(1) A heterotrophic nitrifier, named strain HN, was isolated from the greenhouse soil. The cells of isolates were Gram positive, rod or coccus.

(2) Al was significantly poisonous to soil nitrifier, dinitrifier and azotobacter at high concentration, and the maximum inhibition ratio reached 96%, 98% and 89%, respectively.

(3) Advance in molecular biology of heterotrophic nitrifier is reviewed in this paper.

(4) This product is a new type of nitrifier, which has special good effect for the degradation of the nitrite.

(5) The experimental results showed that the nitrite accumulation obtained from selective inhibition of high concentration free ammonia to nitrifier was unstable.

(6) Ihese two issues can be solved simultaneously by bioaugment, that is sewage sludge water is used to enrichment the nitrifier, and then added to the sewage treatment system.