Chloramination of partially nitrified or un-nitrified wastewater is seldom carried far enough to produce free chlorine, because of the substantial demand from ammonia, amine and organic compounds present in the wastewater. Depending on relative concentrations of ammonia and organic nitrogen present and on the realtive feed rate of chlorine, reaction time, temperature and sample pH, monochloramine or other forms of combined chlorine may be formed.

Process Control Strategy

Dechlorinatin of chloraminated wastewater requires the detection of combined chlorine residuals. One strategy is to feed a dechlorinating agent such as sodium thosulfite, sulfur dioxide or other similar compound based on the desired effluent residual, which will be in the combined chlorine (chloramine) form.

Apparatus

ChemScan^® Process Analyzers are designed to detect ammonia, chloramine or both in wastewater from one or more points in the treatment process.

Monochloramine is detected directly in wastewater at a standard pH of 6-9, without the need for reagents or pH buffer. Results may be reported as ppm or NH₂Cl or as ppm of Cl. Trace concentrations (less tham 0.3 ppm of NH₂Cl) may require an expanded path length flow cell for analysis down to concentrations of 0.05 of NH₂Cl or less.