| In recent years,due to the rapid development of industries and abuse of fertilizer in agriculture,the eutrophication of source waters has increased dramatically,odor problem of drinking water due to wild algae growth has become common,and complaints from tapwater customers has being increased.2-methylisoborneo(2-MIB)and geosmin(GSM)are the main algae-induced odor substances of the drinking water,which have stable chemical structures and extremely low odor thresholds and are difficult to be effectively removed by conventional water treatment processes.Therefore,it is very important to develop an efficient deodorization technology for ensuring the safety of drinking water.In this study,the typical odor substances of 2-MIB and GSM were taken as study objects.Centring on ultrasonic(US)and persulfate(PS)activation advanced oxidation technique,the effectiveness and influencing factors of ultrasonic system,ultrasonic activated persulfate(US/PS)system and UV-enhanced ultrasonic activated persulfate(UV/US/PS)system were systematically investigated.Meanwhile,the reaction kinetics was also analyzed.The main research results are as follows:(1)The US radiation with 40 k Hz could be used to remove 2-MIB and GSM,after a treatment time of 60 mins,the removal rates of 2-MIB and GSM reached 46.36%and43.20%,respectively.Reducing the reactor’s water depth and increasing the ultrasonic sound intensity could increase the removal rate of odorant substances.Under concentration range of 100-800 ng/L,degradation of typical odorant substances corresponds to the first-order reaction kinetics,and the reaction rate constant was not sensitive to the concentration.The performance of removing typical odorant substances was not affected by the substrate concentration and the presence of humic acid.The degradation is mainly caused by ultrasonic pyrolysis.(2)The removal of typical odorants with PS alone was very poor,while the removal performance using US activated PS advanced oxidation technology was very satisfactory even after a treatment time of 10 mins.Compared with US method,the removal rates of 2-MIB and GSM for US/PS combination technology could be increased by 61.78%and 69.53%,respectively.In the first 2.5 mins,degradation process is consistent with the first-order reaction kinetics model.Higher removal rates for the US/PS combination technology could be achieved under lower concentrations(100 ng/L).Increasing the persulfate dosage and ultrasonic sound intensity could increase the reaction rate.Besides,the humic acid in the raw water would inhibit the degradation of 2-MIB and GSM.(3)UV-enhanced US/PS combined technology(US/UV/PS)can further improve the degradation of typical olfactory substances.The removal rates of 2-MIB and GSM could reach 93.17%and 98.49%in 5mins,respectively.Similar to the US/PS combination process,increasing the UV intensity,ultrasonic intensity and persulfate concentration within certain ranges can increase the removal rate and reaction rate of typical olfactory substance,but excessive light intensity(0.73m W/cm~2),sound intensity(0.53W/cm~2)and persulfate concentration(2mmol/L)were not effective in improving the removal rates of olfactory substances.The presence of humic acid inhibited the removal of the olfactory substances 2-MIB and GSM,and the presence of dissolved organic matter and various inorganic ions in water could also significantly affect the removal of 2-MIB and GSM.(4)For the US/PS hybrid technology and US/UV/PS hybrid technology,the rapid degradation of odorants 2-MIB and GSM is caused by synergetic effects of sulfate radicals and hydroxyl groups,and the sulfate free degradation plays a leading role under acidic and neutral conditions. |
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