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Experimental conditions of different variables while conducting the inactivation of A .hydrophila through TFFBR
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Background
Controlling fish disease is one of the major concerns in contemporary aquaculture. The use of antibiotics or chemical disinfection cannot provide a healthy aquaculture system without residual effects. Water quality is also important in determining the success or failure of fish production. Several solar photocatalytic reactors have been...
Contexts in source publication
Context 1
... the other hand, with the same experimental conditions, unfiltered pond water showed a log inactivation of 0.2 under aerobic condition and 0.15 log CFU mL -1 under ROS- neutralised condition. During the experiments, several water quality variables (pH, salinity conductivity and tur- bidity levels) were measured before and after treating the water samples through the TFFBR (Table 2). Table 2 shows that there was no major change in pH levels during the experiments for each water sample. ...
Context 2
... the experiments, several water quality variables (pH, salinity conductivity and tur- bidity levels) were measured before and after treating the water samples through the TFFBR (Table 2). Table 2 shows that there was no major change in pH levels during the experiments for each water sample. Sal- inity (conductivity) levels were slightly higher with the pond waters (filtered or un-filtered) once they had passed across the TFFBR. ...
Context 3
... pH and salinity showed no major effect to support this difference in individual experiments (Figures 2 and 4), it seems reasonable to propose that the other measured variable, turbidity, is likely to have a major role. From Table 2, every experiment with unfiltered pond water showed a turbidity level at or above 50, whereas the turbidity levels for spring water and filtered pond water were only 0 and 1-3, respectively. Experi- mental results from Figure 4 also showed that highly turbid water samples have a negative effect on solar photocatalysis. ...
Citations
... Pretreatment technology can prevent some substances in the wastewater and inappropriate reaction conditions from inhibiting the photocatalytic efficiency. For example, a filter device can be installed at the reactor water inlet of the reactor to intercept large particles and prevent high turbidity from negatively impacting wastewater photocatalytic efficiency [159]. Similarly, sulfate and chloride ions in the wastewater need to be treated before the wastewater enters the PWTR, this is because sulfate and chloride ions in wastewater may adversely affect the photocatalytic process by removing ROS or causing photocatalyst aggregation [160]. ...
Photocatalytic wastewater treatment technology has been proposed for more than 30 years, but it is still seldom used in industry. The lack of research on high-performance and cost-effective photocatalytic wastewater treatment reactors (PWTRs) may be one of the major reasons limiting the industrial application of photocatalytic technology. To accelerate the realization of industrial application, this review emphasizes the importance of increased research on PWTRs. In this review, we analyze the role of photocatalytic technology in wastewater treatment, followed by a comprehensive discussion of PWTR design from multiple perspectives, including photocatalyst selection, loading and recovery method of photocatalysts within the reactor, light source design, and reaction conditions control. Additionally, we consider the cost of reactor design. Finally, we summarize the optimization strategy of PWTRs and the criteria for evaluating photocatalytic performance. The main innovation of this review lies in a comprehensive analysis of PWTR design, with a focus on cost-effective and high-performance solutions to promote the industrial use of photocatalytic technology.
... To save energy, various reactors with immobilized TiO 2 -catalyst coatings in combination with solar light have been developed. Illumination/activation of catalysts with artificial light is costly; hence, solar radiation serves as an environmentally friendly and sustainable alternative [21][22][23][24][25]. ...
This study presents a simple and sustainable coating technology for the deposition of
photocatalytic coatings based on titanium dioxide and geopolymers, which requires no thermal
post-treatment. Titania powder P25, potassium silicate and a calcium aluminate-based hardener were
dispersed in water and applied to aluminum substrates using a paintbrush, a roller and a spray gun.
The coatings were air-dried for 12 h. The photocatalytic activities were tested via degradation of an
aqueous methylene blue solution in a batch reactor under artificial UV-A light. The roller and the
spray gun-based coatings yielded well-adhering coatings with high photocatalytic activity. Brushed
coatings were inhomogeneous and unstable. The presented method of producing photocatalytic
coatings is very simple to apply and does not require complex technologies or energy-intensive
thermal treatments.
... At a flowrate of 4.8 L h −1 , the inactivation of 1.3 log units of bacterial cells was achieved in a single pass of spring water through the reactive bed. The bacterial cells displayed injuries due to the attack of the reactive oxygen species [152]. ...
Nowadays, heterogeneous photocatalysis for water treatment and hydrogen production are topics gaining interest for scientists and developers from different areas, such as environmental technology and material science. Most of the efforts and resources are devoted to the development of new photocatalyst materials, while the modeling and development of reaction systems allowing for upscaling the process to pilot or industrial scale are scarce. In this work, we present what is known on the upscaling of heterogeneous photocatalysis to purify water and to produce green H2. The types of reactors successfully used in water treatment plants are presented as study cases. The challenges of upscaling the photocatalysis process to produce green H2 are explored from the perspectives of (a) the adaptation of photoreactors, (b) the competitiveness of the process, and (c) safety. Throughout the text, Green Chemistry and Engineering Principles are described and discussed on how they are currently being applied to the heterogeneous photocatalysis process along with the challenges that are ahead. Lastly, the role of automation and high-throughput methods in the upscaling following the Green Principles is discussed.
... TiO 2 fixed over different support materials such as glass balls, glass plates, cylinders is highly desirable for field-scale disinfection investigation. TiO 2 coated glass plates in a thin-film fixed-bed reactor (TFFBR) were used to study the inactivation of Aeromonas hydrophila and complete inactivation was observed with a flow rate of 4.8 L h − 1 (Khan et al., 2012). N-doped TiO 2 immobilized over glass beads was also utilized to analyze the disinfection studies and observed a 3 log reduction in 120 min of treatment time (Kassahun et al., 2020). ...
A low-cost waste-driven visible active iron-titanium oxide composite was fabricated for the treatment of real municipal wastewater. The structured composite was characterized using morphological and spectroscopic techniques such as FE-SEM, XRD, UV-DRS, indicating that the fabrication procedure could uniformly coat the TiO2 particles over the clay-supported composite spheres. The iron-titanium oxide composite was efficient in introducing a hybrid effect of photocatalysis and photo-Fenton that is being facilitated by the use of waste foundry sand (WFS) and waste fly ash (WFA) (both natural sources of iron) with a TiO2 layer on the outer surface. The main emphasis was given to the disinfection of bacteria along with the degradation of organic matter in terms of BOD and COD present in municipal wastewater. This hybrid technology showed 100% inactivation of bacteria with optimized parameters such as 0.9 g L⁻¹ of H2O2 dose, 5.5 pH, and 100% surface area covered with the catalyst in 60 min of treatment time. 54% and 40% reduction in BOD and COD was also observed in 60 min. The kinetic rate constant was found to be 2 times higher in the hybrid process as compared to the individual process. The damage to the cell wall was confirmed by potassium ion leakage and FE-SEM analysis. Fe–TiO2 composites demonstrated excellent stability even after recycling 35 times, indicating the lasting durability of the composites. The findings of this study demonstrate the possibility for waste materials to be used as a viable approach for the bacterial inactivation application with the potential of the field-scale application.
... Only a few studies have been reported on aquaculture water disinfection by photocatalysis where photocatalyst was used in immobilized form [16,17,[40][41][42]. Hence, the main goal of this work was to evaluate photocatalytic activity of TiO 2 thin films modified with graphene oxide reduced during photocatalysis (rGO) deposited on flexible substrate, which implies a scientific advance from a technological development and water application point of view. Effect of rGO concentration in the thin films was assessed based on the photocatalytic inactivation of microorganisms. ...
In this study TiO2/polysiloxane(SiBi) thin films modified with different concentrations of graphene oxide (GO) were prepared by ink-jet printing on flexible polyethylene terephthalate (PET) substrates. Prepared coatings were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), Raman and water contact angle measurements. During photocatalytic tests strong change of color of prepared coatings modified with GO was observed. XPS analysis of thin films after photocatalytic tests suggests that reduction of GO took place. Prepared coatings were studied for inactivation of microorganisms naturally occurring in aquaculture water under UVA and natural solar irradiation. Effect of rGO concentration in prepared coating on inactivation of target bacteria Aeromonas hydrophila and Citrobacter gillenii was evaluated under UVA irradiation. Aeromonas hydrophila was more sensitive to photocatalytic inactivation in comparison with Citrobacter gillenii. Higher photocatalytic inactivation of target microorganisms was attributed to thin films with concentration of rGO 1 and 5%. The rGO/TiO2/SiBi 5% were further tested for inactivation of Aeromonas salmocida, Serratia fonticola strain and Lactococcus lactis strain under natural solar light. Solar photocatalysis slightly enhanced inactivation of Aeromonas salmocida and Serratia fonticola strain, while opposite was observed for Lactococcus lactis strain.
... An efficient pre-treatment step may also help reduce the overall investment of a PWT unit. Filtration to decrease turbidity when significant may be necessary, as high turbidity affects the penetration of light especially in pilot-scale solar applications (Khan et al., 2012). A high water alkalinity can induce the aggregation of catalyst particles since some common photocatalysts have points of zero charge at pH below 7 (~6 for TiO 2 and ~4 for BiPO 4 ) (Chou and Liao, 2005;Daskalaki et al., 2010). ...
The debate on whether photocatalysis can reach full maturity at commercial level as an effective and economical process for treatment and purification of water and wastewater has recently intensified. Despite a bloom of scientific investigations in the last 30 years, particularly with regards to innovative photocatalytic materials, photocatalysis has so far seen a few industrial applications. Regardless of the points of view, it has been realized that research on reactor design and modeling are now equally urgent to match the extensive research carried out on innovative photocatalytic materials. In reality, the development of photocatalytic reactors has advanced steadily in terms of modeling and reactor design over the last two decades, though this topic has captured a smaller specialized audience. In this critical review, we introduce the latest developments on photocatalytic reactors for water treatment from an engineering perspective. The focus is on the modeling and design of photocatalytic reactors for water treatment at pilot- or at greater scale. Photocatalytic reactors utilizing both natural sunlight and UV irradiation sources are comprehensively discussed. The most promising photoreactor designs and models are examined giving key design guidelines. Other engineering considerations, such as operation, cost analysis, patents, and several industrial applications of photocatalytic reactors for water treatment are also presented. The dissemination of key photocatalytic reactor design principles among the scientific community and the water industry is currently one of the greatest obstacles in translating PWT research into widespread real-world application.
... The presence of suspended particulate matter has an adverse effect on photocatalytic disinfection, as the transmission of light is hindered and scattering paths are obstructed . Generally, the increase of turbidity of an aqueous media inhibits photocatalytic disinfection , Dunlop et al., 2011, Khan et al., 2012, Rincón and Pulgarin, 2003, Sreeja and Shetty, 2017. However, the turbidity value is not the only measure in assessing the effect of suspended materials on photocatalytic disinfection efficiency. ...
... This is especially significant between pH 6 and 7, whereas the decrease is gradual in acidic (pH 4-6) and alkaline (pH 7-9) conditions (Chong et al., 2011;Deng et al., 2017;Liang et al., 2015). It is notable that the effect on the photocatalytic disinfection efficiency is due to the influences of pH change on the photocatalyst material and the photogenerated reactive species, but not the influence on the bacteria cell, of which the viability is stable under the same experimental conditions with a pH range of 5-9 (Chong et al., 2011;Deng et al., 2017;Khan et al., 2012;Liang et al., 2015). ...
This critical review covers ways to improve TiO2-based photocatalysts, how water characteristics may affect photocatalytic disinfection, and strategies to tackle the challenges arising from water characteristics. Photocatalysis has shown much promise in the disinfection of water/wastewater, because photocatalysis does not produce toxic by-products, and is driven by green solar energy. There are however several drawbacks that are curbing the prevalence of photocatalytic disinfection applications: one, the efficiency of photocatalysts may limit popular utilization; two, the water characteristics may present some challenges to the process. TiO2-based photocatalysts may be readily improved if composited with noble metals or carbon nanomaterials. Noble metals give TiO2-based composites a higher affinity for dissolved oxygen, and induce plasmonic and Schottky effects in the TiO2; carbon nanomaterials with a tunable structure, on the other hand, give the composites an improved charge carrier separation performance. Other than photocatalyst materials, the characteristics of water/wastewater is another crucial factor in the photocatalysis process. Also examined in this review are the crucial impacts that water characteristics have on photocatalysts and their interaction with bacteria. Accordingly, strategies to address the challenge of water characteristics on photocatalytic disinfection are explored: one, to modify the semiconductor conduction band to generate long-lifetime reactive species; two, to improve the interaction between bacteria and photocatalysts.
... This feature makes titania active mainly under the UV spectral range, which is a small fraction of the solar light [19]. Nevertheless, and despite this limitation, there are numerous studies that have investigated the efficiency of pure titania regarding the oxidation of chemical compounds and the inactivation of pathogens under solar light (Tables 1 and 2) [3,20]. Fanourgiakis et al. (2014) studied the simultaneous elimination of synthetic estrogen 17α-ethynylestradiol (EE2) and inactivation of Escherichia coli in wastewater, applying simulated solar light and TiO 2 . ...
... Respective attempts have been made in the field of disinfection. Khan et al. (2012) worked with a thin-film fixed-bed reactor (TFFBR) for the inactivation of aquaculture pathogen Aeromonas hydrophila, demonstrating that high sunlight intensities (>600 W/m 2 ) and low flow rates (4.8 L/h) play key role in the inactivation of this fish pathogen [20]. achieved a 6 Log reduction of E. coli within 90 min, using TiO 2 immobilized on Ahlstrom paper in a compound parabolic collector (CPC reactor), highlighting that low flow rates contribute to a more efficient photocatalytic disinfection [50]. ...
... Respective attempts have been made in the field of disinfection. Khan et al. (2012) worked with a thin-film fixed-bed reactor (TFFBR) for the inactivation of aquaculture pathogen Aeromonas hydrophila, demonstrating that high sunlight intensities (>600 W/m 2 ) and low flow rates (4.8 L/h) play key role in the inactivation of this fish pathogen [20]. achieved a 6 Log reduction of E. coli within 90 min, using TiO 2 immobilized on Ahlstrom paper in a compound parabolic collector (CPC reactor), highlighting that low flow rates contribute to a more efficient photocatalytic disinfection [50]. ...
This mini-review article discusses the critical factors that are likely to affect the performance of solar photocatalysis for environmental applications and, in particular, for the simultaneous degradation of emerging micro-pollutants and the inactivation of microbial pathogens in aqueous matrices. Special emphasis is placed on the control of specific operating factors like the type and the form of catalysts used throughout those processes, the intriguing role of the water matrix, and the composition of the microbial load of the sample in each case. The interplay among the visible responsive catalyst, the target pollutants/pathogens, including various types of microorganisms and the non-target water matrix species, dictates performance in an unpredictable and case-specific way. Case studies referring to lab and pilot-scale applications are presented to highlight such peculiarities. Moreover, current trends regarding the elimination of antibiotic-resistant bacteria and resistance genes by means of solar photocatalysis are discussed. The antibiotic resistance dispersion into the aquatic environment and how advanced photocatalytic processes can eliminate antibiotic resistance genes in microbial populations are documented, with a view to investigate the prospect of using those purification methods for the control-resistant microbial populations found in the environment. Understanding the interactions of the various water components (both inherent and target species) is key to the successful operation of a treatment process and its scaling up.
... Similar results observed by Sontakke et al. (2011) reveal that chloride ions have greater affinity to adsorb over the TiO 2 surface. At the same time, Khan et al. (2012) reported that variation in the saline condition has no substantial effect on the solar photocatalytic thin film-fixed bed reactor for the inactivation of Aeromonas hydrophila with high sunlight and low flow rate. Whereas Chong et al. (2010) reported that calcium and magnesium have only negligible effect on the photocatalytic degradation of organic compounds, because of their maximum oxidation states resulted in their inability to inhibit the photocatalytic degradation process. ...
Pilot scale thin film plate reactors (TFPR) were fabricated to study the solar photocatalytic treatment of wastewater obtained from the secondary treatment plant of a sugar refinery. Silver-impregnated titanium dioxide (TiO2) was prepared by a facile chemical reduction method, characterized, and immobilized onto the surface of ceramic tiles used in the pilot scale reactors. On 8 h of solar irradiation, percentage reduction of chemical oxygen demand (COD) of the wastewater by Ag/TiO2, pure TiO2, and control (without catalyst) TFPR was about 95, 86, and 22 % respectively. The effects of operational parameters such as, flow rate, pH, and addition of hydrogen peroxide (H2O2) were optimized as they influence the rate of COD reduction. Under 3 h of solar irradiation, 99 % COD reduction was observed at an optimum flow rate of 15 L h−1, initial pH of 2, and addition of 5 mM of H2O2. The results show that Ag/TiO2 TFPR could be effectively used for the tertiary treatment of sugar refinery effluent using sunlight as the energy source. The treated water could be reused for industrial purposes, thus reducing the water footprint of the industry.
Graphical Abstract
Sugar refinery effluent treatment by solar photocatalytic TFPR
... However, non-concentrating reactors require larger surfaces than the concentrating ones, and therefore must be designed to resist the high operating pressure necessary for pumping the f luid, which substantially increases their cost. NCCs are mainly used in solar pilot plants for photocatalytic treatment of various industrial or agricultural wastewaters containing bio-refractory organic pollutants and for agroindustrial water disinfection using a heterogeneous catalyst (Khan, Reed, and Rasul 2012). ...
