Fulvic acids oxidation and biodegradability

Ivan Kozyatnyka*, Joanna Świetlikc, Ursula Raczyk-Stanisławiakc, Nataliya Klymenko b, Jacek Nawrockic

a Umeå University, Department of Chemistrye-mail:ivan.kozyatnyk@chem.umu.seb Institute of Colloid Chemistry and Chemistry of Water, National Academy of Sciences of UkrainecDepartment of Water Treatment Technology, Adam Mickiewicz University

BDOC content of fulvic acids

• Peat fulvic acids (PFA) – 3,93 mg C/L (57 % DOC)

• River fulvic acids (RFA) - – 0,89 mg C/L (13 % DOC)

Datum Sidfot 2

Fulvic acids properties

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4006008001000120014001600180020002200240026002800300032003400360038004000wavenumber, cm-1

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FA Dnieper Peat FA

FTIR-spectra of fulvic acidsMolecular weight distribution of Dnieper river and high-moor peat FA

FA sample C, % N,% H,% S,%

Dnieper 36.75 1.21 3.83 1,89

Peat 22.45 0.38 3.14 0.72

Elementary composition of FA

Oxidants

• Chlorine – 0.2; 0.8 and 1.4 mg Cl2/L (0.03; 0,12 and 0,21 mg Cl2/mg C)

• Chlorine dioxide – 0.2; 0.8 and 1.4 mg ClO2/L(0.03; 0,12 and 0,21 mg ClO2/mg C)

• Ozone – 6; 12 and 18 mg O3/L (0.03; 0,12 and 0,21 mg O3/mg C)

BDOC content after treatment

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Molecular weight distribution of FA after chlorination

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Molecular weight distribution of FA after treatment with chlorine dioxide.

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Molecular weight distribution of FA after ozonation

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By-product formation after FA treatment

Content of organic acids in solutions of FA

Content of aldehydes in solutions of FA

Conclusion• Peat and Dnipro FA have very similar compositions. FTIR, SEC, and

elementary analysis data confirmed this. However, the BDOC content in peat FA is higher than in Dnipro river FA.

• In the case of FA with low content of BDOC, the vital activity of bacteria was carried out not only due to the mineralization of low molecular weight compounds but also as a consequence of the biotransformation of high molecular ones.

• Using the given doses of chlorine [0.2, 0.8, and 1.4 mg L-1 (0.03, 0.12, and 0.21 mg mg-1 C] did not lead to significant changes of RFA and PFA after 1 and 24 h since treatment. We observed chlorine substitution into the FA structure. PFA with high BDOC content are more susceptible to chlorination because about 1 μg L-1 of THM appear.

• MDW and SUVA in both samples of FA did not change within a 1 h after treatment with chlorine dioxide. Chlorine dioxide oxidized FA stronger than chlorine. Organic matter became more biodegradable. However, ClO2 can remain in treated water for about 24 h, which can decrease the efficiency of microorganisms in biofilters.

• During ozonation of FA, we found the highest increase of BDOD due to the formation of a high amount of organic acids and aldehydes. NOM molecules were transformed into a more biodegradable form. Ozonation is the most preferable process among those observed for pre-treatment of FA before biofiltration.