Enhancing the Biological Oxidation of HS in a Sewer Pipe with Highly Conductive Concrete and Electricity-Producing Bacteria.

Hydrogen sulfide (HS) generated in sewer systems is problematic to public health and the environment, owing to its corrosive consequences, odor concerns, and poison control issues. In a previous work, conductive concrete, based on amorphous carbon with a mechanism that operates as a microbial fuel cell was investigated. The objective of the present study is to develop additional materials for highly conductive concrete, to mitigate the concentration of HS in sewer pipes.

Preferential adsorption and surface precipitation of lead(II) ions onto anatase in artificially contaminated Dixie clay.

During TEM-EDS (transmission electron microscopy coupled with an X-ray energy dispersive spectrometer) analysis of Dixie clay artificially contaminated with Pb(II), we observed that Pb(II) was preferentially adsorbed and precipitated on the surface of TiO. To deepen the understanding of the mechanism and importance of this phenomenon, batch sorption experiments, XANES (X-ray absorption near edge spectroscopy) analysis, and sequential extraction analysis were performed. The TiO in Dixie clay was found to be anatase, and anatase showed a higher Pb(II) sorption propensity than rutile, α-FeOOH, and one of two MnO investigated in this study.

Relationship between performance deterioration of a polyamide reverse osmosis membrane used in a seawater desalination plant and changes in its physicochemical properties.

While it is known that the performance of reverse osmosis membranes is dependent on their physicochemical properties, the existing literature studying membranes used in treatment facilities generally focuses on foulant layers or performance changes due to fouling, not on the performance and physicochemical changes that occur to the membranes themselves. In this study, the performance and physicochemical properties of a polyamide reverse osmosis membrane used for three years in a seawater desalination plant were compared to those of a corresponding unused membrane. The relationship between performance changes during long-term use and changes in physicochemical properties was evaluated.

Immobilization of arsenate in kaolinite by the addition of magnesium oxide: An experimental and modeling investigation.

MgO was chosen as an As(V) immobilization agent and a series of immobilization experiments was performed to obtain insights into the behavior of As(V) and MgO during leaching tests. Our experimental and modeling results demonstrated that As(V) immobilization by MgO consists of the following steps: (i) an increase in sample pH, (ii) desorption of As(V) from the samples, and (iii) the re-immobilization of As(V) by MgO/Mg(OH)2 particles. Regarding the behavior of MgO, the modeling results showed that when the MgO dosage was 25 mgMgO/4 g-drysample or less, the majority of MgO was used to increase pH, and less than 1% of MgO was used to sorb As(V), which was consistent with the result of leaching tests showing that a high level of As(V) was leached at the MgO dosages.

Recovery of Cr as Cr(III) from Cr(VI)-contaminated kaolinite clay by electrokinetics coupled with a permeable reactive barrier.

Zero-valent iron (Fe(0)) and magnetite (Fe3O4) were investigated as potential reductants in an electrokinetic/permeable reactive barrier hybrid system (EK/PRB) for the recovery of Cr as Cr(III) from Cr(VI)-contaminated kaolinite. For the EK/Fe(0) PRB, regardless of the pH in the anode well, the system facilitated the reduction of Cr(VI) into Cr(III), but the recovery of the Cr(III) in the PRB was low. Conversely, the reduction of Cr(VI) occurred only in the PRB for the EK/Fe3O4 PRB.

A mechanistic study of arsenate removal from artificially contaminated clay soils by electrokinetic remediation.

Batch desorption experiments and bench-scale electrokinetic experiments were performed to elucidate the electrokinetic remediation mechanisms of arsenate from artificially contaminated kaolinite. The electrokinetic experiments in which a constant voltage was applied demonstrated that high soil pH favored arsenate remediation with respect to both the remediation time and electricity consumption. It was also demonstrated that applying a pulse voltage (1 h ON, 1 h OFF) significantly improved the electricity consumption efficiency when the soil pH was maintained at the initial value during the experiments; this trend was not observed when the soil pH was gradually increased from the cathode side.

An electrokinetic/Fe0 permeable reactive barrier system for the treatment of nitrate-contaminated subsurface soils.

Effective nitrate removal by Fe(0) permeable reactive barriers (Fe(0) PRB) has been recognized as a challenging task because the iron corrosion product foamed on Fe(0) hinders effective electron transfer from Fe(0) to surface-bound nitrate. The objectives of this study were (i) to demonstrate the effectiveness of an electrokinetic/Fe(0) PRB system for remediating nitrate-contaminated low permeability soils using a bench-scale system and (ii) to deepen the understanding of the behavior and fate of nitrate in the system. Bench-scale laboratory experiments were designed to investigate the influence of the Fe(0) content in the permeable reactive barrier, the pH in the anode well, and the applied voltage on remediation efficiency.

Origins and transport of aquatic dioxins in the Japanese watershed: soil contamination, land use, and soil runoff events.

Significant dioxins accumulations in Japanese forests and paddy fields have been observed, and surface soil runoff caused by rainfall and irrigation (i.e., soil puddling in paddy fields) results in dioxins input into the aquatic environment.

Mass loading and partitioning of dioxins in irrigation runoff from Japanese paddy fields: combination usage of the CALUX assay with HRGC/HRMS.

Lack of understanding of dioxins mass loading into the aquatic environment motivated the quantitative investigation of dioxins runoff from paddy fields during one entire irrigation period in the Minakuchi region, Japan. Combination use of the chemically activated luciferase gene expression (CALUX) bioassay together with high resolution gas chromatography and high resolution mass spectrometry (HRGC/HRMS) enabled efficient investigation of dioxins contamination. The result shows that the congener profile in irrigation runoff is quite similar to those in paddy soil samples and that 1,3,6,8-/1,3,7,9-TeCDD and OCDD derived from pesticides (i.

Performance characterization of nanofiltration membranes based on rigid star amphiphiles.

The objective of this study was to develop new nanofiltration (NF) membranes capable of providing significantly greater water permeability and higher rejection of water contaminants compared to state-of-the-art NF membranes. The active layer of the new NF membranes is prepared with rigid star amphiphiles (RSAs) synthesized as part of this study. Performance characterization for a first generation of RSA membranes in a bench-scale apparatus reveals that most of the new membranes provide water permeability of 1.