Comparing the efficiency of N-doped TiO2 and commercial TiO2 as photo catalysts for amoxicillin and ciprofloxacin photo-degradation under solar irradiation.

Advanced oxidation processes (AOPs) have gained traction as alternative solutions for eliminating pollutants from pharmaceutical wastewater for reuse. In this research, the performance of two photo-catalysts (Commercial TiO2 and synthesis N-doped TiO2) were compared in terms of the degradation of amoxicillin and ciprofloxacin from an aqueous solution using a photo-catalytic batch system under solar irradiation. The influence of five operating factors is: pH (5-11), H2O2 concentrations (200-600) mg/L, catalyst concentrations (25-100 mg/L), Antibiotic concentration (25-100) mg/L and reaction time (30-120 min), on the oxidation of the listed above pollutants were investigated using the central composite design (CCD) of response surface methodology (RSM). The catalyst of N-doping TiO2 was synthesized by sol-gel method, using the urea (CH4N2O) as a nitrogen source. The resulting material was analyzed using Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Additionally, it can be observed from the analysis of the characteristics of N-doped TiO2 the homogenous dispersion of nitrogen molecules, small particle sizes, and energy-gap reduction, prompting a 6% increase in antibiotic degradation compared with Com. TiO2. In the RSM analysis, the ideal conditions were found to be a pH of 5, H2O2 conc. of 400 mg/L, catalyst conc. of 50 mg, and antibiotics conc. of 25 mg/L for an antibiotics reduction rate of 89.31% (AMOX/Com. TiO2/Solar), 90.2 (CFX/Com. TiO2/Solar), 95.8% (AMOX/N-TiO2/Solar) and 97.3% (CFX/N-TiO2/Solar). Experimental results were in good agreement with predictions because the predicted R2 matched well with the adjusted R2.

Ethanethiol gas removal in an anoxic bio-scrubber.

The performance of ethanethiol removal in an anoxic lab-scale bio-scrubber was investigated under different operating parameters and conditions for 300 days. The removal efficiency (RE) of ethanethiol was examined as a function of inlet concentration, empty bed residence time (EBRT) and spray density of irrigation. The results showed the best operation conditions and operation characteristics of the bio-scrubber for this study were at an inlet concentration of 150 mg/m3, a spray density of 0.23 m3/m2 h and an EBRT of 90 s. An average RE of 91% and elimination capacity (EC) of 24.74 g/m3 h was found for all inlet ethanethiol concentrations. Variations in spray density higher than 0.23 m3/m2 h had no effect on ethanethiol RE at different ethanethiol concentrations. The average experimental yield values were closer to the YET/NO3- theoretical value of 0.74 when the main product was elemental sulphur (So). This indicates that So and other forms of sulphur were formed rather than sulphate (SO42-) as the end product. Furthermore, growth kinetics for bio-degradation were evaluated in batch culture experiments using the Monod model, and bio-kinetic parameters of µmax, Ks, Yxs and qmax were obtained as 0.14 1/h, 1.17 mg/L, 0.52 gx/gs and 0.26 gs/gx h, respectively.

Biodegradation of Emerging Pharmaceuticals from Domestic Wastewater by Membrane Bioreactor: The Effect of Solid Retention Time.

Although conventional biological treatment plants can remove basic pollutants, they are ineffective at removing recalcitrant pollutants. Membrane bioreactors contain promising technology and have the advantages of better effluent quality and lower sludge production compared to those of conventional biological treatment processes. In this study, the removal of pharmaceutical compounds by membrane bioreactors under different solid retention times (SRTs) was investigated. To study the effect of SRT on the removal of emerging pharmaceuticals, the levels of pharmaceuticals were measured over 96 days for the following retention times: 20, 30, and 40-day SRT. It was found that the 40-day SRT had the optimum performance in terms of the pharmaceuticals' elimination. The removal efficiencies of the chemical oxygen demand (COD) for each selected SRT were higher than 96% at steady-state conditions. The highest degradation efficiency was observed for paracetamol. Paracetamol was the most removed compound followed by ranitidine, atenolol, bezafibrate, diclofenac, and carbamazepine. The microbial community at the phylum level was also analyzed to understand the biodegradability of pharmaceuticals. It was noticed that the Proteobacteria phylum increased from 46.8% to 60.0% after 96 days with the pharmaceuticals. The Actinobacteria class, which can metabolize paracetamol, carbamazepine, and atenolol, was also increased from 9.1% to 17.9% after adding pharmaceuticals. The by-products of diclofenac, bezafibrate, and carbamazepine were observed in the effluent samples.

Removal of dimethyl sulphide via a bio-scrubber under anoxic conditions.

The removal performance of dimethyl sulphide (DMS) by anoxic laboratory-scale bio-scrubber was studied under different operation conditions for 315 days. DMS removal in bio-scrubber system was performed by controlling and changing the operation parameters, including inlet concentration, empty bed residence time (EBRT) and spraying density (SD) of irrigation. Best conditions in the system were achieved for SD of 0.18 m3/m2 h within EBRT of 40 s at an inlet gas concentration of 150 mg/m3 in which 93% of waste gas stream was removed in the bio-scrubber column and bio-degradation in the bio-reactor tank led to 89% of DMS removal from the transferred bio-reactor, while 91.5% of input chemical oxygen demand (COD) was successfully removed. The use of closer values of the average experimental yield to the theoretical value (YNO3/NO3 -) of 0.74 led to the production of elemental sulphur (S°) and other sulphur forms rather than sulphate (SO42-) , which was also was recognized as a pale-yellow coloured substance of S° that appeared within the biomass.