柠檬酸生产中厌氧消化液的循环回用工艺研究

The novel process of reusing anaerobic digestion effluent in citric acid fermentation

为解决柠檬酸行业废水对环境的污染,特别提出将厌氧消化液循环回用生产柠檬酸。研究发现,厌氧消化液直接作为工艺配料水循环回用对原料的液化没有影响,但对柠檬酸发酵产生抑制。进一步研究证明,厌氧消化液中的氨氮、Na^+、K^+均会抑制柠檬酸发酵,其相应的临界抑制质量浓度分别为100、200、300 mg/L。采用超滤和纳滤的组合膜技术对厌氧消化液进行资源化处理,厌氧消化液中的抑制物得到了有效去除,其中K^+、Na^+的去除达到90%以上,氨氮的去除率也在80%以上。经过资源化处理后的厌氧消化液循环回用后其柠檬酸产量为139.25±1.85 g/L,达到了去离子水的发酵水平(138.70±2.46 g/L),经过资源化后厌氧消化液循环回用生产柠檬酸的新工艺是可行的。

A novel process of reusing anaerobic digestion effluent in citric acid fermentation was developed to resolve waste water pollution in the citric acid industry. Studies showed that direct application of the anaerobic digestion effluent had no effect on liquefaction of the raw materials, but had inhibition effect towards citric acid fermentation. Further studies proved that ammonia-nitrogen, Na＋ , K＋ from the anaerobic digestion effluent can inhibit citric acid production and its corresponding critical inhibition concentration were 100, 200, and 300 mg/L respectively. In this paper, a combination of ultrafiltration and nano-filtration was adopted for the anaerobic digestion effluent treatment. The inhibitors were effectively purified, with efficiency as high as 90% for Na＋ , K＋ removal and 80% for ammonia- nitrogen removal. Application of the treated anaerobic digestion effluent in citric acid fermentation, there was 139.25 ± 1.85 g/L of citric acid, 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 eco- nomic, environmental and social benefit.