Alternative for phenol biodegradation in oil contaminated wastewaters using an adapted bacterial biofilm layer/ Prilagodeni bakterijski biofilm kao alternativa biorazgradnji fenola u otpadnim vodama u naftnom rudarstvu

The project studied the biodegradation potential of phenols in an industrial wastewater from an oil field in the province of Santander, Colombia. An elevated potential was established, according to three important factors: the great abundance of microorganisms found in the wastewater and sludge samples collected, the bacterial adaptation to high phenol concentrations (10 mg/1) and the elevated elimination efficiencies (up to 86%) obtained in the laboratory tests. The laboratory scale treatment system, which consisted of fixed-bed bioreactors with adapted bacterial biofilm, was optimized using a [2.sup.2] factorial experimental design. The selected variables, studied in their maximum and minimum level were: HRT (hydraulic retention time) and the presence or absence of GAC (granular activated carbon) layer. The response variable was phenol concentration. The optimum treatment conditions for low and high phenol concentrations (2.14 y 9.30 mg/1), were obtained with the presence of GAC and 18 hours of HRT. The best result for the intermediate phenol concentration (6.13 mg/1) was obtained with a 24 hour HRT and the presence of GAC. Nevertheless, the presence of the GAC layer was not significantly important in terms of phenol removal. Moreover, the increase of HRT from 18 to 24 hours, showed no significant improvement in phenol removal. Keywords: phenols biodegradation, optimization, activated carbon, petroleum wastewaters Sazetak U okviru projekta proucavan je potencijal biorazgradivosti fenola u otpadnoj vodi iz naftne industrije u provinciji Santander u Kolumbiji. Utvrdeno je povecanje potencijala s obzirom na tri cimbenika: veliki broj mikroorganizama pronadenih u prikupljenim uzorcima otpadne vode i taloga, prilagodbu bakterija na velike koncentracije fenola (10 mg/1) i povecanje djelotvornosti uklanjanja (do 86%) dobiveno laboratorijskim ispitivanj ima Laboratorijski sustav obrade koji se sastoj ao od bioreaktora sa fiksnim slojem sa prilagodenim tankim bakterijskim slojem, optimiziran je koristenjem faktorskog eksperimentalnog pristupa [2.sup.2]. Odabrane varijable, kod kojih se pratila maksimalna i minimalna razina, bile su: hidraulicko vrijeme zadrzavanja (engl. hydraulic retention time--HRT) i prisustvo ili izostanak sloja zmastog aktivnog ugljena. (engl. granular activated carbon--GAC). Varijabla koja se pratila bila je koncentracija fenola. Optimalni uvjeti obrade za male (2,14 mg/1) i velike koncentracije fenola (9,30 mg/1) dobivene su uz prisustvo s