Study On The Combined Removal Processes Of High-concentrations Manganese,Hardness And Sulphate

The polluted water in manganese mining area seriously threatened the production and life of local residents.Existing conventional treatment processes were difficult to effectively treat the water to meet the"Sanitary Standards for Drinking Water"（GB5749-2006）.In view of the current status of ecological security in mining area,the treatment technologies were developed for this high manganese-containing source water.Manganese sand filtration-nanofiltration-ion exchange processes were optimized in the mining area.The operation parameters of the nanofiltration membrane were optimized with control variable method.The optimum values of the operating pressure,pH and influent flow were 0.6 MPa,6.5 and<1.8 m³/h,respectively.Under the optimal operating conditions,the continuous operation of the nanofiltration was conducted to investigate the contamination resistance and stability.Based on the high complexity and high costs in existing processes and the seasonal variation of Mn²⁺concentration,nanofiltration combined with other processes were proposed in this paper.When the Mn²⁺concentration in the contaminated water was no more than 30.0 mg/L,the combination of nanofiltration and manganese sand filtration processes was adopted;when the Mn²⁺concentration in the contaminated water was higher than 30.0mg/L,the combination of pre-oxidation of potassium permanganate and nanofiltration processes was adopted.For the Mn²⁺concentration no more than 30.0 mg/L,nanofiltration-manganese sand filtration processes were used.Firstly,response surface methodology was used to optimize the operating parameters of nanofiltration.The results showed that the Mn²⁺concentration in the nanofiltration product water can be reduced to below 2.0 mg/L under the optimum conditions of operating pressure,pH and temperature of 1.6 MPa,5.0 and 19.6°C,respectively.Secondly,the effects of influent manganese concentration,filtration flow rate,operation cycle,and initial pH on manganese removal from manganese sands were studied.In addition,the static adsorption experiments of natural manganese sand and mature manganese sand were conducted to further explore the removal mechanism of manganese ions.The results showed that the Mn²⁺concentration can be reduced to no more than 0.1mg/L by manganese sand filtration.Because of the limited ability on manganese removal by manganese sand,the combination of potassium permanganate pre-oxidation and nanofiltration was used to treat the water with Mn²⁺concentration higher than 30 mg/L.For the water samples with Mn²⁺concentration of 173.5 mg/L,the optimization experiments were performed on the parameters such as the dosing equivalents of KMnO₄,preoxidation time,hydraulic conditions,and pH.In the system of pre-oxidation,coagulation,sedimentation,and nanofiltration,the effluent quality could meet the"Sanitary Standards for Drinking Water"（GB5749-2006）.In this paper,the processes of nanofiltration-manganese sand filtration and potassium permanganate pre-oxidation-nanofiltration were used to treat contaminated water with Mn²⁺concentrations no more than and above 30 mg/L,respectively.Both of the combined processes can effectively remove pollutants such as Mn²⁺,Ca²⁺,Mg²⁺,SO₄^2-and Ni²⁺contained in the water to meet the"Sanitary Standards for Drinking Water"（GB5749-2006）.Compared with the existing water treatment processes on site,these technologies had better performance,wider range of applicable manganese concentration,simpler operation and lower processing cost.