Abstract: A method and system for decreasing the concentration of at least one metal in an aqueous solution. The metal may be molybdenum, tungsten, or both. An aqueous solution is introduced into at least one reaction zone, and at least one source of hydroxide ions is provided into the at least one reaction zone in an amount sufficient to precipitate at least some of the mass of the at least one metal. The aqueous solution includes a mass of the at least one metal and a mass of at least one reducing agent. The at least one reducing agent includes at least ferrous iron from at least one source of the at least one reducing agent. A composition of tungsten ferrite or molybdenum tungsten ferrite may be formed. The method may be used for purifying water, for the refining of metals, or to facilitate a chemical analytical determination.

Abstract: A method comprises conducting a permeable-reactive barrier (PRB) treatment of a contaminated aqueous medium and in-well monitoring effectiveness of the permeable-barrier treatment. A system comprises a PRB zone to treat a contaminated groundwater and an in-well sensor located within a gradient of the contaminated groundwater or within the PRB zone to sense a characteristic of the groundwater.

Abstract: An on-line sparging sampling system and method sparges polar and non-polar volatile organic compounds from aqueous discharge. The system comprises a network of tubular members that are interconnected to each other to define a fluid passage, in which the network of tubular members comprises an inlet for influent aqueous discharge into the network of tubular members and an outlet for discharge of aqueous discharge from the on-line sparging sampling and monitoring system; a sparger disposed in the network of tubular members, in which the sparger is disposed between the inlet and the outlet of the aqueous discharge so that aqueous discharge flows by the sparger, the sparger providing inert non-reactive gas to the on-line sparging sampling and monitoring system; and at least one analytic device connected to the on-line sparging sampling and monitoring system for analyzing volatile organic compounds in the aqueous discharge.

Abstract: A headspace sampling system monitors materials in wastewater. The headspace sampling system comprises a sample receptacle that can contain a wastewater sample; a sparger chamber vapor column; a sample receptacle cover assembly that connects the sparger chamber vapor column to the sample receptacle; a sparger tube; at least one sensing device; and at least one analytic device. The sparger tube and the sample receptacle define a headspace. The sparger chamber vapor column is in communication with the sample receptacle and is closed by a sparger chamber vapor column cover at a second end that is opposed to the sample receptacle. The sparger tube extends into the sample receptacle and the wastewater sample in the sample receptacle. The sparger tube is connected to a source of inert gas at a first end opposed to the sample receptacle and comprises a dispersion device at an end opposed to the first end. The sensing device is disposed in the headspace sampling system in the headspace.

Abstract: A sampling device can monitor contaminants in groundwater. The sampling device comprises a semi-permeable membrane for contact with groundwater, in which the semi-permeable membrane is permeable to contaminants and impermeable to groundwater; an inner chamber formed by the semi-permeable membrane for containing the contaminants from the groundwater that diffuse through the semi-permeable membrane; and a sensor device communicating with the inner chamber. The sensor device is in contact with the contaminants contained within the inner chamber for monitoring the contaminants.

Abstract: An improved method and apparatus for monitoring the concentration of contaminants, including volatile organic compounds, in groundwater is provided comprising a semipermeable membrane defining an inner chamber. The chamber is carried within a mesh protective sleeve of cover to prevent abrasion or puncture of the chamber. The membrane is permeable to contaminants but impermeable to a reference fluid, which is distilled water. The method of sampling comprises placing the semipermeable membrane chamber, which contains the reference fluid, in contact with contaminated groundwater, thereby allowing contaminants to diffuse through the semipermeable membrane.