AWWA ACE95156

This paper addresses the following major design considerations for adding ammonia to form chloramines: advantages and disadvantages of chloramine disinfection, ammonia availability, chemical properties, ammonia dosing requirements, ammonia feed systems, and safety systems. Anhydrous ammonia and aqueous ammonia are being used in water treatment to form chloramines to reduce trihalomethanes (THMs) and other disinfection by-products (DBPs). Trade-offs exist between reduced DBPs, disinfection, oxidation, taste, and odors for the various application location of chlorine and ammonia. Ammonia concentrations of less than 1 to 2 mg/L of ammonia are sufficient to form chloramine residual of 1 to 5 mg/L. For chloramination, the preferred chloramine species to form is monochloramine because of its stability and low taste and odor problems. Monochloramines are preferentially formed at pHs greater than 7.0 and theoretical chlorine to ammonia dose ration less than 5. For anhydrous ammonia two types of feed system exists: direct and solution feed. Direct feed systems inject ammonia gas directly into the process stream. Typical application points for the direct feed system are at open channels and basin facilities. Solution feed system are similar to chlorine vacuum systems requiring a carrier water stream to be injected to the process stream. Aqueous ammonia feed systems are similar to other liquid feed systems. However, a low pressure tank with a water trap is required because of the vaporizing of ammonia at ambient temperatures.

Product Details

Published:

01/01/1995

ISBN(s):

0898678358

Number of Pages:

11

File Size:

1 file , 370 KB