Experimental Study On Treatment Of Groundwater With High Manganese By Modified River Sand

Water resource is very poor in China. Groundwater as main source of watersupply for life of urban-rural residents and industrial-agricultural production hasalready become very important, even only water source in many areas, especially inNorth China. Moreover, water that contains too much Fe2+and Mn²⁺can be harmfulto people’s production and living. If drinking groundwater with high manganese for along time, it will cause chronic poisoning.But due to the high oxidation potential from Manganese ion to Manganeseoxide,it is quite hard to be completely oxidized so as to be removed. Traditional filtermaturation period is quite long during the process of removal of manganese and theremoval efficiency is not steady. Therefore, developing the technique to removemanganese with cheap and efficient is still an urgent task.Recently, coating with metal oxide or hydroxide on media to improving removalcapacity, has become a fashionable technique for water treatment at home and abroad.The research described here was designed to test the properties of manganese oxidecoated river sand by KMnO₄for removing manganese ions from syntheticsolutions.The removal mechanisms of Mn²⁺by modified river sand were alsoinvestigated.The river sand was employed as carrier, as well as KMnO₄was employed asmodifier, a kind of coated filter-modified river sand was prepared. Making optimalchoice of modified river sand was conducted in static methods. It clearly indicatedthat, the best quality percentage concentration of potassium permanganate is1%andthe best particle size of river sand is0.85-1mm. The modified river sand wasconfirmed to be a good absorbent for removal of manganese ions compared to theoriginal river sand. The modified river sand has high physical-chemical endurance inneutral and weakly alkaline. It is unstable under acidic conditions.The treatment effect of Mn²⁺in aqueous solution was studied with filter column.The results showed that the Mn²⁺concentration of effluent was lower than0.1mg/Lconstantly, which conformed the state standards for drinking water, in the optimum conditions: the water residence time was about24min, the content of dissolvedoxygen was more than7mg/L, the pH of the inflow was neutral or alkaline, theconcentration of manganese was less than2mg/L. Under these conditions, the filtercycle is6days, the reverse wash strength is18L/s m²。The modified river sand was filled in pumping wells, with aeration inunderground aquifer, this method is used to simulate to remove manganese in-situ.The comprehensive studies on the optimal important factor were carried. The resultshow that, the best aeration pattern is dispersed aeration process, the water residencetime was about12min and the concentration of Fe²⁺ was more than3mg/L. Under thebest conditions, the flume simulated experiment was carried for a long time, we foundthat the time for backwashing of the modified river sand have been extended. Aquiferalso played a role in removing iron and manganese by aeration, this method canachieve to remove iron and manganese simultaneously.Surface area analysis, SEM/DEAX, XPS, XRD were employed to examine theprocess and mechanism of Mn²⁺ removal by the modified river sand. From theseresearches, we found that the modified river sand has large surface areas. Weprimarily determined that the membrane of modified river sand surface played ancrucial role and the mechanism of manganese removal of was adsorption andself-catalysis processes.