| Algae have a serious impact on human health and drinking water safety.Advanced oxida-tion processes based on ozone is widely investigated for algae killing.Because of low mass transfer efficiency,low ozone concentration and high cost of this process,a helical static mixer enhanced the advanced oxidation processes of ozone for algae killing is proposed and studied.The effects of various factors on the inactivation of Chlorella by ozone oxidation and ozone catalytic oxidation processes and the process optimization are investigated,and finally the scale up water treatment test is further carried out.The main contents are as follows:（1）The ozone oxidation process system was used to carry out the algae killing test,taking Chlorella as the research object.The inactivation effect of each single factor on Chlorella were explored and the kinetic analysis was also carried out.When the oxygen flow rate,the liquid flow rate and the initial algal cell optical density(OD680)were 2.0 L·min-1,5 L·min-1 and 0.4,respectively,and the initial reaction temperature was 25°C,the initial p H=9,the algae killing rate can reached to 96.02%after 12 min of treatment.When the oxygen flow is between 1.0L·min-1 and 2.5 L·min-1,liquid flow more than 3 L·min-1,OD680less than 0.5,and the initial reaction temperature more than 15°C,the algae killing reaction by ozone oxidation can be described by first-order kinetics.When the oxygen flow rate less than 1.0 L·min-1(or it more than 2.5 L·min-1),the liquid flow rate is less than 3 L·min-1,OD680more than 0.5,the initial reaction temperature is less than 15°C,and the initial p H value is in the range of 6～9,the secondary-order kinetics is better fitting.There was no significant proliferation of Chlorella after reculture at different oxidation times.Increasing the volume of algal liquid can be achieved by extending the treatment time to achieve better algae killing.Using oxygen as the gas source was better than using air as the gas source.Using the spiral cutter as the gas-liquid mixing method was better than the jet method and microporous aeration method.（2）The air is chosen in above test system and the catalyst was introduced to carry out algae killing test in view of the high cost of algae killing.The influence of catalyst,air flow rate and other factors on the algae killing effect and kinetics of algae killing were also investigated,further the orthogonal test was carried out taking the algae killing rate as the index,and com-parison of the effect and cost of ozone and ozone catalytic oxidation processes for algae killing.The experimental results showed that the adsorption performance of bothγ-Al2O3 and silica-aluminium complex catalysts were poor,while the catalytic stability ofγ-Al2O3 was better.The kinetic model ofγ-Al2O3-catalyzed ozone algae killing was obtained,which was verified to be more accurate.The degree of influence of each process parameters on the algae killing rate was:catalyst dosage>air flow>initial p H value>initial reaction temperature.Optimal process combination was:air flow of 2 L·min-1,γ-Al2O3 dosage of 5 g·L-1,the initial reaction temper-ature of 30°C and the initial p H=8,the average algae killing rate under this process combination can reach 96.79%,which is 12.61%higher than before optimization.The ozone oxidation pro-cess is only about 8 percentage points higher than the algae killing rate under theγ-Al2O3 cata-lytic ozonation process,but theγ-Al2O3 catalytic ozonation process is more economically effi-cient at algae killing rate of 90%for both.（3）An industrial ozone advanced oxidation water treatment system was built for medium-sized operational study in the field.The results showed that the experimental system was effec-tive in the removal of chemical oxygen demand（COD）,ammonia nitrogen（NH3-N）,nitrite nitrogen（NO2-N）and algal biomass,with the removal rates of COD,NH3-N,NO2-N and algal biomass being 61.69%,62.26%,41.62%and 79.69%respectively,after 30 days of operation.There was no significant effect on the removal of nitrate nitrogen（NO3-N）,and the NO3-N content in the water increased by 31.58%at the end of the experiment.The effect on the removal of total phosphorus（TP）was limited,and the TP content in the water did not change much,and its maximum removal rate was 10.04%.After 10 days of the experiment,the dissolved oxygen（DO）content in the water was basically stabilized around 7.90 mg·L-1.The current technology for algae-containing water based on the helical static mixer enhanced ozone advanced oxidation was proposed.The experimental studies of small laboratory and out-door medium-sized have proved that this technology has the advantages of better effect and high economic efficiency,and it also provided experimental basis for the industrial application. |
