Removal of Lipitor (atorvastatin calcium) in a lab-scale ecological wastewater treatment system

Abstract

It is important to understand the fate of Lipitor (atorvastatin calcium) in wastewater treatment system due to its persistence and the harmful effects that it might cause to the humans and nature. Laboratory experiments were carried out to study the sorptive behavior of Lipitor in XAD4, XAD7HP, XAD16, activated carbon (AC), and sand. The 7-day or 14-day isotherm experiments were conducted to compare the sorption capacities of these selected adsorbents. The objective of these isotherm studies was to determine the most suitable adsorbent(s) to remove Lipitor from synthetic wastewater made using cat food and tea. Results showed that AC was most effective in removing atorvastatin, followed by XAD4, XAD7HP, and XAD16 resins, while sand showed no significant effect in the sorption of atorvastatin.

The suitability of Langmuir isotherm to fit all the sorption data indicated that only monolayer sorption of atorvastatin took place in the tested adsorbents. A filter that was specially designed for the removal of Lipitor was constructed using AC and XAD4 as filter media. Additionally, sand and gravel were used to remove turbidity. Results had shown that 100% removal efficiency was achieved when the synthetic wastewater with an initial atorvastatin concentration of 19.76 mg/L was pumped at a rate of 6.40 mL/min into the filter. Increasing the inflow rate would decrease the atorvastatin removal efficiency due to the reduction in contact time for sorption to take place. The filter was combined to a lab-scale ecological wastewater treatment plant that was designed and constructed using the Eco-Machine as the model. The synthetic wastewater that contained 13.33 mg/L of Lipitor was allowed to flow through the whole wastewater treatment system by gravitational means. The results demonstrated that near 100% removal efficiency was achieved during the first day of operation, but the concentration of atorvastatin in the effluent increased afterward due to the saturation of some sorption sites of the adsorbents in the filter. The lab-scale ecological wastewater treatment plant was also proved to work effectively in removing the turbidity of wastewater. It was appropriate to conclude that this study provided useful knowledge in the removal of atorvastatin from synthetic wastewater.