Ammonia, Nitrite and Nitrate Nitrogen Removal From Polluted Source Water With Ozonation and BAC Processes
Studies on the removal of ammonia-, nitrite-, and nitrate nitrogen with ozonation (p3), sand filtration (SF), biological activated carbon (BAC), SF-BAC, and/or O3-BAC processes were carried out in two pilot plants and a full scale plant, respectively. The results showed that all of the tested processes exhibited certain nitrogen removal efficiencies, of which both the O3-SF-BAC and O3-BAC processes were most effective and efficient in removing ammonia nitrogen, with mean removal efficiencies of some 90 and 80 percent, respectively.
Ozonation was found able to oxidize some organic nitrogen into ammonia, and nitrite ion into nitrate ion. It was also found out, with interest, that the O3-BAC process can carry the nitrification process to the end under sufficient DO content, as well as more hydrocarbon substrates through ozonation that are more easily assimilated by some strains of nitrobacter that can multiply hetero- trophically in its carbon beds. In the BAC process, both the DO and easily assimilated substrate contents were too low in its carbon beds due to no ozonation to sustain nitrobacter growth; but the nitrite conversion bacteria, like nitrosornas, can survive under such conditions. As a result, nitrite or nitrate ion content increased multiply in the effluents from BAC or O3-BAC processes over their influents, respectively.
The removal mechanisms of various processes for the three forms of nitrogen were studied and discussed, and the optimum design parameters were determined as well.