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Novel black oxygen deficient bismuth oxide (Bi2O3-Bi2O3–x) photocatalytic material is successfully prepared by a two zone temperature controlled muffle furnace method. The lanthanum, cerium and erbium ions are successfully doped into Bi2O3-Bi2O3–x with the average contents of 10.77%, 7.62% and 8.14%, respectively. The results show that a large number of oxygen vacancies existence in Bi2O3-Bi2O3–x. La3+, Ce3+ and Er3+ act as electron acceptors to temporarily trap the photo-generated electrons. The XPS spectrum show Bi-O band in Bi2O3-Bi2O3–x and the O 1s peak of Ce/Bi2O3-Bi2O3–x move toward the direction of low binding energy. These phenomena fully proved that the separation of photogenerated electron-hole pairs will be more effectual, so as to reduce the possibility of charge carrier recombination. The radical scavenging experiments and Electron spin resonance detections confirmed the conduction band of the original Bi2O3 can easily receive photogenerated electrons, while the valence band of the modified Bi2O3-Bi2O3–x tend to accept photogenerated holes and then form the circulation system. Therefore, Ce/Bi2O3-Bi2O3–x can degrade tetracycline hydrochloride up to 90.15%. This research provides some new insights into developing green and recyclable photocatalysts for the remediation of antibiotic contamination.

Activated sludge process is the common industrial wastewater treatment scheme. However, intensive aeration requirements made it impossible for wastewater treatment plants (WWTPs) to be energy- positive. The current study designed energy positive industrial wastewater treatment trains by using innovative technologies such as micro-sieving, up-flow anaerobic sludge blanket (UASB), and partial nitrification/Anammox (PN/A). Excel-based models were developed to compare the innovative treatment systems and the activated sludge system based on unit energy, cost and environmental indicators. Results showed that the innovative systems could save unit energy and cost by 67–85% and 59–85%, respectively. Innovative technologies increase the average unit energy production for meat processing, tannery, and textile wastewater treatment up to 1.71, 1.63, and 1.58 kWh/kg BODremoved. Furthermore, the high energy recovery reduces the overall global warming potential of these systems. Electrical self-sufficiency in industrial wastewater treatment could be obtained by using innovative technologies, which present great potential for future designs of industrial wastewater treatment.

Micro-sieving is an effective way to prevent organic pollutants enter the main biological process and reduce aeration intensity and sludge production. However, few researchers quantified the effect of micro-sieving on meat processing wastewater treatment. The current study developed Excel-based models to compare the energy consumption and production of historical, conventional and innovative systems. Historical and conventional systems employ activated sludge (AS), nitrification, and denitrification as the main biological processes. Innovative systems are designed by using up-flow anaerobic sludge blanket (UASB) and partial nitrification/Anammox (PN/A) as the main treatment processes. Results show that the CH

Electrochemical processes have proven their potential as effective technologies to treat wastewater from industrial, urban and agricultural activities, and thus, contribute towards a cleaner environment. In this study, we aimed to assess the effectiveness of the leading electrochemical technologies, such as electro-oxidation, electrochemical coagulation and electrochemical advanced oxidation processes (EAOPs), statistically for different types of anodes for the removal of various pollutants from wastewater along with their treatment efficiency. Anode is considered as a source of electron and an essential part of electrochemical processes. So, we have evaluated the relationship between different anode features such as anodic material, surface area versus removal of chemical oxygen demand (COD), dissolved organic carbon (DOC) and colour in various wastewater treatment plants (WWTPs) by IBM SPSS Statistics 26. Apart from that, various process characteristics such as inter-electrode distance, system pH, reactor volume, current density and voltage were also considered in this investigation. From the regression analysis of the electrochemical coagulation system, it was found that the removal efficiency of pollutants is enhanced by the surface area of the electrodes along with the inter-electrode distance. Regarding electro-oxidation, it was seen that COD and colour removal are both dependent on the reaction time of the system, while the DOC removal rate of different EAOPs was strongly related to the reactor volume. Furthermore, the uncertainty of the regression analysis on pollutant removal efficiency prediction was assessed. Finally, sensitivity analysis was done by Monte-Carlo method to check modest changes from input variables.

Unit energy consumption per kg pollutant removed (kWh/kgCODremoved) is used for the first time in assessing and ranking the sustainability of main treatment technologies of 1215 wastewater treatment plants (WWTPs) in China. The metric better measures the sustainability of main treatment technologies in WWTPs than unit energy consumption per cubic meter treated (kWh/m3). The energy consumption data of these WWTPs were selected from the database of 1399 WWTPs to evaluate the energy efficiency of different treatment technologies. 80.3% of the WWTPs applied anaerobic-oxic plus anaerobic-anoxic-oxic, oxidation ditch, and sequencing batch reactor as main technologies. Statistical analysis shows that the unit energy consumption of WWTPs decreases with increasing design flow rate, operation loading rate, and influent COD concentration. For example, the average unit energy consumption of SBR decreases from 2.76 kWh/kgCODremoved to 0.83 kWh/kgCODremoved when the design flow rate increases from less than 10,000 m3/d to 100,000-200,000 m3/d. The mean unit energy consumption of SBR decreases from 1.71 kWh/kgCODremoved to 1.32 kWh/ kgCODremoved and 2.85 kWh/ kgCODremoved to 0.63 kWh/kgCODremoved as the operation loading rate and COD removal increase from 40% to 100% and from less than 150 mg/L to over 450 mg/L, respectively. SBR has the lowest unit energy consumption among all the technologies. Therefore, SBR might be the most appropriate technology in small and medium-scale WWTPs in China. Regression equations were developed to predict the unit energy consumption for sustainable design treatment trains by input variables such as design flow rate, operation loading rate, and influent COD concentration.

Algal biodiesel is one of the most promising renewable and eco-friendly source of energy for transportation, when algae is produced from wastewater. During the process, both goals of biodiesel production and wastewater treatment could be achieved simultaneously. However, the optimal condition for algae production remained unanswered. Algal biodiesel could be produced from various wastewater treatments. In this study the relationship between biomass production versus lipid productivity in various wastewater sources is statistically analyzed. Chemical oxidation demand, total nitrogen, total phosphorus, and CO2 sequestration could be achieved during the production of different algal biomass in numerous type of wastewater effluent. The regression of different system models and interpretation of linear coefficients were represented in this statistically approached studies. Apart from that the paper also discuss the uncertainty of linear regressions using Monte Carlo method, influence of physical parameters on biomass production, energy potential and efficiency of nutrient removal using different phototrophic systems.

Activated sludge (AS) process has been used as the conventional industrial wastewater treatment process in the past decades. However, intensive aeration requirements made it impossible for WWTPs to be energy positive. In addition, there are few cases of research assessing the efficiency and economic feasibility of innovative technologies in treating industrial wastewater to achieve energy positive. This study tries to assess the effect of different kinds of industrial wastewater on treatment efficiency, unit energy, environmental sustainability, and unit cost of treatment systems using innovative technologies such as micro sieving, UASB, and PN/A. Our Excel model showed that micro-sieving could remove 32.50-39.72% of COD from industrial wastewater. UASB reactor could removes 15.8%-53.5%, 14.0%-49.0% and 22.9%-51.0% of COD from three different wastewater streams. Mean unit energy production by the innovative system could reach 1.80, 1.77, and 1.73 kWh/kg BODremoved, respectively. The average unit cost of three kinds of wastewater is 0.54, 0.57, and 1.12 $/kg CODremoved, respectively. Treating meat processing wastewater with innovative technologies is the economical treatment method. However, this method could not be considered as the sustainable design due to the high effluent COD concentration. The economic advantages and limitations of innovative technologies in treating industrial wastewater have been quantified by energy, cost and environmental indicators. These metrics provide valuable references for future sustainable design of industrial wastewater treatment systems.

Anaerobic co-digestion of lignocellulosic biomass and food waste (FW) has been extensively applied. However, whether hydrothermal pretreatment (HTP) of lignocellulosic biomass can enhance the performance in co-digestion deserves further investigation. In this study, corn cob (CC) was adopted as a typical lignocellulosic biomass for co-digestion with FW at different VS ratios of 1:3 (S1–S4) and 1:6 (S5–S8), attempting to evaluate the effect of HTP of CC at different temperature gradients (125, 150 and 175 °C) on the co-digestion performance. The emphasis was placed on hydrolysis, acidification and methanogenesis for different feedstock conditions. Results illustrated that the HTP had a certain destroying effect on the lignocellulose structure in CC and the crystallinity of cellulose decreased, significantly facilitating its co-digestion with FW. For FW/CC co-digestion at the VS ratio of 1:3, the S3 group (CC was pretreated at 150 °C) reached the maximum cumulative biogas yield (CBY) of 4660 mL and the maximum specific methane yield (SMY) of 316.9 mL/g·VS. Moreover, at 1:6, S7 group (pretreated at 150 °C) exhibited the optimal CBY of 4100 mL while achieving the SMY of 277.6 mL/g·VS among the digesters, indicating that the co-digestion of pretreated CC and FW could achieve higher methane production, and 150 °C refers to the optimal pretreatment temperature. Moreover, the peak values of the accumulated VFAs in digesters S1–S4 (2000–3000 mg/L) is higher than that in digesters S5–S8 (800–1500 mg/L). As suggested from microbial community and diversity date, the HTP expedited the enrichment of system hydrolyzing and acidogenic bacteria. These results are significant and provide certain guidance for optimizing the co-digestion of FW and CC in actual engineering.

The intensification of milk production in Brazil in the past decade has imposed great stress on the environment. Therefore, it is very important to find a balance between economic, social, and environmental objectives. The paper assesses the economic costs by production systems: confined feedlot, semi-confined feedlot, and pasture in the south of the country. The economic assessment was realized on some investment analysis tools and the GHG emissions costs for the different production systems indicated. Our results show that hectare and the total area of rural properties were lower in the confined feedlot system, followed by the semi-confined feedlot system and pasture-based grazing system. However, the reduction of the need for feed inputs in the pasture system resulted in lower feeding costs when compared to the other systems. The hectare analysis suggested that the superior productivity of the semi-confined system conditioned higher emission costs in relation to the other systems. However, considered the total emissions of the systems, the pasture system obtained higher values, justified by the greater need for an area for production. The results showed that the higher the food efficiency of a system, the greater the profitability.

One of the challenging tasks of the century is to clean up the contaminants of the environment by ecofriendly, sustainable and economically adoptable technologies. The application of quantum dots (QDs) is growing rapidly in to the field of nanotechnology. The electronic properties such as the energy of the highest occupied molecular orbital (EHOMO), the lowest unoccupied molecular orbital (ELUMO), the energy gap ΔE are correlated to the size of quantum dots (QDs) such as CdSe in the presence of different ligands. Linear regression equations were developed through statistical analysis using SPSS. In terms of correlation coefficient R2, both the size and nature of organic ligand capping affect the EHOMO, ELUMO and ΔE levels of QDs. Among all QDs, CdSe has the strongest correlation between its frontier molecular orbital energy levels with the QDs size. The R2 value is greater than 0.63 for a regression equation with a coefficient value of −0.17 and a constant of 2.9. This result implies that a unit decrease of size in the range lower than 7 nm would increase the band gap ΔE by 17%. Potential environmental applications of QDs are presented.

Remediation of uranium (U) contamination in the deep vadose zone (VZ) sediments abundant in calcite mineral is a challenging task considering the formation of highly stable and mobile uranyl complexes with carbonate and calcium in pore water composition. There is a concern that uranium contamination in the VZ can serve as a continued source for groundwater pollution, creating a risk to human health and the environment through the groundwater pathway. This requires in-situ remediation of the radionuclide-contaminated VZ to convert soluble U species to low solubility precipitates that are stable in the natural environment. Injection of reactive gasses (e.g., NH3) is a promising technology to decrease U mobility in the unsaturated zone without the addition of liquid amendments. The NH3 injection creates alkaline conditions that can alter the sediment pore water composition due to a release of elements from minerals (via desorption and dissolution) that are present in the sediment. However, it is not known how VZ pore water constituents (Si, Al3+, HCO3−, and Ca2+) would affect U(VI) removal/precipitation in alkaline conditions. This study quantified the role of major pore water constituents typically present in the arid and semi-arid environments of the western regions of the U.S and identified solid uranium-bearing phases that could potentially precipitate from solutions approximating pore water compositions after pH manipulations via ammonia gas injections. Triplicate samples were prepared using six Si (5, 50 100, 150, 200, and 250 mM), six HCO3− (0, 3, 25, 50, 75, and 100 mM), and two Ca2+ (5 and 10 mM) concentrations. The concentration of aluminum and uranium was kept constant at 5 mM and 0.0084 mM, respectively, in all synthetic formulations tested. Results showed that the percentage of U(VI) removal was controlled by the Si/Al molar ratios and Ca2+ concentrations. Regardless of the bicarbonate concentration tested, the percentage of U(VI) removed increased as the Si/Al ratios were increased. However, higher Ca concentrations correlated with higher U(VI) removal, ranging between 96% and 99%, at low Si/Al ratios. The SEM images of dried precipitates displayed dense amorphous regions high in silica content, where EDS elemental analysis unveiled higher U atomic percentages. The formation of uranyl silicate and carbonate minerals was also predicted by the speciation modeling. XRD analysis revealed the presence of uranyl carbonate mineral phases (andersonite, grimselite); however, uranyl silicates predicted (Na-boltwoodite) were not identified experimentally, possibly due to the amorphous nature of the silica solid phases observed in our experiments.

Bleaching technology by ozone dissolved in water offers alternative measures to prevent pollution in the textile industry for sustainable development at organizational and economic levels. In this paper, jeans fabric was treated with ozone injected in water combined with ultrasound and H2O2. Effectiveness of Fenton process regarding dye degradation was also tested with confirmation of hydroxyl radicals detected by fluorescence and electron paramagnetic resonance (EPR) spectroscopy. Results showed that individual ozone was more effective regarding the bleaching of the jeans samples than the hydroxyl radicals especially when coupled with ultrasound. The mechanical action of ultrasonic cavitations enhanced the diffusion of ozone through the fabric which increased the degradation of the indigo dye. The fading degree of samples treated with ultrasound and 100 g/Nm3 of ozone for 60 min in acidic condition reached 64.49 which gave a full bleach appearance. Scanning electron microscopy (SEM), ultimate tensile strength and fastness tests were performed in order to evaluate the effect of such treatment on the cotton fabric. The said tests proved that moderated concentrations of ozone caused no damage to the cotton fiber and results were very close to those obtained with ordinary bleaching processes.

These days electrodialysis is recognized as a promising process for the removal and recovery of nutrients from wastewater. However, the electrodialysis process for nutrient recovery is different from traditional desalination electrodialysis, and limited knowledge exists regarding its new application. Therefore, a comprehensive review and critical comparison of the different parameters and optimal operation conditions for nutrient recovery by electrodialysis in various studies are discussed in this manuscript. The relationship between the nutrient recovery rate and critical operating parameters such as voltage, the total effective area of the membrane, number of cell pairs, and feed composition in various wastewater sources is statistically analyzed. Regression results showed that increasing voltages, membrane, and cell numbers improved the recovery rate, respectively. However, it should be mentioned that different mobility behavior of ions are influenced by an electric double layer, selectivity, repulsion of the ion-exchange membrane, and operation conditions including voltage, current density, operation time, and ion concentrations. Hybrid processes enhance the electrodialysis efficiency in wastewater by increasing the feed concentration. The capital and operating costs of the electrodialysis process can be significantly affected by the pump, electrode, and ion-exchange membrane characteristics. Fouling and scaling as a challenge in electrodialysis are investigated in our study.

The present study investigated the effects of acid/alkali pretreatments on wheat straw mono-digestion and its co-digestion with waste activated sludge (WAS). The effects of pretreatment conditions on different anaerobic digestion (AD) stages (hydrolysis, acidogenesis, acetogenesis and methanogenesis) were discussed. At first, this study analyzed the impacts of acid/alkali pretreatments on wheat straw morphology, lignocellulosic components and evaluated these impacts on subsequent AD process by SEM, XRD, FT-IR and 3D-EEM analysis. The results of AD process showed that both acid and alkali pretreatments can enhance the hydrolytic performance of substrates. W12 (0.01 mol/L NaOH pretreated wheat straw mono-digestion) obtained the highest cumulative specific methane yield (CSMY) of 227.4 mL/g·VS. However, due to the formation of humic substances in liquid fraction, 0.1 mol/L NaOH pretreated wheat straw (W13) presented inhibition in converting propionic acid into acetic acid process. Co-digestion with sludge can relieve this inhibition and obtain the highest CSMY of 221.4 mL/g·VS. This study also exhibited the effects of pretreatments on microbial community and diversity: the inhibition of acetogens in AD process was revealed. Eventually, this study summarizes the positive and negative effects of acid/alkali pretreatments on the different digestive stages, aiming to provide references for future research and engineering implementation.

Fenton reaction was used to produce hydroxyl radicals under conditions similar to AOPs with 5,5-dimethyl-1-pyrroline- N -oxide (DMPO) as a spin trap agent in electron paramagnetic resonance (EPR) analysis. A theoretical kinetics model was developed to determine conditions under which the spin-adduct DMPO-OH is not further oxidized by Fe 3+ and excessive radicals, so that hydroxyl radicals concentration could be accurately inferred. Experiments were designed based upon the model and H 2 O 2 and Fe 2+ concentrations were varied from 1 to 100 mM and from 0.1 to 10 mM, respectively, with a constant H 2 O 2 : Fe 2+ ratio of 10:1. Results confirmed that DMPO concentration should be at least 20 times higher than the concentration of H 2 O 2 and 200 times higher than iron concentration to produce stable DMPO-OH EPR signal. When DMPO: H 2 O 2 ratio varied from 1 to 10, DMPO-OH could generate intermediates and be further oxidized leading to the apparition of an additional triplet. This signal was attributed to a paramagnetic dimer: its structure and a formation mechanism were proposed. Finally, the utilization of sodium sulfite and catalase to terminate Fenton reaction was discussed. Catalase appeared to be compatible with DMPO. However, sodium sulfite should be avoided since it reacted with DMPO-OH to form DMPO-SO 3 .

Hydrophobicity, as measured by Log P, is an important molecular property in assessing toxicity and carcinogenicity of disinfection by-products (DBPs). With increasing public health concerns of DPBs, there are considerable benefits in developing Quantitative Structure Activity Relationship (QSAR) models, capable of accurately predicting Log P, which could be used in health risk assessment of DBPs. In this research, Log P values of 46 halogenated alkanes, as one class of DBP compounds, were used to develop QSAR models for this class. Three molecular descriptors, namely, Energy of the Lowest Unoccupied Molecular Orbital (ELUMO), Number of Chlorine (NCl) and Number of Carbon (NC) were used in Multiple Linear Regression (MLR) analysis. The QSAR models developed were validated according to the principles set up by the Organization for Economic Co-operation and Development (OECD). Model Applicability Domain (AD) of the developed QSAR models was defined and mechanisms were interpreted. Considering large number of halogenated alkane compounds, the established QSAR models performed very well in terms of goodness-of-fit, robustness and predictability. The predicted values of Log P of DBPs by the QSAR models have correlation coefficient R2 from 81 % to 98 % with the observed Log P. The leverage approach by Williams plot was applied to detect and remove outliers. As a result, the correlation coefficient, R2, of the QSAR models increased by approximately 2 % to 13 %, before and after removing the outliers, respectively. The developed QSAR model was statistically validated for its predictive power of Log P by the Leave-One-Out (LOO) and Leave-Many-Out (LMO) cross validation methods.

Sulphate tailings and iron sand – industrial solid wastes containing iron oxide/hydroxides – were investigated as potential adsorbents for arsenic removal from water. Two effective methods of surface modification by NaOH treatment and atomic layer deposition of TiO2 and Al2O3 thin films were used for increasing As(III) and As(V) removal capacities of both adsorbents. The structure and surface area of the materials were characterised by scanning electron microscopy, middle infrared region spectroscopy, energy dispersive X-ray spectroscopy, and nitrogen adsorption. The iron sand waste was capable of binding significant amounts of As(III) and As(V) from synthetic solutions and wastewater. The sulphate tailings also showed a high adsorption capacity. Adsorption kinetics showed that equilibrium was reached within 240 min and fit to a pseudo second-order model with correlation coefficients greater than 0.99. Adsorption capacity was at the highest value at a solution pH range of 6–8. The Langmuir and Toth models can be used to fit the adsorption isotherms. The research showed that the proposed solid wastes can be successfully used for the adsorption of As(III) and As(V).

In research, design, and validation of UV disinfection systems of a given bacteria, shoulder effect makes prediction of fluence required difficult. This study theoretically analyzes the fluence required to inactivate any bacteria vs. E. coli as the reference bacteria, at the same Log I. Bacteria sensitivity index (BSI) is defined as the ratio between the inactivation rate constant ki of any bacteria for the linear portion of the dose response curve to that kir of E. coli. Among three sets of fluence requirement reported by the US EPA [4] , Sommer et al. [5] , [20] , and Chang et al. [6] , the fluence required from the EPA is selected as the most suitable reference according to its predictive power as well as regulatory purpose. In the present study, shoulder broadness (SB), H0, is approximated with the intercept of the linear portion at the Log I = 0. A universal equation which can be used to predict the fluence required of any bacteria with a shoulder: H = (0.914 ± 0.055) * (BSI)E * (Log I) + H0. Furthermore, shoulder broadness index (SBI) is defined as the ratio between the fluence difference of any bacteria and the reference bacteria such as E. coli divided by the SB of E. coli. To validate the equation, an independent set of fluence data during UV disinfection of four different ARBs reported by McKinney and Pruden [8] was used. When the predicted fluence by using BSI of the ARBs is compared with the reported fluence at different Log I levels with less than 10% error with Log I up to 5.

Global awareness regarding the effects of Climate Change has led to a more restrictive society and demanding concerned with Greenhouse Gas Emissions associated with consumption. In this context, the livestock sector is seen as a major contributor to various impacts, as it is implemented throughout different climatic zones, with high variations in production and food systems, which, in turn, present direct impacts on productivity and environmental externalities. In this context, the aim of this study was to rank possible improvement actions that allow the reduction of the Carbon Footprint originated from Brazilian beef exports considering multiple criteria, from the identification of the impact profile associated with the final product. Thus, the Carbon Footprint was first estimated considering the production phase, in the Brazilian Central-West, and beef processing and transport until its delivery at three main final export destinations: Rotterdam, Shanghai and St. Petersburg. Subsequently, multicriteria decision-making methods were applied in order to quantify and rank possible improvement actions, with the joint application of the Fuzzy Set Theory and the TOPSIS method. Finally, the criteria are presented in the form of a SWOT (Strengths, Weaknesses, Opportunities and Threats) matrix for each evaluated alternative. The animal production stage represented the main impacts of Climate Change on the product system (over 96% for all export destinations) due to the digestive fermentation of the animals, leading to methane emissions. The option to implement improvement actions for the evaluated productive arrangement, the use of protein-energetic supplementation and pasture fertilization-rotation in the animal production phase, alongside the replacement of road transport units by more modern vehicles in the industrial phase, were identified as alternatives that decrease the impact potential and facilitate the animal production phase. In this sense, the results point to possible improvements that, in addition to presenting low restrictions for implementation, can significantly reduce the beef Carbon Footprint. Improving Brazilian efficiency in terms of Carbon Footprint in this production chain can, in addition to provide a strategic differential concerning production and commercialization, contribute to reduce environmental impacts resulting from the sector at a global level. However, it is necessary to search for measures that facilitate the implementation of these actions, mainly at the rural producer level, considering both technical aspects and the qualification, training, consulting and financial aspects, such as credit and subsidies, improving the environmental performance of this arrangement with a view to balancing it with the other dimensions.

Decolorization of Acid Blue 161 (AB161) by solid peroxides such as CaO2 and Na2O2 catalyzed by iron in aqueous solution was investigated. The effect of initial pH, concentration of H2O2, Fe2+, and AB161 on the decolorization kinetics was investigated and compared with the results by liquid H2O2. The experimental results show that decolorization of AB161 follows the second-order kinetic. The second decolorization rate constants and oxidation efficiency at different initial pH, Fe2+, H2O2, and AB161 concentration were correlated with dimensionless ratios such as H2O2/Fe2+ or H2O2/AB161. About two dozens of correlation equations are developed in this paper to quantify the effect of the variables on the decolorization rate constants of AB161. Among solid peroxides such as CaO2 and Na2O2 and liquid H2O2, the optimal pH and [Fe2+] are 2.5 and 5.0 × 10−4 mol L−1, while the concentration of CaO2, Na2O2, and H2O2 is 0.30, 0.25 g L−1 and 3.1 × 10−3 mol L−1, respectively. Our experimental results show that d...

Degradation kinetics of azo dye, Acid Blue 161 (AB161), by Fenton and photo-Fenton processes in aqueous solution was investigated. At pH 3.5, the effects of H2O2, Fe2+, and H2O2/Fe2+ molar ratios, on the AB161 decolorization kinetic rates, were evaluated. Experimental results confirmed that the optimal H2O2/Fe2+ molar ratio of 12 is close to the theoretical value of 11 as predicted by previously developed model. The influence of azo bond loading (L azo bond), from 0.25 to 1.0, and pH values from 2.5 to 4.0 were evaluated on AB161 decolorization kinetic rates. A correlation between the natural logarithm of the decolorization rates and L azo bond was established at the different pH values. The decolorization rate increased linearly with decreasing L azo bond, in the order of pH: 3.5 > 3.0 > 2.5 > 4.0. UV radiation of Fenton processes increases degradation of AB161 more than 40 % due to the regeneration of Fe2+ through photo-catalytic reactions. This phenomenon was confirmed by measuring H2O2 concentration during the photo-Fenton processes. The results suggest that Fenton processes can effectively decolorize or degrade wastewater containing azo dye, AB161. Photo-Fenton processes may further increase the degradation efficiency of AB161 by 40 %.

The present paper describes a green and economic approach to explore EDTA/DTPA-functionalized magnetic chitosan as adsorbents for the removal of aqueous metal ions, such as Cd(II), Pb(II), Co(II), and Ni(II). EDTA and DTPA play roles not only as cross-linkers but also as functional groups in chelating metal ions. The morphology, structure, and property of the magnetic adsorbents were characterized by SEM, TEM, XRD, EDS, FT-IR, TGA, and VSM techniques. Their adsorption properties for the removal of metal ions by varying experimental conditions were also investigated. The kinetic results revealed that the transportation of adsorbates from the bulk phase to the exterior surface of adsorbents was the rate-controlling step. The obtained maximum adsorption capacities of magnetic adsorbents for the metal ions ranged from 0.878 to 1.561 mmol g–1. Bi-Langmuir and Sips isotherm models fitting well to the experimental data revealed the surface heterogeneity of the adsorbents. More significantly, the resulting EDTA-/...

A novel magnetic hydroxamic acid modified polyacrylamide/Fe 3 O 4 adsorbent (M-PAM-HA) was prepared with acrylamide by microemulsion polymerization and then nucleophilic substitution of hydroxamic acid. The morphology, structure of the magnetic adsorbents before (M-PAM) and after modification (M-PAM-HA) were characterized and their adsorption properties for the removal of metal ions by varying test conditions were also investigated. The modified M-PAM exhibited lower swelling property and less magnetic leaching than M-PAM. Their adsorption kinetics followed the pseudo-second order model. The maximum adsorption capacities of metal ions ranged from 0.11 to 0.29 mmol g −1 for M-PAM and 0.88–1.93 mmol g −1 for M-PAM-HA, respectively. Sips model fitting well to experimental data revealed the surface heterogeneity of the prepared adsorbents. In multi-metal systems, M-PAM-HA showed the relative selectivity toward Pb(II), although Pb(II) was adsorbed the least in their corresponding one-metal systems. The adsorption mechanism was proposed based on the results of FTIR and density functional theory (DFT) calculation.

Lake Okeechobee is a large shallow lake with over 44% (as of 2006) being underlain with phosphorus-enriched mud sediments. Wind-induced sediment re-suspension may play a significant role in the nutrient cycling of this lake. It is critical to develop optimal models with low uncertainty to map the distribution and changes of total phosphorus (TP) over time. Geographically Weighted Regression (GWR) is a powerful spatial regression method that examines the details of relationship between the target variable and independent variables and their changes over space. The calibrated GWR models were applied to data sets of organic mud sediment from Lake Okeechobee collected in 1988, 1998 and 2006. Three sets of ancillary data were also used in the models: total iron (Fe), which was strongly and positively correlated to TP (0.69–0.72); mud thickness, which was moderately and positively correlated to TP (0.57–0.72); and site elevation, which was weakly but negatively correlated to TP (−0.46- −0.55). The GWR models we...

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.

Retrofitting municipal wastewater treatment plants (WWTPs) to energy positive is a major challenge faced by many water utilities. Selection of innovative technologies to achieve retrofitting goals is critical for capital improvement programs in WWTPs. This paper aims to provide a statistical analysis method of unit energy consumption in conventional Finnish WWTPs, presenting Mikkeli WWTP as a case study. The average energy consumption at Finnish WWTPs was quantified as a mean of 0.49 kWh/m3 with a standard deviation of 0.197. The statistical analysis showed that the total energy consumption in Finnish WWTPs are positively correlated with inflow rate and sludge production. However, the unit energy consumption decreases with increasing plant capacity. The energy benchmarking of Mikkeli WWTP confirmed the energy gap of 0.11 kWh/kg COD in electricity. The major energy saving potentials are attributed to secondary treatment, screening and grit removal, and influent pump stations. A plausible innovative retrofitting strategy comprising four emerging energy-neutral or positive technologies is proposed to maximally harness the chemical energy content in wastewater: enhanced primary sedimentation, staged anaerobic fludized membrane bioreactor (SAF-MBR) with completely autotrophic nitrogen removal over nitrite process (CANON), and co-digestion of sludge with organic food-waste. The net energy balance of emerging technologies showed a maximum energy saving potential of 1.26 kWh/kg COD, which could be sufficient to overcome the energy gap of Mikkeli WWTP, providing net positive energy surplus of 1.15 kWh/kg COD.

Chlorinated Alkane (CA) is one of the major classes of Disinfection By-Products (DBPs) in chlorinated drinking water. Multi-multivariate regression methods have been used to develop Quantitative Structure-Activity Relationship (QSAR) models between the Energy of the Lowest Unoccupied Molecular Orbital (ELUMO) and three molecular descriptors: namely, number of chlorine (NCl), number of carbon (NC) and the Energy of the Highest Occupied Molecular Orbital (EHOMO). Among different linear QSAR models, the most robust model is ELUMO=-0.1474NCl-0.003766NC+1.9528EHOMO+1.0664 (N=30, R2=0.956, F=188.498, RMSE=0.00762, P=0.000). The model is validated by using internal and external cross validation techniques. The model uncertainties are also quantified through the Bootstrapping and the Taylor methods. Among all the molecular descriptors, number of chlorine (NCl) contributes to the most to the ELUMO of chlorinated alkanes.

A new concept of Virus Sensitivity Index (VSI) is defined as the ratio between the first-order inactivation rate constant of a virus, ki, and that of MS2-phage during UV disinfection, kr. MS2-phage is chosen as the reference virus because it is recommended as a virus indicator during UV reactor design and validation by the US Environmental Protection Agency. VSI has wide applications in research, design, and validation of UV disinfection systems. For example, it can be used to rank the UV disinfection sensitivity of viruses in reference to MS2-phage. There are four major steps in deriving the equation between Hi/Hr and 1/VSI. First, the first-order inactivation rate constants are determined by regression analysis between Log I and fluence required. Second, the inactivation rate constants of MS2-phage are statistically analysed at 3, 4, 5, and 6 Log I levels. Third, different VSI values are obtained from the ki of different viruses dividing by the kr of MS2-phage. Fourth, correlation between Hi/Hr and 1/VSI is analysed by using linear, quadratic, and cubic models. As expected from the theoretical analysis, a linear relationship adequately correlates Hi/Hr and 1/VSI without an intercept. VSI is used to quantitatively predict the UV fluence required for any virus at any log inactivation (Log I). Four equations were developed at 3, 4, 5, and 6 Log I. These equations have been validated using external data which are not used for the virus development. At Log I less than 3, the equation tends to under-predict the required fluence at both low Log I such as 1 and 2 Log I. At Log I greater than 3 Log I, the equation tends to over-predict the fluence required. The reasons for these may very likely be due to the shoulder at the beginning and the tailing at the end of the collimated beam test experiments. At 3 Log I, the error percentage is less than 6%. The VSI is also used to predict inactivation rate constants under two different UV disinfection scenarios such as under sunlight and different virus aggregates. The correlation analysis shows that viruses will be about 40% more sensitive to sunlight than to UV254. On the other hand, virus size of 500 nm will reduce their VSI by 10%. This is the first attempt to use VSI to predict the required fluence at any given Log I. The equation can be used to quantitatively evaluate other parameters influencing UV disinfection. These factors include environmental species, antibiotic-resistant bacteria or genes, photo and dark repair, water quality such as suspended solids, and UV transmittance.

This study assessed anaerobic biodegradability of organic compounds from microorganism activity. Dehydrogenase activity can be a good parameter characterizing the microorganism activity. A modified method of 2-(p-iodophenyl-3-(p-nitrophenyl)-5-pheny tetrazolium chloride-dehydrogenase activity determination was proposed in anaerobic biodegradability assessment. Cubic spline curves were adopted to link the data points. This curve was integrated twice to calculate areas. The microorganism activity index in anaerobic biodegradability assessment was calculated by standardizing the integral. According to the results of the activity index, 14 kinds of organic compounds were classified into readily, partially, and poorly biodegradable under anaerobic conditions, respectively. As a result, some conclusions for anaerobic biodegradability of organic compounds were reached, based on the activity index value.

In the present study, microfibrillated cellulose (MFC) was modified by aminopropyltriethoxysilane (APS), hydroxy-carbonated apatite (HAP), or epoxy in order to produce novel nanostructured adsorbents for the removal of hydrogen sulphide (H2S) from the aqueous solutions. Structural properties of the modified MFC materials were examined using a scanning electron microscope, Fourier transform infrared spectroscopy and acid/base titration. These methods were used to verify the presence of nanostructures on the adsorbents surfaces as well as functionalities suitable for H2S adsorption. Adsorption of H2S by prepared adsorbents was investigated in batch mode under different experimental conditions, i.e., varying pH and H2S concentrations. H2S uptake was found to be 103.95, 13.38 and 12.73 mg/g by APS/MFC, HAP/MFC and epoxy/MFC, respectively from 80 mg/L H2S solution. The equilibrium data were best described by the Langmuir isotherm for HAP/MFC and APS/MFC and the Sips isotherm for epoxy/MFC.

Experiments of nano-filtration (NF) and reverse osmosis (RO) were conducted to remove most pollutants from the biological treated leachate. For example, the purified permeate after reverse osmosis treatment with spiral membranes reached effluent water quality as follows: COD of 57 mg O2/l, BOD7 of 35 mg O2/l, and suspended solid of 1 mg/l which satisfies the discharge standards in Estonia. For both RO and NF, conductivity can be reduced by 91% from 6.06 to 0.371 mS/cm by RO and 99% from 200 to 1 mS/cm by NF. To test the service life of the RO spiral membranes, the process was able to reduce chemical oxygen demand (COD) and biological oxygen demand (BOD) of biologically treated leachate by 97.9% and 93.2% even after 328 and 586 hours, respectively. However, only 39.0% and 21.7% reductions of Ptot and Ntot were achieved. As a result, neither RO (spiral membranes process) nor NF was able to reduce the total nitrogen (TN) to the required discharge limit of 15 mg/l.

Mixed metal oxide (MMO) electrodes have been applied to different technologies including chlorine production, organic compounds oxidation, water electrolysis, electroplating, etc. due to their catalytic, optical and electronic properties. Most of the existing MMO electrodes contain either toxic metals or precious metals of the platinum group. The aim of this study was to develop environmentally friendly and cost-effective MMO electrodes for water and organic compounds oxidation. Ti/Ta2O5-SnO2 electrodes of different nominal composition were prepared, and electrochemically and physically characterized. For water oxidation, Ti/SnO2 electrode with 5 at.% of Ta produced the highest electroactivity. Ti/SnO2 electrode with 7.5 at.% of Ta showed the best performance for the oxidation of methylene blue (MB). The electrocatalytic activity of the Ti/Ta2O5-SnO2 electrodes increased with the number of active layers. The maximum current of water oxidation reached 3.5 mA at 2.5 V when the electrode was covered with ten layers of Ta2O5. In case of the oxidation of 0.1 mM MB, eight and ten active layers of Ta2O5 significantly increased the electrode activity. The prepared electrodes have been found applicable for both water electrolysis and organic compounds oxidation. This work was supported by the Maj and Tor Nessling foundation. We also acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through projects PRI-PIBIN-2011-0816 and MAT 2012-37676 (Fondos FEDER) as well as to the Vice presidency of Research of the Universitat d’Alacant.

Oxidation kinetics and mechanisms of four trihalomethanes (THMs) commonly found in chlorinated drinking water by Fenton's reagent were investigated. All the experiments were carried out in air-tight and well-mixed batch reactors in which no headspace was allowed in order to minimize volatilization of any THM during reaction. The optimum dosages of H 2 O 2 and Fe 2+ in the oxidation of bromoform was 3.7-1.9 m m for all the initial concentrations at pH 3.5. The maximum bromoform degradations of 85, 78 and 65% at 3 min were achieved for bromoform concentrations of 295, 98.3 and 49.2 μg/l, respectively. The pseudo-first-order oxidation constants of THMs increase with the increasing number of bromine atoms present in a THM molecule, with bromoform being oxidized the fastest and bromodichloromethane being oxidized the slowest. No oxidative degradation of chloroform was oberved, because the losses in chloroform concentration during the oxidation experiments are the same as what was observed in control experiments. Experiments conducted on the THM mixtures gave similar results in terms of extent of observed oxidative degradation, the amount of THM oxidized increased with increasing initial organic concentrations. The oxidation rate constants for each THM in the mixture also increased as the number of bromine atoms present in a THM molecule increased, with bromoform exhibiting the fastest kinetic rates and bromodichloromethane exhibiting the slowest kinetic rates.

Photocatalytic degradation kinetics of eleven azo dyes by TiO2/UV was studied using a Rayonet photoreactor. The degradation kinetics of azo dyes seems to be significantly influenced by their electrical nature, the number of azo bonds present in a dye molecule, and type of auxiliary groups attached to the azo bond. For example, trisazo dyes were the most difficult to degrade, and monoazo dyes were the most readily degradable, while the disazo dyes were in the middle range. The experimental results indicate that positive hole oxidation is the dominant mechanism contributing to the degradation of neutral or negatively charged dyes at pH 3. The degradation kinetics of positively charged basic dyes may be through reduction by electrons in the conduction bands of the excited TiO2 particles. On the other hand, hydroxyl radicals should be the major oxidation species at pH greater than 7. The pH effects on the degradation kinetics of different dyes may be due to the intrinsic reactivities of the neutral and ionize...

The stoichiometry of Fenton's reagent in the oxidation of dichloroethylene (DCE), trichloroethylene (TCE), tetrachloroethylene (tetra-CE), and dichloroethane (DCEA) was investigated. The theoretical optimal ratio between H2O2 and Fe2+ is found to be 11. However, the experimentally determined optimal ratio between H2O2 and Fe2+ ranged from 5 to 11 at optimal pH of 3.5. The amount of H2O2 required for a specific percentage removal of the organic compounds depends upon the initial organic concentration to be oxidized. The accumulation of chloride ion released also depends upon the initial organic substance concentrations. The typical percentage removal of organic compounds and percentage release of chloride ion were reported at 100%, 70%, 50%, 40%, 30%, 20%, 10%, and 1%. The amount of H2O2 required to achieve a certain percentage removal follows the order of TCE < Tetra-CE < DCE << DCEA. However, the amount of chloride ion detected at a constant concentration of H2O2 follows the order of DCEA << DCE < TCE < ...

Oxidation kinetics and mechanisms of 2,4-dichlorophenol (2,4-DCP) by Fenton's reagent were studied. The effect of pH, concentration of H2O2, and Fe2+, and 2,4-DCP on both oxidation and dechlorination kinetics was investigated. A mathematical model was developed to describe the kinetics of 2,4-DCP oxidation and chloride ion production at constant concentrations of H2O2 and Fe2+. The optimal ratio of H2O2 to Fe2+ for the oxidation of 2,4-DCP was determined to be 11 which is the same as predicted by the previously developed kinetic model.

An oxidation kinetic model of trichloroethylene (TCE) by Fenton's reagent is developed based upon transition state theory. Hydroxylated active complexes are assumed to be the transition state after hydroxyl radicals have attacked the organic compound. The complex can either disproportionate into Cl‐ and the other products, or return to their original reactants. Because both hydroxyl radicals and the active complexes have extremely high reactivity, their steady‐state concentrations are assumed constant in developing the kinetic model. The model indicates that Fenton oxidation is first order with respect to the organic concentration. The degree of oxidation is dependent upon the dosage of H2O2 and Fe2+. Because H2O2 and Fe2+ can also react with hydroxyl radicals, neither of them should be overdosed if maximal reaction rate is to be achieved. Experiments have been conducted to obtain rate constants for three different chloroethylenes and chloroethane. It is found that the model is valid only for uns...

The effect of chlorine content of chlorinated phenols on their oxidation kinetics by Fenton's reagent was evaluated through different kinetic studies. First, elementary oxidation rate constants between hydroxyl radicals and 2,4-DCP, 2,4,6-TCP as determined in this study are 7.2∗10 9 M −1 s −1 and 6.3∗10 9 M −1 s −1 respectively.The relative ratios between the rate constants of 2-CP and 2,4,6-TCP referred to the rate constant of 2,4-DCP indicates that the reactivity of chorophenols decreases with increasing substitution of chlorine on the aromatic ring. Second, the pseudo-first order oxidation kinetic constants at overdosed H 2 O 2 and Fe 2+ were proportional to the number of unsubstituted positions, while no correlation between dechlorination constants and the number of unoccupied sites on the aromatic ring was found.Third, dechlorination kinetic model as a function of 11202, Fe, and chlorophenol concentration was developed. At constant 11202 concentration of 5 ∗ 10 −3 M, the observed dechlorination rate constants for 2-MCP, 2,4-DCP, and 2,4,6-TCP are 1.16∗10 7 M −1 s −1 , 2.28∗ 10 7 M −1 s −1 and 4.36∗10 8 M −1 s −1 , respectively. All of these results demonstrated that the oxidation rate constants decrease with increasing content of chlorine. In addition, the initial dechlorination rates do not change significantly for all the chlorinated phenols studied at constant 11202 and Fee* concentration, which suggests that the limiting step in Fenton chemistry is the generation of hydroxyl radicals through H 2 O 2 and Fe 2+ .

The oxidation kinetics and mechanisms of Reactive Red 120, Direct Blue 160, and Acid Blue 40 by H2O2/iron powder system were investigated in a well-mixed batch reactor. Optimal pH ranged from 2.0 to 3.0 depending upon the dye molecular structure and the iron dissolution rate. The optimal ratio of H2O2 to iron metal was 0.001 M to 1.0 g/L. The initial oxidation rates were obtained according to pseudo-first-order kinetics. Dye molecular structure is an important factor that influences decolorization kinetics. The results suggest that the structure chromophore including Azo bonds are the primary target oxidized by H2O2/Fe powder system. The less substituted anthraquinone ring in Acid Blue 40 is more readily to be destroyed than the Azo dyes. Dimerization may take place at high concentration of Acid Blue 40, which decreases the decolorization efficiency. In addition, the color change during decolorization processes may also result from the dye complexes with the iron species. As a result, H2O2/iron powder system is better than the Fenton s reagent system, e.g., H2O2Fe2+, due to the continuous dissolution of iron powder and the dye adsorption on the iron powder, despite the fact that Fenton's reaction was the major process contributing to decolorization.

Photocatalytic oxidation kinetics of five commercial dyes, namely Acid Blue 40, Basic Yellow 15, Direct Blue 87, Direct Blue 160, and Reactive Red 120 was studied in a TiO2/UV slurry reactor. The oxidation kinetics of Direct Blue 160 and Reactive Red 120 follows the Langmuir-Hinshelwood kinetic model at all the pH values studied. However, the oxidation kinetics of Acid Blue 40 fits the model at pH 3, Basic Yellow at pH 3, 5, and 11, and Direct Blue 87 at pH 7 and 9 only. In neutral solution of pH 7, the oxidation rates follow the decreasing order: Direct Blue 87 > Reactive Red 120 > Basic Yellow 15 > Acid Blue 40 > Direct Blue 160. At pH 3, the number of azo linkages in dye molecules seems to be the most important factor. For example, the oxidation rate of monoazo dye of Basic Yellow 15 is faster than disazo dye of Reactive Red 120 which in turn is faster than triazo dye of Direct Blue 160. The fastest reaction rate constants are 0.0160-0.0109 mM/min for monoazo dye of Basic Yellow 15, and the slowest reaction rate constants are 0.0013–0.0021 mM/min for the triazo dye of Direct Blue 160. The effect of Fe2+ and H2O2 on the reaction kinetics was also explored.