Effects Of Ammonium And Water Quality On Manganese Removal By Manganese Co-oxide Film In Surface Water

In recent years,manganese pollution in surface water has become a serious issue,mainly manifested in seasonal and periodic pollution.Excess manganese in drinking water can damage the central nervous system,endanger human health,accelerate the accumulation of sediment on the wall of water pipeline,block water meter and water equipment,shorten the service life of the pipeline,make spots on the sanitary ware and discolor the clothes.Therefore,it is of great significance to study the removal of manganese in surface water treatment.Catalytic oxidation is a new method proposed in recent years to remove iron,manganese and ammonium from drinking water.In this study,the removal performance of manganese in surface water by manganese co-oxide film(MeO_x)and its influencing factors were studied.The mechanism underlying the effect of ammonium on manganese removal was also discussed.The main results and conclusions of this study are as follows:(1)The influencing factors of manganese removal in surface water were studied,including cultured time,temperature,alkalinity,anions and cations.The removal efficiency of manganese was related to the cultured time of the filter material.There was a large amount of MeO_x on the surface of the filter material with three years cultured,and MeO_x was tightly combined with the filter material.The filter material cultured for three years had high manganese removal activity,and the oxidation process of manganese was in accordance with the first order kinetics.The removal efficiency of manganese was affected by temperature.When temperature was lower than 11℃,manganese removal activity reduced obviously,and by reducing the filtration rate to increase the reaction time could improve the manganese removal efficiency.When alkalinity of inlet water was 0-200 mg/L,the removal efficiency of manganese could be improved by increasing alkalinity of inlet water.The alkalinity concentration in this experiment was positively correlated with the volume removal rate of manganese.When the concentration of anions and cations in inlet water was 100 mg/L respectively,the anions and cations in water also had effects on the manganese removal.Among them,Mg2+ and Ca2+ had great effect on the removal of manganese,while Na+,K+,Cl-and SO42-had little effect.(2)The effect of ammonium on manganese removal from surface water was studied.When the feed water without ammonium addition,MeO_x had long-term high efficiency and stable removal activity for 0.8 mg/L of manganese.The activity of MeO_x decreased at low temperature,but the removal rate of manganese could still reach 70% even the temperature was lower than 5.5℃.When the feed water with ammonium addition,MeO_x could effectively and simultaneously remove ammonium and manganese in surface water at high temperature(17.5-21.2℃).At low temperature(5.5-14.1℃),MeO_x could realize the short-term effective simultaneous removal of ammonium and manganese,and the manganese removal activity of MeO_x gradually decreased with the running time.After 10 days operation,the concentration of manganese exceeded the standard.During the whole process,MeO_x showed high ammonium removal activity.(3)The mechanism of ammonium effect on manganese removal was discussed.When ammonium and manganese were removed simultaneously,it was found that ammonium had a side effect on manganese removal when the concentration of ammonium was higher than 1.0 mg/L.The main reason was that H+ was produced in the process of ammonium oxidation,which was unfavorable for the process of manganese oxidation.In addition,the presence of ammonium slowed the growth of new MeO_x and retarded the increase in the specific surface area of the MeO_x-coated sand.The SEM and XRD results showed that the presence of ammonium induced changes in the morphology and crystal structure of MeO_x.Especially,the decrease of the intensity of the peaks at 9.06° and 18.04° directly led to the decrease of manganese removal activity of MeO_x.