Highest Total Organic Carbon Removal Research Articles

Magnetic CoFe2O4 nanoparticles supported on titanate nanotubes (CoFe2O4/TNTs) as a novel heterogeneous catalyst for peroxymonosulfate activation and degradation of organic pollutants

Magnetic spinel ferrites, as heterogeneous catalysts to generate powerful radicals from peroxymonosulfate (PMS) for the degradation of organic pollutants, have received much attention in recent years due to the characteristic of environmental benefits. In this study, with titanate nanotubes (TNTs) as catalyst support, a novel CoFe2O4/TNTs hybrid was constructed by an impregnation-calcination method. Characterization results revealed that TNTs support could promise small size and good dispersion of CoFe2O4 nanoparticles. Compared to the pure CoFe2O4, the as-prepared CoFe2O4/TNTs not only exhibited better performance in catalytic decomposition of Rhodamine B, but also realized higher total organic carbon removal and less cobalt leaching, which could be attributed to the enhanced catalytic ability from smaller CoFe2O4 nanoparticles and the unique ion-exchange ability from TNTs support. Some influential factors, including reaction temperature, dosages of PMS and CoFe2O4/TNTs, and pH values were investigated and analyzed. Moreover, CoFe2O4/TNTs maintained its catalytic efficiency during the repeated batch experiments and also displayed functional advantages in the catalytic degradation of phenol. We believe the CoFe2O4/TNTs hybrid can be an efficient and green heterogeneous catalyst for the degradation of organic pollutants, and this study provides insights into the rational design and development of alternative catalysts for wastewater treatment.

Long-term performance of a membrane bioreactor treating table olive processing wastewater

BACKGROUND: Table olive processing wastewater (TOPW) is a seriously polluting and difficult to treat effluent, characterized by widely fluctuating pH and salinity, as well as high concentrations of organic matter and polyphenols. This systematic long-term study in a laboratory-scale pilot demonstrates that membrane bioreactor (MBR) technology is effective in substantially bio-degrading TOPW. RESULTS: After implementation of an appropriate protocol of active biomass acclimatization/proliferation, the MBR pilot was operated for 6 months with real TOPW effluent, under various operating conditions. Total organic carbon (TOC) and total polyphenol (TPh) compounds removal efficiencies were very high with mean values 91.5 and 82.8%, respectively; nutrient (N and P) removal was also satisfactory. The membrane exhibited stable performance at moderate biomass concentration, with a tendency to deteriorate at higher biomass concentration. Fouled membrane permeability could be fully restored by implementing the usual chemical cleaning protocols. CONCLUSIONS: Despite the high percentage TOC and TPh removal, the MBR effluent requires final post-treatment to remove a yellowish tint and further reduce its organic content, depending on local discharge standards. The MBR can serve as the basic treatment process in an integrated scheme for TOPW management, which needs additional R&D to further develop and optimize.

Recycling wool-dyeing effluents after renovation through photocatalysis with Cu-Fe bimetallic-grafted polytetrafluoroethylene fiber complex and H2O2

A Cu-Fe bimetallic-poly acrylic acid-grafted polytetrafluoroethylene (PTFE) fiber complex (Cu-Fe-PAA-g-PTFE) was prepared as an effective heterogeneous photo-Fenton catalyst for oxidative treatment and recycling of acid dye effluents from dyeing of wool fabric. Important factors affecting acid dye degradation, namely catalyst loading, H2O2 concentration, solution pH, and dye concentration, were examined to optimize the photo-Fenton process conditions for the treatment of acidic dyeing effluents. Three acid dyes were used for the coloration of wool fabrics by a regular exhaustion process. The resulting wool-dyeing effluents were then treated using the optimized photo-Fenton process. The impact of recycling on the quality of the dyed wool fabric was also investigated. A photo-Fenton reaction system consisting of Cu-Fe-PAA-g-PTFE and H2O2 successfully degraded the acid dyes in water. Complete decoloration and a relatively high TOC (total organic carbon) removal percentage were achieved in 4.0 h under ultraviolet radiation for real wool-dyeing effluents when 7.0 g/l Cu-Fe-PAA-g-PTFE and 7.0 mmol/l H2O2 were used. The number of recycled effluents was found to be highly determined by their quality and dyeing properties of the acid dyes used. The dyeing quality was not affected for three successive cycles. However, lighter shades, significant color differences, and deteriorated fastness were observed for dyed wool fabrics in the fourth dyeing cycle, possibly because of an increase in the residual TOC value of the renovated effluents. Further TOC reduction of the treated effluents is therefore needed for their repeated reuse in more than three dyeing cycles.

Sequential ozone advanced oxidation and biological oxidation processes to remove selected pharmaceutical contaminants from an urban wastewater

Sequential treatments consisting in a chemical process followed by a conventional biological treatment, have been applied to remove mixtures of nine contaminants of pharmaceutical type spiked in a primary sedimentation effluent of a municipal wastewater. Combinations of ozone, UVA black light (BL) and Fe(III) or Fe3O4 catalysts constituted the chemical systems. Regardless of the Advanced Oxidation Process (AOP), the removal of pharmaceutical compounds was achieved in 1 h of reaction, while total organic carbon (TOC) only diminished between 3.4 and 6%. Among selected ozonation systems to be implemented before the biological treatment, the application of ozone alone in the pre-treatment stage is recommended due to the increase of the biodegradability observed. The application of ozone followed by the conventional biological treatment leads high TOC and COD removal rates, 60 and 61%, respectively, and allows the subsequent biological treatment works with shorter hydraulic residence time (HRT). Moreover, the influence of the application of AOPs before and after a conventional biological process was compared, concluding that the decision to take depends on the characterization of the initial wastewater with pharmaceutical compounds.

Biodegradability Enhancement of Mature Landfill Leachate Using Fenton Process under Different COD Loading Factors

The Fenton process is evaluated as a treatment method to reduce the total organic carbon (TOC) and increase biodegradability of the organic substrate in a mature landfill leachate. Biodegradability was quantified in terms of the ratios between biochemical oxygen demand after 5 days (BOD5) to chemical oxygen demand (COD) (after different Fenton reaction times), and BOD5 (after different Fenton reaction times) to initial BOD5 (original leachate sample), termed as BOD5,0, respectively. An increased TOC removal and improved BOD5/COD ratios were observed following the pH sequence of 3.5 > 6.0 > 2.0. The maximum TOC removal of 61 % and the highest BOD5/COD ratio from 0.11 to 0.37 were observed at pH 3.5. To quantify biodegradability enhancement at different COD loading factors (LCOD) by the Fenton process, the H2O2/Fe2+ ratio was fixed at 1.8 (w/w) and LCOD ranged from 0.22 to 1.19. Experimental results showed that higher TOC removal and biodegradability enhancement were obtained at lower LCOD. Quantitatively, two linear regression equations between LCOD and biodegradability (in terms of BOD5/COD and BOD5/BOD5,0) were established, as: BOD5/COD = 0.57–0.38 LCOD and BOD5/BOD5,0 = 1.40–0.40 LCOD with correlation coefficients (R 2 ) of 0.87 and 0.51, respectively. The experimental work described here, demonstrated that the Fenton process can be used as an effective pre-treatment strategy to increase leachate biodegradability within a short reaction time from 1 to 5 min.

Degradation of phenol by synergistic chlorine-enhanced photo-assisted electrochemical oxidation

Hybridization of a UV-C photoreactor with an electrochemical cell led to the discovery of a distinctive synergistic mechanism for the degradation and mineralization of phenol when free chlorine-producing anodes were utilized in the presence of chloride. After 6h, photochemical (UV) treatment resulted in 29% phenol mineralization and electrochemical (EL) treatment resulted in 35% and 52% mineralization using boron-doped diamond (BDD) and ruthenium oxide on titanium (DSA-Cl2) anodes, respectively. However, the photo-assisted electrochemical (UVEL) process removed 88% and 96% of total organic carbon (TOC) after 6h with BDD and DSA-Cl2 anodes, respectively. The hybrid UVEL process generated highly reactive hydroxyl and chlorine radicals by the photolysis of in situ electrogenerated free chlorine. As a result, the UVEL treatment produced fewer chlorinated by-products compared to EL alone. UVEL with DSA-Cl2 had the highest TOC removal after 6h (96%), one of the highest mineralization rates (0.38h−1), and the lowest energy demand per order TOC removed (EEO=104kWhm−3order−1) without any residual toxicity after dechlorination. Generally, conventional advanced oxidation processes (UV/O3 and UV/H2O2) were most effective at mineralization up to 50%, but UVEL appeared more cost effective for mineralization beyond 75%.

Comparing atrazine and cyanuric acid electro-oxidation on mixed oxide and boron-doped diamond electrodes

The breakdown of pesticides has been promoted by many methods for clean up of contaminated soil and wastewaters. The main goal is to decrease the toxicity of the parent compound to achieve non-toxic compounds or even, when complete mineralization occurs, carbon dioxide and water. Therefore, electrochemical degradation (potentiostatic and galvanostatic) of both the pesticide atrazine and cyanuric acid (CA) at boron-doped diamond (BDD) and Ti/Ru0.3Ti0.7O2 dimensionally stable anode (DSA®) electrodes, in different supporting electrolytes (NaCl and Na2SO4), is presented with the aim of establishing the influence of the operational parameters on the process efficiency. The results demonstrate that both the electrode material and the supporting electrolyte have a strong influence on the rate of atrazine removal. In the chloride medium, the rate of atrazine removal is always greater than in sulfate under all conditions employed. Furthermore, in the sulfate medium, atrazine degradation was significant only at the BDD electrode. The total organic carbon (TOC) load decreased by 79% and 56% at the BDD and DSA® electrodes, respectively, in the chloride medium. This trend was maintained in the sulfate medium but the TOC removal was lower (i.e. 33% and 13% at BDD and DSA® electrodes, respectively). CA, a stable atrazine degradation intermediate, was also studied and it is efficiently removed using the BDD electrode in both media, mainly when high current densities are employed. The use of the BDD electrode in the chloride medium not only degrades atrazine but also mineralized cyanuric acid leading to the higher TOC removal.

Optimization and Modeling of the Photocatalytic Degradation of the Insect Repellent DEET in Aqueous TiO2 Suspensions

AbstractResponse surface methodology (RSM) and artificial neural networks (ANNs) based on a multivariate central composite design (CCD) were applied to model and optimize the photocatalytic degradation of N,N‐diethyl‐m‐toluamide (DEET). The individual and interaction effects of three main operating factors (mass of TiO2, initial DEET concentration, and irradiation intensity) on process efficiency were estimated, proving their important effect on % DEET removal. Among the independent variables, TiO2 concentration displayed the highest effect on DEET degradation followed by initial DEET concentration and UV intensity. The optimization and prediction capabilities of ANNs and RSM were compared on the basis of root mean squared error, mean absolute error, absolute average deviation, and correlation coefficient values. Results proved the usefulness and capability of the experimental design strategy for successful investigation and modeling of the photocatalytic process. Moreover, the selected ANN gave better estimation capabilities throughout the range of variables than RSM. Based on the models and the related experimental conditions, the optimal values of each parameter were determined. Under optimum conditions, DEET and total organic carbon (TOC) followed pseudo‐first order kinetics. Nearly complete degradation of DEET took place within 15 min whereas high TOC removal percentages (>85%) was achieved after 90 min irradiation time.

P.6.e.004 Smoking, nicotine dependence and anxiety in medical students

This work demonstrated that the catalytic wet oxidation (CWO) of high-strength alcohol-distillery waste liquors is feasible. Two distillery liquors (TOC=10 500; 22 500 mg/l; COD=26 000; 50 000 mg/l) produced by alcohol fermentation of enzymatic hydrolyzates from steam- and ammonia-exploded timothy grass were treated in a batch stirred autoclave over three different catalysts, 1% Pt/Al2O3, Mn/Ce oxides, and Cu(II)-exchanged NaY zeolite. The temperature and oxygen partial pressure ranges were (453–523 K) and (0.5–2.5 MPa), respectively. Effects of temperature, oxygen partial pressure, TOC content, and type of catalyst on the removal of total organic carbon (TOC) were investigated. The CWO initial rates were found to be first-order with respect to TOC, and the activation energies ranged from 34 to 51 kJ/mol. The highest TOC removal was achieved with Mn/Ce oxides and Cu(II)/NaY catalysts. The catalysts were found to be very effective for short contact times, while for prolonged exposures coke laydown was shown to be the prime factor responsible for the loss of catalyst activity. The carbonaceous deposits were characterized by electron spectroscopy for chemical analysis (ESCA) and temperature-programmed oxidation (TPO).

Treatment of phenol-formaldehyde resin manufacturing wastewater by the electrocoagulation process

Abstract The removal of total organic carbon (TOC) from wastewater generated from phenolformaldehyde resin manufacturing industry using the electrocoagulation process was studied in this paper. Experiments were carried out at current densities of 5.0, 7.5 and 10.0 mA/cm2 using iron electrodes connected in parallel arrangement in an undivided electrochemical reactor. TOC content was determined during the different stages of electrolysis in order to know the feasibility of the electrocoagulation treatment for highly concentrated bio-refractory organic pollutants present in the industrial wastewater. Different operational conditions such as pH, time, and electrical conductivity were studied for TOC removal. Experimental values indicated that the electrocoagulation process showed high TOC removal efficiencies, 78.7% within 60 min of electrolysis, with an initial concentration of 23.8 × 103 mg/l TOC. Thus, these results showed that the electrocoagulation process is effective for the removal of initially high T...

Effect of molecular mass on boron-doped diamond anodic mineralization of water-soluble organic polymers

Anodic oxidation of a number of water soluble organic compounds with increasing molecular mass from 46 Da to 72,000 Da was systematically investigated in a cell with a boron-doped diamond (BDD) anode under total recycle batch galvanostatic operation conditions. The experiments were designed to start with a similar initial total organic carbon (TOC) level of 200 mg dm −3, thus allowing for elucidating the dependencies of TOC removal kinetics, change in solutions’ pH and mineralization current efficiencies (MCE) on the type and molecular mass of target compound. The TOC removal rates were fitted to pseudo-first order exponential decay expressions, and the apparent kinetic constants for the anodic oxidation of each target compound were estimated. The process performance depended strongly on the compound molecular mass with apparent TOC removal kinetic constants lying in an order-of-magnitude range from 0.17 × 10 −4 s −1 for poly(vinyl alcohol) to 1.67 × 10 −4 s −1 for ethanol. This respectively led to different degrees of TOC removal in the experiments: from high TOC removal (>94%) for the low-molecular mass compounds to much lower one (down to 54%) for poly(vinyl alcohol), which was the compound with the highest molecular mass studied. The changes in the solution pH were well correlated with the respective degrees of TOC removal, thus additionally reflecting the slower kinetics of their oxidation. The results obtained might be useful for process design and optimization, especially when dealing with anodic mineralization of water-soluble polymeric fractions, for which the total organic content is easily assessable.

Effect of ageing on the microfiltration performance of ceramic membranes

The present work considers the influence of time or ageing on the electrokinetic characteristics of ceramic microfiltration and their subsequent impact on the microfiltration performances of whey suspensions. The filtration performance is assessed both in terms of permeate flux and total organic carbon (TOC). As the ageing period increases, the zeta potential of the membrane increases and plateaus towards the end of the ageing period. Higher permeate fluxes are found over the ageing period. The effect of ageing seems to have the greatest influence on the zeta potential and fluxes at the alkaline pH compared to the acidic pH and at the pH corresponding to the isoelectric point. Highest TOC removals were found at alkaline conditions. The main consequences of these results concern the interactions between membrane and whey particles. Despite the fact that the surface charge only depends on the pH, the various surface states of alumina may induce different strengths of electrostatic interactions or hydrophobic interactions between membrane and particles.

Photocatalytic water treatment over WO 3 under visible light irradiation combined with ozonation

Photocatalytic water treatment over bare WO 3 under visible light irradiation combined with ozonation (O 3/vis/WO 3) was investigated using an aqueous phenol solution as model wastewater. The O 3/vis/WO 3 treatment exhibited a much higher total organic carbon removal than ozonation alone. Bare WO 3 was found to function as an active visible-light-responsive photocatalyst for decomposition of organic compounds in the presence of ozone, which readily reacts with photoexcited electrons in the conduction band of WO 3.

<i>Technical note</i> Biological treatment of industrial wastewater containing formaldehyde and formic acid

The biological treatment of wastewater from an aminoplastic resin-producing industry was studied in a pre-denitrification system. This study reports results on the removal of organic matter and nitrogen compounds from wastewater which contained high levels of formaldehyde and formic acid. The formaldehyde concentration in the feed varied between 2 087.0 and 2 200.0 mg/ℓ, the mean removal being 99.9%. The mean efficiency of formic acid removal was 99.7%, and its concentration in the feed ranged between 1 384.6 and 1 513.9 mg/ℓ. The total organic carbon (TOC) values in the feed varied from 1 423.0 to 1 599.5 mg/ℓ, corresponding to an organic loading rate of about 0.20 kg TOC/m3·d. High TOC removal was achieved, around 92.0%. With regard to nitrogen compounds, the total Kjeldahl nitrogen (TKN) concentration in the feed ranged between 467.8 and 492.3 mg/ℓ. The applied nitrogen loading rate was around 0.06 kg TKN/m3·d, and the mean percentage of TKN removal was 76.7%. Water SA Vol 32(1)pp:115-118

Nanofiltration and ozonation for decolorisation and salt recovery from reactive dyebath

Three commercially available high exhaust dyes were used to prepare dyebaths of different shades and subjected to nanofiltration and ozonation. Colour removal, chemical oxygen demand reduction, permeate flux, ozone consumption and total organic carbon removal were analysed to determine the efficiency of nanofiltration and ozonation. It was found that both nanofiltration and ozonation showed a high degree of (>90%) decolorising efficiency. High total organic carbon removal (80%) could be achieved by nanofiltration while ozonation could achieve only a maximum of 55% total organic carbon removal. The treated dyebath was reused for dyeing the fabric and the fabric quality was compared for the different shades. It was found that the quality of the dyed fabric was good for all shades dyed with nanofiltration permeate. The quality of the dyed fabric was affected for dark shades dyed with the ozone decolorised dyebath.

Surface water treatment by the nanofiltration method

Studies concerning the removal of natural organic matter (NOM) from surface and tap water by nanofiltration are presented. The separation and transport characteristics of nanofiltration membranes were determined. The degree of NOM coefficient and water hardness removal from surface water and a reduction of water hardness were studied. The content of organic matter, both in the feed and the permeate, was estimated by the determination of total organic carbon (TOC), colour, turbidity, chemical oxygen demand (CODMn) and the absorbance in ultraviolet at a wavelength of 254 nm. The investigations demonstrated the complete removal of humic acids determined as the UV254 absorbance, and a high removal of colour (93.3%), TOC (93.5%) and turbidity (85.5%).

Biological treatment of saline wastewaters from marine‐products processing factories by a fixed‐bed reactor

AbstractWastewaters generated by a factory processing marine products are characterized by high concentrations of organic compounds and salt constituents (>30 g dm−3). Biological treatment of these saline wastewaters in conventional systems usually results in low chemical oxygen demand (COD) removal efficiency, because of the plasmolysis of the organisms. In order to overcome this problem a specific flora was adapted to the wastewater from the fish‐processing industry by a gradual increase in salt concentrations. Biological treatment of this effluent was then studied in a continuous fixed biofilm reactor. Experiments were conducted at different organic loading rates (OLR), varying from 250 to 1000 mg COD dm−3 day−1. Under low OLR (250 mg COD dm−3 day−1), COD and total organic carbon (TOC) removal efficiencies were 92.5 and 95.4%, respectively. Thereafter, fluctuations in COD and TOC were observed during the experiment, provoked by the progressive increase of OLR and the nature of the wastewater introduced. High COD (87%) and TOC (99%) removal efficiencies were obtained at 1000 mg COD dm−3 day−1.© 2002 Society of Chemical Industry

EDTA destruction using the solar ferrioxalate advanced oxidation technology (AOT): Comparison with solar photo-Fenton treatment

Degradation of ethylenediaminetetraacetic acid (EDTA; in the mmol/l range) at pH 3 was studied by the ferrioxalate/H2O2 process under solar irradiation. A rapid total organic carbon (TOC) removal was attained in all cases, reaching almost 100% after 1h solar exposure under the best conditions. In order to attain a high TOC removal yield, the pH must be rigorously controlled. The reaction rate increased with H2O2 concentration; but its effect was not very marked. The final extent of degradation was found to decrease with higher ferrioxalate concentrations, probably by competition of oxalate with EDTA or its degradation products. In the absence of oxalate, EDTA could also be degraded to a reasonably good extent, with a TOC removal only slightly lower than when using ferrioxalate, which constitutes a good advantage from the economical point of view. The intensity of solar light was found to be a very important factor to improve the reaction.

Catalytic wet oxidation of high-strength alcohol-distillery liquors

This work demonstrated that the catalytic wet oxidation (CWO) of high-strength alcohol-distillery waste liquors is feasible. Two distillery liquors (TOC=10 500; 22 500 mg/l; COD=26 000; 50 000 mg/l) produced by alcohol fermentation of enzymatic hydrolyzates from steam- and ammonia-exploded timothy grass were treated in a batch stirred autoclave over three different catalysts, 1% Pt/Al 2O 3, Mn/Ce oxides, and Cu(II)-exchanged NaY zeolite. The temperature and oxygen partial pressure ranges were (453–523 K) and (0.5–2.5 MPa), respectively. Effects of temperature, oxygen partial pressure, TOC content, and type of catalyst on the removal of total organic carbon (TOC) were investigated. The CWO initial rates were found to be first-order with respect to TOC, and the activation energies ranged from 34 to 51 kJ/mol. The highest TOC removal was achieved with Mn/Ce oxides and Cu(II)/NaY catalysts. The catalysts were found to be very effective for short contact times, while for prolonged exposures coke laydown was shown to be the prime factor responsible for the loss of catalyst activity. The carbonaceous deposits were characterized by electron spectroscopy for chemical analysis (ESCA) and temperature-programmed oxidation (TPO).

Simultaneous removal of carbon, nitrogen and phosphorus from wastewater by coupling two-step anaerobic digestion with a sequencing batch reactor

The objective of this study was to develop an integrated process for simultaneous removal of carbon, nitrogen and phosphorus from industrial wastewaters. The process consisted of a-two step anaerobic digestion reactor, for carbon removal, coupled with a sequencing batch reactor (SBR) for nutrient removal. In the proposed process, carbon is eliminated into biogas by anaerobic digestion: acidogenesis and methanogenesis. The volatile fatty acids (VFA) produced during the first step of anaerobic digestion can be used as electron donors for both dephosphatation and denitrification. In the third reactor (SBR) dephosphatation and nitrification are induced through the application of an anaerobic–aerobic cycle. This paper describes the first trials and experiments on the SBR and a period of 210 days during which the SBR was connected to the acidogenic and methanogenic reactors. It was shown that nitrification of ammonia took place in the SBR reactor, during the aerobic phase. Furthermore, denitrification and VFA production were achieved together in the acidogenic reactor, when the efflux of nitrates from the SBR reactor was added to the first reactor influx. The proposed process was fed with a synthetic industrial wastewater, the composition of which was: total organic carbon (TOC)=2200 mg dm−3, total Kjeldahl nitrogen (TKN)=86 mg dm−3, phosphorus under phosphate form (P-PO4)=20 mg dm−3. In these conditions, removals of carbon, nitrogen and phosphorus were 98%, 78% and 95% respectively. The results show that the combination of the two-step anaerobic digestion reactor and an SBR reactor is effective for simultaneous carbon, nitrogen and phosphorus removal. Reactor arrangements enabled zones of bacterial populations to exist. Complete denitrification occurred in the acidogenic reactor and hence the anaerobic activity was not reduced or inhibited by the presence of nitrate, thus allowing high TOC removal. Stable phosphorus release and phosphorus uptake took place in the SBR after coupling of the three reactors. A fast-settling compact sludge was generated in the SBR with the operational conditions applied, thus giving good separation of supernatant fluid. The benefits from this process are the saving of (i) an external carbon source for denitrification and phosphorus removal, (ii) a reactor for the denitrification step. © 1998 Society of Chemical Industry