Pilot-scale Studies On Catalytic Oxidation Of Ammonium From Groundwater By Iron And Manganese Co-oxide Filter Film

In the northern area of China, groundwater is an important source of fresh water. Due to the increasing environmental pollution in recent years, the concentration of ammonium of groundwater is continuously increasing with the over standard rate of ammonium being high. In order to remove the ammonium from groundwater effectively, the study of removing ammonium through catalytic oxidation using the co-oxide filter film is then conducted.Firstly, the stratification of removal of ammonium, iron and manganese along filter depth and the effect and consumption of dissolved oxygen on removal of these pollutants from micro-polluted groundwater was studied. Then, the assay was used to investigate the catalytic oxidation of ammonium from groundwater by co-oxide filter film coating on quartz sands by filtering inlet water only containing ammonium for long term, which includes the stability of performance of catalytic oxidation of ammonium, operating technology, and the maximum ammonium removal capacity. Finally, to investigate the performance of catalytic oxidation of ammonium under actual conditions, the studying of ammonium removal using water from the local underground network was conducted. The main results are as follows:(1) when ammonium、total iron and manganese in raw groundwater were 1.3 mg/L、0.5 mg/L and 1.0 mg/L respectively and dissolved oxygen was 4.5-8.6 mg/L, no stratification of the ability for iron and manganese oxidation was observed, while the performance of catalytic oxidation of ammonium decreased among top、middle and bottom layers; The dissolved oxygen is mainly consumed at the upper 30 cm of the filter; There was no influence of influent DO concentration increased on iron oxidation, which prompts the oxidation of ammonium and manganese; iron was removed superior to manganese and ammonium, however, removal of ammonium and manganese occurred simultaneously.(2) In the experimental conditions of the concentration of ammonium nitrogen was 0.8-1.3 mg/L, the temperature of raw water was 20-23℃, and the flow rate was 7 m/h, the performance of catalytic oxidation of ammonium of co-oxide filter film remained stable and high-efficient for a long time. The maximum ammonium removal capacity of the filter was determined to be 22.2 gNH4+-N?m-3?h-1 with ammonium removal rate(ARR) determined by the ammonium loading rate(ALR) if the dissolved oxygen(DO) was enough. The maximum concentration of ammonium was limited by DO. When the DO in influent was not enough, flow rates had significant influence on consumption of dissolved oxygen along the filter layer.(3) When the inlet ammonium solution was prepared by the raw water from the local ground network, the performance of catalytic oxidation of ammonium of co-oxide filter film also remained stable and high-efficient for a long time, however, in order to keep dissolved oxygen enough, it is necessary that filter was back washed regularly.