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UNDERSTANDING CHLORINE AND CHLORAMINE DECAY KINETICS IN OLD CAST IRON PIPES, 2. CONVERSION FROM CONVENTIONAL TREATMENT TO MICROFILTRATION IN A SMALL WATER SYSTEM
Citation:
Haught*, R C., C Patterson*, S. Panguluri, W. Roman, D. S. Lingireddy, F. A. DiGiano, AND D. E. Francisco. UNDERSTANDING CHLORINE AND CHLORAMINE DECAY KINETICS IN OLD CAST IRON PIPES, 2. CONVERSION FROM CONVENTIONAL TREATMENT TO MICROFILTRATION IN A SMALL WATER SYSTEM. Presented at WSWRD Peer Review, Cincinnati, OH, September 27 - 29, 2004.
Impact/Purpose:
To inform the public.
Description:
This insitu pipe loop study was designed to determine the disinfectant kinetics associated with very old unlined cast iron pipelines with both chlorine and chloramination residuals. An abandoned 90-year-old unlined cast iron pipeline about 2000 ft long was acclimated to conduct an elaborate set of field measurements to assess the disinfectant kinetics. The field measurement efforts included measuring flow rates and pressures at various locations within the loop, and measuring various water quality parameters (temperature, pH, ORP, conductivity, disinfectant concentrations) at the source and at several different locations within the loop. Using the results from this study, EPANET was able to model disinfectant decay in unlined cast iron distribution systems.
2: Conversion from Conventional Treatment to Microfiltration in a Small Water System
This water treatment plant conversion project in Carthage, NC afforded an opportunity to assess the impact of replacement of a 50-year old conventional water treatment plant, consisting of alum coagulation-sedimentation-granular filtration, with only MF. Impacts on the treatment efficiency and water quality at the customer taps were measured throughout the distribution system. An increase in TOC in finished water after the conversion to MF caused more chlorine demand. Free chlorine and chloramine residuals were greatly depleted resulting in very severe bacterial regrowth and nitrification. The extent of regrowth was similar before and after the conversion, especially at locations with long residence times. A key element of the study was to evaluate the production of NDMA. NDMA concentrations between 3 and 8 ng/L were reported during chloramination in the finished water and at locations with long residence times (one sample contained 85 ng/L NDMA).