Study On Treatment Of Heavy Metal Pollution In Groundwater By Micro Nano Bubble Remediation Technology

Groundwater heavy metal wastewater is one of the most harmful to the environment.At present,the common treatment methods are chemical precipitation,ion exchange and so on.In this paper,we use the interface zeta potential of micro nano bubbles,hydroxyl radicals,no secondary pollution and other advantages to treat heavy metal abwasser by ozone micro nano aeration.The micro nano bubble aeration of tap water proves that the micro nano bubble aeration is rapid and the peak value of dissolved oxygen is high.When ozone micro nano bubble aerates for 50 min,the DO concentration in water body reaches 13.9mg/L,which is 1.8 times of the initial value.The aeration capacity of micro nano bubble of air source is slightly lower than that of ozone source;the residence time of micro nano bubbles in water is longer than that of ordinary bubbles in water,with an average residence time of 297s;after the micro nano bubbles operate stably,the volume ratio of micro nano bubbles generated by the device in micro nano bubble water reaches 3.36%.The removal of Cu²⁺,Fe²⁺,Pb²⁺,Zn²⁺was analyzed by single factor experiment with different pH,initial concentration,NaCl dosage and H₂O₂ dosage.The results showed that the removal rates of the four heavy metals reached the maximum under weak alkali conditions,and the initial concentration had little effect on the removal rate.The removal rates of the four heavy metals were higher when the dosage of NaCl was 4mg/L.too high or too low dosage of NaCl inhibited the treatment effect of micro nano bubbles on pollutants.The addition of H₂O₂ enhanced the release of hydroxyl radicals in a certain range,and the addition of Cu²⁺in H₂O₂ increased the removal rate The removal effect is better when 3ml/L is added,and the effect of other pollutants is better when 2ml/L is added.Considering the interaction between various factors,the orthogonal experiment was used to optimize the experimental scheme.The optimal conditions of Cu²⁺were as follows:pH 8.5,initial concentration 3mg/L,NaCl dosage 4 mg/L,H₂O₂ dosage 3ml/L,the maximum removal rate was 97.8%;the optimal scheme of ferrous ion was as follows:pH 8.5,initial concentration 3.5 mg/L,NaCl dosage 3 mg/L,H₂O₂dosage 2 ml/L.The maximum removal rate of Pb²⁺was 97.7%;the optimal solution of Pb²⁺was pH 8,initial concentration 3.5mg/L,NaCl dosage 4mg/L,H₂O₂ dosage2ml/L.The maximum removal rate of Zn²⁺was 88.1%;the optimal solution of Zn²⁺was pH 9,initial concentration was 2.5mg/L,NaCl dosage was 4mg/L,H₂O₂ dosage was 2m/L.The maximum removal rate was 46.5%.Considering that the pollution types are often complex in reality,the remediation of organic abwasser by the device and the influence trend of different factors on the removal rates of COD and ammonia nitrogen are studied.The removal effects of COD and ammonia nitrogen are more ideal under acidic conditions.When the initial pH is 5,the maximum removal rates of COD and ammonia nitrogen by ozone micro nano bubbles are 37.1%and 26.7%,respectively The experiment shows that the removal rate of COD reaches the maximum of 36.7%after 6 hours of micro aeration with 3 mg/L NaCl.The removal rate of ammonia nitrogen reaches the maximum of 31.3%when the dosage of NaCl is 4mg/L;when the dosage of H₂O₂ is1ml/L,the maximum removal rates of COD and ammonia nitrogen are 35.9%and29.1%respectively.The excessive addition of H₂O₂ inhibited the release of hydroxyl.