Date of Award
Bachelor of Science
Paper Science and Engineering
Dr. Raja Aravamuthan
Pulp bleaching is a multi-staged process which uses different chemicals and conditions in each stage, with washing performed between these stages. With chlorine compounds being the most widely used bleaching agents, the water from bleaching and washing stages subsequently contains a high chloride content as well as chloro-organic compounds which makes them incompatible with pulping chemical recovery processes. They are, therefore, discharged as wastewater. This leads to the need for regulations regarding the effluent quality of the wastewater. The purpose of this study is to compare effluents from various dimethyl dioxirane bleaching sequences with those of commonly used industry bleaching sequences and to determine if these effluents will meet the Environmental Protection Agency's proposed Effluent Guidelines. This paper summarized the characteristics of the effluents produced during bleaching sequences which use dimethyl dioxirane as the primary bleaching agent. This characterization was based on the proposed EPA discharging limits regarding:
A. Biochemical oxygen demand (BOD),
B. Chemical oxygen demand (COD), and
This study was also incorporated the total organic carbon (TOC) fraction to characterize the effluent streams. When DMD is used a bleaching agent for kraft hardwood pulps, the organic content of the effluent streams is greatly increased. This is due to the increased levels of delignification taking place during the A stage. The most environmentally friendly DMD bleaching sequence would be optimized OAE sequence with the stepwise addition of the A stage. Here, the organic content of the combined effluent streams is decreased from that of the optimized OAE sequence by 27.1% and 23.4% according to the BOD and COD tests, respectively. However, there was a 12.6% increase in TOC from that of the optimized OAE sequence.
Dunnill, Holly L., "Characterization of Effluent from Dioxirane Bleaching Sequences" (1995). Paper Engineering Senior Theses. 112.