Search

Abstract 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 CO 2 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. Highlights • The biomass production versus lipid productivity of various algal biomass in wastewater sources is statistically analyzed. • Influence nutrients amount and CO2 sequestration during the production of algal biomass in wastewater sources are studied. • The regression analysis of various system models and interpretation of linear coefficients are examined. • It confers uncertainty of linear regressions using Monte Carlo method, the effect of physical factors on algal production. • The nutrient removal efficiency and energy potential of different phototrophic systems are discussed. [ABSTRACT FROM AUTHOR]

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 decolorization kinetics of AB161 using liquid H2O2 is faster than that using CaO2 and Na2O2 catalyzed by Fe2+, while decolorization rate of AB161 by CaO2 is slightly faster than that by Na2O2 due to the fact that the CaO2 is a fine powder of an average diameter of 0.74 mm and Na2O2 is a particle with an average diameter of 1 mm. Regardless of the solid or liquid peroxide forms, e.g. CaO2, Na2O2, or liquid H2O2, the optimal molar ratio H2O2/Fe2+ of 12 obtained experimentally agreed reasonably with the theoretical predicted value of 11. In addition, the decolorization efficiency, η, is also not affected by the form of peroxides and decreases with the H2O2/AB161 when H2O2, Fe2+, and pH were fixed at 3.1 × 10−3, 5.0 × 10−4 mol L−1, and 2.5, respectively. [ABSTRACT FROM AUTHOR]

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 k i 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), H 0 , 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 ) + H 0 . 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. [ABSTRACT FROM AUTHOR]

Highlights: [•] Application of COD loading factor (L COD) to derive optimum H2O2 dose was examined. [•] Organic matter removal efficiency was linearly dependent on L COD. [•] L COD of 0.75 was determined to be the optimum L COD for leachate treatment. [•] Using L COD to select H2O2 dose may reduce task of performing multiple experiments. [ABSTRACT FROM AUTHOR]

Abstract: Optimal operating conditions observed by peer reviewed publications for Fenton oxidation of raw and biological and coagulation treated leachates were reviewed and statistically analyzed. For the first-stage Fenton oxidation, the optimal pH range of 2.5–4.5 was observed for raw and coagulation treated leachates with a median pH of 3.0, whereas, for biologically treated leachate the optimum pH range was 2.5–6.0 with a median pH of 4.2. Theoretically, the optimal ratio of H2O2/Fe2+ should be the ratio of rate constants of the reactions between OH radical with Fe2+ and H2O2, which is approximately 11; however, for leachate treatment, a median optimum relative dose of 1.8 (w/w) (3.0M/M) was observed. Biologically treated leachate showed relatively lower optimum ratio of H2O2/Fe2+ doses (median: 0.9 w/w) as compared to raw (median: 2.4 w/w) and coagulation treated (median: 2.8 w/w) leachate. Median absolute doses of H2O2 and Fe2+ were 1.2mg H2O2/mg of initial COD (COD0) and 0.9mg Fe2+/mg COD0, respectively and raw leachate required higher reagent doses compared to pretreated leachates. A universal Fenton oxidation relationship between COD removal efficiency (η) and COD loading factor (LCOD ) for landfill leachate treatment was developed. As LCOD increases from 0.03 to 72.0, η varies linearly as This robust linear relationship between LCOD and η holds for Fenton oxidation of raw as well as biological and coagulation treated leachates. The relationship was validated using Leave-one-out cross validation technique and errors in predicting η using LCOD were evaluated by applying Monte Carlo Simulation. As a result, the relationship can be used as a universal equation to predict Fenton treatment efficiency for a given COD0 loading in the range of 0.03–72.0 for landfill leachate treatment. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

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 TiO 2 and Al 2 O 3 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). [ABSTRACT FROM AUTHOR]

Abstract: 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 3.5mA at 2.5V when the electrode was covered with ten layers of Ta2O5. In case of the oxidation of 0.1mM 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. [Copyright &y& Elsevier]

• Effects of HTP on the co-digestion of FW and CC were cleared. • HTP reduces the crystallinity of cellulose. • Properly increasing the proportion of FW can promote the process of acidogenesis. • Participation of FW relieved the negative effects of HTP. • HTP can enhance methane yields i n co-digestion. 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. Unlabelled Image [ABSTRACT FROM AUTHOR]

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. • The effects of acid/alkali pretreatments on mono-/co-digestion were evaluated. • Both acid and alkali pretreatments enhanced the hydrolytic performance of straw. • Alkali pretreatment of wheat straw inhibited the activities of acetogens. • Co-digestion with sludge relieved the negative effects caused by pretreatments. [ABSTRACT FROM AUTHOR]