Degradation Of Organophosphorus Pesticides By Ultrasound Enhancement Ozonization

It is difficulty to disposal the organophosphorus pesticides wastewater which ischaracterized as high concentration of organic matter, high toxicity for biotic systems,biorecalcitrant. As a potential method for wastewater treatment, the ultrasound enhancementozonization is one of the advanced oxidation technologies with strong oxidation ability, littlerecontamination and none selectivity.In this paper, the effect of ultrasound enhancement ozonization on the degradation oforganophosphorus pesticides dichlorovos and omethoate was studied. Ozonization andultrasound enhancement ozonization were carried out to degrade the organophosphoruspesticide wastewater, respectively. Influence aspects, such as ozone inflow, pH value, the initialconcentration of wastewater, media temperature and the reaction time are investigated. Thecomparison of two methods was also carried out.For ozonization, the degrade rate of organophosphorus pesticide and removal of CODincrease with the increasing of ozone inflow at first but there is a maximum value. Themaximum removal rate of COD of dichlorovos is 28 percent when the pH value is equal toabout 10, and for omethoate, the value is 32.9 percent at pH 8 to 10. The removal rate of CODincreased with increasing reaction time and reach a maximum after 30 minutes. The removalrate of COD decreased with the increasing of initial concentration of dichlorovos or omethoate.For ultrasound enhancement ozonization, the removal rate of organophosphorus pesticideand of COD increase with the increasing of ozone inflow. However the removal efficiency willnot varied with the change of ozone inflow when the inflow reaches a certain quality(such as25.06 m~3/h). The removal efficiency of COD of dichlorovos and of omethoate are 50.5 percentand 79.2 percent, respectively. The removal rate of COD of wastewater decreased withincreasing of the initial concentration of dichlorovos or of omethoate. There is no effect on theultrasound enhancement ozonization when media temperature range from 20 to 50℃. And thereis little effect on the degradation of dichlorovos or of omethoate by ultrasound alone(thefrequency is 40 kHz and the power is 250 W). The removal efficiency of omethoate is contrastedon ozonization and ultrasound enhancenment ozonization. It shows that the degradation reactionis more quickly when the ultrasound is added. When the other conditions are the same, theremoval rate of omethoate is only 24.5 percent with ozonization while the rate is 85.4 percent byultrasound enhancement ozonization.The relation between logarithm of C0 to C and reaction time is linear, which shows that thedegradation reaction of dichlorovos wastewater and of omethoate pertain to first order.The results prove that it is feasible to degrade biorecalcitrant organophosphorus pesticidewastewater using ultrasound enhancement ozonization.