Characterization And Oxidization Of Algae Organic Matter With Potassium Permanganate

A big amount of algae organic matter（AOM） is metabolized when algae blooms, which brings odor or stench to water body. Potassium permanganate（KMnO₄） is a commonly used oxidants and disinfectants in water treatment, and often exerted in pre-oxidation process. This research further studied the oxidation of AOM and DOM with KMnO₄ after characterizing them. AOM and DOM were classified into different fractions by synchronous fluorescence, and oxidation properties of each fraction was evaluated. The influence of pH value at 5, 7 and 9 and KMnO₄ concentration at 1, 2, 3 and 5 mg/L were taken into consideration during the oxidation process. Oxidation properties of tyrosine-like, tryptophan-like and humic-like substance degradation characteristics were discussed. This study has a great significance in determining organic species, understanding oxidation properties of specific organic matter and improving oxidizing conditions during algae blooming season.Result showed that algae density was about 1.33 x 10⁴ cell/ml, and the dominant algae were Microcystis aeruginosa and Oscillatoria tenuis, both of which belong to cyanobacteria. The spectrum of AOM and DOM revealed that they both contained tyrosine-like, tryptophan-like, fulvic acid and soluble metabolities substance. However, the specific ingredients and proportion of five fractions substance were different. Spectra range of AOM was much broader than DOM. This demonstrated that the fluorescing composition in AOM was more homogeneous than DOM. In AOM, tryptophan-like substance was the dominant ingredient, while in DOM, only tyrosine-like and /fulvic-like were found.The removal efficiency of AOM and DOM increased as KMnO₄ concentration improving, and sometimes high KMnO₄ concentration could eliminate the influence of p H value. Organic matter in AOM and DOM degraded very fast, more than 50% removal efficiency was achieved in the first minute. Organic matter in DOM was more stable than in AOM, which was more apparent in tyrosine-like and tryptophan-like substance. The removal efficiency of three fractions in AOM was higher than in DOM after 20-minute’s reaction.Tyrosine-like and tryptophan-like substance in AOM acquired the best removal effect in acid condition, while humic-like substance obtained best removal effect in alkaline condition. Tyrosine-like substance in DOM achieved best removal effect in neutral condition, and tryptophan-like and humic-like substance acquired best removal effect in acid condition. However, the differences of final removal efficiency among the three conditions were not big. The ratio of KMnO₄ and organic matter concentration（TOC） at 0.8 should be avoid no matter in acidic or alkaline condition. In acidic condition, the removal efficiency of tyrosine-like and tryptophan-like substance decreased. In alkaline condition, removal efficiency of three fractions in this point all declined.