Adsorption to a chelating resin is a method for recovering heavy metals from wastewater containing very light quantities of heavy metals ( B0.3 mol m − 3 , which approximately corresponds to 20 ppm). A thermodynamical study in a closed vessel showed that equilibrium is well represented by a Langmuir isotherm. Adsorption kinetics in a continuous stirred tank reactor were also conducted. Experiments were simulated by a global kinetics model comprising mass transfer in a liquid film around the resin particles, with diffusion through the pores and reaction on the adsorption sites. Kinetics has been found to be limited by film mass transfer for all metals studied (Cu 2 + , Ni 2 + , Co 2 + and Zn 2 + ). The mass transfer coefficient k L was found to be around 10 − 4 m s − 1 . Adsorption of heavy metals was then carried out at mini-pilot scale. Problems due to a decrease in particles mean radius during the adsorption prompted us to use a fluidized bed. It is also possible with this reactor to treat solutions containing suspended solids which would clog fixed beds. The decrease in particle radius (or increase in apparent density of the resin) produces a contraction of the fluidized bed: unloaded particles remain at the top of the bed and a density gradient appears throughout the column, leading to a stabilization of the fluidized bed. The measured phenomenon is well described by a liquid plug flow model with immobile resin in the column. As for the adsorption in the continuous stirred tank, the Langmuir model and the kinetics limited by film mass transfer were considered. The mass transfer coefficient k L was adjusted to a value around 10 − 5 m s − 1 .

In this paper, we examine a biofilm process for simultaneous removal of ammonia and NOX (nitrite and nitrate). SiporaxTM, a porous Raschig-ring type filter specifically designed and manufactured for fast colonisation by micro-organisms, was used to demonstrate the feasibility of simultaneous nitrification (usually an aerobic process) and denitrification (usually an anaerobic or anoxic process) inside a single reactor. Clear evidence was found that denitrification occurred inside the internal pore structure of SiporaxTMrather than in an anoxic zone near the outlet of the reactor. The reactor was operated continuously and maximum nitrification and denitrification capacities of 0.61 and 0.83 g N/(1.day), respectively were observed in this study.

SummaryThe surfactant concentration is an important parameter for optimizing protein extraction with microemulsions. Equilibrium and kinetic experiments show that the surfactant concentration can be reduced by a factor of 20 compared to published data. The masstransfer coefficient is found to be only about 18% lower for small AOT concentrations.

Currently the accepted practice for swine wastewater disposal is lagoon stabilisation followed by land application. This disposal method can exacerbate odour emissions and contribute to soil contamination and eutrophication of waterways. Intensification of the pig industry has increased the impact of individual piggeries; this combined with tightening legislation is causing the pig industry in Australia to look at alternative treatment methods. A pilot scale sequencing batch reactor (SBR) was built to treat piggery wastewater. It achieved NH4+ and odour reductions of greater than 99% as well as 79% removal of COD and a 49% reduction of PO43−on a mass balance basis. The reactor experienced problems with foaming for the first 2 months of operation, which was controlled with vegetable oil until the foaming stopped. Struvite formation also occurred within the reactor and influent pipes but it was calculated that sufficient nutrients were removed to prevent precipitation down stream of the SBR.

An alternative to the classical acid‐base regeneration of chelating resins loaded with heavy metals is investigated. The new process consists in recovering the heavy metals with recyclable soluble complexing agents. The semiclosed reactor includes a fixed bed and a stirred tank. A three‐parameter model, which implies a double equilibrium in series, is introduced. When less than 10 % of the metal is still fixed on the resin at the end of the desorption, a simplified form of the model with two parameters, which describes a quick equilibrium followed by a first‐order kinetics reaction, is proposed. Both forms of the model can simulate results for different experimental conditions (polymer and metal types, polymer initial concentration). It was observed for both cases that the first equilibrium constant depends on the polymer type and that the rate constant of desorption depends on the metal type. The scale‐up of desorption is then conducted at mini‐pilot scale. Scale‐up criteria tend to minimize the desorption time and the soluble polymer quantity used.