Abstract: The present disclosure relates to methods of detecting manganese in a solution using resacetophenone oxime by spectrophotometric analysis wherein the resacetophenone oxime produces colorimetric responses to indicate the presence of manganese. The resacetophenone oxime is not only stable in solution, but it also may be inserted into a hydrocolloid gel to facilitate a “spot test” for the detection of manganese, resulting in a long shelf life. These manganese testing methods disclosed herein may be used at the pre-disinfection process at water treatment facilities. The disclosed methods of manganese testing may be combined with an ammoniacal buffer reagent that may be used by water processing facilities, prior to final disinfection, to augment existing manganese (II) efforts of removal. A secondary flocculation with this buffer will scavenge additional manganese (II), that can then be removed by sedimentation or filtration.