Jar testing is one of the most common tools that water treatment facilities use to determine the treatment conditions necessary to meet finished water quality goals. A six-place stirrer is normally used for jar testing to provide identical mixing conditions while coagulant dose and pH vary in each jar to create “floc” that is removed via sedimentation. There are some utilities that are unable to utilize jar testing, since the current jar testing procedures do not identify optimum treatment conditions for their water supply. This is particularly true for those utilities treating low-turbidity, low-TOC waters because low coagulant doses can produce small floc that does not settle efficiently (even though it is removed efficiently by filters). A modified jar test procedure was developed with the goal of providing consistent and reliable results for all treatment facilities without having to make site-specific changes to the mixing speeds and times to try to match the plant performance. Instead of sedimentation, the modified jar test procedure uses a novel granular media filter along with a standardized mixing protocol and titrations to predict and control the pH of the coagulated water. Contour mapping of jar test data was utilized to provide a detailed visual description of zones of effective treatment. Research found that the application of direct filtration (instead of traditional sedimentation) reduced testing time and showed better correlation to treatment plant performance. A method of optimizing coagulant dose and coagulated pH based on titrations is proposed, which is based on an alternating, single-variable optimization method with experimentally determined starting points. Treatment with coagulant only (i.e., without prior pH adjustment) limits the range of coagulation conditions a water treatment plant can operate at. Coagulants are acidic and their addition during treatment causes both the pH and coagulant dose to change simultaneously. Treating water with coagulant only provides only one diagonal path for treatment to occur across a two-dimensional area of pH and coagulant dose combinations, which sometimes misses optimal treatment conditions entirely.
|Commitee:||Bowen, James, Keen, Olya|
|School:||The University of North Carolina at Charlotte|
|School Location:||United States -- North Carolina|
|Source:||MAI 57/01M(E), Masters Abstracts International|
|Keywords:||Coagulation, Coagulation optimization, Filtration, Flocculation, Jar test, Water treatment optimization|
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