Study On Pretreatment Technology Of Micro-polluted By Fe²⁺、Mn²⁺ Source Water In Mountainous Countryside

In recent years,water sources of iron and manganese exceeded pollution problems become increasingly serious in China mountainous rural areas.When the water source have too much iron and manganese,people’s production and life will affect or even harm.There are many ways to remove iron and manganese,in which the chemical oxidation method is of great concern because of its high efficiency,rapid and thorough advantage.This paper mainly studied the removal of iron and manganese in the micro-polluted source water of mountainous rural areas,so as to provide some technical reference and theoretical basis for the treatment of micro-polluted iron and manganese water in mountainous rural areas.Through the investigation and sampling of several typical areas of mountainous rural in Chongqing,detect and analyze the water quality.Design of static beaker test,select sodium hypochlorite,potassium permanganate and hydrogen peroxide as oxidant to treatment water sources of iron and manganese.Through single factor experiment to study the pre-oxidation process of iron removal and manganese removal about the three kinds of oxidants,and select optimal oxidant to design orthogonal test to determine the best process of removing iron and removing manganese.As the iron and manganese usually coexist,so further research oxidation method to removing the coexisting iron and manganese water,in order to more effectively remove iron and manganese,a pre-oxidation-ultrafiltration combined process test.The main findings are as follows:（1）The water quality research was mainly carried in the typical sampling points of Chongqing,such as Chongqing area typical rural water to the four corners of Chongqing: Bishan,Fuling,Liang Ping,Qijiang.According to the results,there was a phenomenon of excessive Fe²⁺ and Mn²⁺ in the water source of Chongqing mountainous area,including Fe²⁺ excessive or Mn²⁺ excessive or Fe²⁺ and Mn²⁺ both excessive.（2）Fe²⁺and Mn²⁺in the raw water were removed by the preoxidation process,using three oxidants including sodium hypochlorite,potassium permanganate and hydrogen peroxide.The effect of oxidant dosage,solution pH,preoxidation time,coagulant（Al2（SO4）3·18H2O）dosage and preoxidation temperature on Fe²⁺and Mn²⁺removal was studied.The results showed that the above factors could affect the removal rate of Fe²⁺ and Mn²⁺,and the effect of solution pH was significant.Fe²⁺ oxidation was very efficient,Mn²⁺oxidation was not as efficient as Fe²⁺,in which sodium hypochlorite had the best effect on the removal of Fe and Mn,followed by potassium permanganate,and the effect of addition of Fe²⁺in hydrogen peroxide was better.（3）The orthogonal test was carried out using sodium hypochlorite as oxidant to select the best process of removing iron and manganese.The results of range analysis showed that the main factors affecting the removal efficiency of Fe²⁺and Mn²⁺were as follows: pH> oxidant dosage > coagulant dosage > preoxidation time.The best process of removing iron was: when the concentration of influent Fe²⁺ of 1mg/L,0.9mg/L of sodium hypochlorite and 90mg/L coagulant were added at room temperature,pH was8.13,the residual Fe²⁺ concentration was 0.056mg/L,after pre-oxidation for 9min,the removal rate reached 94.4%;The best process of removing manganese was: when the influent Mn²⁺concentration was 1mg/L,1.3mg/L of sodium hypochlorite and 90mg/L coagulant were added at room temperature,pH was 9.12,the residual Mn²⁺concentration was 0.073mg/L,after pre-oxidation for 9min,the removal rate reached92.7%.After pre-oxidation treatment,Fe²⁺and Mn²⁺in raw water reached the national drinking water standard.（4）The purification effect of pre-oxidation on Fe²⁺ and Mn²⁺ coexisting water was investigated.The results show that when the raw water Fe²⁺and Mn²⁺concentration were 0.75mg/L and 0.25mg/L,at room temperature,the sodium hypochlorite dosage was 1.05mg/L,pH was 8.56,pre-oxidation time was 9min,the coagulant was 90mg/L,the removal rate of Fe²⁺and Mn²⁺were 96.70% and 96.10%.The total removal rate was96.55%,and reached the national standard for drinking water.（5）Without chemicals,the removal efficiency of Fe²⁺ and Mn²⁺ in raw water by direct ultrafiltration was not good,but it had a certain effect on the remove of Fe²⁺and Mn²⁺ that coexist in water.The combination of ultrafiltration process and pre-oxidation process had a better effect on the remove of Fe²⁺ and Mn²⁺ than the pure pre-oxidation process.The removal efficiency of Fe²⁺and Mn²⁺were 100% and 97.4% respectively,and the total removal efficiency was 99.35%.The combined process of pre-oxidation and ultrafiltration to remove Fe²⁺ and Mn²⁺ and its coexisting water,the removal efficiency of Fe²⁺had significantly enhanced,and the removal efficiency of Mn²⁺also had a certain improvement.This study has been supported by the project of development and demonstration integrated drinking water ultrafiltration integrated treatment and installation in mountainous areas.The research results have important practical value.