[Efficient and Stable Operation of Shortcut Nitrification by Entrapping Ammonia Oxidizing Bacteria]

In order to improve the efficiency of shortcut nitrification by entrapping ammonia oxidizing bacteria, the technique of ammonia oxidizing bacteria(AOB) enrichment culture was studied. The continuous operation method was used to inhibit the growth of nitrite-oxidizing bacteria(NOB) by free ammonia, at the same time, the NOB was gradually washed out of the system through the technology of sludge discharge. Polyvinyl alcohol(PVA) was used as the embedding material to immobilize the ammonia oxidizing bacteria after enrichment culture. The embedding rate of the reactor was 8%. The ammonia oxidation rate was increased by improving ammonia nitrogen loading in the continuous operation mode. The results showed that the ammonia oxidation rate(NH₄⁺-N/VSS)was as high as 2.028 g·(g·d)^-1 and the nitrite nitrogen accumulation rate was stabilized at more than 90%. High-throughput sequencing analysis was conducted on the bacterial community composition before and after enrichment culture, and the experimental result indicated that the culture diversity of raw sludge was larger. Nitrosomonas and Nitrospirae, which have nitrification function, accounted for 0.24% and 2.7%, respectively. The diversity of the activated sludge decreased significantly after the enrichment culture, Nitrosomonas(18%) became the dominant bacteria whereas Nitrospira occupied only 0.02%. After he embedding of ammonia oxidizing bacteria, the shortcut nitrification was realized rapidly. Finally, the shortcut nitrification rate reached 50 mg·(L·h)^-1and the nitrite nitrogen accumulation was above 90%.