Validation of krypton as a new tracer gas for the standardization tests of collective and individual protection systems.

Sulfur hexafluoride (SF6) is the reference tracer gas in many international standards for characterizing respiratory protective devices (RPD), fume cupboards, building ventilations, and other installations. However, due to its significant impact on global warming, its use is becoming increasingly restrictive. Krypton 84 (Kr) was chosen to be a possible replacement based on theoretical and practical criteria for the properties that a substitute gas should possess.

Rare earth elements (REE) in the urban wastewater of Cotonou (Benin, West Africa).

The rare earth element (REE) contamination of urban wastewater, which was collected from open sewers and the inlet of a wastewater treatment plant in Cotonou (Benin), was assessed. The drinking water distributed to the inhabitants of Cotonou and water samples from private wells were also analyzed. The sampling occurred between October and December 2016 and the samples were analyzed by ICP-MS.

Population mobility and urban wastewater dynamics.

Dynamic influent models, which have been proposed to test control strategies using virtual wastewater treatment plants, should be as realistic as possible. The number of inhabitants in the catchment at any given time and their ways of life are among the parameters affecting the quality of these models. Census data related to work and school commutes were used to evaluate the number of people present in a given urban area.

Removal of Cr(III) from chrome tanning wastewater by adsorption using two natural carbonaceous materials: Eggshell and powdered marble.

In the present paper, eggshell and powdered marble, two carbonaceous materials, were used to remove Cr(III) ions from a real chrome tanning wastewater. The effects of initial effluent pH, adsorbent dose, contact time and temperature were studied. The maximum uptake of chromium ions was obtained at pH 5.

Aeration efficiency over stepped cascades: better predictions from flow regimes.

Stepped cascades are recognized as high potential air-water gas exchangers. In natural rivers, these structures enhance oxygen transfer to water by creating turbulence at interface with increasing air entrainment in water and air-water surface exchange. Stepped cascades could be really useful to improve the natural self-purification process by providing oxygen to aerobic micro-organisms.

Electrocoagulation for the treatment of textile wastewaters with Al or Fe electrodes: compared variations of COD levels, turbidity and absorbance.

Electrocoagulation technique has been used for the treatment of two wastewaters issued by textile industry. Treatment was carried out in a discontinuous system provided with aluminium or iron electrodes, and with recirculation of the liquid. The efficiency of the technique was followed depending on the electrode material in terms of water treatment, current efficiency of the dissolution, cell voltage, energy consumption to reach the same COD or turbidity abatement: regardless of the quality of the phase separation in the flocculation section downstream of the electrocoagulation cell, the two metals were found to be of comparable efficiency.

Characterization of two-phase flow regimes in horizontal tubes using 81mKr tracer experiments.

The diagnosis of heat exchangers on duty with respect to flow mal-distributions needs the development of non-intrusive inlet-outlet experimental techniques in order to perform an online fault diagnosis. Tracer experiments are an example of such techniques. They can be applied to mono-phase heat exchangers but also to multi-phase ones.

A general correlation to predict axial dispersion coefficients in aerated channel reactors.

Tracer studies have been widely applied to characterize the flow behavior in activated sludge reactors. The channel reactor with bottom aerators is one of the widespread designs in large wastewater treatment plants. Its flow behavior is well modeled either as a plug flow reactor with axial dispersion or as the perfect mixing cells in series.

Interpretation of radiotracer experiments in an industrial battery of desanders with simultaneous stochastic and non-stochastic flows.

Radiotracer experiments have been conducted in an industrial battery of twelve desanders located at the water treatment plant of Lima. The flow behavior is complex because it includes the superposition of a stochastic flow, which is intrinsic to the process itself, and of a non-stochastic flow induced by local strong currents at the surface. These currents are non-stochastic because they are different from one desander to another one even if all the desanders are identical.

Influence of inlet positions on the flow behavior inside a photoreactor using radiotracers and colored tracer investigations.

The influence of the inlet positions on the flow behavior inside a photoreactor has been studied using colored tracer and radiotracer investigations. The photoreactor for water disinfection is a tubular reactor inside which UV emitting lamps are placed. The key to its good performance is a combination of optimum irradiation dose and fluid residence time distributions (RTD).

Influence of geometrical and operational parameters on the axial dispersion in an aerated channel reactor.

Residence time distribution experiments have been performed on an activated sludge 3000 m3 channel reactor aerated by gas diffusion (for different liquid flowrates under constant aeration rate and constant water depth) and on a bench-scale channel reactor aerated from the bottom (for different liquid and gas flowrates and water depths) in order to characterize their hydrodynamics. Both units can be modeled as plug flow reactors with axial dispersion. A general correlation has been obtained to predict the axial dispersion coefficient as a function of the gas and liquid velocities and the geometrical parameters of the full-scale and bench-scale reactors.