Assessment of Selected Antibiotics in Ngong River and Their Removal Using Activated Carbon

Abstract

Occurrence of antibiotics in aquatic environment has become of concern in the recent past due to development of antibiotic resistance among microorganisms. In addition, most Pharmaceuticals and Personal Care Products (PPCPs) are known to disrupt reproduction and hormone function of some aquatic organisms. The objective of this study was to determine the existence and distribution of three active ingredients of Amoxicillin (AMX), Sulfamethoxazole (SMX) and Trimethoprim (TMP) antibiotics in water from Ngong River Kenya, and their removal from water using activated carbon. Water samples were collected from seven sites along Ngong River profile constituting the up-, mid- and down-stream. Liquid/Liquid Extraction (LLE) method was used to extract antibiotics from the water samples. The extracts were analyzed for the presence of AMX, SMX and TMP using High Performance Liquid Chromatography (HPLC) coupled with UV/VIS detector. The levels of AMX, SMX and TMP were between <0.20 to 9.07±7.78 μg/l, 10.69±1.33 μg/L and 1.91±0.02 μg/L, respectively. Lower concentrations of antibiotics were detected during the wet season due to dilution by rain water. The detection limits for AMX, SMX and TMP were 0.20, 2.20 and 1.30 μg/l, respectively. The trend in the sum concentration (μg/L) was SMX>TMP>AMX in the wet season and SMX>AMX>TMP in the dry season. The presence of SMX in wastewater effluent from Ruai outlet showed that the treatment plant was ineffective at completely removing antibiotic contaminants from the wastewater. Adsorption of AMX, SMX and TMP was notably greater on Powdered Activated Carbon (PAC) than on Granulated Activated Carbon (GAC), suggesting that PAC was a better adsorbent for the antibiotics in both distilled and surface water. Adsorption data fitted better on Freundlich isotherm than Langmuir isotherm, suggesting a physical process. The results revealed contamination of Ngong River water by antibiotic residues, which has a potential impact on antibiotic resistance. In addition, the removal of antibiotic residues

from water could be improved by introducing activated carbon filters in the water treatment train. However, further studies should be conducted using water from the wastewater treatment plant to understand the effect of organic load on adsorption processes using PAC and GAC.