Degradation of antibiotics in biological wastewater treatment

Antibiotike vedno več uporabljamo v humani medicini, veterini in kmetijstvu. Čiščenje antibiotičnih odpadnih voda je zelo zahtevno, saj te odpadne vode poleg antibiotikov vsebujejo tako različne anorganske kot organske spojine, kar vse skupaj pogosto zavira delovanje mikroorganizmov, ki delujejo v čistilnih napravah. Zaviralni učinek na mikroorganizme v čistilnih napravah je še posbej izrazit pri konvencionalnih čistilnih napravah, ki uporabljajo procese aktivnega blata, biološke filtre in membranske biorektorje za čiščenje odpadnih voda. Posledično narašča onesnaženje odpadnih in izcednih voda z antibiotiki in njihovimi ostanki, ki predstavljajo skupino mikroonesnažil. Koncentracije antibiotikov v odpadnih vodah so od nekaj ng/L do nekaj mg/L, v naravnih vodah so koncentracije zaradi redčenja manjše, od nekaj ng/L do nekaj 100 µg/L. Ker so antibiotiki na čistilnih napravah in v okolju nasploh slabo razgradljivi, ima njihovo kopičenje v vodi lahko resne okoljske posledice. Tudi majhne koncentracije vodijo v širjenje antibiotske rezistence, spodbujajo nastanek biofilma pri patogenih bakterijah in imajo lahko toksičen učinek na vodne organizme. Trenutni postopek kvantifikacije antibiotikov v vodnih sistemih zajema ekstrakcijo na trdni fazi, kateri sledi tekočinska kromatografija sklopljena s tandemsko masno spektrometrijo. Taka analiza je zelo primerna za detekcijo večine antibiotikov, tudi ko so ti prisotni v zelo majhnih koncentracijah. Zato je v prihodnosti nujno, da bolj natančno determiniramo kritične koncentracije antibiotikov, ter tako zavarujemo naravno okolje in človeško zdravje pred njihovimi negativnimi učinki.Antibiotics application is increasing in human medicine, veterinary medicine and agriculture. Treatment of antibiotic wastewater is very difficult since these wastewaters do not only contain antibiotics but also inorganic and organic compounds that all together can slow down the activity of microorganisms operating in wastewater treatment plants (WWTP). The inhibitory effect on micro-organisms in WWTPs is especially seen in conventional treatment plants that use active sludge process, biological filters or membrane biorectors for the treatment of wastewaters. Contamination of wastewaters and leachates with antibiotics and their residues, represents a group of emerging micro-pollutans. Concentrations of antibiotics range from ng/l to mg/L in wastewaters, to a few ng/L or 100 μg/L in natural waters due to dilution effect. Because antibiotics in the environment are as poorly degradable as in wastewater treatments, their accumulation in the water can have serious environmental consequences. Even low concentrations can cause dissemination of antibiotic resistance, biofilm formation in pathogenic bacteria and toxic effects on aquatic organisms. Quantification of antibiotics in aqueous systems is carried out by solid phase extraction followed by liquid chromatography and tandem mass spectrometry. This analytical system is quite efficient for detecting all major classes of antibiotics, even when they are present at very low concentrations. Therefore, it is necessary to take decisive steps in the future, aimed at the determination of critical concentrations of antibiotics, which will make it possible to maintain safe values that will not exert a negative impact on the natural environment and human health