Removal of COD and SO42− from Oil Refinery Wastewater Using a Photo-Catalytic System—Comparing TiO2 and Zeolite Efficiencies

Exploring zeolite-based composites in adsorption and photocatalysis for toxic wastewater treatment: Preparation, mechanisms, and future perspectives

Water scarcity has become a critical global concern exacerbated by population growth, globalization, and industrial expansion, resulting in the production of wastewater containing a wide array of contaminants. Tackling this challenge necessitates the adoption of innovative materials and technologies for effective wastewater treatment. This review article provides a comprehensive exploration of the preparation, applications, mechanisms, and economic environmental analysis of zeolite-based composites in wastewater treatment. Zeolite, renowned for its versatility and porous nature, is of paramount importance due to its exceptional properties, including high surface area, ion exchange capability, and adsorption capacity. Various synthetic methods for zeolite-based composites are discussed. The utilization of zeolites in wastewater treatment, particularly in adsorption and photocatalysis, is thoroughly investigated. The significance of zeolite in adsorption and its role in the photocatalytic degradation of pollutants are examined, along with its applications in treating volatile organic compounds (VOCs), dye wastewater, oil-field wastewater, and radioactive waste. Mechanisms underlying zeolite-based adsorption and photocatalysis, including physical and chemical adsorption, ion exchange, and surface modification, are elucidated. Additionally, the role of micropores in the adsorption process is explored. Furthermore, the review delves into regeneration and desorption studies of zeolite-based composites, crucial for sustainable wastewater treatment practices. Economic and environmental analyses are conducted to assess the feasibility and sustainability of employing zeolite-based composites in wastewater treatment applications. Future recommendations are provided to guide further research and development in the field of zeolite-based composites, aiming to enhance wastewater treatment efficiency and environmental sustainability. By exploring the latest advancements and insights into zeolite-based nanocomposites, this paper aims to contribute to the development of more efficient and sustainable wastewater treatment strategies. The integration of zeolite-based materials in wastewater treatment processes shows promise for mitigating water pollution and addressing water scarcity challenges, ultimately contributing to environmental preservation and public health protection.

A Case Study of Swine Wastewater Treatment via Electrochemical Oxidation by Ti4O7 Anode

With the rapid development of breeding industry, the efficient treatment of dramatically increasing swine wastewater is gradually becoming urgent. In particular, the development of application technologies suitable for the relatively small piggeries is critical due to the time cost and space requirements of conventional biological methods. In this study, Electrochemical oxidation (EO) was selected to systematically explore the treatment performance of three different swine wastewaters by Ti₄O₇ anode. It was observed that the colors changed from dark brown to light yellow after 60 min treatment at 50 mA/cm², and the removal rates of turbidity and suspended solids ranged from 89.36% to 93.65% and 81.31% to 92.55%, respectively. The chemical oxygen demand (COD), ammonia nitrogen (NH₃-N) and total phosphorus (TP) of all the three swine wastewaters were simultaneously removed to a very low concentration in 120 min, especially for sample III, 61 ± 9 mg/L of COD, 6.6 ± 0.4 mg/L of NH₃-N and 5.7 ± 1.1 mg/L of TP, which met the Discharge Standard of Pollutants for Livestock and Poultry Breeding (GB 18596-2001). Moreover, 70.93%-85.37% mineralization rates were also achieved in 120 min, confirming that EO treatment by Ti₄O₇ could efficiently remove the organic matters in wastewater. Excitation-emission matrix (EEM) and UV-vis spectrum characterization results further proved that aromatic compounds and macromolecules in wastewater were rapidly removed, which played important roles in the mineralization processes. The findings here provided an efficient and environment-friendly technology for swine wastewater treatment.

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.

Effectiveness of environmental surveillance of SARS-CoV-2 as an early warning system during the first year of the COVID-19 pandemic: a systematic review

Since infected persons shed SARS-CoV-2 in faeces before symptoms appear, environmental surveillance (ES) may serve as an early warning system (EWS) for COVID-19 and new variants of concern. The ES of SARS-CoV-2 has been widely reviewed; however, its effectiveness as an EWS for SARS-CoV-2 in terms of timeliness, sensitivity and specificity has not been systematically assessed. We conducted a systematic review to identify and synthesise evidence on the ES of SARS-CoV-2 as an EWS to evaluate the added value for public health. Of 1,014 studies identified, we considered 29 for a qualitative synthesis of the timeliness of ES as an EWS for COVID-19, while six studies were assessed for the ability to detect new variants and two for both aims. The synthesis indicates ES may serve as an EWS of 1-2 weeks. ES could complement clinical surveillance for SARS-CoV-2; however, its cost-benefit value for public health decisions needs to be assessed based on the stage of the pandemic and resources available. Studies focusing methodological knowledge gaps as well as how to use and interpret ES signals for public health actions are needed, as is the sharing of knowledge within countries/areas with long experience of such surveillance.

Review of concerned SARS-CoV-2 variants like Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2), and Omicron (B.1.1.529), as well as novel methods for reducing and inactivating SARS-CoV-2 mutants in wastewater treatment facilities

The coronavirus known as COVID-19, which causes pandemics, is causing a global epidemic at a critical stage today. Furthermore, novel mutations in the SARS-CoV-2 spike protein have been discovered in an entirely new strain, impacting the clinical and epidemiological features of COVID-19. Variants of these viruses can increase the transmission in wastewater, lead to reinfection, and reduce immunity provided by monoclonal antibodies and vaccinations. According to the research, a large quantity of viral RNA was discovered in wastewater, suggesting that wastewater can be a crucial source of epidemiological data and health hazards. The purpose of this paper is to introduce a few basic concepts regarding wastewater surveillance as a starting point for comprehending COVID-19′s epidemiological aspects. Next, the observation of Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2), and Omicron (B.1.1.529) in wastewater is discussed in detail. Secondly, the essential information for the initial, primary, and final treating sewage in SARS-CoV-2 is introduced. Following that, a thorough examination is provided to highlight the newly developed methods for eradicating SARS-CoV-2 using a combination of solar water disinfection (SODIS) and ultraviolet radiation A (UVA (315-400 nm)), ultraviolet radiation B (UVB (280-315 nm)), and ultraviolet radiation C (UVC (100-280 nm)) processes. SARS-CoV-2 eradication requires high temperatures (above 56°C) and UVC. However, SODIS technologies are based on UVA and operate at cooler temperatures (less than 45°C). Hence, it is not appropriate for sewage treatment (or water consumption) to be conducted using SODIS methods in the current pandemic. Finally, SARS-CoV-2 may be discovered in sewage utilizing the wastewater-based epidemiology (WBE) monitoring method.

Consequence of COVID-19 occurrences in wastewater with promising recognition and healing technologies: A review

Presently, the coronavirus (COVID-19) epidemic presents a major threat to global communal fitness also socio-financial development. Ignoring worldwide isolation as well as shutdown attempts, the occurrence of COVID-19 infected patients continues to be extremely large. Nonetheless, COVID-19's final course, combined with the prevalence of emerging contaminants (antibiotics, pharmaceuticals, nanoplastics, pesticides, and so forth) in wastewater treatment plants (WWTPs), presents a major problem in wastewater situations. The research, therefore, intends near examine an interdisciplinary as well as technical greet to succor COVID-19 with subsequent COVID cycles of an epidemic as a framework for wastewater treatment settings. This research investigated the potential for wastewater-based epidemiology to detect SARS-CoV-2 also the enzymes happening in wastewater conditions. In addition, a chance for the incorporation into the WWTPs of emerging and robust technologies such as mesmeric nanobiotechnology, electrochemical oxidation, microscopy, and membrane processes to enhance the overall likelihood of environmental consequences of COVID-19 also strengthen such quality of water is resolved.

Membrane Bioreactors for Produced Water Treatment: A Mini-Review

Environmentalists are prioritizing reuse, recycling, and recovery systems to meet rising water demand. Diving into produced water treatment to enable compliance by the petroleum industry to meet discharge limits has increased research into advanced treatment technologies. The integration of biological degradation of pollutants and membrane separation has been recognized as a versatile technology in dealing with produced water with strength of salts, minerals, and oils being produced during crude refining operation. This review article presents highlights on produced water, fundamental principles of membrane bioreactors (MBRs), advantages of MBRs over conventional technologies, and research progress in the application of MBRs in treating produced water. Having limited literature that specifically addresses MBRs for PW treatment, this review also attempts to elucidate the treatment efficiency of MBRs PW treatment, integrated MBR systems, general fouling, and fouling mitigation strategies.

Assessment of Forward Osmosis in PRO Mode during Desalination of a Local Oil Refinery Effluent

In this study, the performance of a forward osmosis system was assessed over a 30-h period during desalination of a local oil refinery effluent using NaCl as the draw solute. The study was conducted with the active layer of the membrane facing the draw solution. Assessment was done based on the water flux, salt rejection (SO₄²⁻ and CO₃²⁻), membrane fouling and fouling reversal after membrane cleaning. Critical to this study was the performance of manual scrubbing of the membrane after each run and the application of chemically enhanced osmotic backwash. Scanning electron microscope (SEM) analysis of the cellulose triacetate (CTA) membrane was conducted before and after cleaning to ascertain the degree of fouling and fouling reversal after membrane cleaning. The results showed an average water flux of 3.78 ± 0.13 L/m² h, reverse solute flux (RSF) of 1.56 ± 0.11 g/m²·h, SO₄²⁻ rejection of 100%, CO₃²⁻ rejection of 95.66 ± 0.32% and flux recovery of 95% after membrane cleaning. This study identifies that intermittent manual scrubbing of the membrane plays a major role in overall membrane performance. It also provides a practical basis for further research and decision making in the use of FO and CTA membranes for oil refinery effluent desalination.

Performance Evaluation of Ultra-Violet Light and Iron Oxide Nanoparticles for the Treatment of Synthetic Petroleum Wastewater: Kinetics of COD Removal

In this study, the use of ultra-violet (UV) light with or without iron oxide nanoparticles (IONPs) for the degradation of synthetic petroleum wastewater was investigated. The IONPs was synthesised by sodium borohydride reduction of ferric chloride solution and was characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FTIR), x-ray fluorescence spectrophotometry (XRF), and energy dispersive spectroscopy (EDS). The amount of degradation was evaluated by chemical oxygen demand (COD) determination. Experimental results show that the COD removal from synthetic petroleum wastewater by IONPs/UV system was more effective than they were independently. The combination of UV light at a wavelength of 254 nm, pH of 8, and 1.0 g of IONPs resulted in COD removal from 10.5% up to 95.5%. The photocatalytic degradation of synthetic petroleum wastewater is about 1.3-2.0 times faster in comparison to UV light only. The removal of COD from synthetic petroleum wastewater by UV light and IONPs follows the pseudo-first-order kinetic model with rate constant k ranging from 0.0133 min^-1 to 0.0269 min^-1. Consequently, this study has shown that the use of UV light in the presence of IONPs is favourable and effective for the removal of organic pollutants from petroleum refinery wastewater.

Prospects of Synthesized Magnetic TiO2-Based Membranes for Wastewater Treatment: A Review

Global accessibility to clean water has stressed the need to develop advanced technologies for the removal of toxic organic and inorganic pollutants and pathogens from wastewater to meet stringent discharge water quality limits. Conventionally, the high separation efficiencies, relative low costs, small footprint, and ease of operation associated with integrated photocatalytic-membrane (IPM) technologies are gaining an all-inclusive attention. Conversely, photocatalysis and membrane technologies face some degree of setbacks, which limit their worldwide application in wastewater settings for the treatment of emerging contaminants. Therefore, this review elucidated titanium dioxide (TiO2), based on its unique properties (low cost, non-toxicity, biocompatibility, and high chemical stability), to have great potential in engineering photocatalytic-based membranes for reclamation of wastewater for re-use. The environmental pathway of TiO2 nanoparticles, membranes and configuration types, modification process, characteristics, and applications of IPMs in water settings are discussed. Future research and prospects of magnetized TiO2-based membrane technology is highlighted as a viable water purification technology to mitigate fouling in the membrane process and photocatalyst recoverability. In addition, exploring life cycle assessment research would also aid in utilizing the concept and pressing for large-scale application of this technology.

Response Surface Methodology: Photocatalytic Degradation Kinetics of Basic Blue 41 Dye Using Activated Carbon with TiO2

Water decontamination still remains a major challenge to some developing countries not having centralized wastewater systems. Therefore, this study presents the optimization of photocatalytic degradation of Basic Blue 41 dye in an aqueous medium by an activated carbon (AC)-TiO₂ photocatalyst under UV irradiation. The mesoporous AC-TiO₂ synthesized by a sonication method was characterized by X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy for crystal phase identification and molecular bond structures, respectively. The efficiency of the AC-TiO₂ was evaluated as a function of three input variables viz. catalyst load (2-4 g), reaction time (15-45 min) and pH (6-9) by using Box-Behnken design (BBD) adapted from response surface methodology. Using color and turbidity removal as responses, a 17 run experiment matrix was generated by the BBD to investigate the interaction effects of the three aforementioned input factors. From the results, a reduced quadratic model was generated, which showed good predictability of results agreeable to the experimental data. The analysis of variance (ANOVA), signposted the selected models for color and turbidity, was highly significant (p < 0.05) with coefficients of determination (R²) values of 0.972 and 0.988, respectively. The catalyst load was found as the most significant factor with a high antagonistic impact on the process, whereas the interactive effect of reaction time and pH affected the process positively. At optimal conditions of catalyst load (2.6 g), reaction time (45 min), and pH (6); the desirability of 96% was obtained by a numerical optimization approach representing turbidity removal of 93% and color of 96%.

Fate of COVID-19 Occurrences in Wastewater Systems: Emerging Detection and Treatment Technologies—A Review

The coronavirus (COVID-19) pandemic is currently posing a significant threat to the world’s public health and social-economic growth. Despite the rigorous international lockdown and quarantine efforts, the rate of COVID-19 infectious cases remains exceptionally high. Notwithstanding, the end route of COVID-19, together with emerging contaminants’ (antibiotics, pharmaceuticals, nanoplastics, pesticide, etc.) occurrence in wastewater treatment plants (WWTPs), poses a great challenge in wastewater settings. Therefore, this paper seeks to review an inter-disciplinary and technological approach as a roadmap for the water and wastewater settings to help fight COVID-19 and future waves of pandemics. This study explored wastewater–based epidemiology (WBE) potential for detecting SARS-CoV-2 and its metabolites in wastewater settings. Furthermore, the prospects of integrating innovative and robust technologies such as magnetic nanotechnology, advanced oxidation process, biosensors, and membrane bioreactors into the WWTPs to augment the risk of COVID-19’s environmental impacts and improve water quality are discussed. In terms of the diagnostics of COVID-19, potential biosensors such as sample–answer chip-, paper- and nanomaterials-based biosensors are highlighted. In conclusion, sewage treatment systems, together with magnetic biosensor diagnostics and WBE, could be a possible way to keep a surveillance on the outbreak of COVID-19 in communities around the globe, thereby identifying hotspots and curbing the diagnostic costs of testing. Photocatalysis prospects are high to inactivate coronavirus, and therefore a focus on safe nanotechnology and bioengineering should be encouraged.

Exposure Route of TiO2 NPs from Industrial Applications to Wastewater Treatment and Their Impacts on the Agro-Environment

The tremendous increase in the production and consumption of titanium dioxide (TiO2) nanoparticles (NPs) in numerous industrial products and applications has augmented the need to understand their role in wastewater treatment technologies. Likewise, the deleterious effects of wastewater on the environment and natural resources have compelled researchers to find out most suitable, economical and environment friendly approaches for its treatment. In this context, the use of TiO2 NPs as the representative of photocatalytic technology for industrial wastewater treatment is coming to the horizon. For centuries, the use of industrial wastewater to feed agriculture land has been a common practice across the globe and the sewage sludge generated from wastewater treatment plants is also used as fertilizer in agricultural soils. Therefore, it is necessary to be aware of possible exposure pathways of these NPs, especially in the perspective of wastewater treatment and their impacts on the agro-environment. This review highlights the potential exposure route of TiO2 NPs from industrial applications to wastewater treatment and its impacts on the agro-environment. Key elements of the review present the recent developments of TiO2 NPs in two main sectors including wastewater treatment and the agro-environment along with their potential exposure pathways. Furthermore, the direct exposure routes of these NPs from production to end-user consumption until their end phase needs to be studied in detail and optimization of their suitable applications and controlled use to ensure environmental safety.

Photocatalytic degradation of oily waste and phenol from a local South Africa oil refinery wastewater using response methodology

The photocatalytic degradation of a local South Africa oil refinery wastewater was conducted under UV radiation using an aqueous catalyst of titanium dioxide (TiO2), Degussa P25 (80% anatase, 20% rutile) in suspension. The experiment was carried out in a batch aerated photocatalytic reactor based on a central composite design (CCD) and analyzed using response surface methodology (RSM). The effects of three operational variables viz. TiO2 dosage (2-8 g/L), runtime (30-90 minutes), and airflow rate (0.768-1.48 L/min) were examined for the removal of phenol and soap oil and grease (SOG). The data derived from the CCD, and the successive analysis of variance (ANOVA) showed the TiO2 dosage to be the most influential factor, while the other factors were also significant (P < 0.0001). Also, the ANOVA test revealed the second-order of TiO2 dosage and runtime as the main interaction factors on the removal efficiency. To maximize the pollutant removal, the optimum conditions were found at runtime of 90 minutes, TiO2 dosage of 8 g/L, and an aeration flow rate of 1.225 L/min. Under the conditions stated, the percentage removal of phenol (300 ± 7) and SOG (4000 ± 23) were 76% and 88% respectively. At 95% confidence level, the predicted models developed results were in reasonable agreement with that of the experimental data, which confirms the adaptability of the models. The first-order kinetic constants were estimated as 0.136 min-1 and 0.083 min-1 for SOG and phenol respectively.

Membrane Technologies in Wastewater Treatment: A Review

In the face of water shortages, the world seeks to explore all available options in reducing the over exploitation of limited freshwater resources. One of the surest available water resources is wastewater. As the population grows, industrial, agricultural, and domestic activities increase accordingly in order to cater for the voluminous needs of man. These activities produce large volumes of wastewater from which water can be reclaimed to serve many purposes. Over the years, conventional wastewater treatment processes have succeeded to some extent in treating effluents for discharge purposes. However, improvements in wastewater treatment processes are necessary in order to make treated wastewater re-usable for industrial, agricultural, and domestic purposes. Membrane technology has emerged as a favorite choice for reclaiming water from different wastewater streams for re-use. This review looks at the trending membrane technologies in wastewater treatment, their advantages and disadvantages. It also discusses membrane fouling, membrane cleaning, and membrane modules. Finally, recommendations for future research pertaining to the application of membrane technology in wastewater treatment are made.

Evaluating Pre- and Post-Coagulation Configuration of Dissolved Air Flotation Using Response Surface Methodology

The effects of coagulation-dissolved air flotation (DAF) process configuration was studied on oil refinery wastewater. The configuration was done in two ways: acid-coagulation-DAF (pre-treatment) and acid-DAF-coagulation (post-treatment). Two different cationic and polymeric organic coagulants were employed in this study to compare their treatability performance with the two aforementioned configurations. All the coagulants applied before the DAF were found to be effective, with over 85% more contaminant removal efficiency than their post-treatment. Alum, being the most cost-effective coagulant, was then employed with response surface methodology (RSM) to obtain the optimum conditions. These include a coagulant dosage of 100 mg/L, air saturator pressure of 375 kPa and air–water ratio of 10% vol/vol corresponding to a desirability of 92% for the removal of oily pollutants from a local South Africa oil refinery’s wastewater. With the response quadratic models that were developed, the optimum conditions were tested experimentally, which were consistent with the models predicted results at a 95% confidence level.