Effect Factors Of The Chemical Catalytic Oxidation Of Ammonium By The Iron-manganese Co-oxides Coated Filter Sands

As one kind of drinking water sources,surface water has some special characteristics,such as low water temperature in winter,seasonal variation of water quality.The safety of drinking water has been threatened by the seasonal ammonium contamination in surface water.It is a problem which is difficult to be solved by present water plants.In this study,iron-manganese co-oxides coated sands are used to remove ammonium from surface water.Ammonium removal efficiency and the effects of phosphate,alkalinity and pH under surface water conditions were investigated systematically by pilot-scale filter systems in Xi'an and Lanzhou.The main results and conclusions of my research can be concluded as follows:(1)Ammonium removal rates would decrease when the iron-manganese cooxides coated filter sand was used for treating surface water and dosing phosphate into the feed water of the filter system could removal this negative scenario.With phosphate addition of 30 ?g/L,the average ammonium removal rate was up to 96.6% and 89% even at 6°C(the lowest water temperature in Xi'an)when the influent ammonium concentration was 2 mg/L.(2)Lab-scale inactivation experiment indicated that iron-manganese co-oxides coated sand could remove ammonium from surface water by both biological and chemical catalytic oxidation and chemical catalytic capability was accounted for 58%.Pilot-scale inactivation experiment showed that when nitrifier on the filter media was eliminated,ammonium still could be reduced to about 0.15 mg/L only through chemical catalytic oxidation.(3)XPS spectra showed that the proportion of aluminum accumulated on the surface of the co-oxides operated in groundwater,surface water with phosphate and surface water without phosphate was the value under detection limit,4.88% and 8.07% respectively.The accumulate aluminum may be the reason for the decrease in ammonium removal rates and phosphate can reduce the amount of accumulated aluminum.(4)When ammonium removal rates decreased under the condition of continuous operation or stopping use for a long time,effluent ammonium could be reduced below 0.1 mg/L again after operating with phosphate dosing of 30 ?g/L for 4 and 11 days respectively at the influent ammonium concentration of 2.0 mg/L and the filtration rates of 7 m/h.(5)Alkalinity and pH have obvious effects on ammonium removal.Ammonium removal rates will increase with the increase of p H in the range of 6.5-8.5.When the alkalinity in feed water was adjusted to 50-150 mg/L(as CaCO3)by adding NaHCO3,ammonium removal rates increased slightly with the increase of alkalinity;when Na2CO3 was added into feed water to adjust the alkalinity in the range of 50-150 mg/L,ammonium removal rates were almost unchanged.When alkalinity was adjusted to 200 mg/L by adding NaHCO3 or Na2CO3,ammonium removal rates decreased.(6)The filter media,which was mature for about 4 years,could remove ammonium of 2 mg/L from the surface water in Lanzhou;the filter media,which was mature for about 3 months,could also remove ammonium of 2 mg/L after the remove performance was stable.The ammonium removal performance in different regions(Xi'an and Lanzhou)showed that the co-oxides coated sand can removal ammonium from surface water effectively.