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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.

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.

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 .

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.

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.

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.

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.

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.

Photocatalytic oxidation of 2,4-dichlorophenol (2,4-DCP) by CdS in the presence and absence of thioacetamide as a function of pH has been studied. Based upon the trends in the appearance of different intermediates such as benzene and hydroxylated biphenyl, it is proposed that 2,4-DCP oxidation by positive holes (h+) is favored at pH less than 6, while oxidation by hydroxyl radicals (·OH) becomes dominant at pH greater than 6. This is evidenced by the intermediates detected at different pH values. In the absence of thioacetamide (TA), benzene was detected as the only intermediate at pH ranging from 4 to 5. When pH changed from 5 to 9, no benzene was detected. Highly hydroxylated intermediates, such as hydroxylated biphenyl, were the major intermediates. When TA was present, it may act as a “bridge” between, 2,4-DCP and CdS through its thiol functional group. Therefore, a shift of the optimal pH for 2,4-DCP oxidation from 5 to 9 was observed and no hydroxylated biphenyl were detected.

Chlorine position of chlorophenol isomers has a significant effect on the dechlorination kinetics of monochlorophenols, dichlorophenols, and trichlorophenols during Fenton oxidation. The effects have been evaluated by the rate constants of the dechlorination kinetic model developed in this study. It is found that the dechlorination rate of 3-CP is faster than that of 4-CP, which is faster than that of 2-CP. Since OH and Cl groups on the aromatic ring are ortho and para directors, the directory effect of OH and Cl groups enhances the dechlorination kinetics of 2-CP due to acceleration of the hydroxylation of 2-CP. Therefore, the dechlorination kinetics increases accordingly. For trichlorophenols (TCP), steric hindrance plays an important role during their dechlorination process. Specifically, the closer the chlorine atoms locate with each other on the aromatic ring, the more difficult the dechlorination processes will be. The dechlorination kinetics of dichlorophenols seems to be affected by both directory effect of OH and Cl groups and the effect of steric hindrance of chlorine atoms. The directory effect of OH and Cl groups on trichlorophenols decreases since the chlorine atom occupied the positions which are the most favorable for hydroxyl radical attack.

The application of Fenton treatment technology for treatment of landfill leachate greatly depends on the optimum Fenton operating conditions for a specific leachate. Determining optimum Fenton conditions requires multiple experiments using variable reaction parameters (pH, temperature, and H2O2 and Fe(2+) doses) and previous researches show a wide range of optimal operating conditions. In this study, the applicability of the dimensionless loading factor (LCOD), which is defined as the initial COD (COD0) of leachate with respect to available O2 for oxidation, was examined to derive optimum Fenton oxidant dose using reduced set of experiments. The Fenton experiments were conducted using leachates with three different COD0 concentrations, 1092, 546, and 273mgL(-1), LCOD in the range of 0.25-1.0, and H2O2/Fe(2+) 1.8 (w/w). The experimental data were analyzed to determine the correlation between the LCOD factor and selected feasibility parameters, amongst which were: (i) the COD removal kinetics, (ii) the total COD removal, (iii) the usability of H2O2 with respect to COD removal, (iv) leachate biodegradability, and (v) treatment cost incurred by chemical usage. The experimental COD removal with respect to the amount of O2 supplied by H2O2 was compared with respect to the optimum COD removal efficiency by the equation: η(FP(optimum)=0.733L(COD)-0.182 as developed by Singh and Tang (2013) and a LCOD of 0.75 was determined to be the optimum L(COD) for leachate treatment.

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 H(2)O(2)/Fe(2+) should be the ratio of rate constants of the reactions between OH() radical with Fe(2+) and H(2)O(2), 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 H(2)O(2)/Fe(2+) 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 H(2)O(2) and Fe(2+) were 1.2mg H(2)O(2)/mg of initial COD (COD(0)) and 0.9 mg Fe(2+)/mg COD(0), 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 (L(COD)) for landfill leachate treatment was developed. As L(COD) increases from 0.03 to 72.0, η varies linearly as η=0.733 L(COD)-0.182. This robust linear relationship between L(COD) 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 L(COD) 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 COD(0) loading in the range of 0.03-72.0 for landfill leachate treatment.