Removal and Recovery of Nitroimidazoles (Metronidazole and Trimethoprim) Antibiotics from a Pharmaceutical Industry Wastewater Using Reverse Osmosis

Abstract: In the practice of medicine, antibiotics are extremely important and are employed in the treatment of infections. A lot of antibiotics are consumed by humans and excreted via urine and feces into sewage systems and treatment plants. These are considered to be non-biodegradable, and over the years they accumulate in the aquatic environment. The presence of antibiotics in water resources causes the emergence of antibiotic-resistant bacteria, posing a serious threat to the health of human beings. Water bodies must be adequately treated before being discharged to prevent the spread of antibiotic resistance. A reverse osmosis reactor with a two membranes namely hollow fiber osmosis (HF–O) and hollow fiber composite (HF-C) modules was used in the removals and recoveries of Metronidazole (MET, C6H9N3O3) and Trimethoprim (TMP, C14H18N4O3) antibiotics at different concentrations. Nitroimidazoles (Metronidazole and Trimethoprim) were selected because they are antimicrobials with bactericidal action that present a moderately broad antibacterial spectrum. They are used in infections of the urinary tract, ears, lungs, intestines and liver. The effects of applied pressures (10, 20, 30, and 40 bar), feed concentrations (25, 50, 100, 250 and 1500 mg/l), operating temperatures (25, 35, and 45°C), and feed flow rates of 5, 7, 10, and 15 l/min on the removals and recoveries of both antibiotics were researched. Js/Jw is also increased with feed flow rate for the HF–C membranes but remains relatively constant for HF–O membranes for all tested feed flow rates. Therefore, Js/Jw is much lower for HF–O membranes (Js/Jw = 0.15 ± 0.02 g/l) than it is for HF–C membranes (Js/Jw = 0.40 ± 0.10 g/l). For the HF–C membrane, Jw was higher than for the HF–O membrane at any draw flow rate investigated, and it increased from 24.9 ± 0.6 l/m2.h permeate flux at 25 l/h feed flow rate to 31.30 l/m2.h at 100 l/h, respectively (Jw increase of 25.40%). Jw increased from 17.90 ± 0.50 l/m2.h to 19.20±0.50 l/m2.h (7.30% increase in Jw) for HF–O modules and from 24.0 ± 1.3 l/m2.h to 27.70 ± 0.20 l/m2.h (15% increase in Jw) for HF–C modules. The water permeability coefficient (Aw) and solute rejection efficiency (R) were constant at 6.73 l/m2/h/bar and 99.20%, respectively, while the solute permeability coefficients varied with pressure and correlated with Jw Antibiotic rejections varied from 94.0 to 99.80% depending on pH rejection was highest at a pH of 6.0, at 99.80%. For both membranes, the rejection rate was obtained at 295oK (22oC) for maximum antibiotic yields 60.80% and 71.60% for HF–O and, HF–C, respectively. The maximum antibiotic removal rates were 90.70% and 86.40%, respectively. The HF-C membrane was relatively more efficient at all concentrations tested than the HF-O membrane, because of its smaller pore size and its structure. 99% Metronidazole and 99% Trimethoprim removal yields were obtained in HF-C RO membrane, at 100 mg/l initial Metronidazole, at 100 mg/l initial Trimethoprim, at 180 l/h, at 4.2 l/m2.h, respectively. 99% Metronidazole and 99% Trimethoprim removal yields were observed in HF-O RO membrane, at 100 mg/l initial Metronidazole, at 100 mg/l initial Trimethoprim, at 30 bar feed pressure, at 7 l/m2.h, respectively. 99% Metronidazole and 99% Trimethoprim removal yields were observed in RO membrane, at 100 mg/l initial Metronidazole, at 100 mg/l initial Trimethoprim, at 30 bar, at 7 l/m2.h, respectively. Conventional wastewater treatment plants are not able to eliminate antibiotics deposition/resistance genes effectively and efficiently. In this regard, the adsorption method is the most effective way of removing antibiotics from wastewater from various sources.