Optimization Of Purifying Filter Of Groundwater Containing High Concentration Of Iron, Manganese Andammonia And The Investigation Of Microbial Community Structure

Since the theory of biological manganese removal was proposed, biological iron and manganese removal was widely used in groundwater treatment plant, whose groundwater contained higher concentration of iron and manganese. However, the hydrogeological structures and environmental conditions were different across China, and the groundwater quality was different accordingly, therefore new problems arised when promoted the application of the technology, and the technology needed to be improved. Why the start-up period of biological filters for iron, manganese and ammonia removal was more longer, the interaction between ammonia removal and manganese removal, and the effect of nitrite generated in nitrification process on manganese removal needed further research.In this report, the effect of double-filtering media, circulation reflux and circulation reflux cooperated with double-filtering media on start-up period of biological filters for iron, manganese and ammonia removal, simultaneous iron, manganese, ammonia and turbidity removal, Interactions among iron, manganese and ammonia removal, the effect of nitrite on biological manganese removal and the variation of the microbial community structure in different stages were investigated. The main conclusions can be drawn as follows:Five kinds of start-up mode, no reflux of single-filtering media, circulation reflux of single-filtering media, no reflux of double-filtering media, constant reflux ratio of double-filtering media, varying reflux ratio of double-filtering media, were adopted to purify groundwater containing high concentration of iron, manganese and ammonia nitrogen, and the start-up periods were103d,81d,82d,61d,51d. At the beginning of the start-up period, the removal efficiency of iron was high, the removal efficiency of ammonia was relatively low, and manganese was adsorbed by manganese sand; in the steady phase, iron, manganese and ammonia were mainly removed in0~0.4m of the filter depth, but manganese was decreased to less than0.05mg/L in0.8m. Double-filtering media, circulation reflux and circulation reflux of double-filtering media were effective ways to shorten the start-up period of biological manganese removal process; the sequence that iron, manganese and ammonia were completely removed was iron, ammonia, and manganese in start-up process.Varying backwashing period, varying backwashing intensity and varying backwashing time had no influence on iron, manganese and ammonia removal. The shorter backwashing period, higher backwashing intensity and longer backwashing time, the lower turbidity in effluent. Turbidity was mainly removed in0~0.4m, and the turbidity in effluent had nothing to do with the height of the media; turbidity removal was obviously effected by backwashing period, backwashing intensity and backwashing time.When the concentration of total iron, manganese and ammonia nitrogen in influent was5~10mg/L,0.9~1.3mg/L,0.9~1.3mg/L, respectively, the temperature of raw water was8℃, and the flow rate was6m/h, the maximum concentration of mangaese and ammonia was10.5mg/L and2.5mg/L, respectively. The maximum concentration of manganese was influenced by dissolved oxygen (DO), and the maximum concentration of ammonia was hardly increased because DO was insufficient. There was no influence of manganese concentration increased in influent on iron and ammonia removal, and iron and manganese removal was also not effected by ammonia increasing in influent.When DO in influent was sufficient, iron, manganese and ammonia were removed in0~0.3,0.2~0.8and0~0.4m of the filter depth. When DO was decreased to about6.5,6,5and4mg/L, respectively, iron and manganese were completely removed, while ammonia in effluent was increased with DO was decreased. In addition, the oxidizing velocities of the pollutants were almost not affected compared with that of sufficient DO condition. When total iron was about10mg/L, the oxidizing velocity of ammonia was drastically affected; when manganese was increased to3mg/L, ammonia removal was obviously affected; while when ammonia was less than2.5mg/L, iron and manganese removal were not effected.When nitrite was added to the filter with a concentration of about0.05~0.5mg/L and manganese was about2mg/L, nitrite was not reacted with Mn(Ⅳ) in anaerobic condition. The added nitrite was quickly oxidized and Mn(II) removal was obviously effected about2h in aerobic condition, while when ammonia in influent was increased from about1.1mg/L to about1.5mg/L, nitrite was accumulated in the filter, Mn(II) removal was obviously effected about3d, but iron removal was almost not effected.There were two kinds of microorganism in the biological filter depth, Archaea and Bacteria; the proportion of Archaea in the filter depth was lower then1%, and Euryarchaeota and Crenarchaeota were presented in the filter depth. The phyla of the Bacteria in filter depth were Proteobacteria, Bacteroidetes, Firmicutes, Nitrospirae and Actinobacteria, and the families of the Bacteria in filter depth were Crenotrichaceae, Flavobacteriaceae, Comamonadaceae Methylophilaceae and Bacteriovoracaceae. And when the DO in influent was decreased to about6mg/L and4mg/L, the mainly bacteria in filter depth were Proteobacteria, Bacteroidetes, Firmicutes, Nitrospirae, Actinobacteria, TM7and Verrucomicrobia; Proteobacteria, Bacteroidetes, Firmicutes, Nitrospirae and Actinobacteria were obviously affected by DO, while TM7and Verrucomicrobia could adopt the low DO contition. And Comamonadaceae, Crenotrichaceae, Flavobacteriaceae, Saprospiraceae, Flavobacteriaceae Methylophilaceae, Leptospirillaceae and Opitutaceae were presented in the filter depth.