Research On Treatment Of Groundwater With High Content Iron And Manganese

About50%ground water sources in our country had a certain degree of pollution, andnearly half of urban ground water sources had been polluted seriously. The groundwater qualitywas worsening day by day. The polluted water mainly contained ammonia, organic matters andother pollutants, and owing to the influence of geological condition in North, the concentrationsof iron and manganese were high as well. While, the treatment for groundwater contained iron,manganese, ammonia and organic matters, because of its complex elements, had been one oftechnical difficulty in groundwater treatment, and fixed the attention of experts and scholars athome and abroad. At present, the groundwater contained iron and manganese was mainly treatedby sand filter. But studies indicated that, adding the pollution of ammonia caused a limit infiltering manganese, ammonia and organic matters. In the water treatment process, the exceedingof ammonia and organic matters will produce the chloramines and other materials withcarcinogenicity-mutagenicity-teratogenicity in the following chlorine disinfection process.Therefore, to deal with the difficulty in removing iron, manganese, ammonia and organicmatters from groundwater, the experiment adopted oxidation and adsorption to treat thosepollutants. The final goal of this experiment is seeking for an effective physical and chemicalmethod leading the water quality meet the drinking-water standard. The raw experiment waterwas prepared by the humic acid, the phenol, the ferrous sulfate and the manganese sulfate. Ironconcentration was4⁵mg/L, manganese is5⁶mg/L, ammonia is3⁴mg/L, COD_Mnis3³.5mg/L. The research was mainly divided into three parts: the oxidation process, theoxidized-adsorption process and the compound oxidized-adsorption process. The entireexperiment run under the condition of water temperature at10¹5℃, pH at7.0⁷.5. The mainresearch results are as follows:1) The oxidation process. Added different amounts of potassium permanganate, thepotassium ferrate, the sodium hypochlorite and the ozone respectively to the raw water, and thenstirred at the speed of60r/min for30min. the water quality examination showed that the soleoxidant oxidation cannot make the effluent quality meet the standard..When the dosage ofpotassium permanganate was0¹5mg/L, the ammonia and COD_Mncannot reach the standardafter reaction; for ferrate was0¹2mg/L, all pollutants cannot reach the standard after reaction;for the sodium hypochlorite was0⁵0mg/L, ammonia and COD_Mncannot reach the standardafter reaction; for the ozone was7mg/L, only ammonia cannot reach the standard after reaction.When the ozone was3mg/L, iron and manganese was removed totally, and the best oxidationtime was15min.The pollutants removal has a certain rule in the oxidation process. The first removed wasiron, the next was manganese, the last was ammonia and organic matters. While the removal ofammonia was most difficult, its concentration cannot met the standard. Therefore, adopted thecombination of oxidants to deal with the raw water. When adopted the combination of the ozoneand the potassium permanganate, after reaction30min, the effluent ammonia still didn’t reach the standard. For the combination of ozone and sodium hypochlorite, when added3mg/L ozoneto the raw water with the responding time of30min, then added25mg/L sodium hypochloriteand responds30min, the effluent could meet the standard.2)The oxidized-adsorption process. Selected powder activated charcoal （PAC）, powderzeolite and MAP as absorbents. Stirred the raw water30min under rotation rate60r/min. Theresult indicated that PAC only removed organic matters well; powder zeolite and MAP onlycould remove ammonia, and they nearly had same removal effect, but cannot ensure meeting thestandard. So, adopted the combination of ozone oxidation and adsorption to deal with the rawwater. The concentration of ozone was3mg/L, reaction time was15min. The result showed thatthe oxidized-adsorption process cannot ensure the effluent quality meet the standard. Specially,after using ozone-PAC and ozone-powder zeolite process, ammonia exceeded the standard; afterusing ozone-MAP process, ammonia and COD_Mnboth exceeded the standard.3)The compound oxidized-adsorption process. Because the oxidation had a good removaleffect of iron and manganese and the adsorption had a good removal effect of ammonia andorganic matters, adopted different combinations of oxidation and adsorption, according to thepollutants in water, to ensure the effluent quality could meet the standard.The experiment adopted six different combination plans. The result indicated that all the sixcombinations can make the effluent qualities reach the standard. And the removal effect of PAC-ozone-powder zeolite process was the best, and the dosage of medicaments was the least. The sixcombinations are as follows:The ozone-PAC-sodium hypochlorite process. Ozone concentration was3mg/L, reactiontime was15min; the dosage of PAC was200mg/L, reaction time was10min; the dosage ofsodium hypochlorite was15mg/L, reaction time was15min.The PAC-ozone-sodium hypochlorite process. The dosage of PAC was200mg/L, reactiontime was10min; ozone concentration was3mg/L, reaction time was15min; the dosage ofsodium hypochlorite was6mg/L, reaction time was15min.The PAC-ozone-powder zeolite process. The dosage of PAC was200mg/L, reaction timewas10min; ozone concentration was3mg/L, reaction time was15min; the dosage of powderzeolite was1.5g/L, reaction time was10min.The PAC-powder zeolite-ozone process. The dosage of PAC was200mg/L, reaction timewas10min; the dosage of powder zeolite was1.5g/L, reaction time was10min; ozoneconcentration was3mg/L, reaction time was15min.The PAC-MAP-ozone process. The dosage of PAC was200mg/L, reaction time was10min;added MgSO₄·7H₂O and Na2HPO₄·7H₂O to water, and kept Mg2+:PO₄3-:NH4+at1:1:1,reaction time was15min; ozone concentration was3mg/L, reaction time was15min.The PAC-ozone-MAP process. The dosage of PAC was200mg/L, reaction time was10min;ozone concentration was3mg/L, reaction time was15min; added MgSO₄·7H₂O andNa2HPO₄·7H₂O to water, and kept Mg2+:PO₄3-:NH4+at1:1:1, reaction time was15min.Among them, the treatment cost of the PAC-ozone-powder zeolite process was the lowestof the six, and average treatment cost was1.81yuan each ton water. Compared with ozone- sodium hypochlorite process, the treatment cost of the PAC-ozone-powder zeolite process waslower.