ABSTRACT
The emerging presence of organic micropollutants (OMPs) in water bodies produced by human activities is a source of growing concern due to their environmental and health issues. Biodegradation is a widely employed treatment method for OMPs in wastewater owing to its high efficiency and low operational cost. Compared to aerobic degradation, anaerobic degradation has numerous advantages, including energy efficiency and superior performance for certain recalcitrant compounds. Nonetheless, the low influent concentrations of OMPs in wastewater treatment plants (WWTPs) and their toxicity make it difficult to support the growth of microorganisms. Therefore, co-metabolism is a promising mechanism for OMP biodegradation in which co-substrates are added as carbon and energy sources and stimulate increased metabolic activity. Functional microorganisms and enzymes exhibit significant variations at each stage of anaerobic digestion affecting the environment for the degradation of OMPs with different structural properties, as these factors substantially influence OMPs' biodegradability and transformation pathways. However, there is a paucity of literature reviews that explicate the correlations between OMPs' chemical structure and specific metabolic conditions. This study provides a comprehensive review of the co-metabolic processes which are favored by each stage of anaerobic digestion and attempts to link various functional groups to their favorable degradation pathways. Furthermore, potential co-metabolic processes and strategies that can enhance co-digestion are also identified, providing directions for future research.
Subject(s)
Biodegradation, Environmental , Anaerobiosis , Wastewater/chemistry , Water Pollutants, Chemical/metabolism , Waste Disposal, Fluid/methodsABSTRACT
Photocatalysis has been considered a promising technology for the elimination of a wide range of pollutants in water. Various types of photocatalysts (i.e., homojunction, heterojunction, dual Z-scheme photocatalyst) have been developed in recent years to address the drawbacks of conventional photocatalysts, such as the large energy band gap and rapid recombination rate of photogenerated electrons and holes. However, there are still challenges in the design of photocatalytic reactors that limit their wider application for real (waste)water treatment, such as difficulties in their recovery and reuse from treated (waste)waters. 3D printing technologies have been introduced very recently for the immobilization of materials in novel photocatalytic reactor designs. The present review aims to summarize and discuss the advances and challenges in the application of various 3D printing technologies (i.e., stereolithography, inkjet printing, and direct ink writing) for the fabrication of stable photocatalytic materials for (waste)water treatment purposes. Furthermore, the limitations in the implementation of these technologies to design future generations of photocatalytic reactors have been critically discussed, and recommendations for future studies have been presented.
ABSTRACT
A novel double Z-scheme CuWO4/Bi2S3/ZIF67 ternary heterostructure was synthesized through hydrothermal method. The catalysts were characterized by XRD, FTIR, SEM, EDX, BET, TEM, PL, and UV-vis DRS analyses. The degradations of Metronidazole (MTZ) and Cephalexin (CFX) antibiotics by ternary catalyst were investigated in the batch and continuous slurry photoreactor under LED illumination. The ternary heterostructure exhibited a remarkable improvement in photoactivity compared with CuWO4/Bi2S3, and pristine ZIF67. Indeed, higher surface area, photo-stability, bandgap suppressing as well as better charge separation based on the dual Z-scheme structure caused the enhancement. The optimum values of operating parameters were obtained by the central composite design as: catalyst dose = 0.3 g/L, pH = 7, illumination time = 80 min, and 20 ppm initial concentration of antibiotic. The maximum degradation efficiencies by the new ternary heterostructure were 95.6% and 90.1%, respectively for MTZ and CFX at optimum conditions in the continuous flow mode. Maximum total organic carbon (TOC) removal rates were 83.2% and 74% for MTZ and CFX, respectively. The degradations by ternary composite followed the first-order kinetic, by reaction rate of 9 times, 5.5 times, and 4 times higher than that obtained by Bi2S3, ZIF67, and the binary CuWO4/Bi2S3, respectively. The influences of temperature and light intensity were explored, revealing 25 °C and 400 W/m2 as the optimum values. The new ternary heterostructure demonstrated excellent reusability and chemical stability after six cycles. The dominant active species were explored by trapping tests, indicating OH. free radicals as the most primary oxidant.
Subject(s)
Anti-Bacterial Agents/chemistry , Models, Chemical , Photolysis , Catalysis , LightABSTRACT
The anti-phytoplasma activities of surfactin (derived from Iranian native Bacillus subtilis isolates) and tetracycline towards Candidatus "Phytoplasma aurantifolia", the agent of lime Witches' broom disease, were investigated. HPLC was used to quantify the surfactin production in four previously characterized native surfactin-producing strains, and the one producing the highest amount of surfactin (about 1,500 mg/l) was selected and cultivated following optimized production and extraction protocols. Different combinations of purified surfactin and commercial tetracycline were injected into artificially phytoplasmainfected Mexican lime seedlings using a syringe injection system. An absolute quantitative real-time PCR system was developed to monitor the phytoplasma population shifts in the lime phloem during 3 months following the injections. The results revealed that the injections of surfactin or tetracycline had a significant inhibitory effect on Candidatus "P. aurantifolia". However, the combined treatment with both surfactin and tetracycline (1:1) resulted in the highest inhibition due to a synergic effect, which suppressed the phytoplasma population from about 2×10(5) to less than 10 phytoplasma units/g plant tissue.
