The efficiency of sequential advanced membrane technology wastewater treatment plant towards removal of a widely used non-steroid anti-inflammatory drug (NSAID) mefenamic acid was investigated. The sequential system included activated sludge, ultrafiltration by hollow fibre membranes with 100 kDa cutoff, and spiral wound membranes with 20 kDa cutoff, activated carbon and a reverse osmosis (RO) unit. The performance of the integrated plant showed complete removal of mefenamic acid from spiked wastewater samples. The activated carbon column was the most effective component in removing mefenamic acid with a removal efficiency of 97.2%. Stability study of mefenamic acid in pure water and Al-Quds activated sludge revealed that the anti-inflammatory drug was resistant to degradation in both environments. Batch adsorption of mefenamic acid by activated charcoal and a composite micelle (otadecyltrimethylammonium (ODTMA)-clay (montmorillonite) was determined at 25.0°C. Langmuir isotherm was found to fit the data with Qmax of 90.9 mg g(-1) and 100.0 mg g(-1) for activated carbon and micelle-clay complex, respectively. Filtration experiment by micelle-clay columns mixed with sand in the mg L(-1) range revealed complete removal of the drug with much larger capacity than activated carbon column. The combined results demonstrated that an integration of a micelle-clay column in the plant system has a good potential to improve the removal efficiency of the plant towards NSAID drugs such as mefenamic acid.

Based on density functional theory (DFT) calculations for the acid-catalyzed hydrolysis of several maleamic acid amide derivatives four tranexamic acid prodrugs were designed. The DFT results on the acid catalyzed hydrolysis revealed that the reaction rate-limiting step is determined on the nature of the amine leaving group. When the amine leaving group was a primary amine or tranexamic acid moiety, the tetrahedral intermediate collapse was the rate-limiting step, whereas in the cases by which the amine leaving group was aciclovir or cefuroxime the rate-limiting step was the tetrahedral intermediate formation. The linear correlation between the calculated DFT and experimental rates for N-methylmaleamic acids 1-7 provided a credible basis for designing tranexamic acid prodrugs that have the potential to release the parent drug in a sustained release fashion. For example, based on the calculated B3LYP/6-31G(d,p) rates the predicted t1/2 (a time needed for 50 % of the prodrug to be converted into drug) values for tranexamic acid prodrugs ProD 1-ProD 4 at pH 2 were 556 h [50.5 h as calculated by B3LYP/311+G(d,p)] and 6.2 h as calculated by GGA: MPW1K), 253 h, 70 s and 1.7 h, respectively. Kinetic study on the interconversion of the newly synthesized tranexamic acid prodrug ProD 1 revealed that the t1/2 for its conversion to the parent drug was largely affected by the pH of the medium. The experimental t1/2 values in 1 N HCl, buffer pH 2 and buffer pH 5 were 54 min, 23.9 and 270 h, respectively.

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 ATO, RST and SIM from spiked wastewater produced at the Al-Quds University campus were investigated. All three statins were found to undergo degradation in wastewater (activated sludge). The degradation reactions of the three drugs in wastewater at room temperature follow first-order kinetics with rate constants of 2.2 × 10⁻⁷ s⁻¹ (ATO), 1.8 × 10⁻⁷ s⁻¹ (RST) and 1.8 × 10⁻⁶ s⁻¹ (SIM), which are larger than those obtained in pure water under the same conditions, 1.9 × 10⁻⁸ s⁻¹ (ATO), 2.2 × 10⁻⁸ s⁻¹ (RST) and 6.2 × 10⁻⁷ s⁻¹ (SIM). Degradation products were identified by LC-MS and LC/MS/MS. The overall performance of the wastewater treatment plant (WWTP) installed in the 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. The batch adsorption isotherms for the three statins were found to fit the Langmuir equation, with a larger number of adsorption sites and binding affinity for micelle-clay composite compared with activated carbon and filtration experiments of the three statins and their corresponding metabolites demonstrated a more efficient removal by micelle-clay filters.

DFT calculations at B3LYP/6-31G(d,p) for intramolecular proton transfer in Kirby's enzyme models 1-7 demonstrated that the reaction rate is dependent on the distance between the two reacting centers, rGM, and the hydrogen bonding angle, α, and the rate of the reaction is linearly correlated with rGM and α. Based on these calculation results three simvastatin prodrugs were designed with the potential to provide simvastatin with higher bioavailability. For example, based on the calculated log EM for the three proposed prodrugs, the interconversion of simvastatin prodrug ProD 3 to simvastatin is predicted to be about 10 times faster than that of either simvastatin prodrug ProD 1 or simvastatin ProD 2. Hence, the rate by which the prodrug releases the statin drug can be determined according to the structural features of the promoiety (Kirby's enzyme model).

In this study, the stability of chlorpyrifos, a known pesticide, in fresh water and sludge was investigated. The results showed that chlorpyrifos underwent hydrolysis in both media to give two main metabolites: 3,5,6-trichoro-2-pyridiniol (TCP) and diethylthiophosphoric acid (DETP). The hydrolysis reaction in both media was found to follow first-order kinetics with a rate constant of 7.10 × 10 −8 (R 2 = 0.999) in pure water and of 9.30 × 10 −8 (R 2 = 0.996) in sludge. Chlorpyrifos degradation's half-life value in pure water was 112 d and in sludge was 85.9 d. The efficiency of Al-Quds University wastewater treatment plant demonstrated that the ultrafiltration-hollow fiber unit (UF-HF) was insufficient in removing chlorpyrifos from spiked secondary treated wastewater samples, whereas the combination of ultrafiltration-spiral wound unit (UF-SW) followed by activated carbon (AC) column was quite efficient and yielded a complete removal of the pesticide. Batch adsorption experiments using either AC or micelle-clay complex were performed and the experimental results were fitted to Langmuir and Freundlich isotherms. Adsorption analysis using Langmuir isotherm revealed that Q max for the AC was higher than that of the micelle-clay complex, while Freundlich isotherm showed almost similar values of n (3.413 vs. 3.745) for both adsorbents, despite the fact that the activated carbon filter showed higher k F value. Filtration column of mixed micelle-clay complex and sand demonstrated a breakthrough point after the third fraction for chlorpyrifos removal and a complete removal for all fractions collected in the *Corresponding author.