Treatment Of Real Effluent Research Articles

Advanced oxidation processes by UV/H2O2 for the removal of anionic surfactants in a decentralized wastewater treatment plant in Ecuador

ABSTRACT Surfactants are persistent pollutants that pose risks to ecosystems and human health due to their low removal efficiency in conventional wastewater treatment plants. In Guayaquil, Ecuador, a decentralized facility discharges water with a surfactant concentration that exceeds the national legislation up to 20 times. This work aims to demonstrate the effectiveness of the advanced oxidation process UV/H2O2 in removing anionic surfactants as a tertiary treatment for the decentralized facility investigated. A laboratory-scale batch system was tested for the treatment of real effluent with three hydrogen peroxide concentrations (100, 250, and 500 mg L−1) and UV exposure up to 120 min. All experimental trials were run in duplicate. After 60 min of UV exposure with 250 mg L−1 of H2O2, the anionic surfactant removal was 94.3 ± 4.3%, and the effluent complied with the discharge limits (<0.5 mg L−1). These operational parameters were selected for continuous laboratory-scale experiments to simulate the facility operation, achieving a maximum removal of 92.3 ± 2.5%. Although the reactor demonstrates a high removal rate, improvements to its configuration are necessary to meet discharge limits. The UV/H2O2 process allowed the removal of anionic surfactants, suggesting its feasibility as a complementary treatment in decentralized plants with similar problems.

Visible LED active photocatalyst based on cerium doped titania for Rhodamine B degradation: Radical's contribution, stability and response surface methodology optimization

In this study, cerium modified TiO2 catalyst was prepared and the performance on the photocatalytic degradation of Rhodamine B (RhB) in aqueous solution was evaluated. For the band gap engineering, three different percentages of Ce-doped TiO2 (3, 5 and 7 % mol) were synthesized using the simple, efficient, and low-cost sol-gel method. Structural, morphological, and optical analysis, performed by XRD-Rietveld, HRTEM, EDX, XPS and UV–Vis DRS techniques, indicate the formation of nanostructured Ce-doped TiO2 system with anatase phase and band gap in the visible range. Then, Ce-doping percentage, dose of photocatalyst and initial concentration of RhB effects on the removal efficiency were evaluated. The high removal efficiency of 70 % within 150 min was recorded under the condition of: 7 % Ce-doped TiO2 sample, 1.33 g L−1 of dose, and a concentration of RhB of 5 mg L−1. Additionally, a response surface methodology (RSM) was developed for stablish optimal degradation parameters when varying relevant factors for water treatment of real effluents: pH, NaCl, and Cu concentrations. The resulting model shows that the pH is the variable with the highest effect on the photodegradation. Finally, a scavenger study revealed that OH• radicals play a key role in the reaction; and, albeit TOC analysis reveals only 8.55 % of mineralization yield. Cycling study shows that the photocatalyst kept active after 3 cycles of reutilization. The present paper further examinates the parameters affecting Visible LED driven degradation of organic dye in water using Ce-doped TiO2 system and represents an advance in the comprehension of dye degradation with low use of energy.

Electrocoagulation technique and statistical analysis for treatment of real effluent from the pulp and paper industry

The electrochemical treatment of Organic Pollutants is a promising technique for substances with biodegradability resistance. In this research, the black liquor effluent originating from the Rakta Paper and Paper Company's mill, which employs rice straw as a raw material for paper fiber production, was subjected to treatment using the electrocoagulation method utilizing monopolar aluminum electrodes. The experiments were carried out using a 2.5 L electrochemical cell equipped with monopolar aluminum electrodes connected in parallel. The study examined the impact of operating parameters such as initial pH, current density, number of plates and electrolyte concentration on percentage removal and power consumption. The results revealed a positive correlation between the percentage of color removal and the duration of electrolysis, current density, sodium chloride concentration, and the number of electrodes used. The maximum color removal was observed at initial solution pH 6.5, experimental time 120 min, current density 61.8 A m−2, initial NaCl solution concentration 2 g L−1 and six aluminum plates. The statistical and mathematical data based on experimental results were analyzed using the central composite design from response surface methodology (RSM). The quadratic model is deemed appropriate owing to its substantial coefficient of determination (R2 = 0.99) and statistically significant p-value (≤ 0.0002), suggesting the model's significance. The experimental results indicate that the utilization of electrocoagulation as a treatment method for paper mill effluents has demonstrated superior efficacy compared to the adsorption technique.

Remediation of real industrial hypersaline effluent using sequential approach of precipitation followed by cavitation based oxidative process

The current study aims to develop a cost-effective and efficient treatment method for the remediation of amine-containing real industrial effluent. The method consists of a precipitation to remove chloride ions and TDS, followed by cavitation-based AOPs involving US and chemical oxidants as H2O2, O3, Fenton’s reagent, NaClO, and nTiO2. Different parameters including precipitating agent type and dosage, oxidant loading/flow rate, and time were assessed to determine optimal conditions for effective treatment. Treatment schemes were evaluated based on cavitational yield (mg/J), treatment cost (Rs/L), and COD reduction to select an industrially feasible design for amine-containing real effluent treatment. The optimum conditions elucidated were H2O2 loading of 3 g/L, NaClO loading of 3 g/L, O3 flowrate of 3 LPH, nTiO2 loading of 3 g/L, and Fenton’s reagent ratio (H2O2/Fe2+) as 6:1. Under the optimum conditions, US+nTiO2 (70%) treatment schemes were the most efficient, achieving a maximum COD reduction compared to US+Fenton (65%), US+H2O2 (36%), US+O3 (49%) and US+NaClO (53%) schemes. Additionally, impact of chloride and TDS on the oxidation process in terms of COD reduction was assessed. Using Rotavap instead of precipitation, and subsequent use of the best oxidation method (US/HC+Fenton+CaO) achieved COD and TDS levels below 250 mg/L (discharge limit) at optimum conditions, with minimal operating costs of 0.23 $/L and 0.15 $/L, respectively. Overall, the study concluded that the sequential approach of precipitation/Rotavap and cavitation-assisted oxidation is an effective and sustainable method, providing a promising solution for the wastewater treatment in the metallurgical industry.

Valorization of biomass ash for the effective removal of dipyrone from water: an efficient and low‐cost option

AbstractBackgroundIn order to propose a destination for the bottom ash generated from biomass burning, its morphology, functional groups and mineral phases were studied. Dipyrone has been extensively used as an antipyretic, increased due to cases of COVID‐19, and due to excretion by urine, incorrect disposal and industrial effluents has been destined to wastewater, being harmful to human and animal life. The present study proposes using biomass ash for the adsorption of dipyrone.ResultsThe characterization of biomass ash shows a sufficient surface area size for adsorption, and a mainly amorphous structure with some peaks of quartz, calcite and other mineral phases. The results show that the kinetic model which best describes the adsorption is the pseudo‐first‐order model. The Langmuir model best fits at 25 °C, and the Freundlich model best describes the adsorption at 35 and 45 °C. The thermodynamic parameters indicated that the process is endothermic with a maximum adsorptive capacity of 65.27 mg g−1. In addition, the adsorption is spontaneous, disordered and chemical. The ionic strength study reveals that the adsorbent is promising for real effluent treatment and there is evidence that electrostatic interaction is not the primary adsorptive mechanism, agreeing with the result obtained from pH testing. The proposed mechanism for dipyrone removal involves hydrogen bonds, π bonds and electron donor–acceptor complex.ConclusionsThe results are promising in comparison with recent literature and solve two environmental problems: biomass bottom ash disposal and pharmaceutical removal in aqueous medium. The ash may be regarded as a low‐cost and environmentally friendly adsorbent. © 2023 Society of Chemical Industry (SCI).

A Brief Review of the Status of Low-Pressure Membrane Technology Implementation for Petroleum Industry Effluent Treatment.

Low-pressure membrane technology (ultrafiltration and microfiltration) has been applied to two key effluents generated by the petroleum industry: produced water (PW) from oil exploration, a significant proportion being generated offshore, and onshore refinery/petrochemical effluent. PW is treated physicochemically to remove the oil prior to discharge, whereas the onshore effluents are often treated biologically to remove both the suspended and dissolved organic fractions. This review examines the efficacy and extent of implementation of membrane technology for these two distinct applications, focusing on data and information pertaining to the treatment of real effluents at large/full scale. Reported data trends from PW membrane filtration reveal that, notwithstanding extensive testing of ceramic membrane material for this duty, the mean fluxes sustained are highly variable and generally insufficiently high for offshore treatment on oil platforms where space is limited. This appears to be associated with the use of polymer for chemically-enhanced enhanced oil recovery, which causes significant membrane fouling impairing membrane permeability. Against this, the application of MBRs to onshore oil effluent treatment is well established, with a relatively narrow range of flux values reported (9–17 L·m−2·h−1) and >80% COD removal. It is concluded that the prospects of MBRs for petroleum industry effluent treatment are more favorable than implementation of membrane filtration for offshore PW treatment.

Ion Exchange to Capture Iron after Real Effluent Treatment by Fenton’s Process

The main drawback of Fenton′s process is the formation of ferric sludge. In this work, ion exchange (IE) appears as a complement to the Fenton process, allowing, on the one hand, to remove the iron excess present in the sludge, as well as reduce the COD of the real olive oil industry extraction wastewater (OOIEW) from the Fenton process. The Fenton process uses iron (II) sulfate as catalyst, therefore concentrations of iron up to 2 g L−1 could be present in the treated OOIEW. The iron and COD adsorption equilibrium behavior has been modelized by Langmuir, Freundlich and Temkin isotherms. Moreover, the resin efficiency was tested in a continuous fixed-bed column. It was concluded that the resin maintains iron adsorption capacity over at least three reuse cycles. Overall Fenton’s process followed by ion exchange seems to be a promising approach for the treatment of cumbersome industrial wastewaters.

Application of hybrid oxidative processes based on cavitation for the treatment of commercial dye industry effluents

The present work demonstrates the significant role of ultrasound (US) in intensifying the efficacy of the combination with Fenton reagent and/or ozone for the treatment of real dye industry industrial effluent procured from the local industry. Initial part of the work focused on analysing the literature based on combination approaches of US with different oxidants applied for the treatment of real and simulated effluents focusing on the dyes. The work also provides guidelines for the selection of optimal operating parameters for maximizing the intensification of the degradation. The second part of the work presents an experimental study into combined approaches of ultrasound with ozone (O3) and Fenton’s reagent for treatment of real effluent. Under optimized conditions (100 W, 20 kHz and duty cycle of 70%), maximum COD reductions of 94.79% and 51% were observed using a combined approach of US + Fenton oxidation followed by lime treatment for the treatment of effluent-I and effluent-II respectively at H2O2 loading of 17.5 g/L, H2O2/Fe2+ ratio of 3, pH of 4, CaO dose of 1 g/L and an overall treatment time of 70 min. US + Fenton + O3 followed by lime was also applied for treatment under ozone loading of 1 g/h for the treatment of effluent-I and it was found that maximum COD reduction of 95.12% was obtained within 30 min of treatment time, indicating use of ozone did not result in significant value addition in terms of COD reduction but resulted in faster treatment. HC (inlet pressure: 4 bar) + Fenton + Lime scheme was successfully replicated on a pilot-scale resulting in maximum COD reduction of 57.65% within 70 min of treatment time. Overall, it has been concluded that the hybrid oxidative processes as US + Fenton followed by lime treatment is established as the best approach ensuring effective COD reduction at the same time obtaining final colourless/reusable effluent.

Continuous flow pulsed power plasma reactor for the treatment of aqueous solution containing volatile organic compounds and real pharmaceutical wastewater

The degradation of four recalcitrant and toxic VOCs (volatile organic compounds) present in pharmaceutical wastewater was studied using a continuous flow plasma reactor, along with evaluating its potential for real effluent treatment. The wastewater was sprayed into the plasma zone of the reactor, and it was re-circulated for better performance. The effect of different HRTs (hydraulic retention time) and initial concentrations of VOCs on the degradation efficiency were evaluated. In continuous reactor, complete removal of 200 mg/L of chloroform, chlorobenzene, and toluene was achieved at a HRT of 33.3 min, with an energy consumption of 22.4 kWh/m3. The study on the effect of different inlet loading rates of VOCs on elimination capacity showed that, the removal was limited initially by diffusion of reactive species and at higher loads, it was limited by insufficient amount of reactive species produced. During degradation of VOC mixture, more than 90% removal of chloroform, chlorobenzene and toluene was achieved at HRT of 33.3 min, and the TOC removal was 78.3%. The degradation efficiency of VOC mixture reduced slightly compared to that of individual compounds, due to insufficient amount of reactive species produced. The COD and BOD removal achieved after 140 min of direct plasma treatment of real pharmaceutical wastewater in batch reactor was 92.7% and 95.2%, respectively. Coagulation pre-treatment did not have a significant effect on the plasma treatment of real wastewater. When pharmaceutical effluent treatment was carried out in continuous flow reactor, 91.8% COD removal, 90.9% BOD removal and more than 90% degradation of all VOCs were achieved at a HRT of 150 min. Plasma treatment alone was capable of effectively treating the real pharmaceutical wastewater without any pre-treatment.

Enhanced biohydrogen production from sugar industry effluent using nickel oxide and cobalt oxide as cathode nanocatalysts in microbial electrolysis cell

SummaryDevelopment of economically viable cathode catalysts with practicability in the treatment of real effluents is one of the strenuous efforts among the multidisciplinary approaches in microbial electrolysis cell (MEC). Treatment of industrial effluents using this technology had resulted in simultaneous energy production in the form of hydrogen along with wastewater treatment, promoting both energy and environmental benefits. In this study, two metal oxides such as, Nickel Oxide (NiO) and Cobalt oxide (Co3O4) were employed as the cathode catalyst using sugar industry effluent as the substrate for biohydrogen production in the MEC. The addition of NiO and Co3O4 on nickel foam (NF) has demonstrated better hydrogen evolution performance than the control (uncoated) cathode. Electrochemical characterization of the modified cathodes revealed the improved capability analogous to the current density and hydrogen production rate (HPR) obtained in the experimentation. The best performance was achieved by NiO/NF with the maximum HPR of 3.39 ± 0.03 mmol/L/D, coloumbic efficiency of 58 ± 1.4%, hydrogen recovery of 27 ± 1.8% and COD removal efficiency of 52 ± 1.6% when operated with the applied voltage of 1.0 V. Hence, the potential of metal oxides was demonstrated for the candidature of efficient and economical cathode materials in MECs.

Plug flow approaching novel reactor employing in-situ dual effect of photocatalysis and photo-Fenton for the degradation of metronidazole

The novel concept of fixed-bed in-situ continuous reactor approaching plug flow (PFR) has been employed for the degradation of Metronidazole (MTZ). Axial dispersion model has been employed to validate the exit age distribution. PFR modeled reactor was employed with novel composite beads composed of fuller’s earth and foundry sand encompassing the properties of the in-situ dual effect of both photocatalysis and photo-Fenton. The optimization was performed under the solar irradiations using reactors in series. Significant reduction in treatment time was achieved as dual effect took only 45 min for 84% removal optimized at three reactors in series with flow rate of 8 L h−1, 75% area covered by the beads.Whereas individual processes of photo-Fenton and photocatalysis engaged nearly 3.5 h for merely 45% removal. The in-situ dual process exhibited 84% synergy, calculated in terms of the rate constant, over the individual processes. Various parameters including flow rate, number of reactors, H2O2 dose, the surface area covered by the beads, etc were optimized. 55% reduction in COD after the third reactor (in once-through mode) and formation of various ions substantiated the mineralization of MTZ into various small compounds. Results were extended to real effluent treatment using once through plug flow reactor approach. The tentative mechanism for the degradation of MTZ was also proposed. The industry viability of the reported process was demonstrated by recycling the composite beads up to 80 cycles and evaluating the approximate cost for the removal of the drug. Various characterizations like SEM, XRD, EDS, FT-IR, DRS confirmed the in-situ dual process.

Electrochemical incineration of glyphosate wastewater using three-dimensional electrode

ABSTRACT Anodic oxidation of recalcitrant organic compounds is still challenging concerning to the anode material and mass transport limitations imposed by the low concentration. In this work, we studied the degradation of a real wastewater containing glyphosate using an electrode of PbO2 electrodeposited on a three-dimensional matrix of reticulated vitreous carbon (RVC). The high mass transfer rate provided by the RVC/PbO2 anode is demonstrated. A Box–Behnken factorial design was used for a systematic analysis of the effects of current density, flow rate and temperature on the degradation and mineralisation kinetics, current efficiency and specific energy consumption. The optimised degradation performance was achieved applying 30 mA cm−2, 3000 mL min−1 and 50°C. As the flow rate increases from 150 to 1500 mL min−1, the current efficiency increases from 18% to 65% and the energy consumption dropped from 72 to 33 kWh kg−1 due to the mass transfer enhancement promoted by the porous matrix. The efficacy of the electrochemical process for the treatment of real effluents using the three-dimensional PbO2 has been demonstrated.

Treatment of textile industry wastewater by electrocoagulation coupled with electrochemical advanced oxidation process

The present study deals with the treatment of real effluents, containing a mixture of reactive dyes (mainly methylene blue), by electrocoagulation (EC) coupled with electrochemical advanced oxidation processes (EAOPs) such as peroxi-coagulation (PC), anodic oxidation (AO), and electro-Fenton (EF), individually. To choose the right treatment process, the key criteria should be higher degradation efficiency and minimal energy consumption. Textile effluents are physico-chemical characterized and the operating parameters i.e. the initial pH, the current density, and the electrolysis time, were investigated. Wastewater treatment energy consumption was evaluated for each combined process. The results highlighted high efficiency of electrochemical processes in effective degradation of organic pollutants at the optimum operating conditions. Among the electrochemical advanced oxidation processes tested, sequential EC-EF treatment was being preferred and quite effective since it provided electro generated hydroxyl radical OH especially when using the boron-doped diamond. Thus, removals of 97%, 100% and 100% for, respectively, TOC, turbidity and color removal were achieved by using the EC-EF combined process. Energy consumption values were evaluated for textile dye decolorization as 0.45–1.5 kW h kg−1 of the removed TOC, depending on the applied current density. Regarding the efficiency level and the operating cost, the EC-EF combined process offers many advantages allowing the reuse of the treated water for other purposes.

Uptake of trivalent chromium from aqueous solutions by xanthate pine bark: Characterization, batch and column studies

Abstract In this study, the performance of chemically modified pine bark for removal of Cr(III) from solutions was investigated. Initially, several chemicals were tested (NaOH, C5H9NO4, H3PO2 and CS2). The xanthate pine bark (XPB) obtained with CS2, was screened as the best adsorbent and thus, it was characterized in respect to morphological and textural properties. Sulfur groups after xanthation reaction were identified on XPB by FTIR and EDS spectroscopies. Equilibrium isotherm and kinetics were determined. The equilibrium data were well described by the Langmuir isotherm allowing to calculate the maximum adsorption capacity (56.5 mg/g). The kinetics is fast and follows a pseudo-second order model. Furthermore, an ion-exchange sorption mechanism between Cr(III) and Na+ was proposed. Among the desorbing agents tested, the best results were achieved with 2.0 M H2SO4. Moreover, in the column tests, a reduction on the breakthrough time and the stoichiometric time from 36.5 and 22.8%, respectively, was observed, when the feed concentration increased from 230 to 500 mg/L. The breakthrough curves were well modeled by Bohard-Adams, Thomas or Yoon-Nelson equations. Globally, XPB revealed to be a promising adsorbent for uptake Cr(III). The scale-up design and the economic assessment indicated potential applicability for the treatment of real effluents.

Optimization of azo printing dye removal with oak leaves-nZVI/H2O2 system using statistically designed experiment

The paper investigates the potential use of nano zero-valent iron (nZVI) particles as a cheap, natural and effective catalyst in the Fenton-like system for the removal of water-based Magenta flexographic dye from aqueous solution. The functional nZVI was successfully synthesized within an environmentally friendly method, by using the natural product extract, oak leaves (OAK-nZVI). The process of Magenta removal was optimized using statistically designed experiment. The influence of four quantitative parameters on decolorization efficiency was investigated: initial dye concentration (20–180 mgL-1), OAK- nZVI dosage (0.75–60 mgL-1), H2O2 concentration (1–11 mM) and pH value (2–10). The results of statistical analysis show that OAK-nZVI dosage and pH significantly contribute to the decolorization efficiency, while the concentration of H2O2 has a significant influence on their impact. The optimization yielded highest removal efficiency of 91.95% under following conditions: initial dye concentration of 180 mgL−1, OAK-nZVI dosage of 60 mgL−1, H2O2 concentration of 11 mM and pH value 2. Optimization results were experimentally verified. Treatment of real effluent under optimized experimental conditions resulted within 84.06% Magenta removal after a reaction time of 60 min. The absorption spectra of Magenta dye clearly indicate the changes in the molecular structure in the form of the destruction of azo bond in the chromophore, leading to the decolorization of dye solution. Based on the GC–MS analysis, the mechanism for Fenton-like oxidation of Magenta was proposed.

Preferable adsorption of phosphate using lanthanum-incorporated porous zeolite: Characteristics and mechanism

The adsorbent, where lanthanum oxide was incorporated onto porous zeolite (La-Z), of preferable adsorption towards phosphate was prepared by hydrothermal synthesis. Based on pH effect results, La-Z would effectively sequestrate phosphate over wider pH range of 3.0–7.0, alkaline conditions were unfavorable for phosphate. The adsorption of phosphate was not significantly influenced by ionic strength and by coexisting anions of chloride, nitrate and sulfate but bicarbonate showed slightly greater negative effects, indicating La-Z possessed highly selectivity to phosphate. Adsorption of phosphate could be well fitted by pseudo-second-order model and the process was mainly controlled by intra-particle diffusion. Equilibrium adsorption demonstrated that Langmuir model was more suitable than Freundlich model for description phosphate adsorption and the adsorption capacity was 17.2mgPg−1, which exhibited 95% utilization of incorporated La. Over 95% phosphate was eliminated in real effluent treatment when the dose was 2gL−1. The underlying mechanism for phosphate capture was probed with Zeta potential and X-ray photoelectron spectroscope analysis, and the formation of La-P inner-sphere complexation was testified to be the dominant pathway. All the results suggested that the porous zeolite-supported lanthanum oxide can serve as a promising adsorbent for phosphate removal in realistic application.

Industrial waste derived biosorbent for toxic metal remediation: Mechanism studies and spent biosorbent management

The dried activated tannery industry sludge was used as complex biosorbent for removal of Ni(II), Co(II), Zn(II) and Cd(II) in single and multi-component system. The mechanism for toxic metals biosorption was analyzed along with equilibrium isotherm and kinetic study. The efficiency of the biosorbent was studied for real effluent treatment. Further, safe disposal of the spent biosorbent in glass form was established which is significant for commercial implementation of the biosorption technology. Zn(II) and Cd(II) showed 99% removal within 10 min while Ni(II) and Co(II) attained 98% removal at 20–24h. The biosorbent showed >96% removal efficiency for these metals in effluents from battery manufacturing industry with simultaneous removal of Pb, Cu and Fe ions. Chemical modification of hydroxyl, carboxyl, amino, phosphate, sulfonyl and carbonyl functional groups were undertaken and surface characterization of the biosorbent was done using zeta-potential, FTIR, FESEM-EDX and XPS technique to elucidate the biosorption mechanism. The biosorption efficiency was found to decrease significantly indicating involvement of functional groups in metal binding which was confirmed by FT-IR. Rapid removal of Zn(II) and Cd(II) was due to binding with functional groups. However, the gradual removal of Ni(II) and Co(II) was governed by ionic exchange mechanism, confirmed by ICP-AES. Deconvolution of N1s and C1s XPS spectra produced two and one additional peaks respectively, suggesting formation of amino-metal complexes. Increase in atomic concentration of total oxygen explained further the formation of different metal complexes on biosorbent surface. Upto 30% of metal laden biosorbent could be inertized in phosphate glass matrix as confirmed by the XRD-analysis. No leaching of heavy metals was observed on the glass with thermal cycle at 75°C for 8h/day up to 35 days.

Treatment of real effluents from the pharmaceutical industry: A comparison between Fenton oxidation and conductive-diamond electro-oxidation

Wastewater produced in pharmaceutical manufacturing plants (PMPs), especially the one coming from organic-synthesis facilities, is characterized by its large variability due to the wide range of solvents and chemical reagents used in the different stages of the production of medicines. Normally, the toxicity of the organic compounds prevent the utilization of biological processes and more powerful treatments are needed becoming advanced oxidation processes (AOPs) a valid alternative. In this work, the efficiency in abatement of pollution by Fenton oxidation (FO) and conductive-diamond electro-oxidation (CDEO) are compared in the treatment of 60 real effluents coming from different processes carried out in a pharmaceutical facility, using standardized tests. In 80% of the samples, CDEO was found to be more efficient than FO and in the remaining 20%, coagulation was found to exhibit a great significance in the COD abatement mechanism during FO, pointing out the effectiveness of the oxidation promoted by the electrochemical technology. Mean oxidation state of carbon was found to be a relevant parameter to understand the behavior of the oxidation technologies. It varied inversely proportional to efficiency in FO and it showed practically no influence in the case of CDEO.

Efficiency comparison of ozonation, photolysis, photocatalysis and photoelectrocatalysis methods in real textile wastewater decolorization

Treatment of real effluents from industries using AOPs stands to be an imperative task of crucial importance yet quite huge a challenge largely given the nature of complexity of these wastewaters. The present work sought to develop a versatile system aimed at the treatment of real wastewater using a bubbling annular reactor, which enables us to test the efficiency of photolysis; photocatalysis, photoelectrocatalysis and direct ozonation using oxygen or ozone as gas flow. A TiO2 nanotubes electrode was used as photocatalyst in photocatalytic and photoelectrocatalytic measurements with and without coupling with ozonation under pH 3.0 and pH 8.0 leading to 50% of color removal after 60 min reaction. However, the results indicated 90% of color removal upon the bubbling of ozone after 15 min of treatment. A synergistic effect was observed in all experiments using the AOPs in the presence of ozone under both pH values. Interestingly though, 85% of decolorization was obtained through direct ozonation without any change in the effluent following 10 min of treatment. The results were discussed in terms of electric energy per order and were compared to those reported previously. For real textile wastewater, ozonation appears to be a promising candidate for full-scale effluent decolorization.

Ion exchange system for the final purification of olive mill wastewater: Performance of model vs. real effluent treatment

Olive mill wastewater (OMW) is a highly pollutant effluent which can be pretreated through an advanced oxidation process. OMW after this secondary treatment (OMW-2ST) presented high sodium and chloride concentrations, responsible for its high conductivity. In this context, two ion exchange (IE) resins were examined (Dowex Marathon C and Amberlite IRA-67) for final OMW-2ST purification. As this effluent is extremely seasonal and deteriorates within few days, the main parameters affecting IE process were previously optimized with lab-made model OMW-2ST. Then the optimum operating conditions were tested with real OMW-2ST. Evolution of conductivity was evaluated as a function of recirculation time to study the effect of resins disposition and resins dosages and compared with both OMW-2ST. Equilibrium was reached in 10 and 20min for model and real OMW-2ST, respectively. Furthermore, continuous mode experiments were carried out in to investigate the evolution of conductivity as a function of operating time. Breakthrough time was lower for real versus model OMW-2ST (120 vs. 147.5min). Minimum 10gL−1 resin dosage ensured 74% and 78% removal efficiencies, thus fulfilling irrigation water legal requirements and rending the production system cost-effective and environmentally respectful. Finally, model OMW-2ST is confirmed as good simulating media to reproduce IE processes.