A. L. Rodrigues

Biofilms formed on humic substances: Response to flow conditions and carbon concentrations

Stream biofilms are exposed to dynamic conditions of flow velocity and organic carbon availability. Thus, the aim of this study was to investigate the response of biofilms formed with and without humic substances (HSs) to an increase in flow velocity (0.04-0.10 ms(-1)) and HSs concentration (9.7+/-1.0 to 19.8+/-0.4 mgL(-1) C). The highest amount of biofilm, measured as volatile suspended solids and total countable cells, was observed at 0.10 m s(-1) without HSs. The bacterial community composition of the biofilm with HSs was characterized by sequences with high similarities (> or =97%) to the genus Dokdonella and to the genera Comamonas, Cupriavidus and, Ralstonia. Sequences retrieved from the biofilm without HSs presented high similarities (> or =97%) to the genus Sphingomonas and the genus Nitrosospira. Experimental results suggested that the presence of HSs under different concentrations and flow velocities did not significantly enhance the cell density of biofilms but influenced its microbial composition.

A flat microbial fuel cell for decentralized wastewater valorization: process performance and optimization potential

A very compact flat microbial fuel cell (MFC), with 64 cm2 each for the anode surface and the cathode surface and 1 cm3 each for the anode and cathode chambers, was tested for wastewater treatment with simultaneous electricity production with the ultimate goal of implementing an autonomous service in decentralized wastewater treatment systems. The MFC was operated with municipal wastewater in sequencing batch reactor mode with re-circulation. Current densities up to 407 W/m3 and a carbon removal of 83% were obtained. Interruption in the operation slightly decreased power density, while the re-circulation ratio did not influence power generation. The anode biofilm presented high conductivity, activity and diversity. The denaturing gradient gel electrophoresis band-pattern of the DNA showed the presence of several ribotypes with different species of Shewanellaceae and Geobacteraceae families.

Influence of carrier concentration on the control of Galactomyces geotrichum bulking and bacterial community of biofilm reactors

Abstract The present work aims to evaluate a strategy to solve Galactomyces geotrichum bulking based on the incorporation of a biofilm carrier in activated sludge systems. For this study, four sequencing batch reactors (SBR) were operated without (SBR1) and with a carrier for biofilm growth (5% [SBR2], 10% [SBR3], and 20% [SBR4] of the reactor volume). As expected, G. geotrichum bulking was observed in the SBR operating just with suspended biomass, as ascertained by direct microscopic inspection. The incorporation of an optimized amount of biofilm carrier (10 and 20%) suppressed the overgrowth of the filamentous fungus probably due to the combined effect of a decreased biomass loading rate and an increased shear stress. Polymerase chain reaction—denaturing gradient gel electrophoresis (PCR–DGGE) analysis of the bacterial community suggested that the incorporation of a biofilm carrier induced increasing differences in the bacterial community structure as the concentration of carrier increased in the SBR. H...

Influence of the organic loading rate on the growth of Galactomyces geotrichum in activated sludge

Recent studies reporting on the useful implementation of fungi in wastewater treatment plants triggered the need to improve fungi based systems. Therefore, it is crucial to investigate the conditions that promote their selection. The present work aims to study the effect of the organic loading rate on the growth of filamentous fungi. Three sequencing batch reactors (SBR), fed with an easily biodegradable substrate (acetate), were operated at different organic loading rates: 4.3 g COD L−1 day−1 (SBR1), 1.0 g COD L−1 day−1 (SBR2) and 0.5 g COD L−1 day−1 (SBR3). High amounts of fungal filaments were observed in the SBR operating at higher organic loading rate, as ascertained by direct microscopic inspection, while, at lower organic loading rates, overabundance of fungal filaments was not observed. Sequence retrieved from the isolated fungal filaments presented high similarity (99 %) to Galactomyces geotrichum.

Use of biopolymers as solid substrates for denitrification

The conventional process to remove nitrate from water, the biological denitrification, uses the addition of dissolved organic carbon that has the potential risk to further deteriorate water quality. Thus, this work aimed to evaluate the specific denitrification activity of a mixed microbial culture and a pure culture of Pseudomonas stutzeri with solid substrates such as polycaprolactone (PCL), polylactic acid (PLA), and starch. The highest nitrate reduction activity was obtained with a microbial mixed culture using starch, 104 mg N(2)-N/(g VSS.d), and PCL, 97 mg N(2)-N/(g VSS.d), followed by PLA, 53 mg N(2)-N/(g VSS.d). A considerable advantage of using biopolymers in water denitrification is the reduced risk of contaminating the water with soluble biodegradable organic carbon.

Phosphorus removal by a fixed-bed hybrid polymer nanocomposite biofilm reactor

Eutrophication is one of the main challenges regarding the ecological quality of surface waters, phosphorus bioavailability being its main driver. In this context, a novel hybrid polymer nanocomposite (HPN-Pr) biofilm reactor aimed at integrated chemical phosphorus adsorption and biological removal was conceived. The assays pointed to removal of 1.2 mg P/g of reactive phosphorus and 1.01 mg P/g of total phosphorus under steady-state conditions. A mathematical adsorption–biological model was applied to predict reactor performance, which indicated that biological activity has a positive effect on reactor performance, increasing the amount of reactive phosphorus removed.