Breakpoint chlorination is accomplished by addition of chlorine to the waste stream in an amount sufficient to oxidize ammonia-nitrogen into nitrogen gas (see Chapter 8). In practice, approximately 9-10 mg/l of chlorine is required for every 1 mg/l of ammonia-nitrogen. In addition, the acidity produced by the process (equation 8.2) must be neutralized. The chemicals add greatly to the total dissolved solids and result in substantial operating expenses.
The method has, however, two advantages:
1) By using sufficient chlorine it is possible to obtain effluents reduced in ammonia concentration to near zero.
2) The low spatial requirement makes it particularly suitable for certain applications, including addition to an existing facility, where nitrogen removal is required, but space is limited. Nitrite and nitrate are not removed by this method, which is a major disadvantage.
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