A highly permeable composite hollow-fibre membrane developed for air separation was used in a membrane aerated biofilm reactor (MABR). The composite membrane consisted of a porous support layer covered with a thin dense film, which was responsible for oxygen enrichment of the permeate stream. Besides oxygen enrichment capability, dense membranes overcome major operational problems that occur when using porous membranes for oxygen transfer to biofilms. Air flow rate and oxygen partial pressure inside the fibres were the variables used to adjust the oxygen transfer rate. The membrane aerated biofilm reactor was operated with hydraulic retention times (HRT) ranging from 1 to 4 hours. High organic load removal rates, like 6.5 kg.m-3.d-1, were achieved due to oxygen transfer rates as high as 107 kg.m-3.d-1. High COD removals, with improved oxygen transfer efficiency, indicate that a MABR is a compact alternative to the conventional activated sludge process and that the selected membrane is suitable for further applications.

Photocatalysis has been used as tertiary treatment for petroleum refinery wastewaters to comply with the regulatory discharge limits and to oxidize persistent compounds that had not been oxidized in the biological treatment. The wastewater is generated by the refinery and directly discharged into the Guanabara Bay (Rio de Janeiro). Although BOD removal is high, a residual and persistent COD, besides a somewhat high phenol content remains. Three photocatalysts were tested - TiO2 (Aldrich), ZnO (Aldrich), and TiO2 (P25, Degussa) - the third being the most active. The optimized conditions obtained with an experimental design were 3.0 g L-1 TiO2 and pH 6.3. The use of hydrogen peroxide (H2O2) showed no beneficial effect. Removal of 93% of phenols, 63% of dissolved organic carbon (DOC), and more than 50% of oil and grease (OG) were achieved in the photocatalytic process, improving the quality of the treated wastewater.

Bioactivation, a procedure to obtain anaerobic sulphidogenic sludge, was developed in order to increase sulphate reduction and, consequently, sulphide production to remove metals from effluents. This procedure, in which the source of carbon/energy (lactate) is gradually replaced, consisted of three operational conditions. It was observed that bioactivation took six months so there was a 100-fold increase in the population of sulphate-reducing bacteria estimated by the most-probable-number (MPN) when molasses was employed as a new source.