Water, Wastewater & Stormwater
381352 - Effect of Various Inline injection and Mixing Conditions on degree of mixing of Chlorine and Ammonia
Wednesday, June 6
2:00 PM - 3:30 PM
Location: Greenway EF
Andrew Kruzic, Arlington, Texas – University of Texas Arlington; Srinivas Prabakar, Arlington, Texas – University of Texas at Arlington
A very common secondary disinfectant used in many water distribution systems in the US is Monochloramine. It is typically generated by injecting chlorine and ammonia into a pipeline at the water treatment plant. Imperfect mixing of the chlorine and ammonia streams in the main flow stream can result in unbalanced chlorine and ammonia ratios at the microscale, reduction of their disinfection power and potentially greater production of disinfection by-products.
An experimental investigation is being carried out to assess the impact of a range of mixing conditions on monochloramine recovery. Chlorine and ammonia can be injected into pipelines in many ways and at several concentrations using different methods of mixing. The objective of this investigation is to quantify degree of mixing by determining Coefficient of Variation (COV) and the Intensity of Segregation (Is) for a number of different conditions. The method is approached by having various feeding conditions in a 4.0-inch pipeline at flow velocities ranging from 1.0 fps to 8.0 fps. The Is and COV are determined by introducing a tracer salt (sodium chloride) into the pipeline at different dilution ratios and tracking its concentration by measuring salt’s conductivity both axially and longitudinally at several distances from injection points. Various mixing conditions include straight run of pipes, static mixers in the pipeline, and adding bends to the pipe. The results determine the time and pipe length required to achieve adequate mixing and is used to design mixing conditions to optimize chemical usage, using the measured values of COV and Is.