| As the eutrophication becomes more and more serious, plankton such as algae propagates heavily. Odor compounds produced in algae metabolizing cause bad smelling problem in water. Improper treatment of odor compounds in water will seriously affect the quality of drinking water. Therefore the research on odor compounds in water has important significance.This determination method of trace odor compounds in water was established in this study. Four typical odor compounds in main water-sources of Yixing city were investigated, and the removal efficiencies of these compounds in waterworks processes were also analyzed. According to the present process in Jiubin waterworks, the removal of odor compounds and its mechanism by coagulation, activated carbon adsorption and ozone oxidation under different conditions were analyzed. The oxidation intermediate of odor compounds was identified, and the possible degradation pathway was explored.The determination method of four typical odor compounds in water by GC/MS with headspace solid phase micro-extraction was established. GSM,2-MIB,β-Cyclocitral and β-Ionone were detected in Yixing main water-sources. The concentrations of 4 odor compounds were higher in spring and summer, while lower in winter.2-MIB and β-Ionone were the main odor compounds in Hangshan reservoir, Youche reservoir and Xijiu reservoir. The removal rates of GSM,2-MIB, β-Cyclocitral and β-Ionone in process of waterworks were 34～42%,34～55%,14～40% and 14～69%, respectively.The removal of odor compounds by coagulation was quite low, but it can remove algae cells effectively and therefore the intracellular odor compounds are also removed. Odor compounds in water can be adsorped by powder activated carbon effectively, and the adsorption process matched with Freundlich isotherm models. The adsorption capacity of β-Ionone was maximum and 2-MIB was minimum. The natural organic matter in raw water showed competition on the adsorption. The removal rates of odor compounds can be improved by increase the dosage of PAC. The removal rates of 4 odor compounds show great difference in extremely acid and alkali environment. It found that humic acid in water will inhibit the adsorption of odor compounds. Pseudo secondary dynamics model can better describe the adsorption laws of odor compounds on PAC. The initial adsorption rate constant of four odor compounds increased along with the increasing of initial concentration, and decreased with the increasing concentration of humic acid. The maximum adsorption capacity of odor compounds on PAC decreased with increasing concentration of humic acid. NOM in water caused inhibition on the removal of odor compounds by adsorption.The ozone oxidation can effectively remove odor compounds in water, and the process followed pseudo first-order reaction kinetics. The rate constants decreased in the following order:β-Ionone(0.0821S-1)>β-Cyclocitral(0.0611S-1)>GSM(0.0366S-1)>2-MIB(0.0184S-1). High reaction rates of four odor compoounds had been observed under sufficient ozone(03/odor compounds>0.03mg/ng) and all the removal efficiencies could reach over 90%. It found that NOM in raw water often inhibits the oxidation of odor compounds. The hydroxyl radicals plays a main role, and ozone molecules play a secondary role in the oxidation of odor compounds. The oxidation of odor compounds is inhibited when the hydroxyl radical inhibitors such as HCO ions and tertiary alcohol present in the oxidation system. Low concentrations (1-2.5mg/L) of humic acid improves the oxidation efficiency and high concentration(≥5mg/L) of humic acid caused a significant inhibition on the degradation efficiency of odor compounds. Ozone oxidation of odor compounds will produce a series of small molecule acid, ketones, aldehydes, alcohols,which will be finally oxidized to CO2 and H2O. |
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