Removal Of Algae And The Impact On Formation Of Chlorinated Byproducts By UV/Chlorine Advanced Oxidation Technology

With the continuous development of China’s economy,the industrial level of the cities and the living standards of residents have improved significantly,but the urban waters have also been seriously polluted,such as the increased eutrophication and the commonly observed algae pollution.The algae blooms not only affect the operation of water plants and endanger the safety of urban drinking water,but also reduce the concentration of dissolved oxygen in urban waters.Furthermore,the odorous substances and algae toxins are produced,which seriously affect the lives of residents and the city image.Therefore,the research and development of efficient algae removal technology will have profounds impact on the safety of drinking water and the restoration of ecological environment.Microcystis aeruginosa was selected as the target here,the treatment system of UV/chlorine advanced oxidation process was established to investigate the removal performance of algae,and the underlying mechaniams was explored,along with the formation of chlorinated byproducts further evaluted.On basis of these wroks,comparative study of UV/hydrogen peroxide,UV/persulfate and UV/monopersulfate was investigated to fully evaluate the potential of UV/chlorine advanced oxidation process to treat real algae-containing water.The main research contents and results were as follows.（1）UV/chlorine advanced oxidation process can directly inactivate and remove Microcystis aeruginosa.The removal efficiency increased with increasing chlorine dose and UV intensity,and the optimal algae removal rate was 94.6%.The common anions had little effect on the removal efficiency of algae,but NH₄⁺and humic acid of a certain concentration showed strong inhibitory effects.The algae removal by UV/Chlorine advanced oxidation process could be attributed to UV radiation,HO^?and HOCl molecules,all of which can destroy the structure of algae cells,lead to the destruction of algae cells,and the degradation of released intracellular organic matters.（2）Compared with chlorination alone,UV/chlorine advanced oxidation process reduced chlorinated byproducts about 28.5%in total during the subsequent chlorination disinfection.During UV/chlorine process,the chlorinated byproducts increased with the increase of chlorine dosage but decreased with the increase of UV intensity.The formation of chlorinated byproducts was the lowest at the p H value of 8.HCO₃^-had little effect on the formation of chlorinated byproducts,but NH₄⁺can singnificantly reduce the formation of chlorinated byproducts.Most of the chlorinated byproducts formed rapidly within the first 30 minutes and remained stable.（3）The algae removal efficiency in real algae-containing water was 49.4%lower than experimental algae-containing water under the same conditions by UV/chlorine advanced oxidation process.Besides the high removal efficiency of algae,the natural organic matter and algae organic matter in real algae-containing water can also be removed.Under the same oxidants dosage,the algae removal efficiency of various UV-based advanced oxidation processes in real algae-containing water was:UV/chlorine>UV/persulfate>UV/monopersulfate>UV/hydrogen peroxide.UV/chlorine following chlorination disinfection led to increase in chlorination byproducts.Because UV/chlorine can achieve disinfection and the algae removal at the same time,it is recommended that UV/chlorine could be used to treat real algae-containing water without following chlorination disinfection.The cost of UV/Chlorine was calculated to be about￥5.0/m³,which is relatively high.It could be used for emergency treatment of algae blooms in urban landscape waters and water source of water plant,treatment of ballast water and pretreatment in water plant.In summary,UV/chlorine advanced oxidation process can effectively remove Microcystis aeruginosa,and has a certain removal efficiency on natural organic matter in real algae-containing water and algae organic matter released by decomposition of algae cells.Although chlorinated byproducts were producted,UV/chlorine process has certain advantages in controlling the chlorinated byproducts compared with chlorination disinfection alone,so it has good potential in algae-containing water treatment.