Biodiesel production from wet municipal sludge: evaluation of in situ transesterification using xylene as a cosolvent.

This study proposes a method to produce biodiesel from wet wastewater sludge. Xylene was used as an alternative cosolvent to hexane for transesterification in order to enhance the biodiesel yield from wet wastewater sludge. The water present in the sludge could be separated during transesterification by employing xylene, which has a higher boiling point than water. Xylene enhanced the biodiesel yield up to 8.12%, which was 2.5 times higher than hexane. It was comparable to the maximum biodiesel yield of 9.68% obtained from dried sludge. Xylene could reduce either the reaction time or methanol consumption, when compared to hexane for a similar yield. The fatty acid methyl esters (FAMEs) content of the biodiesel increased approximately two fold by changing the cosolvent from hexane to xylene. The transesterification method using xylene as a cosolvent can be applied effectively and economically for biodiesel recovery from wet wastewater sludge without drying process.

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

This study presents a screening protocol to evaluate the applicability of the ZVI pretreatment to various industrial wastewaters of which major constituents are not identified. The screening protocol consisted of a sequential analysis of UV-vis spectrophotometry, high-performance liquid chromatograph (HPLC), and bioassay. The UV-vis and HPLC analyses represented the potential reductive transformation of unknown constituents in wastewater by the ZVI. The UV-vis and HPLC results were quantified using principal component analysis (PCA) and Euclidian distance (ED). The short-term bioassay was used to assess the increased biodegradability of wastewater constituents after ZVI treatment. The screening protocol was applied to seven different types of real industrial wastewaters. After identifying one wastewater as the best candidate for the ZVI treatment, the benefit of ZVI pretreatment was verified through continuous operation of an integrated iron-sequencing batch reactor (SBR) resulting in the increased organic removal efficiency compared to the control. The iron pretreatment was suggested as an economical option to modify some costly physico-chemical processes in the existing wastewater treatment facility. The screening protocol could be used as a robust strategy to estimate the applicability of ZVI pretreatment to a certain wastewater with unknown composition.

Zero-valent iron pretreatment for detoxifying iodine in liquid crystal display (LCD) manufacturing wastewater.

This study investigated reductive transformation of iodine by zero-valent iron (ZVI), and the subsequent detoxification of iodine-laden wastewater. ZVI completely reduced aqueous iodine to non-toxic iodide. Respirometric bioassay illustrated that the presence of iodine increase the lag phase before the onset of oxygen consumption. The length of lag phase was proportional to increasing iodine dosage. The reduction products of iodine by ZVI did not exhibit any inhibitory effect on the biodegradation. The cumulative biological oxidation associated with iodine toxicity was closely fitted to Gompertz model. When iodine-laden wastewater was continuously fed to a bench-scale activated sludge unit, chemical oxygen demand (COD) removal efficiencies decreased from above 90% to below 80% along with a marked decrease in biomass concentration. On the other hand, the COD removal efficiency and biomass concentration remained constant in the integrated ZVI-activated sludge system. Respirometric bioassay with real iodine-laden LCD manufacturing wastewater demonstrated that ZVI was effective for detoxifying iodine and consequently enhancing biodegradability of wastewater. This result suggested that ZVI pretreatment may be a feasible option for the removal of iodine in LCD processing wastewater, instead of more costly processes such as adsorption and chemical oxidation, which are commonly in the iodine-laden LCD wastewater treatment facility.

Fatty acid methyl ester (FAME) technology for monitoring biological foaming in activated sludge: full scale plant verification.

Fatty acid methyl ester (FAME) technology was evaluated as a monitoring tool for quantification of Gordonia amarae in activated sludge systems. The fatty acid, 19:1 alcohol, which was identified as a unique fatty acid in G. amarae was not only confirmed to be present in foaming plant samples, but the quantity of the signature peak correlated closely with the degree of foaming. Foaming potential experiment provided a range of critical foaming levels that corresponded to G. amarae population. This range of critical Gordonia levels was correlated to the threshold signature FAME amount. Six full-scale wastewater treatment plants were selected based on a survey to participate in our full-scale study to evaluate the potential application of the FAME technique as the Gordonia monitoring tool. Greater amounts of signature FAME were extracted from the mixed liquor samples obtained from treatment plants experiencing Gordonia foaming problems. The amounts of signature FAME correlated well with the conventional filamentous counting technique. These results demonstrated that the relative abundance of the signature FAMEs can be used to quantitatively monitor the abundance of foam-causing microorganism in activated sludge.

Zero-valent iron treatment of RDX-containing and perchlorate-containing wastewaters from an ammunition-manufacturing plant at elevated temperatures.

The use of zero-valent iron for treating wastewaters containing RDX and perchlorate from an army ammunition plant (AAP) in the USA at elevated temperatures and moderately elevated temperature with chemical addition was evaluated through batch and column experiments. RDX in the wastewater was completely removed in an iron column after 6.4 minutes. Increasing the temperature to 75 degrees C decreased the required retention time to 2.1 minutes for complete RDX removal. Perchlorate in the wastewater was completely removed by iron at an elevated temperature of 150 degrees C in batch reactors in 6 hours without pH control. Significant reduction of perchlorate by zero-valent iron was also achieved at a more moderate temperature (75 degrees C) through use of a 0.2 M acetate buffer. Based on the evaluation results, we propose two innovative processes for treating RDX-containing and perchlorate-containing wastewaters: a temperature and pressure-controlled batch iron reactor and subsequent oxidation by existing industrial wastewater treatment plant; and reduction by consecutive iron columns with heating and acid addition capabilities and subsequent oxidation.

Bioleaching of cadmium and nickel from synthetic sediments by Acidithiobacillus ferrooxidans.

The microbial leaching process was evaluated for the treatment of synthetic sediments contaminated with cadmium and nickel sulfides. A series of batch leaching experiments was conducted to compare metal solubilization in sediment inoculated with Acidithiobacillus ferrooxidans -inoculated sediments to that in sterile control sediment. The rate and extent of metal solubilization were significantly higher in A. ferrooxidans -inoculated reactors than in acidified sterile reactors. The efficiency of cadmium (Cd) solubilization (80) in the bioleaching process was higher than that of nickel (Ni) solubilization (60). The performance of leaching reactors containing only culture supernatants was comparable to that of A. ferrooxidans -inoculated reactors, indicating that indirect non-contact leaching by the products of microbial metabolism is the predominant mechanism for metal solubilization rather than direct microbial sulfide oxidation. Moreover, the similar (60-75%) extents of Cd(2+) leaching with A. ferrooxidans , cell-free filtrate, and Fe(3+) suggest that abiotic oxidation of CdS by Fe(3+) controls the overall leaching rate, and the role of A. ferrooxidans is most likely not to oxidize CdS mineral directly but to regenerate Fe(3+) as an oxidant.

Conceptual comparison of pink water treatment technologies: granular activated carbon, anaerobic fluidized bed, and zero-valent iron-Fenton process.

Pink water, explosive-laden wastewater produced in army ammunition plants is often treated using expensive and non-destructive granular activated carbon (GAC) adsorption. This paper compares GAC adsorption and two alternative treatment technologies, anaerobic GAC fluidized bed reactor and zero-valent iron-Fenton process. The bench-scale demonstration of the zero-valent iron-Fenton process with real pink water is reported. The features of three technologies are compared and their advantages and drawbacks are discussed.

Enhancing oxidation of TNT and RDX in wastewater: pre-treatment with elemental iron.

Munitions manufacturing wastewater is commonly treated by adsorption to activated carbon. We are proposing a new munitions manufacturing wastewater treatment system consisting of a reductive pre-treatment process and subsequent Fenton's oxidation to mineralize energetic compounds such as TNT and RDX. The pre-treatment involves reduction of electron-withdrawing nitro groups of TNT and RDX with elemental iron. The iron-treated explosives are then oxidized by Fenton's reagent through the addition of H2O2. The objective of this work is to investigate the feasibility of using elemental iron to convert TNT and RDX to reduction products which may be more oxidizable in subsequent Fenton's oxidation. Results of batch reduction experiments with elemental iron showed complete removal of TNT and RDX and formation of the reduction products within 60 minutes. Results of column experiments showed a rapid and complete removal of TNTand RDX within 9.7 minutes retention time. Fitting observed effluent concentrations to a one-dimensional advection-dispersion equation, we were able to predict the concentration profiles of TNT and RDX in the iron column and calculate the iron column length required for the desired removal. The results of Fenton's oxidation experiments showed that iron pre-treatment enhanced both the rate and extent of TNT and RDX mineralization by Fenton's oxidation.

Physicochemical factors affecting the sensitivity of Ceriodaphnia dubia to copper.

The effects of physicochemical conditions, such as pH, water hardness, flow rates and natural organic substances on the sensitivity of Ceriodaphnia dubia to the toxic effects of copper were investigated using static bioassay cups and specially designed flow-through bioassay chambers. We found that C. dubia was very sensitive to pH changes and the total copper LC50 values of C. dubia neonates increased by 15-fold as the pH increased from pH 7 to 10. It was also observed that the LC50 values increased sharply upon increasing the water hardness value to 2.4 meq. In addition, increasing flow rates from zero to 50 mL hr(-1) also increased its sensitivity to copper, which was possibly due to hydrodynamic stress. The presence of natural organic substances (humic acid and dissolved organic matter) and suspended particles decreased the toxic effect of copper. This significant decrease in the toxicity of copper in the presence of natural organic materials can be explained by a reduction in the free ion concentration due to complexation. Furthermore, we observed that the kinetics of copper interactions with natural organic materials are a significant factor in the toxic effect of copper and that the acute LC50 values increased with increasing reaction time between solubilized copper and water-borne organics.

Reductive dehalogenation of chlorinated ethenes with elemental iron: the role of microorganisms.

Trichloroethene (TCE) transformation and the product distribution in an aqueous medium containing zero-valent iron (Fe(0)) was investigated in the presence of an anaerobic mixed culture to assess the potential role of microorganisms in permeable iron barriers. The presence of the culture increased the rate of TCE disappearance and changed the product distribution. Rapid formation and degradation of cis-dichloroethene (cis-DCE) was observed in reactors containing cells plus Fe(0) or H2 as a bulk reducing agent. High levels of vinyl chloride (VC) were formed and very similar profiles were obtained in the Fe(0) plus cell and H2 plus cell reactors, but not in Fe(0)-only reactors. The similar trends observed in Fe(0)-cell and H2-cell reactors suggest that most cis-DCE and VC in the Fe(0)-cell reactors were produced and transformed biologically rather than abiotically. Accumulation of methane in the Fe(0)-cell system indicates that hydrogen gas generated during anaerobic iron corrosion could support a methanogenic culture. Digital confocal images showed that the microorganisms were able to colonize the iron surface. The results suggest that potential development of dechlorinating populations in Fe(0) barriers may alter the TCE reduction pathway and produce VC, which would have significant impact on the performance of Fe(0) barriers.

Phenanthrene degradation in soils co-inoculated with phenanthrene-degrading and biosurfactant-producing bacteria.

Contaminant sorption within the soil matrix frequently limits biodegradation. However, contaminant bioavailability can be species-specific. This study investigated bioavailability of phenanthrene (PHE) to two PHE-degrading bacteria (Pseudomonas strain R and isolate P5-2) in the presence of rhamnolipid biosurfactant and/or a biosurfactant-producing bacterium, Pseudomonas aeruginosa ATCC 9027. Pseudomonas strain R mineralized more soil-sorbed PHE than strain P5-2, but in aqueous cultures the rate and extent of PHE mineralization by P5-2 exceeded that by P. strain R. In Fallsington sandy loam (fine-loamy, mixed, active, mesic Typic Endoaquult) (high PHE-sorption capacity) the addition of rhamnolipid increased PHE mineralization by P. strain R. Phenanthrene mineralization in soils inoculated with P5-2 was minimal and no enhancement in PHE degradation was observed when biosurfactant was added. Co-inoculation of Fallsington sandy loam with the biosurfactant producer did not affect PHE mineralization by isolate P5-2, but significantly enhanced PHE mineralization by P. strain R. The enhancement of PHE mineralization could not be explained by P. aeruginosa-mediated PHE degradation. The addition of rhamnolipid at concentrations above the critical micelle concentration (CMC) resulted in enhanced PHE release from test soils. These results suggest that the PHE-degrading strains were able to access different pools of PHE and that the biosurfactant-enhanced release of PHE from soils did not result in enhanced biodegradation. The results also demonstrated that bacteria with the catabolic potential to degrade sorbed hydrophobic contaminants could interact commensally with surfactant-producing strains by an unknown mechanism to hasten the biodegradation of aromatic hydrocarbons. Thus, understanding interactions among microbes may provide opportunities to further enhance biodegradation of soil-bound organic contaminants.