Evaluating Chloramine Loss in Raw Water Supply Pipelines

Monochloramine loss was studied in two, approximately 70-mile pipelines within the Tarrant Regional Water District (TRWD) raw water supply and transmission main system. Both bench-scale studies and full-scale sampling were used to determine the impact of several factors that may affect monochloramine loss in the pipelines. The conditions of bench-scale study were representative of the range of water quality conditions encountered at the pump stations. Bench-scale results were compared to full-scale samples taken along the pipeline. Samples collected along the 70-mile pipeline were measured for chloramine concentration, pH, dissolved oxygen, as well as parameters known to indicate nitrification such as nitrite and free ammonia. Samples collected along the pipeline were also filtered with a 0.2 µm filter. Filtering the samples removed any nitrifying bacteria potentially present. Comparing the chloramine decay between the filtered and unfiltered samples allowed the affect of nitrification in the pipeline to be observed.