Advanced Oxidation Treatment Research Articles

Characterization and advanced oxidation treatment of dyeing effluent by Fenton’s reagent

Textile effluent from dyeing process has been a serious environmental threat for years. This study was intended to evaluate the performance of Fenton’s process for the removal of chemical oxygen demand (COD), colour and turbidity. Experiments were conducted by laboratory-scale reactors fed with cotton dyeing effluent. The Fenton process employs ferrous ions and hydrogen peroxide H2O2 under acidic pH conditions. The experimental variables studied include doses of iron salts and hydrogen peroxide, oxidation time, pH for oxidation and coagulation. The COD, color and turbidity removal reached a maximum of 97.2, 96.8 and 84.8% respectively at a reaction time of 20 min under optimum doses of H2O2 and Fe2+. Hydrogen peroxide dose ranging from 0.5 to 2.0 mL/500 mL and FeSO4 · 7H2O in the range of 0.5–4.0 gm/500 mL were selected to be examined at different reaction times between 10 and 30 min. Optimum dose of hydrogen peroxide and ferrous sulphate were 2.0 mL and 1.0 gm respectively for 500 mL of sample. In this study optimized pH 4.0 and 6.0 was found effective for oxidation and coagulation respectively.

Impact of electrochemical treatment of soil washing solution on PAH degradation efficiency and soil respirometry

The remediation of a genuinely PAH-contaminated soil was performed, for the first time, through a new and complete investigation, including PAH extraction followed by advanced oxidation treatment of the washing solution and its recirculation, and an analysis of the impact of the PAH extraction on soil respirometry. The study has been performed on the remediation of genuine PAH-contaminated soil, in the following three steps: (i) PAH extraction with soil washing (SW) techniques, (ii) PAH degradation with an electro-Fenton (EF) process, and (iii) recirculation of the partially oxidized effluent for another SW cycle. The following criteria were monitored during the successive washing cycles: PAH extraction efficiency, PAH oxidation rates and yields, extracting agent recovery, soil microbial activity, and pH of soil. Two representative extracting agents were compared: hydroxypropyl-beta-cyclodextrin (HPCD) and a non-ionic surfactant, Tween® 80. Six PAH with different numbers of rings were monitored: acenaphthene (ACE), phenanthrene (PHE), fluoranthene (FLA), pyrene (PYR), benzo(a)pyrene (BaP), and benzo(g,h,i)perylene (BghiP). Tween® 80 showed much better PAH extraction efficiency (after several SW cycles) than HPCD, regardless of the number of washing cycles. Based on successive SW experiments, a new mathematical relation taking into account the soil/water partition coefficient (Kd*) was established, and could predict the amount of each PAH extracted by the surfactant with a good correlation with experimental results (R2 > 0.975). More HPCD was recovered (89%) than Tween® 80 (79%), while the monitored pollutants were completely degraded (>99%) after 4 h and 8 h, respectively. Even after being washed with partially oxidized solutions, the Tween® 80 solutions extracted significantly more PAH than HPCD and promoted better soil microbial activity, with higher oxygen consumption rates. Moreover, neither the oxidation by-products nor the acidic media (pH approximately 3) of the partially oxidized solution inhibited the general soil microbial activity during the washing cycle.

Technology Options in a Dairy Plant: Assessing Whole-System Eco-Efficiency

<p class="emsd"><span lang="EN-GB">Industries are increasingly looking beyond their own fences to optimise their supply and delivery chains. Increasing industrial production costs for resources and costs to comply with stringent legislation have led many industries to look for more cost effective solutions. Establishing collaboration with water and energy utilities and other industries in the neighbourhood of the industrial production site is one option being analysed.</span></p><p class="emsd"><span lang="EN-GB">This paper presents how eco-efficiency analysis - at a system level going beyond the fences of an industrial production site - can calculate economic value and environmental impacts in such wider systems. The paper presents how the analysis can lead to the identification of eco-efficient solutions at a system level as well as at the level of each actor in the system.</span></p><p class="emsd"><span lang="EN-GB">The eco-efficiency analyses are based on the ISO standard ISO 14045. The water use system analysis comprises a dairy plant producing milk powder located in a production site in Holstebro, Denmark. The dairy uses water in its utility operation and in the dairy processes for purposes like cleaning (Cleaning in Place, CIP), rinse processes and standardization of products. </span></p><p class="emsd"><span lang="EN-GB">In the eco-efficiency analysis a water value chain is modelled in five stages: water supply, dairy production, wastewater treatment, energy production (biogas) and transport. The eco-efficiency analysis thus has another focus than a Water Footprint analysis, which also includes water use for feed production, water used at farm level and in some cases also includes the water use at retail and consumer level. The eco-efficiency study focus not only on water efficiency but also on and how energy saving technology options linked to water use could upgrade the whole-system eco-efficiency. </span></p><p class="emsd"><span lang="EN-GB">The identification of the environmentally weak stages as being emissions of climate gasses resulting from energy use and water resource enables the selection of alternative actions, which could upgrade the whole value chain and improve the overall eco-efficiency. Four innovative technologies in the dairy production stage and one in the wastewater treatment stage are examined and three alternative technology scenarios combining these technologies are formulated. All scenarios focus on resource efficiency, while one also focuses on reducing the emissions to water.</span></p><p class="emsd"><span lang="EN-GB">The eco-efficiency assessments showed that advanced oxidation and UV light treatment of the water stream separated from the milk stream had the highest eco-efficiency corresponding to an increase of 130% compared to the baseline for the freshwater resource depletion indicator. Anaerobic pretreatment of the dairy wastewater in the dairy plant had the highest eco-efficiency showing an increase of 10% as compared to the baseline for the climate gas indicator. For all other technologies and combinations of technologies the increases were significantly smaller. </span></p><p class="emsd"><span lang="EN-GB">The eco-efficiency assessment results provided a basis for workshops with the actors in the value chain to discuss how to anticipate distributional effects. The analysis of the economic performance clearly showed that the dairy plant had the highest economic performance due to the high value of their product and that investments in new technologies increased the economic performance even more. This was mainly caused by savings on costs for water supply and wastewater treatment services, which left the water utility with a reduced economic performance.</span></p>

Toxicological and chemical assessment of arsenic-contaminated groundwater after electrochemical and advanced oxidation treatments

Owing to its proven toxicity and mutagenicity, arsenic is regarded a principal pollutant in water used for drinking. The objective of this study was the toxicological and chemical evaluation of groundwater samples obtained from arsenic enriched drinking water wells before and after electrochemical and ozone–UV–H2O2-based advanced oxidation processes (EAOP). For this purpose, acute toxicity test with Daphnia magna and chronic toxicity test with Lemna minor L. were employed as well as in vitro bioassays using human peripheral blood lymphocytes (HPBLs). Several oxidative stress parameters were estimated in L.minor. Physicochemical analysis showed that EAOP treatment was highly efficient in arsenic but also in ammonia and organic compound removal from contaminated groundwater. Untreated groundwater caused only slight toxicity to HPBLs and D. magna in acute experiments. However, 7-day exposure of L. minor to raw groundwater elicited genotoxicity, a significant growth inhibition and oxidative stress injury. The observed genotoxicity and toxicity of raw groundwater samples was almost completely eliminated by EAOP treatment. Generally, the results obtained with L. minor were in agreement with those obtained in the chemical analysis suggesting the sensitivity of the model organism in monitoring of arsenic-contaminated groundwater. In parallel to chemical analysis, the implementation of chronic toxicity bioassays in a battery is recommended in the assessment of the toxic and genotoxic potential of such complex mixtures.

Impact of leachate composition on the advanced oxidation treatment

Advanced oxidation processes (AOPs) are gaining importance as an alternative to the biological or physicochemical treatments for the management of leachates. In this work, it has been studied the effect of the characteristics of the leachate (content in humic acids, landfill age and degree of stabilization) on the wet oxidation process and final quality of the treated effluent. A high concentration of humic acids in the leachate had a positive effect on the COD removal because this fraction is more easily oxidizable. Additionally, it has been demonstrated that the simultaneous presence of humic acid and the intermediates generated during the oxidation process improved the degradation of this acid, since such intermediates are stronger initiators of free radicals than the humic acid itself. Similar values of COD removals (49% and 51%) and biodegradability indices (0.30 and 0.35) were observed, after 8 h of wet oxidation, for the stabilised leachate (biologically pretreated) and the raw one, respectively. Nevertheless, final colour removal was much higher for the stabilised leachate, achieving values up to 91%, whereas for the raw one only 56% removal was attained for the same reaction time. Besides, wet oxidation treatment was more efficient for the young leachate than for the old one, with final COD conversions of 60% and 37%, respectively. Eventually, a triangular “three-lump” kinetic model, which considered direct oxidation to CO2 and partial oxidation through intermediate compounds, was here proposed.

Insight into the composition and degradation potential of dissolved organic matter with different hydrophobicity in landfill leachates.

Dissolved organic matter (DOM) isolated from the leachates with different landfill ages was fractionated into hydrophobic acid (HOA), hydrophobic neutral (HON), hydrophobic base (HOB) fractions and hydrophilic matter (HIM) based on hydrophobicity, and the composition and degradation potential of the bulk DOM and its fractions were investigated by excitation-emission matrix fluorescence spectra coupled with parallel factor analysis. Results showed that the bulk DOM comprised fulvic-, humic-, tryptophan- and tyrosine-like substances, as well as component C1, whose composition and origin was unidentified. Landfill process increased the content of component C1, fulvic- and humic-like matter. The HON fractions comprised primarily component C1 and tyrosine-like matter. The HOA, HOB and HIM fractions isolated from the young leachates consisted mainly of tryptophan- and tyrosine-like substances. As to the intermediate and old leachates, the HOA and HOB fractions comprised mainly component C1, while the HIM comprised mainly fulvic-like matter. The HIM showed the most resistant against biodegradation among the four fractions, and was the main component of leachate treatment. Advanced oxidation and/or membrane treatment are recommended to remove the HIM fraction due to its hydrophilic and stable characteristics.

Application of a new sandwich of granular activated and fiber carbon as cathode in the electrochemical advanced oxidation treatment of pharmaceutical effluents

Society technological advances and environmental requirements claim for the development of highly effective, low cost and environmental friendly technologies able to degrade emerging organic pollutants widely used such as pharmaceuticals. The development of electrochemical advanced oxidation processes may increase the efficiency of the traditional treatments used on the remediation of polluted water. Therefore, this work has been devoted to the design of a cathode that permits to enhance the generation of hydroxyl radicals on the system. The best results were obtained when a cathode made with granular activated carbon and carbon fiber (SGAFC) was used. After determining the efficiency of this cathode on the decoloration of two model dyes, its application to the chloramphenicol antibiotic reduction was evaluated, obtaining near complete removal after 120min. In addition, the treatment on successive batches and different continuous electrochemical cell configurations has emphasized the ability of this new cathode to be used on different water treatment facilities.

Advanced Oxidation Treatment of Recalcitrant Wastewater from a Wood-Based Industry: a Comparative Study of O3 and O3/UV

Ozone and ozone-based advanced oxidation processes were applied for the treatment of a recalcitrant wastewater generated by wood-based industries that contains different inorganic and organic constituents and high chemical oxygen demand (COD) varying between 3,400 and 4,000 mg/L. The investigation used a tubular ozone reactor combined with an UV reactor designed for different hydraulic retention times. The dependent variables addressed to evaluate the treatment efficiency were the reduction of COD and total organic carbon (TOC) and the biodegradability of the treated effluent based on respirometric studies using activated sludge from a wastewater treatment. The results showed that even though ozonation alone at acid pH promoted COD and TOC reductions of 65 and 31 % respectively, a decrease in the biodegradability was observed. The most effective treatment (COD and TOC reductions of 93 and 43 %, respectively) was obtained when applying ozone combined with UV light at basic pH. The ozone-UV combination was capable of increasing the amount of readily available COD by 75 % with an additional reduction of TOC by 60 %. In conclusion, ozonation at low pH effectively reduces the COD content in wastewater generated by the wood-based industry; however, in order to combine advanced oxidation with biological process, ozone combined with UV is recommended.

Reduction in energy consumption of electrochemical pesticide degradation through combination with membrane filtration

A significant challenge for large-scale use of electrochemical oxidation (EO) is high energy consumption, and for EO to become accepted as a standard technique, the amount of energy consumed in the process must be reduced.In this study, it was investigated how the energy consumption of EO could be lowered by combining the process with membrane filtration, in a setup where EO was applied to the membrane retentate stream. Use of two types of membranes, a nanofiltration (NF) and a reverse osmosis (RO) membrane, was investigated, and to provide realistic estimates on the energy consumption of the treatment, natural groundwater spiked with the pesticide residue 2,6-dichlorobenzamide (BAM) was used as matrix in the experiments. To understand the effect of the membranes on the energy consumption, their effect on the EO degradation efficiency was also determined.The results showed that membranes significantly reduced the energy consumption of the EO processes. Using the RO membrane with a recovery of 90%, the energy consumption of the combined EO and membrane setup used 95% less energy (0.96kWh/m3) compared to the stand-alone EO treatment (18.5kWh/m3). The reduction in energy consumption was found to be a result of primarily two factors; (1) a smaller volume of water was in need in the energy intensive EO treatment, and (2) the high rejection of chloride by the RO membrane increased the rate of degradation through mediated active chlorine oxidation in the membrane retentate. It was not possible to obtain the same positive benefits using the NF membrane, which was mainly due to a lower chloride rejection and a too low rejection of BAM. The investigation showed that combining RO filtration with EO of the contaminants in the concentrate provides a promising strategy for the dissemination of advanced oxidative treatment techniques in larger scale and actual use for protection of the environment.

Modeling and optimization of advanced oxidation treatment of beer industry wastewater using Electro‐Fenton process

The main objective of this study was to investigate and optimize the operating parameters in Electro‐Fenton (E‐Fenton) process such as current density, H2O2/Fe2+ molar ratio, treatment time, and temperature for the removal of turbidity and chemical oxygen demand from Beer wastewater. Response surface methodology (RSM) coupled with four factors three levels Box‐Behnken response surface design (BBD) was used for the optimization. Significant quadratic polynomial models were obtained with high coefficient determination (R2 = 0.9796 and 0.9804 for turbidity and COD removals) and numerical optimization was employed to determine the optimal conditions. Current density of 9 mA cm−2, H2O2/Fe2+ molar ratio of 1.1, treatment time of 10 min, and temperature of 30°C. Under these conditions, 98% of turbidity and 94% of COD were reduced. Results indicates that E‐Fenton process was an effective pretreatment technology for the treatment of Beer wastewater. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1072–1079, 2015

The roles of halides in the acetaminophen degradation by UV/H2O2 treatment: Kinetics, mechanisms, and products analysis

This study evaluated the effects of halide ions (chloride and bromide) on the degradation of acetaminophen, a widely used drug, with the UV/H2O2 advanced oxidation treatment. Chloride showed minimal effects on the acetaminophen degradation, whereas increasing bromide concentration reduced the degradation rate because bromide promoted the formation of Br2−, which had a lower reaction rate than OH. Interestingly, acetaminophen degradation was enhanced when both chloride and bromide were present in the solution. This was probably attributed to the high yield of ClBr- radicals predicted by using the Kintecus model. Additional tests using five model compounds (4-chlorophenol, 4-methoxyphenol, 4-hydroxylbenzoic acid, 17β-estradiol, and bisphenol A) suggested that ClBr- radicals selectively reacted with electron-rich moieties of the organic pollutants. In the presence of natural organic matter (NOM), increasing concentration of chloride or bromide reduced the degradation rate of acetaminophen. In contrast, with a constant concentration of co-existing chloride, the acetaminophen degradation was promoted by increasing bromide concentration. The product analysis showed that the HO and halide radicals resulted in different pathways of acetaminophen degradation. The HO radicals favored electrophilic aromatic substitution at the ortho and para positions, forming the –OH substituted acetaminophen, whereas halide radicals preferentially led to one-electron oxidation and formation of phenoxyl radicals as intermediates. These results highlight the multiple roles of salinity in water and wastewater treatment. In addition to acting as HO scavengers, halogen radicals may significantly contribute to the organics degradation via their high selectivity towards electron-rich moieties. The resultant intermediate products require further toxicity assessment.

Supported Photocatalyst for Removal of Emerging Contaminants from Wastewater in a Continuous Packed-Bed Photoreactor Configuration

Water pollution from emerging contaminants (ECs) or emerging pollutants is an important environmental problem. Heterogeneous photocatalytic treatment, as advanced oxidation treatment of wastewater effluents, has been proposed to solve this problem. In this paper, a heterogeneous photocatalytic process was studied for emergent contaminants removal using paracetamol as a model contaminant molecule. TiO2 photocatalytic activity was evaluated using two photocatalytic reactor configurations: Photocatalyst solid suspension in wastewater in a stirred photoreactor and TiO2 supported on glass spheres (TGS) configuring a packed bed photoreactor. The surface morphology and texture of the TGS were monitored by scanning electron microscope (SEM). The influence of photocatalyst amount and wastewater pH were evaluated in the stirred photoreactor and the influence of wastewater flowrate was tested in the packed bed photoreactor, in order to obtain the optimal operation conditions. Moreover, results obtained were compared with those obtained from photolysis and adsorption studies, using the optimal operation conditions. Good photocatalytic activities have been observed and leads to the conclusion that the heterogeneous photocatalytic system in a packed bed is an effective method for removal of emerging pollutants.

Combined treatment of olive mill wastewater by Fenton's reagent and anaerobic biological process

This work presents the application of Fenton's reagent process combined with anaerobic digestion to treat an olive mill wastewater (OMW). Firstly, OMW was pre-treated by chemical oxidation in a batch reactor with Fenton's reagent, using a fixed H2O2/COD ratio of 0.20, pH = 3.5 and a H2O2/Fe2+ molar ratio of 15:1. This advanced oxidation treatment allowed reaching reductions of 17.6 and 82.5% of chemical oxygen demand (COD) and total polyphenols (TP), respectively. Secondly, OMW treatment by anaerobic digestion was performed using previously adapted microorganisms immobilized in Sepiolite. These biological tests were carried out varying the substrate concentration supplied to the reactor and COD conversions from 52 to 74% were obtained. Afterwards, Fenton's reagent followed by anaerobic digestion was applied to OMW treatment. This combined process presented a significant improvement on organic load removal, reaching COD degradations from 64 to 88%. Beyond the pollutant load removal, it was also monitored the yield of methane generated throughout anaerobic experiments. The methane produced ranged from 281 cm3 to 322 cm3 of CH4/g COD removed. Additionally, a methane generation kinetic study was performed using the Monod Model. The application of this model allowed observing a kinetic constant increase of the combined process (kFN = 0.036 h−1) when compared to the single anaerobic process (kF = 0.017 h−1).

Impact of UV-H2O2 Advanced Oxidation and Aging Processes on GAC Capacity for the Removal of Cyanobacterial Taste and Odor Compounds.

Cyanobacteria and their taste and odor (T&O) compounds are a growing concern in water sources globally. Geosmin and 2-methylisoborneol (MIB) are the most commonly detected T&O compounds associated with cyanobacterial presence in drinking water sources. The use of ultraviolet and hydrogen peroxide (H2O2) as an advanced oxidation treatment for T&O control is an emerging technology. However, residual H2O2 (>80% of the initial dose) has to be removed from water prior final disinfection. Recently, granular activated carbon (GAC) is used to remove H2O2 residual. The objective of this study is to assess the impact of H2O2 quenching and aging processes on GAC capacity for the removal of geosmin and MIB. Pilot columns with different types of GAC and presence/absence of H2O2 have been used for this study. H2O2 removal for the operational period of 6 months has no significant impact on GAC capacity to remove the geosmin and MIB from water.

Degradation pathways of lamotrigine under advanced treatment by direct UV photolysis, hydroxyl radicals, and ozone

Lamotrigine is recently recognized as a persistent pharmaceutical in the water environment and wastewater effluents. Its degradation was studied under UV and ozone advanced oxidation treatments with reaction kinetics of lamotrigine with ozone (≈4M−1s−1), hydroxyl radical [(2.1±0.3)×109M−1s−1] and by UV photolysis with low and medium pressure mercury vapor lamps [quantum yields ≈0 and (2.7±0.4)×10−4 respectively] determined. All constants were measured at pH 6 and at temperature ≈20°C. The results indicate that lamotrigine is slow to respond to direct photolysis or oxidation by ozone and no attenuation of the contaminant is expected in UV or ozone disinfection applications. The compound reacts rapidly with hydroxyl radicals indicating that advanced oxidation processes would be effective for its treatment. Degradation products were identified under each treatment process using accurate mass time-of-flight spectrometry and pathways of decay were proposed. The main transformation pathways in each process were: dechlorination of the benzene ring during direct photolysis; hydroxyl group addition to the benzene ring during the reaction with hydroxyl radicals; and triazine ring opening after reaction with ozone. Different products that form in each process may be to a varying degree less environmentally stable than the parent lamotrigine. In addition, a novel method of ozone quenching without addition of salts is presented. The new quenching method would allow subsequent mass spectrometry analysis without a solid phase extraction clean-up step. The method involves raising the pH of the sample to approximately 10 for a few seconds and lowering it back and is therefore limited to applications for which temporary pH change is not expected to affect the outcome of the analysis.

Technique for advanced electrochemical oxidation treatment of nanofiltration concentrate of landfill leachate

Landfill leachate treated with combined process of “pretreatment +biological treatment +advanced treatment (NF)” to produce nanofiltration concentrate, which bio-chemical ratio (B/C) is less than 0.1 and CODcr concentration is 2 000–2 500 mg/L, high salt content. Which cannot be discharged under existing environmental standards. According to analysis based on electrochemical advanced oxidation mechanism, a two-step electrochemical technique was recommended. In the first step, a pulse electrochemical technique was adopted. With Fe as consumption electrode and current density of 10 mA/cm2, the pollutants were removed by means of Fenton reaction, electroflotation and electrocoagulation. In the second step, a double function electrode was used to perform electrocatalytic oxidation by means of titanium metallic oxidates. In the condition that current density being 12.5 mA/cm2, the pollutants were further removed by oxidation and electrolytic deposition. Result shows that the removing rate of CODcr, NH3-N and Cl- were 70%–85%, 90% and 25%, respectively; average value of B/C ratio increased from 0.09 to 0.38 and conductivity reduced by 10%.

Detoxification of waters contaminated with phenol, formaldehyde and phenol–formaldehyde mixtures using a combination of biological treatments and advanced oxidation techniques

The detoxification process of waters contaminated with phenol, formaldehyde and phenol–formaldehyde mixtures was studied using advanced oxidation treatments (heterogeneous photocatalysis and Fenton), biological techniques (aerated biological and wetland reactors) and combinations of the two. It is shown that photocatalysis was efficient in the detoxification of concentrations below 50mgL−1 of those compounds. Sample toxicity increased at higher concentrations due to the generated intermediates. Phenol–formaldehyde mixtures were impossible to detoxify by heterogeneous photocatalysis at any of the studied concentrations. Treatments using the Fenton reaction were able to degrade concentrations above 1000mgL−1, though the use of a reagent such as peroxide makes it a costly technique. The efficiency of the biological aerated filter (BAF) mainly depended on initial concentration and toxicity, with removal rates of 3.08 and 0.26gL−1d−1 obtained for phenol and formaldehyde, respectively. Taking into account the results obtained for the treatment of complex phenol–formaldehyde mixtures, the best combination of techniques for the treatment of concentrations found in the industrial wastewater studied in this paper was the Fenton+BAF technique which was able to detoxify phenol–formaldehyde concentrations (1:1) of 1000mgL−1.

Removal of arsenic, phosphates and ammonia from well water using electrochemical/chemical methods and advanced oxidation: A pilot plant approach

The purpose of this work was to develop a pilot plant purification system and apply it to groundwater used for human consumption, containing high concentrations of arsenic and increased levels of phosphates, ammonia, mercury and color. The groundwater used was obtained from the production well in the Vinkovci County (Eastern Croatia). Due to a complex composition of the treated water, the purification system involved a combined electrochemical treatment, using iron and aluminum electrode plates with simultaneous ozonation, followed by a post-treatment with UV, ozone and hydrogen peroxide. The removal of the contaminant with the waste sludge collected during the electrochemical treatment was also tested. The combined electrochemical and advanced oxidation treatment resulted in the complete removal of arsenic, phosphates, color, turbidity, suspended solids and ammonia, while the removal of other contaminants of interest was up to 96.7%. Comparable removal efficiencies were obtained by using waste sludge as a coagulant.

Online monitoring of Escherichia coli and Bacillus thuringiensis spore inactivation after advanced oxidation treatment

Various studies have shown that advanced oxidation processes (AOPs) such as UV light in combination with hydrogen peroxide is an efficient process for the removal of a large variety of emerging contaminants including microorganisms. The mechanism of destruction in the presence of hydrogen peroxide (H2O2) is the enhanced formation of hydroxyl (·OH) radicals, which have a high oxidation potential. The goal of this study was to utilize in‐line advanced oxidation to inactivate microbes, and document the inactivation via an in‐line, real‐time sensor. Escherichia coli cells and Bacillus thuringiensis spores were exposed to UV/H2O2 treatment in DI water, and the online sensor BioSentry® was evaluated for its potential to monitor inactivation in real‐time. B. thuringiensis was selected as a non‐pathogenic surrogate for B. anthracis, the causative agent of anthrax and a proven biological weapon. UV radiation and UV/H2O2 exposure resulted in a >6 log10 reduction of the viable culturable counts of E. coli vegetative cells, and a 3 log10 reduction of B. thuringiensis spores. Scanning electron microscopy of the treated samples revealed severe damage on the surface of most E. coli cells, yet there was no significant change observed in the morphology of the B. thuringiensis spores. Following AOP exposure, the BioSentry sensor showed an increase in the categories of unknown, rod and spores counts, but overall, did not correspond well with viable count assays. Data from this study show that advanced oxidation processes effectively inactivate E. coli vegetative cells, but not B. thuringiensis spores, which were more resistant to AOP. Further, the BioSentry in‐line sensor was not successful in documenting destruction of the microbial cells in real‐time.

Photodegradation of 2-methyl-4-chlorophenol in a KrCl exciplex flow-through photoreactor: a kinetic study

The removal of 2-methyl-4-chlorophenol (MC), the main photoproduct from 4-chloro-2-methylphenoxyacetic acid oxidation, has been studied with an advanced oxidation treatment and, for this purpose, a KrCl exciplex flow-through photoreactor was tested. Preliminary results show that the use of UV treatment leads to practically total MC degradation in 10, 60 or 90 min for the initial concentrations of 0.2, 1.0 or 2.0 mM, respectively. However, to attain higher elimination of the main photoproducts, 2-MH and 2-MB, addition of an oxidizing agent, such as hydrogen peroxide, is necessary. With molar ratios H2O2/MC/1 or higher, smaller concentrations of photoproducts are obtained after the treatment. Additional chemical analysis, such as chemical oxygen demand (COD) suggests that although COD is smaller after the treatment than before, for the highest H2O2 concentrations an excess of H2O2 remains in the medium, which increases this parameter, being required longer treatment times. Total phenols, pH, and residual chlorine also confirm these results. Besides, a photodegradation mechanism, based on the formation of an unstable intermediate compound that quickly degrades to the photoproducts, was also proposed. A kinetic model was developed and the good level of approximation between experimental and theoretical conversion values for all the experiments confirms the validity of the model.