In recent years, natural particles in drinking water have attracted attention due to their carry of toxic organic matter. However, the adsorption behavior of multiple antibiotics at very low concentrations on different sized particles has not been revealed. Here, the content of 17 antibiotics in water samples collected from four process stages of the water supply plant was detected. Results showed the concentration of antibiotics in water plant was in the range of 0-69.24 ng L-1. Characterization of natural particles obtained directly from raw water of waterworks showed that the surface of large particles (>1 μm) was rougher and the composition was more complex than that of small particles (0.05-1 μm). Besides, the adsorption experiments of four antibiotics (nalidixic acid (NAL), trimethoprim (TMP), roxithromycin (ROX), and penicillin G potassium salt (PG)) on small (0.05-1 μm) and large (>1 μm) natural particles were studied. The results indicated that in the binary antibiotic system, the competition and synergy between antibiotics made a greater proportion of antibiotics soluble in water comparing with single systems, and the particle-water partition coefficient (kp-w) of the total antibiotics ranged from 1.13-1.78 was reduced to 0.57-0.84. The competitive adsorption of antibiotics appeared in the binary system showed that ROX and PG had a higher adsorption capacity than NAL and TMP. Furthermore, in the binary antibiotic systems, small particles played an important role in adsorption, suggesting the urgency of their removing. This work could help predict the possible risks of drinking water and provide some insights into future drinking water treatment.
Keywords: Antibiotic occurrence; Competitive adsorption; Risk exposure; Small particle.
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