Study On The Performance Of ICPB Technology For Treatment Of Two Typical Ordor Compounds

In recent years,the eutrophication level of lakes,reservoirs and rivers in China has been improved,but the situation of cyanobacteria outbreaks is still serious and the odor issue of natural waters is appearing gradually.Therefore,it is of great significance to explore economical and efficient techniques to solve above issues.Intimately coupled of photocatalysis and biodegradation（ICPB）,which combines the high oxidation efficiency of photocatalysis with the effectiveness of biodegradation has been paid more attention recently.However,improvement of the supported ability between the photocatalyst and carrier,and the removal mechanism of emerging contaminants need to be studied.In this thesis,the ICPB systems are built to remove two kinds of typical taste and odor compounds,which are 2-MIB and GSM.An optimized method using silane coupling agent（SCA）as the coupling agent to improve the supported ability between the photocatalyst and carrier is developed,and used to built a noval ICPB system.In order to reveal the removal mechanism of 2-MIB and GSM,the removal efficiency of ICPB system,intermediate species and microbial community of biofilm in carrier are investigated.Major results are as follows:1. The ICPB system based on nano-sized Ti O₂ is constructed to explore the capacity of 2-MIB and GSM removal.When the influent concentration of 2-MIB and GSM is 500μg/L,the removal efficiencies of 2-MIB and GSM by the ICPB system reached 98.4%±1.1%and 96.1%±0.7%after 12 hours of reaction with the adding carrier of 2.0 g/L and light intensity of 2.5 m W/cm².The removal efficiency of 2-MIB and GSM increased 7.7%-13.1%and 7.3%-18.9%,compared with the photocatalytic group（P）,microbial degradation group（B）,and the adsorption group（AD）.The biomass and biological activity of biofilm remained at a high level（117.2±5.7 ng ATP/g）after 12 hours of reaction,indicating that the ICPB system can remove these two kinds of taste and odor compounds effectively.2. Because the existing supported methods show the abstacles like obvious agglomeration of photocatalysts on carrier and poor supported ability,an optimized method using SCA as coupling agent to improve the supported ability between the photocatalyst and carrier is explored.Results showed that the supported amount of Ti O₂on the surface of carrier obtained by four-step supported method was 2-3 times higher than that of the five-step supported method,and the Ti O₂ agglomeration is improved significantly.When KH560 was used as the coupling agent,the supported amount of Ti O₂ was 196.5±16.1 mg/g and 359.7±86.8 mg/g at 65℃and 150℃,which were more than those of KH550 and KH570 under the same condition.At the same time,Most of Ti O₂ was adhereing on the outer surface of carrier and was less susceptible to the temperature.Further applying the four-step supported method and selecting KH560as the coupling agent,the optimal Ti O₂ supported condition was achieved as:alcohol-water ratio of 8:1,hydrolysis time of 48h,silane coupling agent concentration of 15%,and the heating temperature of 85℃,and the photocatalyst supported polyurethane sponge carrier enhanced by silane coupling agent（SCA-Ti O₂-PU）was obtained.3. The photocatalyst supported polyurethane sponge enhanced by silane coupling agent（SCA-Ti O₂-PU）was used to built a noval ICPB system.When the influent concentration of 2-MIB and GSM was 500 ng/L,the removal efficiencies of 2-MIB and GSM in the ICPB system reached 98.4%±1.1%and 96.1%±0.7%after 12 hours of reaction respectively,with the adding carrier quality of 2.0g/L and light intensity of 2.5m W/cm².Compared with control groups,the removal efficiency of 2-MIB and GSM increased by more than 15%,and their effluent concentration in 24 hours met the demand of annnex A of"Standard for Drinking Water Quality"（GB 5749-2006）.After five reaction cycles,the detached ratio of Ti O₂ from the carrier was only 5.0%±2.8%,and a large number of bilfilm still colonized.The intermediates were analyzed by GC-MS,and results showed that terpenoids,alcohols,esters,organic acids and four kinds of aldehyde intermediates were detected in the photocatalytic system,and none aldehyde intermediate was detected in the ICPB system.The results of microbial community showed that the microbial diversity and abundance were improved in the ICPB system.There into,Zoogloea spp.（24.6%）,Thaauera spp.（15.0%）and Commamonas spp.（4.2%）with function of flocculation as well as Flavobacterium spp.（2.4%）,Sphingopyxis spp.（0.16%）and Stenotrophomonas spp.（0.15%）capable of degrading 2-MIB and GSM were enriched in the carrier.In summary,the ICPB system enhances the removal efficiency of typical odor compounds through improvement of pollutants adsorption,reduction of free radical competition and regulation of microbial community,and has a potential for the application in the treatment of emerging contaminants.