Stability and removal of several statins from wastewater using different treatment technologies
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Atorvastatin (ATO), Rosuvastatin (RST) and Simvastatin (SIM) are commonly used drugs that belong to the statin family (lowering human blood cholesterol levels) and have been detected as contaminants in natural waters. Stability and removal of statins from wastewater produced at Al-Quds University Campus were investigated. Kinetic studies in pure water (abiotic degradation), in sludge (biodegradability) and in Advanced Oxidation Processes (AOPs) at room temperature were investigated. Heterogeneous photocatalysis using the semi- conductor titanium dioxide (TiO2) has proven to be a promising treatment technology for water purification. The degradation reactions of the three drugs in wastewater at room temperature follow first order kinetics with rate constants of 2.2 x 10-7 s-1(ATO), 1.8 x 10-7s-1 (RST) and 1.8 x 10-6 s-1 (SIM), which are larger than those obtained in pure water under the same conditions, 1.9x 10-8 s-1 (ATO), 2.2x 10-8s-1 (RST) and 6.2 x 10-7 s-1 (SIM). AOPs process was proposed and applied. TiO2, used as catalyst, owns two important properties: high photo-catalytic activity and low cost. Photo-degradation of Atorvastatin was much faster under light irradiation in presence of TiO2 (photocatalysis) (t1/2 = 1.15 hours, 0.704h-1) than under Suntest irradiation (photolysis) (t1/2 = 5.0 hours, 0.165h-1). Degradation products were identified by LC-MS and LC/MS/MS. The overall performance of the wastewater treatment plant (WWTP) installed in Al-Quds University Campus towards the removal of these drugs was assessed showing that more than 90% of spiked ATO, RST and SIM were removed. In order to evaluate the efficiency of alternative removal methods to replace ultra-filtration membranes, adsorption isotherms for the three statins were investigated using both activated carbon and clay-micelle complex as adsorbents and AOP’s as a post treatment. The batch adsorption isotherms for the three statins were found to fit Langmuir equation, with larger number of adsorption sites and binding affinity for micelle-clay composite compared to activated carbon and filtration experiments of the three statins and their corresponding metabolites demonstrated a more efficient removal by micelle-clay filters.