E-peroxone with a novel GDE decorated with hydrophobic membrane for the degradation of pyridine: Stability, byproducts and toxicity.

E-peroxone process is an emerging electrochemical oxidation process, based on ozone and the in-situ cathodic generation of H2O2, but the stability of cathode is one of the key restraining factors. In this study, we designed a multilayer gas diffusion electrode (GDE) decorated with a commercial hydrophobic membrane for the degradation of pyridine. It was found that a proper control of membrane pore sizes and hot-pressing temperature can significantly promote the GDE stability. Subsequently, key operational parameters of the constructed E-peroxone system were investigated, including the ozone concentration, current density, pH value, electrolyte type and initial concentration of pyridine. The degradation pathways were proposed according to six identified transformation products. The toxicity variation along the degradation progress was evaluated with microbial respiration tests and Toxicity Estimation Software Tool (T.E.S.T.) calculation and an efficient detoxification capacity of E-peroxone was observed. This research provides a theoretical basis and technical support for the development of highly efficient and stable E-peroxone system for the elimination of toxic organic contaminants.

High-efficiently utilizing micro-nano ozone bubbles to enhance electro-peroxone process for rapid removal of trace pharmaceutical contaminants from hospital wastewater.

The electro-peroxone (EP) process encounters two inherent challenges in wastewater treatment: sluggish O2/O3 transfer and substantial ozone waste. To overcome these limitations, we introduced micro-nano bubbles (MNBs) aeration to enhance O2/O3 dissolution and diffusion, ultimately aiming to improve the removal of trace pharmaceutical contaminants from hospital wastewater. In the MNBs aeration system, the ozone transfer coefficient ranging from 0.536 to 0.265 min-1, significantly surpassing that of conventional aeration (0.220 to 0.090 min-1) by approximately 2 to 4.5 times. Consequently, the EP process under MNBs aeration significantly enhanced ozone-resistant ibuprofen (IBU) removal, achieving a removal rate of 98.4 ± 1.5 %, far exceeding the 47.3 ± 4.7 % observed with conventional aeration. This significant improvement was attributed to the heightened production of hydroxyl radicals (•OH), reaching 0.97 × 10-9 M s, compared to only 0.28 × 10-9 M s in conventional aeration. The mechanism behind the enhanced •OH production in the MNBs-EP process relied primarily on two factors: improved O2/O3 dissolution due to high internal pressure/large surface and enhanced O3/H2O2 activation from high collapse energy. These factors together contributed to the robust oxidation capability of the MNBs-EP system. As a result, over 97 % removal efficiency was achieved for five representative pharmaceutical pollutants (sulfamethoxazole, ribavirin, norfloxacin, tetracycline and ampicillin) in just 1 min. Furthermore, when applied to real hospital wastewater, the MNBs-O3-E treatment system reduced all 15 detected trace pharmaceutical compounds to below 10 ng L-1 and achieved 14 types of pollutants with removal rates of over 85 % within 15 min, resulting in an ultrahigh total removal rate of 98.6 %, from an initial total concentration of 2108 ng L-1 to less than 30 ng L-1. Thus, micro-nano aeration endowed the EP process as a promising advanced oxidation system for rapid and highly-effective removal of trace pharmaceutical contaminants from hospital wastewater.

Simultaneous electrocoagulation and E-peroxone coupled with ultrafiltration membrane for shale gas produced water treatment.

Membrane fouling caused by the organics-coated particles was the main obstacle for the highly efficient shale gas produced water (SGPW) treatment and recycling. In this study, a novel hybrid electrocoagulation (EC) and E-peroxone process coupled with UF (ECP-UF) process was proposed to examine the efficacy and elucidate the mechanism for UF fouling mitigation in assisting SGPW reuse. Compared to the TMP (transmembrane pressure) increase of -15 kPa in the EC-UF process, TMP in ECP-UF system marginally increased to -1.4 kPa for 3 filtration cycles under the current density of 15 mA/cm2. Both the total fouling index and hydraulically irreversible fouling index of the ECP-UF process were significantly lower than those of EC-UF process. According to the extended Derjaguin-Landau-Verwey-Overbeek theory, the potential barriers was the highest for ECP-UF processes due to the substantial increase of the acid-base interaction energy in ECP-UF process, which was well consistent with the TMP and SEM results. Turbidity and TOC of ECP-UF process were 63.6% and 45.8% lower than those of EC-UF process, respectively. According to the MW distribution, the variations of compounds and their relative contents were probably due to the oxidation and decomposing products of the macromolecular organics. The number of aromatic compound decreased, while the number of open-chain compounds (i.e., alkenes, alkanes and alcohols) increased in the permeate of ECP-UF process. Notably, the substantial decrease in the relative abundance of di-phthalate compounds was attributed to the high reactivity of these compounds with ·OH. Mechanism study indicated that ECP could realize the simultaneous coagulation, H2O2 generation and activation by O3, facilitating the enhancement of ·OH and Alb production and therefore beneficial for the improved water quality and UF fouling mitigation. Therefore, the ECP-UF process emerges as a high-efficient and space-saving approach, yielding a synergistic effect in mitigating UF fouling for SGPW recycling.

Insight into roles of carbon anodes for removal of refractory organic contaminants in electro-peroxone system: Mechanism, performance and stability.

Electro-peroxone (EP) is a novel technique for the removal of refractory organic contaminants (ROCs), while the role of anode in this system is neglected. In this work, the EP system with graphite felt anode (EP-GF) and activated carbon fiber anode (EP-ACF) was developed to enhance ibuprofen (IBP) removal. The results showed that 91.2% and 98.6% of IBP was removed within 20 min in EP-GF and EP-ACF, respectively. Hydroxy radical (O⋅H) was identified as the dominant reactive species, contributing 80.9% and 54.0% of IBP removal in EP-ACF and EP-GF systems, respectively. The roles of adsorption in EP-ACF and direct electron transfer in EP-GF cannot be ignored. Due to the differences in mechanism, EP-GF and EP-ACF systems were suitable for the removal of O⋅H-resistant ROCs (e.g., oxalic acid and pyruvic acid) and non-O⋅H-resistant ROCs (e.g., IBP and nitrobenzene), respectively. Both systems had excellent stability relying on the introduction of oxygen functional groups on the anode, and their electrolysis energy consumption was significantly lower than that of EP-Pt system. The three degradation pathways of IBP were proposed, and the toxicity of intermediates were evaluated. In general, carbon anodes have a good application prospect in the removal of ROCs in EP systems.

Kinetic modelling assisted balancing of organic pollutant removal and bromate formation during peroxone treatment of bromide-containing waters.

The peroxone process (O3/H2O2) is reported to be a more effective process than the ozonation process due to an increased rate of generation of hydroxyl radicals (•OH) and inhibition of bromate (BrO3-) formation which is otherwise formed on ozonation of bromide containing waters. However, the trade-off between the H2O2 dosage required for minimization of BrO3- formation and effective pollutant removal has not been clearly delineated. In this study, employing experimental investigations as well as chemical modelling, we show that the concentration of H2O2 required to achieve maximum pollutant removal may not be the same as that required for minimization of BrO3- formation. At the H2O2 dosage required to minimize BrO3- formation (<10 µg/L), only pollutants with high to moderate reactivity towards O3 and •OH are effectively removed. For pollutants with low reactivity towards O3/•OH, high O3 (O3:DOC>>1 g/g) and high H2O2 dosages (O3:H2O2 ∼1 (g/g)) are required for minimizing BrO3- formation along with effective pollutant removal which may result in a very high residual of H2O2 in the effluent, causing secondary pollution. On balance, we conclude that the peroxone process is not effective for the removal of low reactivity micropollutants if minimization of BrO3- formation is also required.

Degradation of atrazine by electro-peroxone enhanced by Fe and N co-doped carbon nanotubes with simultaneous catalysis of H2O2 and O3.

Fe and N co-doped carbon nanotubes (Fe-N-CNT) was synthesized and attempted as efficient heterogeneous catalysts for simultaneous catalysis of H2O2 and O3 to improve electro-peroxone (Fe-N-CNT/EP) process efficiency for atrazine (ATZ) degradation. The removal and mineralization of ATZ was significantly enhanced, obtaining the degradation rate constant (k) by Fe-N-CNT/EP (0.23 min-1) about two times that of EP (0.12 min-1) owing to the formation of Fe0 and Fe-N coordination in Fe-N-CNT catalyst for co-catalysis of H2O2 and O3. The important factors such as applied current and ozone concentration were investigated, demonstrating that the optimized performance could be achieved at current of 30 mA and ozone concentration of 55 mg L-1. The oxidation capacity of Fe-N-CNT/EP maintained stably under wide pH range of 3∼7, obtaining the degradation rate constant 1.23-1.92 times that of EP and overcoming the defect of EP at acidic and neutral conditions. Capture experiments and electron paramagnetic resonance (EPR) experiments verified that .OH, generated by accelerating decomposition of H2O2/O3 and peroxone reaction, was the dominant active specie in Fe-N-CNT/EP. Besides, Fe-N-CNT showed high catalytic activity and good stability during six cycles. This work provides an efficient activator for enhanced EP process, exhibiting a promising prospect for water and wastewater purification.

A comparative study of response surface methodology and artificial neural network based algorithm genetic for modeling and optimization of EP/US/GAC oxidation process in dexamethasone degradation: Application for real wastewater, electrical energy consumption.

Dexamethasone (DXM) is a broadly used drug, which is frequently identified in the water environments due to its improper disposal and incomplete removal in wastewater treatment plant. The inability of conventional treatment processes of wastewater causes that researchers pay a great attention to study and develop effective wastewater treatment systems. This work deals with the study of integrated electro-peroxone/granular activated carbon (EP/US/GAC) process in the degradation of dexamethasone (DXM) from a water environment and the remediation of real pharmaceutical wastewater. Two approaches of response surface methodology based on central composite design (RSM-CCD) and artificial neural network based on algorithm genetic (ANN-GA) were employed for modeling and optimization of the process. Both the models presented significant adequacy for modeling and prediction of the process according to statistical linear and nonlinear metrics (R2 = 0.9998 and 0.9996 and RMSE = 0.2128 and 0.1784 for ANN-GA and RSM-CCD, respectively). The optimization study provided the same outcomes for both ANN-GA and RSM-CCD approaches, where approximately complete DEX oxidation was achieved at pH = 9.3, operating time = 10 min, US power = 300 W/L, applied current = 470 mA, and electrolyte concentration = 0.05 M. A synergistic study signified that the EP/US/GAC process made an 82% synergy index as compared to the individual US and EP processes. The calculated energy consumption for the integrated process was achieved to be 2.79 kW h/gCOD. Quenching test by tert-butanol and p-benzoquinone revealed that HO• radical possessed the largest contribution in DEX degradation. The efficiency of EP/US/GAC process in the remediation of real pharmaceutical wastewater showed a significant decline in COD content (92% removal after 180 min), and the ratio of initial BOD/COD ratio of 0.27 was elevated up to 0.7 after 100 min treatment time. The performance stability of EP/US/GAC system showed no remarkable drop in removal efficiency, and leakage of lead ions from the anode surface was negligible and below WHO guideline for drinking water. Generally, this research work manifested that the integrated EP/US/GAC system elevated the degradation efficiency and can be proposed as a pretreatment step before biological treatment processes for the remediation of recalcitrant wastewaters.

Nanofiltration combined with ozone-based processes for the removal of antineoplastic drugs from wastewater effluents.

Over the past years, there has been an increasing concern about the occurrence of antineoplastic drugs in water bodies. The incomplete removal of these pharmaceuticals from wastewaters has been confirmed by several scientists, making it urgent to find a reliable technique or a combination of techniques capable to produce clean and safe water. In this work, the combination of nanofiltration and ozone (O3)-based processes (NF + O3, NF + O3/H2O2 and NF + O3/H2O2/UVA) was studied aiming to produce clean water from wastewater treatment plant (WWTP) secondary effluents to be safely discharged into water bodies, reused in daily practices such as aquaculture activities or for recharging aquifers used as abstraction sources for drinking water production. Nanofiltration was performed in a pilot-scale unit and O3-based processes in a continuous-flow column. The peroxone process (O3/H2O2) was considered the most promising technology to be coupled to nanofiltration, all the target pharmaceuticals being removed at an extent higher than 98% from WWTP secondary effluents, with a DOC reduction up to 92%. The applicability of the clean water stream for recharging aquifers used as abstraction sources for drinking water production was supported by a risk assessment approach, regarding the final concentrations of the target pharmaceuticals. Moreover, the toxicity of the nanofiltration retentate, a polluted stream generated from the nanofiltration system, was greatly decreased after the application of the peroxone process, which evidences the positive impact on the environment of implementing a NF + O3/H2O2 process.

Mechanisms of interfacial catalysis and mass transfer in a flow-through electro-peroxone process.

To investigate the catalytic mechanism and mass transfer efficiency in the removal of amitriptyline using an electro-peroxide process, a CuFe2O4-modified carbon cloth cathode was prepared and utilized in a reaction unit. The results demonstrated a remarkable efficacy of the system, achieving 91.0% amitriptyline removal, 68.3% mineralization, 41.2% mineralization current efficiency, and 0.24 kWh/m3 energy consumption within just five minutes of treatment. The study revealed that the exposed Fe atoms of the ferrite nanoparticles, with a size of 22.7 nm and 89.7% crystallinity, functioned as mediators to bind the adsorbed O atoms. The 3dxy, 3dxz, and 3d2z orbitals of Fe atoms interacted with the 2pz orbital of O atoms of H2O2 and O3 to form σ and π bonds, facilitating the adsorption-activation of H2O2 and O3 into hydroxyl radicals. These hydroxyl radicals (∼ 1.15 × 1013 mol/L) were distributed at the cathode-solution interface and rapidly consumed along the direction of liquid flow. The flow-through cathode design improved the mass transfer of aqueous O3 and in-situ generated H2O2, leading to an increased yield of hydroxyl radicals, as well as the contact time and space between hydroxyl radicals and amitriptyline. Ultimately, this resulted in a higher degradation efficiency of the system.

Treatment of synthetic textile wastewater containing Acid Red 182 by electro-Peroxone process using RSM.

The Azo dyes are primarily utilized in textile industries. Treatment of textile wastewater because of the presence of recalcitrant dyes using conventional processes is greatly challenging and ineffective. So far, no experimental work has been conducted on the decolorization of Acid Red 182 (AR182) in aqueous media. Hence, in this novel experimental work, the treatment of AR182 from the Azo dyes family was explored using the electro-Peroxone (EP) process. For the optimization of operating factors, including AR182 concentration, pH, applied current, and O3 flowrate in the decolorization of AR182, Central Composite Design (CCD) was utilized. The statistical optimization presented a highly satisfactory determination coefficient value and a satisfactory second-order model. The expected optimum conditions by the experimental design were as the following: AR182 concentration at 483.12 mg.L-1, applied current at 0.627,113 A, pH at 8.18284 and O3 flowrate at 1.13548 L min-1. The current density is directly proportional to dye removal. However, increasing the amount of applied current beyond a critical value has a contradictory impact on dye removal performance. The dye removal performance in both acidic and highly alkaline environments was negligible. Hence, ascertaining the optimum pH value and conduction of the experiment at that point is critical. At optimum points, the decolorization performance in predicted and experimental conditions for AR182 were 99 and 98.5%, respectively. The outcomes of this work clearly substantiated that the EP can be successfully utilized for the decolorization of AR182 in textile wastewater.

Removal of antibiotic resistant bacteria and plasmid-encoded antibiotic resistance genes in water by ozonation and electro-peroxone process.

The electro-peroxone (EP) process is an electricity-based oxidation process enabled by electrochemically generating hydrogen peroxide (H2O2) from cathodic oxygen (O2) reduction during ozonation. In this study, the removal of antibiotic resistant bacteria (ARB) and plasmid-encoded antibiotic resistance genes (ARGs) during groundwater treatment by ozonation alone and the EP process was compared. Owing to the H2O2-promoted ozone (O3) conversion to hydroxyl radicals (•OH), higher •OH exposures, but lower O3 exposures were obtained during the EP process than ozonation alone. This opposite change of O3 and •OH exposures decreases the efficiency of ARB inactivation and ARG degradation moderately during the EP process compared with ozonation alone. These results suggest that regarding ARB inactivation and ARG degradation, the reduction of O3 exposures may not be fully counterbalanced by the rise of •OH exposures when changing ozonation to the EP process. However, due to the rise of •OH exposure, plasmid DNA was more effectively cleaved to shorter fragments during the EP process than ozonation alone, which may decrease the risks of natural transformation of ARGs. These findings highlight that the influence of the EP process on ARB and ARG inactivation needs to be considered when implementing this process in water treatment.

Treatment of refractory organics in biologically treated landfill leachate by a zero valent iron enhanced Peroxone process: Degradation efficiency and mechanism study.

A zero valent iron (ZVI) enhanced Peroxone process (ZVI/Peroxone) was used to treat biologically treated landfill leachate (BTL). The treatment efficiency of the ZVI/Peroxone process was compared to single (ZVI, O3 and H2O2) and dual (ZVI/H2O2, Fe0/O3 and Peroxone) processes. The results showed that ZVI can greatly enhance the treatment capability of the Peroxone process, and the color number (CN), absorbance at 254 nm (UV254), and total organic carbon (TOC) removal efficiencies were 98.82, 84.30 and 66.38%, respectively. In the ZVI/Peroxone process, higher O3 and ZVI dosages improved organics removal, and H2O2 could promote organics removal within a certain dosage range. However, too much H2O2 decreased treatment efficiency. The best treatment performance by the ZVI/Peroxone process was obtained under acidic conditions. The three-dimensional excitation and emission matrix analysis showed that BTL mainly contained two fluorescent substances, which were fulvic-like substances in the ultraviolet region (Ex/Em = 235-255 nm/410-450 nm) and fulvic-like substances in the visible light region (Ex/Em = 310-360 nm/370-450 nm). Fluorescent substances could be substantially degraded by the ZVI/Peroxone process during the early stages of the reaction. An analysis of ZVI morphology and element valency changes showed that the micro Fe0 particles used in this study remained highly reactive during the process. The ZVI enhanced the homogenous Fenton, heterogeneous Fenton, and coagulation-flocculation effects during the Peroxone process.

Synchronous removal of pharmaceutical contaminants and inactivation of pathogenic microorganisms in real hospital wastewater by electro-peroxone process.

Herein, a highly efficient electro-peroxone (E-peroxone) process with graphite felt as ozone diffusion electrode (ODE) was developed for the synchronous removal of pharmaceutical contaminants and inactivation of pathogenic microorganisms in real hospital wastewater. Under optimal conditions, the total organic carbon (TOC) removal rate of real hospital wastewater could reach 93.9%. Importantly, 126 pharmaceutical compounds (antibiotics, antivirals, analgesics, antiepileptics, hormones, and others) were determined in hospital wastewater by using ultra performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS). 110 pharmaceutical compounds could be efficiently degraded in E-peroxone system. Concurrently, the microbial community analysis through high-throughput sequencing showed that E-peroxone process exhibited an excellent disinfection effect in real hospital wastewater. Escherichia coli as a bacterial indicator could be completely inactivated in E-peroxone process·H2O2 and hydroxyl radical (OH) were found in E-peroxone system based on the results of chemical probe experiments and electron paramagnetic resonance (EPR) analysis. The in-situ generation of H2O2 from cathodic oxygen reduction in ODE can react with ozone to produce OH, and realize high efficiencies for the elimination of pharmaceutical and sterilization. This work established a green and effective way without extra addition of chemical reagents for high-efficiency treatment of real hospital wastewater.

Fluidized ZnO@BCFPs Particle Electrodes for Efficient Degradation and Detoxification of Metronidazole in 3D Electro-Peroxone Process.

A novel material of self-shaped ZnO-embedded biomass carbon foam pellets (ZnO@BCFPs) was successfully synthesized and used as fluidized particle electrodes in three-dimensional (3D) electro-peroxone systems for metronidazole degradation. Compared with 3D and 2D + O3 systems, the energy consumption was greatly reduced and the removal efficiencies of metronidazole were improved in the 3D + O3 system. The degradation rate constants increased from 0.0369 min-1 and 0.0337 min-1 to 0.0553 min-1, respectively. The removal efficiencies of metronidazole and total organic carbon reached 100% and 50.5% within 60 min under optimal conditions. It indicated that adding ZnO@BCFPs particle electrodes was beneficial to simultaneous adsorption and degradation of metronidazole due to improving mass transfer of metronidazole and forming numerous tiny electrolytic cells. In addition, the process of metronidazole degradation in 3D electro-peroxone systems involved hydroxyethyl cleavage, hydroxylation, nitro-reduction, N-denitrification and ring-opening. The active species of ·OH and ·O2- played an important role. Furthermore, the acute toxicity LD50 and the bioconcentration factor of intermediate products decreased with the increasing reaction time.

Electro-peroxone enables efficient Cr removal and recovery from Cr(III) complexes and inhibits intermediate Cr(VI) generation in wastewater: Performance and mechanism.

Available oxidation processes for removing Cr(III) complexes from water/wastewater usually encounter the formation of highly toxic Cr(VI) and the generation of Cr enriched waste sludge, posing challenges on the subsequent disposal. Herein, we achieve efficient removal of Cr(III)-organic complexes and simultaneous recovery of Cr from wastewater with enhanced curtailment of intermediate Cr(VI), by using an electrochemically driven peroxone (i.e., electro-peroxone) process with activated carbon fiber (ACF) electrodes. For Cr(III)-EDTA, electro-peroxone could remove ∼90% total Cr from 11.50 mg/L to 1.20 mg/L and ∼80% total organic carbon, with a strong curtailment of Cr(VI) to less than 0.2 mg/L. Additionally, the process could obtain a complete recovery of the removable Cr, of which 78.3% are enriched at ACF cathode as amorphous Cr(OH)3 deposits and the remaining 21.7% are adsorbed at the anode, thus avoiding the generation of Cr laden sludge. Mechanism studies show the electro-generated H2O2 reacts with O3 to generate abundant HO· for decomplexation, which sequentially oxidizes Cr(III) to Cr(VI), and degrades the released EDTA via stepwise decarboxylated process, as confirmed by HPLC analysis. Multiple pathways including electro-reduction, H2O2 reduction and electro-adsorption synergistically curtail and immobilize the formed intermediate Cr(VI). ACF characterizations and continuous 5-cycle experiments substantiate the excellent reusability of the ACF electrodes. Moreover, this process exhibits satisfactory effectiveness to Cr(III) complexed with other ligands (e.g., citrate and oxalate), and complexed Cr(III) in the real electroplating wastewater. We believe this study would provide an efficient and eco-friendly alternative for Cr(III) complexes removal from wastewater.

Electro-peroxone with solid polymer electrolytes: A novel system for degradation of plasticizers in natural effluents.

Electro-peroxone (EP) reaction has been considered as a promising process for real effluent treatments. However, the use of the technology in natural water conditions is limited by low electrical conductivity and high operating costs. Herein, a novel electrochemical system was designed to overcome this constrain by coupling EP with a solid polymer electrolyte (EP-SPE). Performances of EP-SPE system were thoroughly evaluated by comparing the decomposition and energy efficiencies of various plasticizers in different systems. The EP-SPE system achieved 50% of pollutants mineralization in only 10 min with the electrolysis energy consumption of 1.0kWh·m-3, While the conventional EP system (not) adding salt compounds (CEP-(N) AS) need 30 (60) min to reach 50% of pollutants mineralization with 3.8(26.6)kWh·m-3. Kinetics and mechanisms of EP-SPE were investigated in detail, while electronic paramagnetic resonance (EPR) detection and kinetic model revealed the occurrence, transient concentration and degradation contribution of reactive oxidizing species (ROS). Furthermore, tests of variety of SPEs and natural waters demonstrated universal applicability of EP-SPE. Additionally, EP-SPE did not show any performance deterioration after 15 runs. Therefore, this work provides a feasible technology for plasticizer purification in natural water.

An electro-peroxone oxidation-Fe(III) coagulation sequential conditioning process for the enhanced waste activated sludge dewatering: Bound water release and organics multivariate change.

As a by-product of wastewater treatment, waste activated sludge (WAS) has complex composition, strong hydrophilic extracellular polymeric substance (EPS), which make it difficult to dewater. In this study, an electro-peroxone oxidation-Fe(III) coagulation (E-peroxone-Fe(III)) sequential conditioning approach was developed to improve WAS dewaterability. At E-peroxone oxidation stage, hydrogen peroxide was generated through 2-electron path on a carbon polytetrafluoroethylene cathode, and reacted with the sparged O3 to produce hydroxyl radicals. At the subsequent coagulation stage, Fe(III) was dosed to coagulate the small WAS fragments and release water from WAS. Along E-peroxone-Fe(III) subsequent conditioning process, the physicochemical properties of WAS, main components, functional groups and evolution of protein secondary structure, and typical amino acids in EPS, as well as the type and semi-quantitative of elements in WAS, were investigated. The results indicated that under the optimal conditions, the reductions of specific resistance to filterability (SRF) and capillary suction time (CST) for WAS equalled 78.18% and 71.06%, respectively, and its bound water content decreased from 8.87 g/g TSS to 7.67 g/g TSS. After E-peroxone oxidation, part of protein and polysaccharide migrated outside from TB-EPS to slime, the ratio of α-helix/(ß-sheet + random coil) declined, even some of organic-N disintegrated to inorganic-N. At Fe(III) coagulation stage, re-coagulation of the dispersed WAS fragments and easy extraction from inner EPS for protein and polysaccharide occurred. Furthermore, the protein secondary structure of ß-sheet increased by 13.48%, the contents of hydrophobic and hydrophilic amino acids also increased. In addition, a strong negative correlation between the hydrophobic amino acid content of Met in slime and CST or SRF (R2CST = -0.999, p < 0.05 or R2SRF = -0.948, p < 0.05) occurred, while a strong positive correlation between the hydrophilic amino acid content of Cys in TB-EPS and CST or SRF (R2CST = 0.992, p < 0.05 or R2SRF = 0.921, p < 0.05) occurred, which could be related to the WAS dewaterability.

Efficient removal of ibuprofen and ofloxacin pharmaceuticals using biofilm reactors for hospital wastewater treatment.

Hospital wastewater is harmful to the environment and human health due to its complex chemical composition and high potency towards becoming a source of disease outbreaks. Due to these complexities, its treatment is neither efficient nor cost-effective. It is a challenging issue that requires immediate attention. This effort focuses on the treatment of hospital wastewater (HWW) by removing two selected drugs, namely ibuprofen (IBU) and ofloxacin (OFX) using individual biological treatment methods, such as moving bed biofilm reactors (MBBR) and physicochemical treatment, such as ozonation and peroxane process. The both methods are compared to find the best method overall based on effectiveness and removal efficiency. The optimal removal for ozone dosing range was nitrate (9.00% and 62.00%), biological oxygen demand (BOD) (92.00% and 64.00%), and chemical oxygen demand (COD) (96.00% and 92.00%) that required at least 10 min to reach considerable degradation. The MBBR process assured a better performance for ibuprofen removal, overall. The IBU and OFX removal was found to be 14.32-96.00% at a higher COD value and 11.33-94.00% at a lower COD value due to its biodegradation. This work strives to pave the way forward to build an HWW treatment technology using integrated MBBR processes for better efficiency and cost-effectiveness.

Enhancement of H2O2 yield and TOC removal in electro-peroxone process by electrochemically modified graphite felt: Performance, mechanism and stability.

Electro-peroxone (EP) is an emerging advanced oxidation process which combines electro-generation H2O2 and ozone for removing organic contaminants. In this paper, a platinum plate as anode, a method of electrochemical oxidation is adopted to modify graphite felt (GF) cathode to promote H2O2 yield and TOC removal from oxalic acid solution in EP process, its performance, mechanism and stability were discussed. Compared with original GF cathode, 2.6 times H2O2 yield can be achieved by the 5 min electrochemically modified GF (GF-5). The high electrochemical activity of the modified GF can be ascribed to introducing numerous surface oxygen-containing functional groups (OGs), which not only decreased the impedance, but also increased the amount of active site of O2 reduction. The production of H2O2 with GF-5 cathode improved with the increased initial pH, cathodic potential and O2 flow rate, while this promoting effect was not observed in GF cathode. Compared with GF cathode, TOC removal rate was improved by 21.5% with GF-5 cathode due to higher H2O2 yield in EP process. The primary pathway of TOC removal is electrochemically-driven peroxone process, and hydroxyl radical (·OH) is the dominant reactive species. Furthermore, GF-5 cathode had a good stability due to the protection of H2O2 and free electrons injected. The results indicate that the electrochemically modified GF severed as the cathode of EP processes has significant efficiency and stability in the removal of ozone-refractory organic contaminants.

Employing electro-peroxone process for degradation of Acid Red 88 in aqueous environment by Central Composite Design: A new kinetic study and energy consumption.

The Azo dyes are primarily employed in textile industries to produce high amounts of colored organic and inorganic wastewater. Therefore, their treatments are critical. In this research, the removal and mineralization of Acid red 88 (AR88), as a widely used mono Azo dye, was inspected by the Electro-peroxone(E-peroxone) method. It is a coupling of electrochemically produced H2O2 and ozone that can produce robust hydroxyl radicals. The Central Composite Design (CCD) was applied to explore the influence of operational variables on the removal of AR88 as a response. The optimal conditions predicted by the CCD were as the following; Applied current at 0.7 A, pH at 7.35, O3 Flowrate at 1.03 L min-1 and the concentration of AR88 at 527.29 mg. L-1. The Pareto chart showed that the concentration of AR88 has a significant influence on the response. At the predicted optimal conditions, the actual and predicted AR 88 removal were 95.4 and 92.96%, respectively. The removal of COD after 45 min was 70% representing the excessive efficiency of E-peroxone in mineralization of AR88. The E-peroxone follows the pseudo-first-order kinetics (kobs-E-peroxone = 6.56 × 10-2 min-1), which was more remarkable than the single ozonation, and electrolysis. The calculated specific energy consumption (SEC) in the E-peroxone was 40.14 kWh/Kg AR 18 removal, which was lower than the individual ozonation, and electrolysis methods. The operative production of H2O2 from O2 at the cathode is the critical factor in the high removal of AR88 in this process.