Considerations on the use of carbon and nitrogen isotopic ratios for sediment fingerprinting.

Carbon and nitrogen stable isotopic ratios are increasingly used in sediment fingerprinting studies. However, questions remain regarding tracer conservativeness during sediment transport and other error considerations. We investigate conservativeness processes, including carbon oxidation and nitrogen mineralization, using experiments.

Selenium removal by activated alumina in batch and continuous-flow reactors.

Selenium removal by activated alumina (AA) in batch and continuous-flow reactors was investigated in this study. The adsorption kinetics fitted pseudo-first as well as pseudo-second order models with equilibrium time for Se(VI) and Se(IV) adsorption of 8 and 12 hr, respectively. A significant higher adsorption capacity for Se(IV) than Se(VI) was observed in isothermal adsorption experiments.

Selenium reduction by a defined co-culture of Shigella fergusonii strain TB42616 and Pantoea vagans strain EWB32213-2.

Selenium reduction was evaluated with pure batch cultures of Shigella fergusonii strain TB42616 (TB) and Pantoea vagans strain EWB32213-2 (EWB), respectively. A two-stage process, from Se(VI) to Se(IV) and then from Se(IV) to Se(0), was observed. The second stage of reduction, from Se(IV) to Se(0), was observed as the rate-limiting step resulting in accumulation of the more toxic Se(IV).

Modeling arsenite oxidation by chemoautotrophic Thiomonas arsenivorans strain b6 in a packed-bed bioreactor.

Arsenic is a major toxic pollutant of concern for the human health. Biological treatment of arsenic contaminated water is an alternative strategy to the prevalent conventional treatments. The biological treatment involves a pre-oxidation step transforming the most toxic form of arsenic, As (III), to the least toxic form, As (V), respectively.

Arsenite oxidation by immobilized cells of Alcaligenes faecalis strain O1201 in a fluidized-bed reactor.

Arsenic(III) oxidation was evaluated in a continuous-flow fluidized-bed reactor (FBR) with Alcaligenes faecalis strain 01201 immobilized in gel beads. The FBR was operated under 300 mg/L citrate and a range of influent As(III) concentrations (75 to 3000 mg/L) at short hydraulic retention times (1.06 to 3.

Modeling hexavalent chromium removal in a Bacillus sp. fixed-film bioreactor.

A one-dimensional diffusion-reaction model was developed to simulate Cr(VI) reduction in a Bacillus sp. pure culture biofilm reactor with glucose as a sole supplied carbon and energy source. Substrate utilization and Cr(VI) reduction in the biofilm was best represented by a system of (second-order) partial differential equations (PDEs).