The Study On The Removal Of Manganese In Drinking Water Through Chlorine Dioxide Contact Oxidization Filtration

In recent years,the phenomenon of manganese concentration exceeding theregulated standard has appeared with ground water, which is regarded as sources ofdrinking water. In dry seasons, underground water flows back to the surface as groundwater, along with the external changes in temperature and dissolved oxygen,manganese concentration in ground water exceeds the regulated standard seasonally.As a new type of water treatment chemicals, chlorine dioxide has become more andmore important in the treatment of drinking water for its safe and efficient oxidationcharacteristic. Oxidation for removing manganese is one of its important applications.Based on the conventional water treatment process, chlorine dioxide was addedbefore filtering in this study, chlorine dioxide was used to resolve burst， seasonalmanganese pollution problems of surface water for its contact oxidation effect. Thisthesis described research to quantify the kinetics of Mn(Ⅱ) oxidation by chlorinedioxide and used the model filter column to simulate the real industrial procedure.The results showed that3mg/L of chlorine dioxide was needed for the oxidationof1mg/L of Mn(II), according chemistry theory, reaction with two levels of dynamics,kinetics model: d M n Ⅱ/dt k M n Ⅱ C lO2O H c.At the initial stage of the experiment, both pH value and chlorine dioxide dosagehad significant effect on the removal of manganese. When pH value equaled to8.3and the chlorine dioxide was two times as the influent concentration of manganese,the effluent concentration of manganese can reach the standard. If manganeseconcentration in raw water was0.5-3mg/L,EBCT was3-15min,it was discovered thatthe manganese concentration could always be qualified only if at appropriate pH valueand chlorine dioxide dosage to manganese concentration ratio. Besides, lowtemperature had inhibition effect on the removal of manganese.The experiment of four columns with different pH value and chlorine dioxidedosage underwent28days. Generally, the mature period of column was6-18days.The increase of pH value and chlorine dioxide was helpful for the maturation ofcolumn. After the column had been matured, the necessary condition for manganeseremoving became less critical, and the manganese could be removed efficiently if pHvalue at7.0, and ClO2/Mn2+ratio at0.5, because the contact oxidation of chlorinedioxide is a self-catalyzed process. The mature column failed to remove manganese without ClO2being added. After steadily being re-added ClO2for several days，thecolumn regained the ability of removing manganese. Analyzed by X-ray photoelectronspectroscopy, manganese oxide covering on filter media was composed of63%MnO2and37%Mn3O4,the structure was MnO1.75.H2O.This technique requires no extra constructions and a local modification is needfor the emergency treatment of manganese, thus it has an significant prospect in thesolution for sudden manganese pollution in water source, both economically andefficiently.