Pre-treatment of Yeast Production Wastewater and Hydrogen Production Based on MF-CSTR Process

Abstract

Wastewater produced during the yeast production has high COD concentration, chroma and turbidity and it is difficult to dissolve the water, which has constrained the development of yeast industry. This thesis researched the process of pretreatment of wastewater from yeast production wastewater. Membrane filtering was introduced to hold back the yeast existed in the wastewater. The filtered water was sent to produce hydrogen in anaerobic environment, while the residue was sent to extract protein. The filtering process utilized the PVDF membrane with an aperture of 0.2µm can hold back the yeast sufficiently. According to the transmembrane pressure, 10days worked as a period to clean the membrane at the aeration of 0.15m3·h-1. The cost as well as the profit is compared, which showed that for a yeast factory which had a daily wastewater production of 1 000m3, the profit could be as high as 1 090 yuan·d-1. Intermittent shake flask tests were conducted to study the difference of hydrogen production between direct anaerobic digestion and anaerobic digestion after filtration. When influent pH was 5.00, the hydrogen percentage of filtered group was 49.69%, which exceeded the group without filtration by 20.34%. The HRT and OLR were tested for CSTR to get the highest hydrogen production through anaerobic fermentation of the filtered yeast industry wastewater. Results showed that, when HRT was 8h and OLR was 24kgCOD·m-3·d-1, the system can get the highest biohydrogen production rate at 13.2L·d-1. This test suggested that MF-CSTR pretreatment process can simultaneously treat yeast industry wastewater effectively and realize resource recovery from yeast protein and energy recovery and utilization from hydrogen, which provides the theoretical foundation for the treatment and resource utilization from yeast industry wastewater