

This project examines the effect of black liquor carryover from the brownstock washing section on the bleach plant effluent qualities of COD. Black liquor carryover not only directly effects the organic loading to the effluent treatment plant, but also interferes with bleaching chemicals during the bleaching sequence. The goal of the project was to establish the relationship and quantify the effects of this carryover on the bleaching effluent COD. Samples of pulp were spiked with black liquor and then bleached by a D-E bleaching sequence to a specific target Kappa number. The effluents from both of the bleaching stages were analyzed for the organic wasteload in terms of COD.The effect of the carryover on the COD of the chlorine dioxide stage effluent is increasingly more significant as increasing amounts of carryover are used. The carryover cannot be shown to have any effects on the COD of the extraction stage of the bleaching process. This is a direct reversal of the carryover effects when using a typical chlorination first stage bleaching, where most of the effluent COD is from the extraction stage of the bleaching process. The information from this project can be utilized to determine if improved washing efficiency will eliminate the need for additional wastewater treatment to meet the proposed Federal regulations.

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