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Biosorption and biodegradation of fulvic acids by mixed culture of microorganisms

Organohalogen compounds as a group are listed as dangerous to living organisms. Of particular concern in the context of drinking water disinfection by chlorination are the trihalomethanes (THM-s), which are formed from the reaction between free chlorine and naturally occurring humic substances in water. Being so, the removal of humic substances is one of the important objectives in water purification technology. They are chemically very complex, and their composition varies according to the origin. The main fractions of humic substances (HS-s) are humic acids (HA-s) and fulvic acids (FA-s). The aim of this work was to study the biosorption and bidegradation of water soluble fulvic acids, as one of the fractions of HS-s isolated from the ground water, by mixed culture of microorganisms. In mixed culture dominated two bacterial strains Aeromonas hydrophila and Pseudomonas sp. and two fungi Aspergillus ustus and Stachybotrys sp. Experiments were carried out on a rotary shaker at 25 oC and pH = 6.5. Removal of FA-s from aqueous phase was monitored by following the COD-elimination, microbial growth and decrease of absorbance at &#61548 ; ; ; ; = 340 nm. Within three days 99 % of FA-s was removed from solution. During that period exponential growth of mixed culture of microorganisms, determined by optical density measurement at &#61548 ; ; ; ; = 540 nm, was also observed. In the first 24 hours biosorption of fulvic acids was dominant. Afterwards, biodegradation of remaining fulvic acids in the solution continued for another two day. At the end of experiments, the desorption of FA-s from mixed microbial culture was also carried out. The results suggested that in the process of removal of fulvic acids from aqueous solution 61.6 % was adsorbed onto biomass, while 38.4 % was biodegraded.

fulvic acids; mixed culture of microorganisms; biosorption; biodegradation

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