Occurrence, distribution, and potential sources of antibiotics pollution in the water-sediment of the northern coastline of the Persian Gulf, Iran

Highlights: • 6 antibiotics occur in Persian Gulf, Iran (water: 0.8-89 ng/L, sediments: 1–118 ng/g). • Winter- and summer-time content of 2 antibiotics was different in seawater (p 0.05). • Direct correlation was seen between antibiotics and pH, TOC, Mg and K in water. • Processes in WWTPs showed antibiotics cannot be fully removed (0.1–88%). • Pseudo-partitioning coefficient (k_d,s) of antibiotics was obtained 88–28,436 L/kg. Occurrence and frequency of six most prescribed antibiotics (tetracycline, norfloxacin, azithromycin, anhydro erythromycin, cephalexin, and amoxicillin) were assessed in three wastewater treatment plants (WWTPs), and in water and sediments of the Persian Gulf at Bushehr coastline, Iran. The antibiotics concentration in the influent and effluent of septic tank (the hospital WWTP), activated sludge (the hospital WWTP), and stabilization pond (municipal WWTP) ranged between 7.89 and 149.63, 13.49–198.47, 6.55–16.37 ng/L, respectively. Conventional treatment resulted in incomplete removal of most of the studied antibiotics. Furthermore, the activated sludge was more effective in terms of antibiotic elimination compared to the stabilization pond or septic tank. The mean concentration of antibiotics ranged 1.21–51.50 ng/L in seawater and 1.40–25.32 ng/g in sediments during summer and winter. Norfloxacin was the dominant detected antibiotic in seawater, sediments, and influent of two hospital WWTPs. Seasonal comparisons showed significant differences for erythromycin and amoxicillin concentrations in seawater. Spatial variation indicated the role of physicochemical properties on distribution of antibiotics in seawater and sediments. The results emphasize the need to pay attention to antibiotic contamination in water and sediments of the Persian Gulf.