Reusing Treated Municipal Wastewater for Fermentation of Ethanol Production

The bioethanol industry exerts a significant water demand. Current water consumption rate in dry grind corn-to-ethanol production is 2.7 gallons of water per gallon of ethanol production. This research was to examine the use of treated municipal wastewater (TMW) in the liquefaction and fermentation processes for ethanol production. The objective of this research was to evaluate the effects of TMW on corn starch hydrolysis, yeast reproduction and viability, as well as the final yield of ethanol and co-products. At the end of liquefaction process, concentration of sugars produced in TMW and concentration of sugars produced in deionized (DI) water were similar, which on average were 10.78 g/100mL and 9.92 g/100mL, respectively. The effects by TMW on the reproduction and viability of yeast were negative during the first 18 hours of fermentation; but were neutral or positive thereafter. Final molar yields of ethanol in TMW and in DI water were comparable at on average of 89.81% (w/w) and 87.08% (w/w), respectively. This research indicated that TMW can be used as a substitute of fresh water in liquefaction and fermentation for ethanol production, hence help to reduce water consumption of the ethanol industry.