Abstract:
In order to explore the effects of different C/N(C is the quality of carbon elements in glucose; N is the total nitrogen content in feed) on bio-flocculation nitrification intensity and microbial community, five different gradients of C/N ratio were set(10:1, 15:1, 20:1, 25:1 and 30:1). The results showed that the accumulation of NO3-in C/N(10:1, 15:1) were significantly higher than that in other groups(P<0.05), and also between C/N(10:1, 15:1)(P<0.05).Oxidation-reduction potential(ORP) of the five groups dropped to a negative value in the first day, but there were no significant differences about the change of ORP among the five groups(P>0.05). Based on saving carbon source, another five different gradients(C/N=10:1, 11:1, 12:1, 13:1, 14:1) were set, and the control group added with no glucose. The results showed that the accumulation of NO3-was gradually decreased with the increase of C/N, and the accumulation of NO3-in the group added with no glucose was significantly higher than that in other groups(P<0.05). There were significant differences about accumulation of NO3-between the group added with no glucose and C/N(10:1, 11:1), and also between C/N(10:1, 11:1) and C/N(12:1, 13:1, 14:1)(P<0.05). ORP dropped rapidly to a negative value in the second batch of experiment, but there were no significant differences in the change of ORP among the six groups(P>0.05). Then, high-throughput sequencing was carried out in three groups(Control group, C/N(10:1, 12:1) which had significant differences about the accumulation of NO3-, and the results showed that the first dominant phylum and class in the three groups were actinomycetes phylum and actinomycetes class,respectively. And the abundance of Bacillus generic gradually increased with the increase with C/N in the three groups. In conclusion, the nitrification intensity in the control group added with no glucose was better than that in other groups, and the nitrification intensity gradually decreased with the increase of C/N.