Date of Award
Master of Science in Environmental Science - (M.S.)
Chemical Engineering, Chemistry and Environmental Science
Samir S. Sofer
Richard B. Trattner
John L. Gerwig
This study is undertaken from the standpoint of water pollution evaluation in bioethanol technology, using immobilized yeast cells. Evaluation of water pollution caused by immobilized yeast fermentation is the main objective of this research.
The pollution in water remaining at the end of ethanol production, which is normally discharged in the wastewater stream, has been analyzed by the measurement of biological oxygen demand (BOD), since BOD measurement is one of the widely used parameters for water pollution evaluation. BOD obtained from produced water (stillage) was between the range of 115- 360 mg/l. The variation in BOD depended upon the removal of ethanol and concentration of organic matters present in water. Waters with more ethanol and high organic concentration showed higher BOD levels.
This work has demonstrated the following technical accomplishments. A recirculation reactor with total working capacity of 2-3 liters was set up and operated for ethanol production using immobilized yeast cells. This bioeactor has been operated for 37 fermentations using the same yeast cells repeatedly. Amounts ranging from 0.054-0.002 l/g dry yeast of alcohol were produced. Analytical measurement of this alcohol indicated concentration of 2-4% w/v.
Cake obtained after filtration of saccharification slurry, was evaluated as a high-protein supplementary feed for dairy and beef cattle. This product contained 7-8% w/w protein in wet and 28-33% w/w protein in dry state. As a rough estimation, this high-protein feed can be used for 12 days as a complete protein feed or can be supplemented for 36 days with regular feed for growing bulls and Heifer cattle.
Filter cake wash water (1 ml/g cake) was also analyzed for BOD. A range of 360 + 10 mg/1 was obtained which can be a cause of pollution.
Zarnegar, Minoo Kandy, "Environmental assessment in bioethanol technology using immobilized yeast cells" (1989). Theses. 1927.