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High temperature biological treatment of Kraft pulping effluent

University of British Columbia

The pulp and paper process produces hot effluent streams which currently must be cooled prior to biological treatment. Cooling such streams requires capital for construction of cooling towers or heat exchangers, as well as additional money for maintenance and operating costs. This project was to develop and test a high temperature activated sludge (HTAS) technology for the treatment of Kraft pulping effluents. Studies are based on two laboratory scale activated sludge bioreactors. The operating temperature of the laboratory reactors was increased over the temperature range 35°C to 55°C. The response of the reactors was measured in a number of ways. First, conventional treatment parameters such as biochemical oxygen demand (BOD), chemical oxygen demand (COD), solids content, oxygen uptake rate (OUR), toxicity and pH were monitored. Second, changes in the microbial ecosystem were indirectly monitored by measurement of changes in substrate uptake profiles, floe structure, settleability, and kinetics of methanol and formate uptake. Results have proven that the bioreactor was able to achieve BOD, COD and toxicity reductions of 94.8%, 35.8% and 93.8% respectively at 55°C. Effluent volatile suspended solids concentration increased with increasing temperature and averaged 63.3 mg/L at 55°C. Most probable number analyses of substrate use profiles indicated that the population of microorganisms responsible for degrading methanol, formate and resin acids decreased at temperatures over 45°C. The high temperature bioreactor recovered from a rapid drop in temperature within 24 hours. Kinetic constants obtained from measuring the substrate uptake of methanol and formate show that biomass has a weaker capacity to degrade methanol at elevated temperatures but an approximately equal formate-degrading activity at both temperatures.

Thesis/Dissertation

application/pdf

2009-05-04

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http://hdl.handle.net/2429/7867

Chemical and Biological Engineering

University of British Columbia

UBCV

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