Isolement de nitrobacter des eaux potables et des eaux urbaines

Abstract

This study is the first step toward an optimization of the bacterial oxidation of nitrogen compounds in water plants. The goal is to develop a bacterial inoculum, which could be introduced into treatment plants and therefore improve their efficiency for ammonia removal. Nitrobacteria were isolated from sludge and sand used in sewage and drinking water treatment plants. Biomass extraction from inert material was made by means of an Ultrasonic rod. The enrichment in nitrobacteria was made by series of seedings in liquid medium containing only nitrite and mineral salts. Simultaneously the number of heterotrophic bacteria decreased due to the low organic concentration in the medium. When the nitrobacteria population was higher than the heterotrophic one, a drop of the culture was plated on petri-dishes. These dishes used the same mineral medium, added of 60/00 of agar-agar. After 2 weeks of incubation small colonies of nitrobacteria were detected under a stereoscopic magnifying glass. The colonies were collected by a sterile capillary and inoculated in the mineral medium for a check of their ability to oxidize nitrite in nitrate. The purity of the strain was verified with different organic media revealing the presence of heterotrophic contaminants. Pure strains serotypes were characterized with imunofluorescence. All the isolated bacteria were of the same serotype. Nitrobacter winogradskyi serotype agilis.