Aerobic biodegradation of dominant micropollutants in the Ergene river by river microcosms and pure cultures of bacteria

The Ergene River is the most polluted surface water in Turkey. A great number of micropollutants, which have potential toxic and endocrine-disruptive effects and play a role in antibiotic resistance, are identified in the Ergene River. Once discharged into the environment, micropollutants are exposed to various natural attenuation processes such as dilution, sorption onto solids and sediments, photolysis, hydrolysis, and biodegradation. However, biodegradation is considered the most important process for the removal of most micropollutants. In this study, aerobic biodegradation of forty-three micropollutants belonging to different chemical groups such as industrial chemicals i.e. plasticizers, UV blockers, surfactants etc., antibiotics, pesticides and personal care products i.e. fragrances, pharmaceuticals etc. were investigated in river water samples taken in August 2017, November 2017, February 2018, and May 2018. Analysis of the micropollutants was performed using ultra-high-performance liquid chromatography and tandem mass spectrometry (UHPLC-MSn). At the end of the study, most compounds such as acetaminophen, celestolide, piperonyl butoxide, oxybenzone, and 3-chloraniline were degraded via river microcosms at different rates whereas diuron, N-Ethyl-p-toluenesulfonamide, benzo[a]pyrene, benzanthrone, terbutryn, prochloraz, and omethoate were not removed in any samples. Aerobic biodegradability of hexa(methoxymethyl)melamine, the most abundant target micropollutant in the river was also investigated using different bacterial strains previously isolated at BIOMIG Lab. A strain named Pseudomonas sp. BIOMIG1 transformed almost all hexa(methoxymethyl)melamine into melamine in 45 days. With this study, aerobic biodegradability of various micropollutants in the Ergene River and the biotransformation of hexa(methoxymethyl)melamine have been first revealed