Theoretical Study On Algae Secondary Odor Metabolic Pollution Characteristics And Control By Photo-Oxidation Of High Algae Raw Water

Taste and odor compounds, such as2-MIB、 GSM、DMTS、β-cyclocitral and β-ionone were determined by HS-SPME coupled withGC/MS.A long-term investigation on algae and its secondary metabolicpollution of Hangzhou source water and landscape water was carried out.Algae detected in survey water were mainly consisted of Cyanophyta,Chlorophyta, Bacillariophyta, Euglenophyta and Cryptophyta with itssecondary metabolic odor polluants including β-cyclocitral, GSM andβ-ionone, and water quality has a certain effect on algae and its secondarymetabolites.The pollution characteristics of odor contaminants released byMicrocystis aeruginosa from high algae-laden raw water were discussed.The results showed that algae biomass, initital pH value and lightingconditions have significant effects on the release of T&O,extracelluar organics and water circumstances during the anaerobic oranoxic process. β-cyclocitral was the major odor compound released byMicrocystis aeruginosa, as the dioxygenase pyrolysis prouduct of β-carotene after algae cells broken, with a bit of β-ionone and DMTSdetected, and DMTS was the anaerobic degradation product of algae cellsthat only existed in exocellular solution. It was found that odorcompounds were obviously increased as released by high levels of algaebiomass. Meanwhile, pH value of algae solution held importantimplications for odor pollution because of its promotion on ahead of timerelease. The impact of lighting condition on odor release was alsorevealed as the light/dark alternative pattern was easier to push forwardon releasing than dark only. The extracellular organic matters induced byalgae cells were mainly alkanes, alcohols, aldehydes, kotone and eters.Degradation of β-cyclocitral was conducted by using ultravioletoxidation technique, influent factors and dynamics of the reaction wereconcluded. It was proved that β-cyclocitral could be well degraded by UVirradiation and the reaction followed first-order reaction kinetics model.The degradation rate can be improved as the initial concentration ofreactants and UV intensity increased. Reaction rate constant for raw waterdistribution condition was obviously lower than that of distilled and tapwater distribution conditions, indicating that β-cyclocitral degradationcan be influenced by the organic matters with specific structure on UVabsorption, as well as suspended matters and chroma also affected. Inaddition, the degradation rate of β-cyclocitral could be greatly enhancedby the existence of H₂O₂for its synergy effects to UV. Solution pH had a great effect on the degradation of β-cyclocitral, and the reaction rateconstant was the largest in weakly alkaline condition, followed by otherconditions for the order of highlyacid＞acidulous＞neutral＞stronglyalkaline. Furthermore, the presence of kations were demonstrated to havelittle impact on β-cyclocitral degradation as consequce of K⁺＞Ca²⁺＞Mg²⁺, while the negions were proved to be the favorable factors withconsequce of NO₃^-＞CO₃^2-＞HCO₃^-＞SO₄^2-.