Pilot Study On Dual-stage Technology For The Treatment Of Complex Polluted Groundwater

Groundwater, showing advantages in good quality, stable quantity and distributionwidely, is an important component of water source in urban water supply industry. Inrecent years, human ignore their responsibility for the protection of environment,resulting in the pollution of groundwater by iron, manganese, ammonia and othercontamination, which has become an serious threaten to the safety of urban watersupply. This paper was based on the11thtube-well of Northwest Groundwater Source inXi’an. The water quality of11thtube-well was monitored for long-term, and the resultshowed that the concentration of iron, manganese and ammonia nitrogen was seriouslyoverweight in this tube-well, with occasionally over standard in turbidity and color. Thestudy took iron, manganese and ammonia as the main subject, and carried out on-sitepilot test research in order to providing parameters for the technological transformationof the groundwater plant.In this experiment, the filter material, the quartz sand, was fully mature, and itssurface covered with a layer of "black film". The study was based on dual-filter process,“sand filter+activated carbon filter”, and the water was oxygenized by pre-spray andfree overfall before filtration.The study measured the concentration variation of contamination under differentinfluent concentration and different filtration rate. The result showed the averageremoval efficiency of Fe, Mn, ammonia nitrogen and turbidity were higher than90%,and the average removal rates of CODMnand UV254were20%and30%. The treatmentefficiency of this dual-stage system was stable, would not fluctuate remarkable by thechange of contamination concentration and filtration rate, which showed strong adapt ability for the treatment of complex polluted groundwater.The study analyzed the concentration variation of contamination along depth ofsand filtration filter. The showed that Fe, Mn, ammonia nitrogen, chrome and turbiditywere largely removed in the former0-70cm depth of column filter, and thus theoptimum thickness of the filter layer was110cm.Backwash water of sand filter was treated in static beaker tests. After comparativetrial, PAC was taken as coagulant, and the suitable dosage was70mg/L. PAM was takenas coagulant agent, and the appropriate dosage was0.9mg/L.