The Research On Impact Of Organic Matter On Both Chemical Oxidation And Coagulation Removal Of Iron From Groundwater

By experimenting in the laboratory, the effects of natural organic matter on both oxidative and coagulation removal of iron from groundwater were researched. Organic compounds evaluated included humic acid, tannic acid, fulvic acid and oxalic acid. Oxidants evaluated were potassium permanganate, chlorine dioxide and free chlorine. Some impact factors such as pH, oxidant contact time and solution temperature were studied, with stress on discussing the influence of DOC molecular weight and the concentration on removing iron. Pro-oxidantion followed by alum coagulation was analyzed for affecting the efficiency of soluble iron and DOC removal.The experiments show that various natural organic compounds had negative impacts of different degree on the ability of oxidants to promote effective removal of iron. The greater the molecular weight or the concentration of organic substances was, and the higher the degree of negative impacts was. Potassium permanganate was found to be the most effective oxidant of the three investigated. Free chlorine was the most ineffective for removal of iron complexed by various organic compounds. Potassium permanganate was very effective for promoting iron removal when iron was complexed by the organic matters with molecular weight less than 4000. Chlorine dioxide and free chlorine were only effective for removal of iron complexed by the organic matters with molecular weight less than 1000. pH value increasing was beneficial to oxidative removal of complexed iron over the pH range from 5.5 to 7.5. Prolonging reaction time could improve the removal of complexed iron during chemical oxidation. Solution temperature had little effect on oxidative removal of complexed iron. The relative molecular weight distribution and the concentration of organic matters had significant effect on coagulation removal of iron. The removal of DOC and iron also increased with the increasing of the molecular weight and the concentration of organic matter during alum coagulation.Alum coagulation was very effective for removal of iron complexed by organic matter with molecular weight greater than 10000 and the residual soluble iron concentration decreased to value below 0.3 mg /I, in the meantime, overall DOC removal attained 75% or above. Soluble Fe(II) complexed by organics with molecular weight less than 4000 was amenable to removal by KMnO4 addition followed by alum coagulation . But when Soluble Fe( II) was complexed by organics with molecular weight greater than 4000,...