Continuous process of aerobic biodegradation of beet molasses vinasse: focus on betaine removal

Abstract

We analyzed the effect of hydraulic retention time (HRT) and pH control of beet molasses vinasse on the efficiency of its continuous aerobic biodegradation with a mixed culture of Bacillus bacteria. Two experimental series were conducted in a 2-L stirred-tank reactor, at an aeration rate of 1 vvm, stirrer speed of 900 rpm, and temperature of 36 °C. The first series was run without medium pH control, whereas the other with pH maintained at 8.0. In both series, HRTs were 26, 47, and 78 h, whereas vinasse pH was raised to 8.0. The extent of its treatment via aerobic biodegradation depended on betaine assimilation phenomenon. High removal of pollutants (over 84%) expressed by the SCODsum index (SCODsum = soluble COD determined with the dichromatic method + theoretical COD of betaine) was achieved at HRTs of 47 and 78 h, whereas medium pH control had no explicit effect on biodegradation efficiency.