Reduced Recharge Capacity of a Pump and Treat System

The North Boundary treatment system at Rocky Mountain Arsenal (RMA), Commerce City, Colorado, involves pumping of contaminated groundwater from an unconfined aquifer from one side of a soil-bentonite (SB) slurry wall to three pulsed-bed activated carbon adsorbers and prefilter and postfilter systems. The treated water is injected into the unconfined aquifer on the other side of the slurry wall via 38 recharge wells and 15 recharge trenches, collectively referred to as the recharge system. Recharge capacity of the recharge system has declined over time, limiting the operating capacity of the system. Two probable causes for reduction of the recharge systems is assessed

Treatment of Contaminated Groundwater Using Chemical Oxidation

Chemical oxidation was evaluated for treatment of a groundwater contaminated with trichloroethylene, acetone, and other organic compounds as measured by the biochemical oxygen demand (BOD) test. Results indicated that maximum contaminant removal was obtained using a combination of hydrogen peroxide, high intensity ultraviolet light, and the addition of tungsten trioxide under acidic conditions

Laboratory Assessment of Advanced Oxidation Processes for Treatment of Explosives and Chlorinated Solvents in Groundwater from the Former Nebraska Ordnance Plant

The study herein was performed through a partnering effort between the U.S. Army Engineer District, Kansas City, Kansas City, MO, and the U.S. Army Engineer Waterways Experiment Station (WES), Vicksburg, MS. The Kansas City District funded portions of this effort as a means of evaluating various treatment options for the contaminated groundwaters at the Nebraska Army Ammunition Plant, Mead, NE. Some of the WES activities were performed under funding from the U.S. Department of Defense\u27s (DoD) Strategic Environmental Research and Development Program (SERDP). WES has been tasked by SERDP to develop peroxone oxidation as an economical means of decontaminating groundwaters contaminated with explosives at DoD sites. This report was prepared by Ms. Elizabeth C. Fleming, Dr. Mark E. Zappi, Ms. Evelyn Toro, and Mr. Rafael Hernandez, all of the Environmental Restoration Branch (ERB), Environmental Engineering Division (EED), Environmental Laboratory (EL), WES; Ms. Karen Myers, Environmental Chemistry Branch (ECB), EED; Dr. Prasad Kodukula, Woodward-Clyde Consultants, Inc., Overland Park, KS; and Ms. Rosemary Gilbertson, Kansas City District This study was performed at WES under the direct supervision of Mr. Daniel E. Averett, Chief, ERB, and under the general supervision of Mr. Norman R. Francingues, Jr., Chief, EED. Drs. John W. Keeley and John Harrison were the Assistant Director and Director of EL, respectively, during this study. Dr. Harrison was also the Director of SERDP, Washington, DC, and Dr. M. John Cullinane was the WES Program Manager of SERDP during this study. At the time of publication of this report, Dr. Robert W. Whalin was the Director of WES. COL Bruce K. Howard, EN, was Commander

Behaviour of trinitrotoluene in electrokinetic soil processing

The behaviour and removal of trinitrotoluene (TNT) in contaminated soil under electrokinetic processes was investigated. The soil used in this study was obtained from the Hastings East Industrial Park site in Nebraska, USA. A current density of 123.3 μA/cm2 was applied to soil specimens compacted in glass cells. Test with water and a surfactant solution, SDS, as anolytes indicated that TNT concentrations in the soil sample decreased significantly at the sections closest to the cathode. This, however, was not due to removal of TNT away from the cathode. Extensive analysis indicated that the disappearance of TNT was possibly due to the transformation of TNT to TNT anions possibly due to reaction of TNT with base and reductive environment generated during electrolysis. These anions were not detected in initial analysis with high performance liquid chromatography using EPA method. The electrokinetic processes needs further engineering in order to enhance removal of TNT from soil

Adsorption kinetic modeling using pseudo-first order and pseudo-second order rate laws: A review

Adsorption for water and wastewater treatment has been the subject of many research in the scientific community, focusing mainly on either equilibrium or kinetic studies. Adsorption kinetics are commonly modeled using pseudo-first and pseudo-second order rate laws. Analyses of published works in the past two decades indicated that the pseudo-second order is considered to be the superior model as it can represent many adsorption systems. However, critical assessment of modeling techniques and practices suggests that its superiority could be a consequence of currently acceptable modeling norms which tend to favor the pseudo-second order model. The partiality was due to several modeling pitfalls that are often neglected. In addition, commonly used model validation tools are often used haphazardly and redundantly. As such, they cannot sufficiently provide any kind of certainty on the validity of a model. To eliminate modeling biasness, a new validation method was proposed and was then employed to re-examine previously published adsorption kinetic data

Using Self-Organizing Map Algorithm to Reveal Stabilities of Parameter Sensitivity Rankings in Microbial Kinetic Models: A Case for Microalgae

Microalgae are multi-purpose microbial agents due to their capability to efficiently sequester carbon dioxide and produce valuable biomass such as protein and single-cell oils. Formulation and tuning of microalgae kinetics models can significantly contribute to the successful design and operation of microalgae reactors. This work aimed to demonstrate the capability of self-organizing map (SOM) algorithm to elucidate the patterns of parameter rankings in microalgae models subject to stochastic variations of input forcing functions–bioprocess influent component concentration levels. These stochastic variations were implemented on a modeled chemostat with a deterministic microalgae kinetic model consists of ten time-dependent variables and eighteen model parameters. The methodology consists of two major stages: (1) global sensitivity analysis (GSA) on the importance of model parameters with stochastic sampling of bioreactor influent component concentrations, and (2) training of self-organizing maps on the datasets of model parameter rankings derived from the GSA indices. Results reveal that functional principal components analysis can project at least 99% of the time-dependent dynamic patterns of the model variables on B-splines basis functions. The component planes for hexagonal lattice SOMs reveal that the sensitivity rankings some parameters in the algae model tested can be stable over a wide range of variations in the levels of influent component concentrations. Therefore, SOM can be used to reveal the trends in multi-dimensional data arrays arising from the implementation of GSA of kinetic models under stochastic perturbation of input forcing functions

Uniform Mesoporous Amorphous Cobalt-Inherent Silicon Oxide as a Highly Active Heterogeneous Catalyst in the Activation of Peroxymonosulfate for Rapid Oxidation of 2,4-Dichlorophenol: The Important Role of Inherent Cobalt in the Catalytic Mechanism

Amorphous cobalt-inherent silicon oxide (Co-SiOx) was synthesized for the first time and employed as a highly active catalyst in the activation of peroxymonosulfate (PMS) for the rapid oxidation of 2,4-dichlorophenol (2,4-DCP). The characterization results revealed that the 0.15Co-SiOx possessed a high specific surface area of 607.95 m2/g with a uniform mesoporous structure (24.33 nm). The X-ray diffraction patterns indicate that the substituted cobalt atoms enlarge the unit cell parameter of the original SiO2, and the selected area electron diffraction pattern confirmed the amorphous nature of Co-SiOx. More bulk oxygen vacancies (Ov) existing in the Co-SiOx were identified to be one of the primary contributors to the significantly enhanced catalytic activation of PMS. The cobalt substitution both creates and stabilizes the surficial Ov and forms the adequately active Co(II)-Ov pairs which engine the electron transfer process during the catalytic activities. The active Co(II)-Ov pairs weaken the average electronegativity of Co/Si and Co/O sites, resulting in the prevalent changes in final state energy, which is the main driving cause of the binding energy shifts in the X-ray photoelectron spectroscopy (XPS) spectra of Si and O among all samples. The increase of the relative proportion of Co(III) in the spent Co-SiOx probably causes the binding energy shifts of the Co XPS spectrum compared to that of the Co-SiOx. The amorphous Co-SiOx outperforms stable and quick 2,4-DCP degradation, achieving a much higher kinetic rate of 0.7139 min-1 at pH = 7.02 than others via sulfate radical advanced oxidation processes (AOPs), photo-Fenton AOPs, H2O2 reagent AOPs, and other AOP approaches. The efficient degradation performance makes the amorphous Co-SiOx as a promising catalyst in removing 2,4-DCP or organic-rich pollutants

Evaluation of the Methane Production Potential of Catfish Processing Wastewater Using Various Anaerobic Digestion Strategies

The U.S. catfish industry is a major industry that has been declining over the years due to imports competition and growing operational costs. Catfish processing wastewater management and high energy requirement put a large financial burden on catfish processing facilities. Recovered protein-based solids have provided some value-added co-products, however, more co-products are needed to offset processing costs. Anaerobic digestion is a proven waste treatment method that produces methane, which is an energetic co-product that can be used within the processing facilities. This study was conducted to evaluate the potential of anaerobic digestion as an alternative to the currently used aerobic biotreatment of catfish processing wastewater. Initial assessments indicated the recalcitrance of the full-strength wastewater to anaerobic digestion, yielding only ~4 m3 per ton (U.S.) of input chemical oxygen demand (CODinput). Thus, several strategies were evaluated to improve the methane yield from the wastewater. These strategies include nutrient (nitrogen and sulfur) amendment, along with ozone, HCl, and NaOH pretreatment. The results showed that nutrient amendment was the most suitable strategy for improving the digestibility of the catfish processing wastewater. A methane yield of 121–236 m3/ton (U.S.) CODinput was obtained, with a purity of 67–80 vol.%. These results are similar to yields and purities of biogas from other feedstock, such as food waste, wastewater solids, and fish canning wastewater. This indicates that anaerobic digestion could be a viable alternative for simultaneous treatment and energetic co-product generation from catfish processing wastewater