Comparing potassium permanganate, chlorine dioxide, and chlorine oxidation for manganese control of a volcanic island surface water treated with a conventional coagulation, sedimentation, and filtration process

摘要

A comparison of the effectiveness of potassium permanganate (KMnO4), chlorine dioxide (ClO2), and chlorine (Cl-2) oxidation pretreatment for manganese (Mn) control from a surface water reservoir on the volcanic island of Guam has been completed. Source water dissolved Mn content was determined to be 7.34 mu g/L at a reservoir intake depth of 10ft, 9.85 mu g/L at a depth of 20ft, 41.6 mu g/L at a depth of 30ft, and 775 mu g/L at a 40 foot depth. For the intake depth of 10ft, it was found that a ClO2 dose of 1.1mg/L reduced Mn by an average of 98.7%, as compared to an average of 95.9% using a KMnO4 dosage of 1.75mg/L. Cl-2 was found not to reduce dissolved Mn to any extent at dosages of 1.25mg/L. It was determined that pink water formation occurred with less than 0.5mg/L of a permanganate overdose. Additionally, a 1.1mg/L ClO2 dose produced an average chlorite and chlorate by-product concentration of 780-1,080 mu g/L, respectively. Results demonstrated that ClO2 would be the preferred oxidant for Mn control as compared to KMnO4 or Cl-2 for the volcanic water supply evaluated in this study. The research also verified that a 0.10-micron filter produced more accurate dissolved Mn results than the standard method use of 0.45-micron filter in laboratory procedures.