Ligy Philip

Adsorption of three pharmaceuticals, namely, atenolol, ciprofloxacin and gemfibrozil using synthesized magnetic polymer clay composite was investigated in detail by conducting batch kinetic, equilibrium and desorption experiments. Optimum ratio of composite adsorbent was found to be clay: chitosan: powdered activated carbon (PAC): magnetic nano particles (MNP) as 1:0.5:0.3:0.3. Characterization studies showed the incorporation of modifiers into the clay structure. Surface area of the synthesized pellets was 94.81 m2/g with mesoporous surface. Freundlich model was able to predict the adsorption equilibrium data. Maximum adsorption capacities were estimated to be 15.6, 39.1 and 24.8 mg/g for atenolol, ciprofloxacin and gemfibrozil, respectively. The main driving force of adsorption was electrostatic interaction. The adsorbent performance was affected at lower and higher pH and by the presence of humic acid. Desorption of atenolol and ciprofloxacin were significantly higher in acid and alkaline solution whereas gemfibrozil was desorbed upto 70% in methanol. Magnetically separable clay composite was found to be a suitable adsorbent for removing pharmaceuticals from water.

The present study focussed on potential application of river bank filtration (RBF) for the effective removal of pharmaceutically active compounds (PhACs), namely, atenolol, ciprofloxacin and gemfibrozil. Experiments on RBF were performed in a pilot scale reactor (3.0 m × 1.0 m × 0.5 m) in which two dimensional unconfined aquifer flow conditions were induced by pumping to depict realistic field conditions. Initially, experiments were carried out in a reactor filled with natural river bed material. The natural attenuation efficiencies were found to be 21, 35 and 8% for atenolol, ciprofloxacin and gemfibrozil, respectively. Pumping experiments conducted through clean sand in RBF indicated that PhACs were highly mobile with minimal degradation. In order to improve the treatment efficiency of RBF, biofilm coated clay composite adsorbent was synthesized and used in a reactive barrier. The reactive barrier could significantly eliminate PhACs up to 80, 90, 75% for atenolol, ciprofloxacin and gemfibrozil, respectively, at the extracting well (located at 125 cm from the inlet) even after 150 h. Pumping experiments showed that 20 cm thick barrier was able to contain the movement of contaminant plume up to 4 h when water was pumped at a rate of 0.0075 L/s and up to 3.2 h when the pumping rate was 0.01 L/s. Further, a 2D reactive transport model was developed and validated based on the experimental data. The transport model would be useful for developing a management model for the optimal design of reactive barrier for enhancing the performance of RBF.

Visible light induced photocatalysis is considered as one of the most potential technologies which can achieve new levels of sustainability in water treatment. The current study explores the performance of immobilized visible light active catalyst on inert media for light driven catalysis of pharmaceuticals. These coated media is used in a continuous flow fluidized column reactor equipped with spirally arranged visible Light Emitting Diodes (LEDs)as irradiation source. The treatment efficiency of the system is evaluated for the removal of pharmaceutical drugs such as carbamazepine, diclofenac and ibuprofen. For the present study, system parameters such as light intensity and flow rate are optimized for maximum removal rate. The system shows complete elimination of the pharmaceuticals under the given experimental conditions. Complete mineralization of the target compounds are confirmed by TOC analysis. Recyclability is an important attribute for full scale commercialization of a treatment technology. An investigation on the reusability study of the photocatalyst displayed no significant reduction in the removal efficiency for a run of six cycles, hence rendering the photocatalyst reusable. The results acquired indicate an immense potential for scaling up the photoreactor as a sustainable tertiary treatment technology in water treatment plants.

The presence of pharmaceuticals, hormones, pesticides and industrial contaminants collectively termed as trace organic compounds (TOrCs) in wastewater has been well-documented in USA, Europe, China and other regions. However, data from India, the second most populous country in the world is severely lacking. This study investigated the occurrence and concentrations of twenty-two indicator TOrCs at three wastewater treatment plants (WWTPs) in South India serving diverse communities across three sampling campaigns. Samples were collected after each WWTP treatment unit and removal efficiencies for TOrCs were determined. Eleven TOrCs were detected in every sample from every location at all sites, while only five TOrCs were detected consistently in effluent samples. Caffeine was present at greatest concentration in the influent of all three plants with average concentrations ranging between 56 and 65 μg/L. In contrast, the x-ray contrast media pharmaceutical, iohexol, was the highest detected compound on average in the effluent at all three WWTPs (2.1-8.7 μg/L). TOrCs were not completely removed in the WWTPs with removal efficiencies being compound specific and most of the attenuation being attributed to the biological treatment processes. Caffeine and triclocarban were well removed (>. 80%), while other compounds were poorly removed (acesulfame, sucralose, iohexol) or maybe even formed (carbamazepine) within the WWTPs. The effluent composition of the 22 TOrCs were similar within the three WWTPs but quite different to those seen in the US, indicating the importance of region-specific monitoring. Diurnal trends indicated that variability is compound specific but trended within certain classes of compounds (artificial sweeteners, and pharmaceuticals). The data collected on TOrCs from this study can be used as a baseline to identify potential remediation and regulatory strategies in this understudied region of India.

The present paper deals with photocatalytic degradation of carbamazepine and diclofenac by using a modified catalyst with band gap excitations in visible light. The C-doped TiO2 was synthesized using a microwave digestion method from titanium oxyacetylacetate with glucose as the carbon source. The synthesized catalyst was then characterized using Scanning Electron microscopy (SEM), X-ray Diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and UV-VIS-NIR spectrophotometer. The TiO2 present was in anatase phase and showed significant absorption in visible region. The catalyst was tested for the degradation of carbamazepine and diclofenac under visible light, where complete removal was achieved and the reaction followed first order kinetics. System parameters like catalyst and pollutant concentration, light intensity and time of reaction, were optimized using response surface methodology. In optimum conditions (catalyst concentration of 244 mg/L and light intensity of 7715 lx) 99% removal was achieved.

Removal of three pharmaceuticals, namely, atenolol, gemfibrozil and ciprofloxacin in three bioreactors namely, activated sludge process (ASP), submerged attached biofilter (SABF) and membrane bioreactor (MBR) was studied. Removal efficiencies at steady state for atenolol were found to be 93%, 82% and 95% in ASP, SABF and MBR, respectively. Removal efficiencies for gemfibrozil were 75%, 90% and 85%, while those for ciprofloxacin were 84%, 95% and 93% in ASP, SABF and MBR, respectively. Nearly 20% of the ciprofloxacin was found to be sorbed on the biomass in the reactors. Reduction in sludge residence time (SRT) decreased the removal of compounds in ASP and MBR, and reduction in hydraulic residence time (HRT) caused a negative impact on the performance of all the reactors. Considerable increase in easily available carbon source reduced the removal efficiency. Sorption coefficient (log Kd) of ciprofloxacin was found to be 3.86 and sorption was negligible in case of atenolol and gemfibrozil. Monod co-metabolic model could simulate biodegradation process satisfactorily. Inhibition concentrations (Ki) of atenolol, ciprofloxacin and gemfibrozil were found to be 2.8 mg/L, 0.6 mg/L and 0.89 mg/L, respectively. Biokinetic parameters μmax, Ks and YX/S were 0.046 h−1, 10 mg/L and 0.36, respectively. Efficiency factor (ηc) was estimated to be 0.002, 0.0006 and 0.001 mg compound/gCOD for atenolol, ciprofloxacin and gemfibrozil, respectively.