Advanced oxidation process (AOP) combined biological process for wastewater treatment: A review on advancements, feasibility and practicability of combined techniques.

Complexity of wastewater is the most challenging phenomenon on successful degradation of pollutant via any wastewater treatment regime. Upon availability of numerous techniques, Advanced Oxidation Processes (AOP) is the most promising technique for treating industrial wastewater. Higher operating cost is the most promising factor that possess challenge for the industrial scale usage of the AOP process. Combination of biological process with AOP helps in achieving sustainable degradation of toxic pollutant in the wastewater. AOP result in complete or partial degradation of toxic emerging pollutants with the help of free radicals like hydroxyl, superoxide, hydroperoxyl and sulphate radicals. In addition to this the presence of bio-enzymes and microorganisms helps in sustainable degradation of pollutant in an economical and environmentally friendly strategy. In this review, a detailed discussion was conducted on various AOP, focusing on catalytic ozonation, electrochemical oxidation, Sono chemical and photocatalytic processes. With the need for sustainable solutions for wastewater treatment, the use of AOP in conjunction with biological process has innumerous opportunities for not only wastewater treatment but also the production of high value by-products. Further, the effect of AOP combined biological processes needs to be analyzed in real time for the different concentration of industrial wastewater and their benefits needs to be explored in future towards achieving SDGs.

Synthesis and application of titanium dioxide photocatalysis for energy, decontamination and viral disinfection: a review.

Global pollution is calling for advanced methods to remove contaminants from water and wastewater, such as TiO2-assisted photocatalysis.  The environmental applications of titanium dioxide have started after the initial TiO2 application for water splitting by Fujishima and Honda in 1972. TiO2 is now used for self-cleaning surfaces, air and water purification systems, microbial inactivation and selective organic conversion. The synthesis of titanium dioxide nanomaterials with high photocatalytic activity is actually a major challenge. Here we review titanium dioxide photocatalysis with focus on mechanims, synthesis, and applications. Synthetic methods include sol-gel, sonochemical, microwave, oxidation, deposition, hydro/solvothermal, and biological techniques. Applications comprise the production of energy, petroleum recovery, and the removal of microplastics, pharmaceuticals, metals, dyes, pesticides, and of viruses such as the severe acute respiratory syndrome coronavirus 2.

A mini-review on innovative strategies for simultaneous microbial bioremediation of toxic heavy metals and dyes from wastewater.

Bioremediation of heavy metals and dyes is one of the emerging techniques globally as it is evident from the numerous publications made by various research groups. Biofilm-assisted bioremediation is one of the trending approaches as it facilitates negatively charged extracellular polymeric substances which makes the bacteria resistant to the toxic chemicals. Genetic engineering of microbes will make them unique in the bioremediation process. This mini-review concentrates on source and toxic effects of heavy metals and dyes on aqueous and living beings. Further, the genetic improvement strategies for effective bioremediation are described. However, the gap between practicability and real-time applicability needs to test with real-time wastewater in the industrial scale.

Removal of toxic metals from wastewater environment by graphene-based composites: A review on isotherm and kinetic models, recent trends, challenges and future directions.

Access to clean water has reduced in recent years due to pollution and man-made activities. Wastewater treatment regimens are many such as electrocoagulation, adsorption, ozonation, membrane and advanced oxidation processes. Owing to economical, resource availability and ease of operation adsorption has upper hand over all other methods employed in wastewater treatment. Graphene based adsorbents attracted researchers due to their ability to play dual role as adsorbent and photo-catalysts. When it comes to removal of heavy metals and dyes graphene-based aerogels are successful. Graphene composites were predominantly synthesized by top-down and bottom-up approach methods. Graphene composites are mesoporous and have microporous structure on surface. Graphene has copper desorption efficiency of 90 % upon 10th consecutive cycle. Graphene based adsorbents have adsorption efficiency of 367, 246 and 106.3 mg-1 for lead, zinc and cadmium respectively. Though graphene possesses numerous applications, this review was devoted towards heavy metals removal from aqueous environment. In detail, the synthesis routes and interaction mechanism were explained and also the adsorption isotherms, kinetics were added. This review will serve as support for future research directions on removal of wastewater contaminants (heavy metals).

Bioremediation of organic pollutants: a mini review on current and critical strategies for wastewater treatment.

The release and prevalence of organic pollutants in an aqueous environment due to industrial discharges, agricultural operations, or inappropriate waste disposal is a huge threat to attaining sustainable development. As a result, wastewater treatment has attained a huge scope as it is evident from the number of articles published in recent years. Among the various techniques, bioremediation is one of the economical and eco-friendly means of wastewater treatment for the removal of organic pollutants. Microbial community and microalgae are the front runners of this process as they result in treated water and sludge or biomass formation. This mini review put forwards the types of organic pollutants and the bioremediation strategies using microbes and micro-algae, the role of genetically engineered microbes on the bio-remediation of organic pollutants and the recent applications of Artificial Intelligence (AI) techniques that have been implemented for improving the efficiency of the methods. The gap between practicability and applicability of the bioremediation process was also identified in this review. In addition, the economics and future research needs are discussed as outcomes.

Adsorptive separation of toxic metals from aquatic environment using agro waste biochar: Application in electroplating industrial wastewater.

In this research, raw jujube seeds (RJS) treated with sulphuric acid followed by ultrasonic treatment such as ultrasonic assisted jujube seeds (UAJS) based biochar have been experimented as a viable material for treating Zn(II) and Pb(II) contaminated water. The adsorption ability of UAJS was compared with RJS through Langmuir adsorption capacity. The produced adsorbents were analysed by using BET surface area and thermogravimetric analyses. The removal kinetics, isotherms and thermodynamic behaviours of metal ions adsorption by UAJS were studied. Adsorption equilibrium data were analysed using various equilibrium models and Freundlich isotherm was appropriate towards explain the adsorption characteristics. UAJS Langmuir capacity of 221.1 mg/g and 119.8 mg/g were obtained for Zn(II) ions and Pb(II) ions, respectively. The results observed that UAJS holds higher capacity as compared with RJS. The pseudo-first order model was relevant to address adsorption behaviour. The mechanism on the separation of metal ions by UAJS was tested using diffusion and Boyd models. The mechanism outcomes observed that the internal and external diffusion controlled the separation process. The thermodynamic results explain the separation process was viable, exothermic and natural. The electroplating industrial wastewater was also treated with UAJS biochar to remove the metal ions such as copper, nickel, chromium and zinc ions from wastewater. Desorption process showed that 0.1 N HCl provide the good results as compared with other desorbing agents. The adsorbent property is not lost till the maximum of 5 adsorption/desorption cycles. The produced UAJS can be a better adsorbent for treating the heavy metal polluted wastewater.

Recent advancements in supporting materials for immobilised photocatalytic applications in waste water treatment.

The aim of this paper is to provide a review on the usage of different anchoring media (supports) for immobilising commonly employed photocatalysts for degradation of organic pollutants. The immobilisation of nano-sized photocatalysts can eliminate costly and impractical post-treatment recovery of spent photocatalysts in largescale operations. Some commonly employed immobilisation aids such as glass, carbonaceous substances, zeolites, clay and ceramics, polymers, cellulosic materials and metallic agents that have been previously discussed by various research groups have been reviewed. The study revealed that factors such as high durability, ease of availability, low density, chemical inertness and mechanical stability are primary factors responsible for the selection of suitable supports for catalysts. Common techniques for immobilisation namely, dip coating, cold plasma discharge, polymer assisted hydrothermal decomposition, RF magnetron sputtering, photoetching, solvent casting, electrophoretic deposition and spray pyrolysis have been discussed in detail. Finally, some common techniques adopted for the characterisation of the catalyst particles and their uses are also discussed.

HPTLC fingerprint profile, in vitro antioxidant and evaluation of antimicrobial compound produced from Brevibacillus brevis-EGS9 against multidrug resistant Staphylococcus aureus.

In the present study, in vitro antimicrobial activity of Brevibacillus brevis EGS9 against multi drug resistant Staphylococcus aureus (MDRSA) and to investigate the antimicrobial, antioxidant activity and HPTLC finger print profile of Brevibacillus brevis EGS9. Primary screening was done using by cross streak method against multi drug resistant Staphylococcus aureus. The bioactive metabolites were extracted from Brevibacillus brevis EGS9 using ethyl acetate extraction. Ethyl acetate extract showed significant antimicrobial activity against Escherichia coli (20.2 ± 0.1) mm, Candida albicans (19.2 ± 0.3) mm and Bacillus cereus (18.6 ± 0.2) mm respectively. Forty three UTI bacterial strains were isolated from mid-urine samples of 50 males and 50 females. Escherichia coli were more predominant (48%) followed by Klebsilla pneumonia (29%), Pseudomonas aeruginosa (17%), Staphylococcus aureus (4%) and Enterobacter faecalis (6%). The ethyl acetate extract was examined to evaluate antibacterial properties against isolated UTIs bacterial pathogens. The results were revealed that the maximum zone was measured in Escherichia coli (18.1 ± 0.4) mm and minimum zone of inhibition was shown against Pseudomonas aeruginosa (10.6 ± 0.3) mm. Based on the results obtained, the extract of Brevibacillus brevis EGS9 exhibited dose dependent manner of antioxidant activity. The DPPH scavenging activity of lowest concentration at 25 µg/ml and high concentration at 1000 µg/ml was measured at 2.4% and 39.5% respectively. HPTLC finger print profile was showed the active compounds present in crude extract, which may responsible for the antioxidant prospective. These results showed that, the significant antimicrobial properties against pathogen; this work will be helpful to explore the active compound identification in the field of pharmaceutical research and able to produce new drug molecules against pathogens.