Visible-light-driven TiO2@Fe2O3/Chitosan nanocomposite with promoted photodegradation of meropenem and imipenem antibiotics by peroxymonosulfate.

This study assessed wastewater treatment by visible-light/Peroxymonosulfate process using its linking with TiO2@Fe3O4 nanoparticles coated on chitosan. Meropenem and Imipenem photodegradation was evaluated as a model-resistant contaminant by TiO2@Fe2O3/chitosan nanocomposite. The synthesised TiO2@Fe2O3/chitosan was characterised using various techniques. Fe2O3 and TiO2 nanoparticles on the chitosan surface were affirmed via XRD, EDX, and FTIR findings. The FESEM and TEM results verified the deposition of TiO2@Fe2O3 on the chitosan surface. Under optimum circumstances (pH = 4, catalyst dosage = 0.5 g/L, antibiotics concentration = 25 mg/L reaction time = 30 min, and PMS = 2 mM), maximum degradation efficiency was obtained at about 95.64 and 93.9% for Meropenem and Imipenem, respectively. Also, the experiments demonstrated that TiO2@Fe2O3/chitosan had a better performance than photolysis and adsorption by catalyst without visible light irradiation in degrading antibiotics. The scavenger tests confirmed that O2⋅-, SO4⋅-, HO⋅, and h+ are present simultaneously during the pollutant photodegradation process. After five recovery cycles, the system eliminated over 80 percent of antibiotics. It suggested that the catalyst's capacity to be reused may be cost-effective.

Life cycle assessment for municipal solid waste management: a case study from Ahvaz, Iran.

This study assessed the available status of waste management system in Ahvaz and its impact on the environment, as well as seven other scenarios in order to quantitatively calculate potential environmental impacts by utilizing the life cycle assessment (LCA) method. These scenarios were as follows: scenario 1: landfilling without biogas collection; scenario 2: landfilling with biogas collection; scenario 3: composting and landfilling without biogas collection; scenario 4: recycling and composting; scenario 5: composting and incineration; scenario 6: anaerobic digestion, recycling, and landfilling; scenario 7: anaerobic digestion and incineration. Emissions were calculated by the integrated waste management (IWM) model and classified into five impact categories: resource consumption, global warming, acidification potential, photochemical oxidation, and eco-toxicity. In terms of resource consumption and the depletion of non-renewable resources, the third scenario showed the worst performance due to its lack of any recycling, energy recovery, and conversion to energy. In terms of greenhouse gas emissions and the effect on global warming, scenario 1 and scenario 2 showed that disposing the whole amount of waste resulted in the most amount of greenhouse gases produced. Moreover, 50% gas and energy recovery from landfills, in comparison with the non-recovery method, reduced the index of global warming by 12%. Finally, scenarios which were based on producing energy from waste showed a reasonably positive performance in terms of greenhouse gases emissions and the influence on global warming.

Performance evaluation of waste stabilization ponds on removal of Listeria spp.: a case study of Isfahan, Iran.

The aim of the present study was to assess performance of waste stabilization ponds (WSPs) on the removal of Listeria spp. in Isfahan, Iran. A total of 104 samples were taken from eight sampling locations from influent and effluent of a wastewater treatment plant (WWTP). Sewage samples were analyzed for the presence of Listeria spp. using selective enrichment protocol. Listeria isolates were also identified by biochemical and polymerase chain reaction (PCR) amplification. Listeria spp. was enumerated by a three tube most probable number (MPN) for total coliform counts (TC), fecal coliform counts (FC), total suspended solids (TSS), and total dissolved solids (TDS). In total, 54/104 (51.92%), 49/104 (47.11%), 36/104 (34.61%), and 27/104 (25.95%) samples were positive for Listeria spp., L. monocytogenes, L. innocua, and L. seeligeri, respectively. The mean MPN/100 mL enumeration of L. monocytogenes for influent, anaerobic, facultative ponds 1, 2, 3, 4 and maturation ponds 1 and 2 were 21.54, 10.61, 8, 5.77, 4, 2.54, 1.38, and 0.46, respectively. The removal percentage of Listeria spp. in the anaerobic, facultative, and maturation ponds were 44.71, 76.5, and 81.4%, respectively. Results showed that the WSPs were able to decrease the Listeria spp. levels significantly, although unable to remove them completely.

Removal optimization of heavy metals from effluent of sludge dewatering process in oil and gas well drilling by nanofiltration.

Oil and gas well drilling industries discharge large volumes of contaminated wastewater produced during oil and gas exploration process. In this study, the effect of different operational variables, including temperature, pH and transmembrane pressure on process performance of a commercially available nanofiltration membrane (JCM-1812-50N, USA) for removing Ba, Ni, Cr, NaCl and TDS from produced wastewater by dewatering unit of an oil and gas well drilling industry was evaluated. In optimum experimental conditions (T = 25 °C, P = 170 psi and pH = 4) resulted from Thaguchi method, 85.3, 77.4, 58.5, 79.6 and 56.3% removal efficiencies were achieved for Ba, Ni, Cr, NaCl and TDS, respectively. Also, results from a comparison of the Schuller and Wilcox diagrams revealed that the effluent of the membrane system is usable for drinking water, irrigating and agriculture purposes. Moreover, the process effluent quality showed a scaling feature, according to Langelier saturation index and illustrated that the necessary proceedings should be taken to prevent scaling for industrial application. The nanofiltration membrane process with an acceptable recovery rate of 47.17% represented a good performance in the wastewater treatment.