A novel process for reuse of anaerobic digestion effluent in citric acid
fermentation was investigated to resolve wastewater pollution in citric acid
industry. Studies showed that anaerobic digestion effluent directly reused had
no effect on liquefaction of raw materials, but produced inhibition for citric
acid fermentation. Further experimental studies proved excess
ammonia-nitrogen, Na+, K+in the anaerobic
digestion effluent can inhibit citric acid fermentation and its corresponding
critical inhibition concentration respectively 100, 200, 300 mg/L. In this
paper, the combination of ultrafiltration and nanofiltration membrane
technology was adopted to deal with the anaerobic digestion effluent, and these
inhibitors have been effectively purified, including Na+, K+removal rate reached 90%, ammonia-nitrogen removal rate is over 80%. The
anaerobic digestion treated by a combination ultrafiltration and nanofiltration
reused in citric acid fermentation, citric acid production was 139.25±1.85 g/L,which was comparable
to the control(138.70±2.46 g/L). The novel
reusing process is feasible and not only reduces wastewater pollution problem
and saves fresh water resources, has high economic benefit, environmental
benefit and social benefit.