Abstract This paper evaluated the treatment of textile wastewater in submerged anaerobic membrane bioreactors (SAMBR) operated on a bench scale. Particularly, the influence of operational conditions, such as the applied organic rate (OLR) and the dilution factor (for toxicity attenuation) of the textile wastewater, was evaluated on color and organic matter removal. In addition, the effect of powdered activated carbon (PAC) on SAMBR-1 and the addition of yeast extract (source of the redox mediator riboflavin) were also investigated. The results showed that reducing the textile wastewater dilution factor from 10× (phase 1) to 4× (phase 2) and 0× (no dilution) decreased the COD and color removal efficiencies in both SAMBRs, probably due to an increase in the toxic load. Nevertheless, PAC adsorbed toxic compounds found in the textile wastewater and helped biomass acclimatization, which led to higher COD and color removal efficiencies in SAMBR-1. The presence of yeast extract enhanced color removal efficiencies 3-fold in both SAMBRs when they were fed with undiluted textile wastewater.

AbstractThis paper investigates the simultaneous removal of arsenic [As(V) or As(III)] and manganese [Mn(II)] from natural waters of low and high turbidity by clarification (with polyaluminum chloride and aluminum sulfate as primary coagulants) associated or not with chlorine pre-oxidation. The results showed that the clarification process exhibited low Mn(II) removal, that varied from 6% to 18% and from 19% to 27% for natural waters of low and high turbidity, respectively. The use of chlorine as pre-oxidant increased Mn(II) removal up to 77% and was associated with the formation of birnessite. Regarding As(V) removal by clarification, particularly for high turbidity water, a concentration lower than that established by the National Drinking Water Quality Standards (10 μg.L-1) was achieved in almost all tests. Oxidation preceding the clarification led to AsIII removal efficiencies from 80% to 90% for both coagulants and types of water.

This work presents an analytical modelling of mass transfer in spheroidal solids using a liquid diffusion model. The diffusion equation, written in cylindrical coordinates, is solved using the Galerkin method with a constant diffusion coefficient and an equilibrium boundary condition at the surface of the solid. Results on the drying kinetics, and moisture content distribution in the solids are presented and analysed. The iso-concentration lines for moisture content show that the drying process is faster in sharp areas,. It was verified that solids with a larger area/volume ratio dry faster. The results obtained are consistent so the model presented can be used to solve diffusion problems such as drying, wetting, heating and cooling of solids with a shape that varies from a circular disk to an infinite cylinder, including a sphere and ellipsoids.