Organic halogen removal from chlorinated humic ground water and lake waterby nitrifying fluidized-bed biomass characterised by electron microscopy and molecular methods

The dechlorinating and gene to xi city-removing activities of nitrifying fl uidized-bed reactor biomass towards chlorinated organic compounds in water were shown at level below 1 ppm. The removal rates of adsorbable organic ha logens were 200 mu g Cl (g VS day)(-1) for chlorinated humic ground water a nd 50 mu g Cl (g VS day)(-1) for chlorinated lake water when studied in bat ch mode. In a sequenced batch mode the removal rates [mu g Cl (g VS day)(-1 )] were 2000 from chlorohumus, 1400-1800 from chlorophenols in chlorinated ground water, and 430-720 from chlorohumus in chlorinated lake water. Genot oxicity was removed to a large extent (60%-80%) from the chlorinated waters upon incubation with nitrifying reactor biomass. 2,6-Di-, 2,4,6-tri and 2, 3,4,6-tetrachlorophenols competed with chlorinated water organohalogens for dechlorination. The dechlorination of chlorophenols and chlorohumus requir ed no ammonia and was not prevented by inhibitors of ammonia oxidation, nit rapyrin, parathion, sodium diethyldithiocarbamate, or allylthiourea. Electr on microscopical inspection of the biomass showed the dominance of clusters of bacteria resembling known nitrifying species, Nitrosomonas, Nitrobacter , and Nitrosospira. This was supported by polymerase chain reaction amplifi cation of the biomass DNA with four different primers, revealing the presen ce of 16S rDNA sequences assignable to the same species. The most intensive band obtained with the Nitroso4E primer was shown to be closely related to Nitrosomonas europaea by restriction analysis.