Combined Biological/Chemical Treatment in RBC (Rotating Biological Contactors) Plants,
TRONDHEIM UNIV (NORWAY) DIV OF HYDRAULIC AND SANITARY ENGINEERING
Pagination or Media Count:
Combined biologicalchemical treatment can be obtained in RBC plants by adding precipitant before or into the RBC tank Simultaneous precipitation, after the RBC-tank and before a flocculationsedimentation system Combined precipitation or with separate chemical step downstream the RBC-settling tank Post-precipitation. The experiences from Norwegian combined precipitation plants and from the project reported in this paper, is that excellent treatment results may be obtained by combined precipitation. Since this process has one sludge separation unit less than post-precipitation, combined precipitation is economically favourable compared to post-precipitation. Simultaneous precipitation may also give acceptable effluent quality, but it seems that separation of flocs is better in acombined precipitation system as a result of better flocculation. Adding precipitant Alum directly to the RBC-tank in simultaneous precipitation does not give any adverse effect on the capability of the biofilm to remove organic matter when pH is kept above pH 6,0. Good removal of both organic matter and phosphate was obtained with combined precipitation at high organic and hydraulic loadings.