Influence Of PH On The Performance Of Manganese Filter For Treating High Concentration Iron, Manganese And Ammonia Contaminated Underground Water

The removal of iron and manganese from groundwater is a research problem oflong history in the water industry. A lot of research on this problem has been done athome and abroad. The theory and technology of the removal of Iron and manganesefrom groundwater has gone through three stages of development: natural oxidation,contact oxidation and biological method. However, our geographical condition iscomplex and diverse, characteristics of groundwater vary, there are many complexfactors affect iron and manganese removal, and for different groundwater treatmentprocess, it is difficult to determine the iron and manganese removal mechanism. In thispaper, pH as the most sensitive factor that affect the removal of iron and manganese wasthe key inspected object, the filter maturated rate and the removal of iron andmanganese were studied with groundwater containing high concentration of iron(15mg/laverage), manganese(1.0mg/l average) and ammonia((2.2mg/l average)) from Harbin indifferent pH, so that deepen their understanding of the mechanism of the removal ofiron and manganese.The study of how pH effect the result of water treatment by sand fliters showedthat: the higher the pH is, the sooner the biofilm forms, the better the water quality. AtpH7.5,7.0and6.5, the filters begin to remove ammonia at40,60and150daysrespectively, but with the extension of culture time, after about80,140and210daysoperation respectively, the removal of ammonia trends to be the same under differentpH, stays at0.4-0.5mg/l; High pH favor the removal of manganese, the concentration ofmanganese effluented from manganese and quartz filters under pH7.5is below0.05mg/lafter150and170days respectively, the filtration column with pH7.0have certainmanganese removing ability(the concentration of Mn2+in the effluent of manganesesand is0.3mg/l, quartz sand is0.6mg/l), manganese can’t be removed when the pHof source water is6.5; there is no effect on iron removal in different pH range, after150days, the concentration of total iron is under0.2mg/l. The iron removal mainly dependson contacting catalytic oxidation. High water pH is conducive to sand filter removingturbidity stably and efficiently. The removal efficiency of iron and ammonia withmanganese and quartz sand at different pH is consistent, there was no significantdifference; For the removal of manganese in pH7.5and7.0, manganese is superior toquartz sand, which is mainly due to high manganese oxide that manganese sandcontaining much more than the quartz sand and manganese sand’s surface is rougherthan quartz sand so that manganese sand is easier to hang over the film than quartz sand;In the pH6.5, both manganese and quartz sand don’t have manganese removal capability.The study of two-step filtration and single-step filtration for removing iron andmanganese from ground water shows that: at pH7.5,the mature speed of two-step filtration is significantly faster than single-step filter of dual media. However, at pH7.0and6.5, there is no significant difference in the removing of iron and manganesebetween the two water treatment processes, indicating that within a certain pH range,pH’s effects on mature speed of filter is much greater than the frequency of backwash.The mechanism analysis of how pH effects the manganese removal by sand filtershowed that: with the decrease of pH, the main removal belt of manganese will movedown with the main removal belt of iron doesn’t change, but the depth of filter columnthat remove iron will increase.when pH declines, the iron concentration in the surface offilter is higher, while the concentration of manganese is lower, ferric hydroxide willcover the filter surface and interfere the generation of active manganese film, and thenaffecting the removal of manganese.The kinetic analysis of manganese sand adsorbing manganese ions could be welldescribed by pseudo-second-order kinetics equation, indicating that the process ofadsorption is chemical adsorption,and the process of ion exchange occurs between theadsorbent and adsorbate; In the preceding6h of manganese sand adsorbing manganeseions, inner diffusion control the adsorption rate, in the6h-12h, adsorption rate iscontrolled by the membrane diffusion, after12h,the process of adsorption trends to theadsorption equilibrium phase. After the elution of manganese sand with different pHsolutions, pH2and3, the concentration of Mn2+in elutant is high when pH is1,2and3,but only at pH1, the regeneration rate of manganese sand reachs121%; when the pHrange from2to8, the regeneration rate is only55-65%; with the pH≥9reproductionrate has improved signs.