Jorge J. Malfeito

Trace organics removal using three membrane bioreactor configurations: MBR, IFAS-MBR and MBMBR

Seventeen pharmaceutically active compounds and 22 other trace organic pollutants were analysed regularly in the influent and permeate from a semi-real plant treating municipal wastewater. The plant was operated during 29 months with different configurations which basically differed in the type of biomass present in the system. These processes were the integrated fixed-film activated sludge membrane bioreactor (IFAS-MBR), which combined suspended and attached biomass, the moving bed membrane bioreactor (MBMBR) (only attached biomass) and the MBR (only suspended biomass). Moreover, removal rates were compared to those of the wastewater treatment plant (WWTP) operating nearby with conventional activated sludge treatment. Reverse osmosis (RO) was used after the pilot plant to improve removal rates. The highest elimination was found for the IFAS-MBR, especially for hormones (100% removal); this was attributed to the presence of biofilm, which may lead to different conditions (aerobic-anoxic-anaerobic) along its profile, which increases the degradation possibilities, and also to a higher sludge age of the biofilm, which allows complete acclimation to the contaminants. Operating conditions played an important role, high mixed liquor suspended solids (MLSS) and sludge retention time (SRT) being necessary to achieve these high removal rates. Although pharmaceuticals and linear alkylbenzene sulfonates showed high removal rates (65-100%), nonylphenols and phthalate could only be removed to 10-30%. RO significantly increased removal rates to 88% mean removal rate.

The IFAS-MBR process: a compact combination of biofilm and MBR tecnnology as RO pretreatment

Abstract An advanced treatment for wastewater reclamation has been studied for nine months in a pilot plant in the south of Spain. This consisted in a combination of integrated fixed-film activated sludge (IFAS) and membrane bioreactor (MBR) technology (called here IFAS-MBR) with posterior reverse osmosis (RO) for the achievement of a high-quality effluent. The pilot plant was obtained from a former MBR plant, where plastic carriers for the support of the biology were introduced in the second aerobic chamber. The system consisted of two parallel lines, one working with a hollow fibre module and the other with a flat sheet module. After the hollow fibre line, an RO system treated the effluent. The permeability of the process decreased gradually along the experimentation period and after six months, the membrane modules of both lines were chemically cleaned. The RO membranes showed a stable permeability working with the IFAS-MBR permeate and chemically cleaned after four months of operation. The studied sys...

Reverse osmosis membranes oxidation by hypochlorite and chlorine dioxide: spectroscopic techniques vs. Fujiwara test

Abstract The aim of this work was the study of degradation of a commercial polyamide membrane by two commonly employed oxidants for disinfection in seawater desalination, hypochlorite, and chlorine dioxide. A conventional reverse osmosis (RO) membrane is a thin film composite membrane composed of three different layers, a polyester support web, a microporous polysulfone interlayer, and a thin cross-linked polyamide barrier layer on the top surface, which is the active layer of the RO membrane. The degree of membrane degradation in seawater was evaluated in terms of decline in membrane performance calculated from permeability and salt rejection. In order to establish a relationship between the hydraulic properties and spectroscopic data, infrared and X-ray photoemission techniques (ATR-FTIR and XPS) were employed. The obtained results were compared with the Fujiwara test which is usually performed in membrane autopsies to check the degradation of polyamides with halogens. The chemical degradation of the su...

Fosetyl-Al photo-Fenton degradation and its endogenous catalyst inhibition

Interferences from many sources can affect photo-Fenton reaction performance. Among them, catalyst inhibition can be caused by the complexation and/or precipitation of iron species by the organic matter and salts present in the reaction media. This is the case of the oxidation of effluents containing organophosphorous fosetyl-Al. The degradation of this fungicide generates phosphate anions that scavenge iron and hinder Fe(II) availability. Experimental design was applied to artificially enlighten photo-Fenton reaction, in order to evaluate fosetyl-Al degradation. The performed experiments suggested how iron inhibition takes place. The monitoring of photo-Fenton reaction over a mixture of fosetyl-Al with other two pesticides also showed the interferences caused by the presence of the fungicide on other species degradation. Solar empowered photo-Fenton was also essayed for comparison purposes. Artificial and solar light photo-Fenton reactions were revealed as effective treatments for the elimination of tested fungicide. However, the phosphate ions generated during fosetyl oxidation decreased iron availability, what hampered organic matter degradation.

High salinity effect on bioremediation of pretreated pesticide lixiviates from greenhouses

Hydroponics culture greenhouses usually work in closed and semi-closed irrigation systems for nutrients and water-saving purposes. Photo-Fenton reaction has been revealed as an efficient way to depollute that kind of recycled effluents containing pesticides, even for high salinity concentrations. However, the inefficacy of organic matter chemical depletion imposes the use of a subsequent treatment. This work proposes the suitability of an integration of advanced oxidation process with a subsequent bioreactor to treat greenhouse lixiviates effluents at high or extremely high conductivity (salts concentration: up to 42 g L−1). As a first step in this study, the performance of a series of sequencing batch reactors was monitored in order to check the biocompatibility of photo-Fenton pretreated effluents depending on their salinity content. In the second step, those same pretreated effluents were loaded to a biofiltration column filled with expanded clay. Finally, bacterial 16S rRNA gene sequencing was carried out to analyse microbial diversity of the biomass developed in the column. Results stated that the chemical–biological coupled system is effective for the treatment of water effluents containing pesticides. The integrated system is able to deplete more than 80% of the organic load, even under extremely high salinity.