• AWWA WQTC60614

AWWA WQTC60614

Metal Removals from Contaminated Acidic Water by Using Physico-Chemical Processes

American Water Works Association , 11/15/2004

Publisher: AWWA

File Format: PDF

$12.00$24.00


This study investigated the conventional physico-chemical treatment technologies for removing aluminum, arsenic, copper, mercury, and selenium from a highly acidic (pH 2.7) groundwater which was contaminated due to the past industrial activities. A bench-scale study was conducted to test pH adjustment technologies and metal removal processes. The processes investigated include chemical coagulation/flocculation followed by sedimentation, dual media (sand/anthracite) filtration, and granular activated carbon (GAC) adsorption. Lime and caustic soda were used for pH alteration. Alum and Iron coagulants were jar tested for their effectiveness in metal removals at different dosages and pH range. The test data indicates that lime addition is not only effective in pH adjustment but also in precipitating out almost all the target metals. Caustic soda is shown to be as effective as lime for pH adjustment. However, caustic soda's cost and handling will be higher. In addition, lime provided an added benefit of imparting alkalinity. The jar test result showed that both Iron and Alum coagulants are effective in metal removals. However, for selenium removal further investigation is recommended. It was also found that chemical coagulation/flocculation/sedimentation process alone is sufficient to reduce almost all the target metals to the required effluent limits. The additional treatment processes, dual filtration and adsorption, may not be needed for polishing the effluent. The existing water treatment plant practices at the industrial facility were looked into and some recommendations were made for better and effective operation. Installation of a lime dose monitoring equipment and a proper settling tank with sludge removal mechanism may be considered. Includes 2 references, tables, figures.

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