Comprehensive experimental design of high iron acid mine drainage treatment based on water treatment engineering

Light-burned magnesium calcined from magnesite tailings is a good neutralizer for acid mine drainage, it has many advantages such as good removal effect, better operation conditions and less sediment.Using industrial composition analysis and XRD analysis, it could be known that the main composition magnesium oxide is higher than 90%.Taking the acid mine drainage from a coal mine in Shanxi as the research object, the general water quality analysis shows that total iron concentration is 230.01 mg/L, ferrous ion concentration is 66.98 mg/L、pH value is 3.24.Designing orthogonal experiment to treat acid mine drainage with light-burned magnesium, the effluence of initial pH value, neutralizer dosage, aeration rate and aeration time on removal effect are discussed respectively.The experimental results show that pH value of the acid mine drainage could be improved from initial 3.15-3.31 to 6-9 when the light-burned magnesium dosage is 0.50-1.00 g/L, the buffer property is well and it is easy to control the dosage to meet the requirements of pH value 6-9.The order of three influencing factors is dosage> stirring time> stirring speed, under the optimal scheme such as light-burned magnesium dosage 0.85 g/L, stirring speed 400 r/min and stirring time 12 min, the removal effect could be the best.To improve the sedimentation characteristic, when initial pH value raised to 7.48, aeration time 5 min, aeration rate 0.5 m³/h, polyaluminium chloride(PAC) dosage 10 mg/L, the ferrous ion and total iron concentration of the acid mine drainage could decreased to 0.07 mg/L and 0.17 mg/L respectively which could fulfill the requirement of discharge and reuse, meanwhile improve the settling performance and greatly shorten the sedimentation time.