Determination And Removal Of Odor Compounds Of Algal Secondary Metabolism

Aiming at the problem of algae pollution from eutrophication ofdrinking water resource, two simple and reliable analytical methods weredeveloped and optimized for the trace determination of the typicalodorous compounds produced by algal secondary metabolism;2-methylisoborneol(MIB) and geosmin(GSM). The removal efficiencyand mechanism of these two compounds by ozonation were furtherstudied. The main results were achieved as follows;(1) A stable isotope dilution technique based on purge-and-trapcoupled to gas chromatography with mass spectrometric detection wasdeveloped and optimized for the trace determination of MIB and GSM.The results showed that, D3-MIB and d5-GSM as the isotopes internalstandards was added to improving the stability of recovery. Recovery wasin the range of82%-101%and precision were0.78%for MIB and5.20%for GSM at100ng/L from a reservior source water sample. The calibrationcurves of them were good linear correlation in the range of5–500ng/L.The limits of detection for MIB and GSM were4.12ng/L and3.60ng/L.This method was suitable for determination of high cleanliness sample,for example, source water and drinking water.(2) A stable isotope dilution technique based on solid-phasemicroextraction coupled to gas chromatography with mass spectrometricdetection was established for the analysis of MIB and GSM inenvironmental water sample. D3-MIB and d5-GSM were added as internalstandards to compensate for any variability in the extraction process.Recovery was in the range of92%-103%and precision were3.80%forMIB and1.72%for GSM at100ng/L from a reservior source water sample.The calibration curves of them were linear in the range of10–500ng/L,with a correlation coefficient above0.9998. The limits of detection forMIB and GSM were7.10ng/L and3.00ng/L. This method was applied toanalyze the environmental sample with high algae. (3) Purge and trap pretreatment was adopted for investigating on theremoval efficiency of MIB and GSM by ozone and the possibledegradation pathway of this process was further studied. The factors ofpH, initial concentrations, reaction time have significant influence on thedegradation of MIB and GSM, and the removal efficiency of them wereover90%in100ng/L at pH7for20min of simulated distribution water.The degradation pathway of them showed that, it may contain theprocesses of dehydration, oxidation of side-chain functional groups,destruction of bicyclic structure, formation of aldehydes, ketones, acids,and eventually mineralized to CO2and H2O.(4) Pretreatment technology of solid-phase micro-extraction wastaken to inspect on the removal and mechanism of Lyngbya kuetzingii andits secondary metabolism GSM. The results showed that, theconcentration of chl-a reduced71%and removal efficiency of GSM wasabove98%by ozonation.The mechanisms of ozonation on Lyngbyakuetzingii showed that ozone exerted a significant inactivation effect onliving cell, and can effectively reduce the concentration of GSMsimultaneously. The final remaining concentration of algae was close tothe standard limit (13.94ng/L), and this concentration can decrease to10ng/L by the following flocculation, filtration in waterworks.Furthermore, ozonation treatment can increase the algal fragment andconcentration of UV254, which indicated that, combined technique shouldbe adopted for better removal of algae and its metabolites.