The purpose of this paper is to present the results of a five-month pilot testing program in
Tucson, Arizona to investigate the factors promoting nitrification and means of control. Twelve
parallel pilot treatment trains each with plug-flow reactors were tested. The reactor systems
reproduced the nitrification process in a manner similar to nitrification events in full-scale
distribution systems. Previous laboratory studies supported by Tucson and full-scale systems in
Texas have indicated that the presence of chlorite ion in water prevented the nitrification process
and stabilized ammonia concentrations. These pilot studies confirmed the previous findings with
chlorite ion and have opened new avenues of research for control of nitrification with minimal
use of additional chemicals. The following conclusions can be drawn from this study:
plug flow reactors designed for this study successfully reproduced nitrification conditions
representative of nitrification episodes in distribution systems;
continuous chlorite ion feed prevented nitrification from ever getting established, even
at a concentration as low as 0.1 mg/L;
in systems that already had serious nitrification underway, intermittent chlorite ion feeds
as low as 0.2 mg/L stopped nitrification completely for several weeks after their
application;
an intermittent dose of only 0.05 mg/L of chlorite ion damaged the ammonia oxidizing
bacteria (AOB) population, which was able to re-establish itself in a few weeks, and a serial
intermittent feed of 0.2 mg/L on the same reactor system badly damaged the AOB and
effectively stopped nitrification;
in other pilot units studied, AOB regrowth was destroyed with an intermittent dose of 0.8
mg/L; and,
in full-scale distribution systems using chloramines, it appears that nitrification can be
prevented by short-term and regularly scheduled applications of chlorite ion at
concentrations as low as 0.2 mg/L. Includes 8 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 16 |
| Published : | 11/15/2004 |
