Wastewater screening method for evaluating applicability of zero-valent iron to industrial wastewater

Characterization and Recovery of In Situ Transesterifiable Lipids (TLs) as Potential Biofuel Feedstock from Sewage Sludge Obtained from Various Sewage Treatment Plants (STPs)

This study purposed to characterize the sewage sludge from various sewage treatment plants (STPs) as a biodiesel feedstock. Crude biodiesel was produced from each dried primary sludge (PS) and waste activated sludge (WAS) via in situ transesterification process. The average yield of transesterifiable lipid (TL) was 77.8% and 60.4% of the total lipid content from PS and WAS, respectively. The TL yield had a greater margin among WAS than PS samples due to differences in the biological processes adopted in each treatment plant. The TL recovered from PS and WAS contained 54.2% and 40.1% fatty acid methyl esters (FAMEs), respectively, which were mostly made up of palmitic acid (C16:0) and stearic acid (C18:0). The FAME composition of the biodiesel in the WAS sample was highly associated with a microbial community that grows otherwise, depending on the purpose of the biological treatment process. In particular, the increase in the proportion of nitrifying bacteria that grow predominantly under a relatively longer solid retention time (SRT) contributed significantly to the improvement in FAME content.

Cosmetic wastewater treatment by the ZVI/H2O2 process

The ZVI/H₂O₂ process was applied for cosmetic wastewater treatment. Two commercial zero-valent iron (ZVI) types with different granulations were chosen: Hepure Ferrox PRB and Hepure Ferrox Target. In addition, the pH and stirring method influence on ZVI/H₂O₂ process efficiency was studied. During the ZVI and ZVI/H₂O₂ processes, linear Fe ions concentration increase was observed. The addition of H₂O₂ significantly accelerated the iron dissolution process. The highest COD removal was obtained using finer ZVI (Hepure Ferrox Target) for doses of reagents ZVI/H₂O₂ 1500/1600 mg/L, in a H₂O₂/COD weight ratio 2:1, at pH 3.0 with stirring on a magnetic stirrer. After 120 min of the process, 84.0% COD removal (from 796 to 127 mg/L) was achieved. It was found that the efficiency of the process depends, as in the case of the Fenton process, on the ratio of the reagents (ZVI/H₂O₂) and their dose in relation to the COD (H₂O₂/COD) but does not depend on the dose of the iron itself. Statistical analysis confirms that COD removal efficiency depends primarily on H₂O₂/COD ratio and ZVI granulation, but ZVI dose influence is not statistically significant. The head space, solid-phase microextraction, gas chromatography, mass spectrometry results confirm high efficiency of the ZVI/H₂O₂ process.

Removal of hexavalent chromium from contaminated waters by ultrasound-assisted aqueous solution ball milling

Batch mode experiments were conducted to study the removal of hexavalent chromium (Cr(VI)) from aqueous solutions using ultrasound-assisted aqueous solution ball milling. The results show that the reduction rate of Cr(VI) by ultrasound-assisted aqueous solution ball milling was significantly faster than that by ball milling or ultrasound treatment alone, and an initial Cr(VI) concentration of 166mg/L could be decreased to 0.35mg/L at 120min. The decisive factors, including initial concentration of Cr(VI), pH value, ultrasonic frequency and filling gas, were studied. It was found that the optimal ultrasonic frequency for ultrasound-assisted aqueous solution ball milling device was 20kHz, and the rate of Cr(VI) reduction as a function of filling gas followed the order: Ar>air>N₂>O₂. Samples were characterized by X-ray diffraction, fluorescence measurements, atomic absorption and the diphenylcarbazide colorimetric method. The Cr(VI) transformed into a precipitate that could be removed from the contaminated water, after which the water could be reused.

Hydrogen inhibition in a wet aluminum dust collection system using dichromate solution

By using dichromate solution, hydrogen production reaction between aluminum dust and water is inhibited.

C, Cl and H compound-specific isotope analysis to assess natural versus Fe(0) barrier-induced degradation of chlorinated ethenes at a contaminated site

Compound-specific isotopic analysis of multiple elements (C, Cl, H) was tested to better assess the effect of a zero-valent iron-permeable reactive barrier (ZVI-PRB) installation at a site contaminated with tetrachloroethene (PCE) and trichloroethene (TCE). The focus was on (1) using (13)C to evaluate natural chlorinated ethene biodegradation and the ZVI-PRB efficiency; (2) using dual element (13)C-(37)Cl isotopic analysis to distinguish biotic from abiotic degradation of cis-dichloroethene (cis-DCE); and (3) using (13)C-(37)Cl-(2)H isotopic analysis of cis-DCE and TCE to elucidate different contaminant sources. Both biodegradation and degradation by ZVI-PRB were indicated by the metabolites that were detected and the (13)C data, with a quantitative estimate of the ZVI-PRB efficiency of less than 10% for PCE. Dual element (13)C-(37)Cl isotopic plots confirmed that biodegradation was the main process at the site including the ZVI-PRB area. Based on the carbon isotope data, approximately 45% and 71% of PCE and TCE, respectively, were estimated to be removed by biodegradation. (2)H combined with (13)C and (37)Cl seems to have identified two discrete sources contributing to the contaminant plume, indicating the potential of δ(2)H to discriminate whether a compound is of industrial origin, or whether a compound is formed as a daughter product during degradation.

Effective removal of nemacide fosthiazate from an aqueous solution using zero-valent iron

In this study, the removal of fosthiazate in an aqueous solution using zero valent iron (ZVI) and the related removal reaction mechanism were investigated. The results indicate that the dissipation of fosthiazate adheres to a pseudo-first order reaction law. The apparent rate constant of fosthiazate removal could be improved by increasing the ZVI dosage, control temperature and initial pH. The observed pseudo-first-order degradation rate constants (Kobs) of fosthiazate removal using ZVI were varied in the different electrolyte solutions, and were determined as follows: Kobs (MgSO4) < Kobs (KCl) < Kobs (Control) <Kobs (NaCl) < Kobs (CaCl2) < Kobs (NaNO3) < Kobs (Na2SO4). In addition, the effects of Fe(2+) and Fe(3+) ions on the fosthiazate removal were also investigated, and the fosthiazate removal efficiencies were measured as 1.3% and 5.7% with Fe(2+) and Fe(3+), respectively. The characterizations of ZVI before/after the reaction were employed to gain insight into the reaction mechanism. Finally, the main degradation products were investigated by means of an Agilent 1100 LC/MSD Ion Trap.

The negative spillover effect of food crises on restaurant firms: Did Jack in the Box really recover from an E. coli scare?

Despite the enormous impact of food crises on restaurants, limited understanding of their long-term impacts and associated factors has undermined crisis managers' ability to handle crisis situations effectively. This article investigated the long-term impact of food crises on the financial performance of restaurant firms and identified the factors that influenced this impact. This explanatory study examined the case of Jack in the Box, whose 1993 Escherichia coli scare was the first and largest restaurant-associated food crisis in modern times. An event study method was used to uncover stock price movements of Jack in the Box, in conjunction with 73 unrelated food crises that occurred from 1994 to 2010. Stock prices of Jack in the Box exhibited significantly negative responses to other firms' food crises, moreover, the negative spillover effect was stronger if the crisis occurred closer in time, was similar in nature, and was accompanied with no recall execution. These findings shed light on the long-term financial impact of food crises and offer insights for crisis managers to develop more effective crisis management strategies.

Enhanced chitosan beads-supported Fe(0)-nanoparticles for removal of heavy metals from electroplating wastewater in permeable reactive barriers

The removal of heavy metals from electroplating wastewater is a matter of paramount importance due to their high toxicity causing major environmental pollution problems. Nanoscale zero-valent iron (NZVI) became more effective to remove heavy metals from electroplating wastewater when enhanced chitosan (CS) beads were introduced as a support material in permeable reactive barriers (PRBs). The removal rate of Cr (VI) decreased with an increase of pH and initial Cr (VI) concentration. However, the removal rates of Cu (II), Cd (II) and Pb (II) increased with an increase of pH while decreased with an increase of their initial concentrations. The initial concentrations of heavy metals showed an effect on their removal sequence. Scanning electron microscope images showed that CS-NZVI beads enhanced by ethylene glycol diglycidyl ether (EGDE) had a loose and porous surface with a nucleus-shell structure. The pore size of the nucleus ranged from 19.2 to 138.6 μm with an average aperture size of around 58.6 μm. The shell showed a tube structure and electroplating wastewaters may reach NZVI through these tubes. X-ray photoelectron spectroscope (XPS) demonstrated that the reduction of Cr (VI) to Cr (III) was complete in less than 2 h. Cu (II) and Pb (II) were removed via predominant reduction and auxiliary adsorption. However, main adsorption and auxiliary reduction worked for the removal of Cd (II). The removal rate of total Cr, Cu (II), Cd (II) and Pb (II) from actual electroplating wastewater was 89.4%, 98.9%, 94.9% and 99.4%, respectively. The findings revealed that EGDE-CS-NZVI-beads PRBs had the capacity to remediate actual electroplating wastewater and may become an effective and promising technology for in situ remediation of heavy metals.

Effects of household detergent on anaerobic fermentation of kitchen wastewater from food waste disposer

This study examines the effects of household detergent on anaerobic methane fermentation of wastewater from food waste disposers (FWDs). Anaerobic toxicity assay (ATA) demonstrated that methane production substantially decreased at a higher detergent concentration. The Gompertz three-parameter model fitted well with the ATA results, and both the extent of methane production (M) and methane production rate (R(m)) obtained from the model were strongly affected by the concentration of the detergent. The 50% inhibitory concentration (IC(50)) of the detergent was 603 mg/L based on R(m). Results from fatty acid methyl esters (FAMEs) analysis of microbial culture revealed that deterioration of methane fermentation was attributed to impaired structure of anaerobic microbial membrane due to detergent. This study suggests that wastewater from FWD could be used for methane production, but it is necessary to reduce the concentration of detergent prior to anaerobic fermentation.

Is ammonification the rate limiting step for nitrification kinetics?

This study investigated relative magnitude of hydrolysis and ammonification by separate analysis of ammonia release and nitrification mechanisms. A peptone mixture was used as substrate in two parallel experiments seeded with nitrifying biomass conducted with and without nitrification inhibitor. Results were evaluated by means of model analysis of the ammonia and the oxygen uptake rate (OUR) profiles. A dual hydrolysis mechanism with maximum rate coefficients of 6.3 and 0.5/day characterized the peptone mixture and a kinetic balance was established for the ammonia release mechanism with a corresponding ammonification rate of 0.08 m(3)/g COD day. The experiments also showed a low soluble ammonia nitrogen generation that was rapidly depleted, confirming the existence of ammonification. These rate coefficients were verified using model calibration of the OUR profile related to simultaneous carbon removal and nitrification. Results indicated that ammonification would not be rate limiting for wastewaters such as domestic sewage, with lower hydrolysis kinetics.

Removal of chromium from Cr(VI) polluted wastewaters by reduction with scrap iron and subsequent precipitation of resulted cations

This work presents investigations on the total removal of chromium from Cr(VI) aqueous solutions by reduction with scrap iron and subsequent precipitation of the resulted cations with NaOH. The process was detrimentally affected by a compactly passivation film occurred at scrap iron surface, mainly composed of Cr(III) and Fe(III). Maximum removal efficiency of the Cr(total) and Fe(total) achieved in the clarifier under circumneutral and alkaline (pH 9.1) conditions was 98.5% and 100%, respectively. The optimum precipitation pH range which resulted from this study is 7.6-8.0. Fe(total) and Cr(total) were almost entirely removed in the clarifier as Fe(III) and Cr(III) species; however, after Cr(VI) breakthrough in column effluent, chromium was partially removed in the clarifier also as Cr(VI), by coprecipitation with cationic species. As long the column effluent was free of Cr(VI), the average Cr(total) removal efficiency of the packed column and clarifier was 10.8% and 78.8%, respectively. Our results clearly indicated that Cr(VI) contaminated wastewater can be successfully treated by combining reduction with scrap iron and chemical precipitation with NaOH.

Effect of layers composition on leachate property from functional layer embedded landfill

Two functional layers embedded landfills (FLELs), namely LR1 (with Layers 1 and 2) and LR2 (with double Layer 1), were conducted to evaluate their efficiency on the reduction of leachate strength at source and the acceleration of waste biodegradation process. It was found that the cumulative COD, NH(3)-N, leachate quantity and landfill settlement in LR1 was 63.0%, 34.6%, 94.8% and 80.4% of that in LR2 in the entire test periods, while the leachate effluents from these two reactors presented almost the same concentration at the end of the operation period. It could be concluded that leachate pollutants was removed immediately in Layer 2 through the physical-chemical reaction, while double Layer 1s contributed to the pollutant removal in a long run through the improvement of the micro-organism activities in landfill. The layer composition should be applied according to the landfill types, i.e. plain landfill using Layer 2 and valley landfill using Layer 1.

Source reduction of the landfill leachate strength in a functional layer embedded landfill (FLEL)

In order to reduce the leachate strength from landfill at source, a novel landfill, functional layer embedded landfill, was developed through the introduction of the functional layers, and a comparative study was conducted between the functional layer embedded landfill (FLEL, R1) and the conventional landfill (CL, R2). It was found that the pollutant in leachate effluent from R1 was 20-50%, 14-43% and 33-75% of that from R2, in terms of COD, TN and NH(3)-N. The cumulative movement of waste settlement was about 16.4 and 13.1cm in R1 and R2 under the test period of 1 years, resulting in 13.7% and 10.9% of the original landfill height. Therefore, FLEL could save the land area and the cost of the leachate treatment process due to the reduction of leachate strength, and more waste could be disposed in landfill through the acceleration of the MSW degradation process, comparing to the CL.