The inhibition effect of limonene on the organisms involved in anaerobic reactors may affect obtaining H2 in this process. Rapid and precise limonene quantification is desirable to characterize wastewaters. The objective of this research was to develop a Gas Chromatography Coupled to Mass Spectrometry (GC-MS) method to determine limonene concentration in liquid samples from batch reactors applied to H2 production at 30 ºC. Method validation was carried out through calibration curves (3 to 20 mg L-1of limonene), in addition to evaluating its precision (CV =0.1%), linearity (R2=0.979), limits of detection (1.7 mg L-1) and quantification (4.2 mg L-1). Its inhibitory effect was evaluated with increasing concentrations of limonene (without addition to 2000 mg L-1). Limonene affected the starting time of H2 production (λ), since λ was 8.7 h in control assays and 15 h with 2000 mg L-1 of limonene. The same was observed for obtaining H2, since 19.5 mmol H2 L-1 was obtained in control assays and 8.7 mmol H2 L-1 was obtained in assays with 2000 mg L-1 of limonene. This method was effective for limonene determination in liquid samples from batch reactors and could be used for characterization and control of anaerobic reactors.

This study evaluated the potential of a microbial consortium collected from a pulp and paper mill wastewater treatment plant (WWTP) for converting cellulose to hydrogen, biogas and organic acids. Fermentation tests were conducted in batch reactors fed with different concentrations of cellulose as substrate: (C1) 2.0 g L -1; (C2) 5.0 g L -1 and (C3) 10.0 g L -1. The parameters investigated were hydrogen, biogas, organic acids, carbohydrates and pH. The maximum hydrogen production was 14.77, 39.25 and 22.53 mmol L -1, and the maximum methane was 4.40, 3.72 and 9.56 mmol L -1, for C1, C2 and C3, respectively. Butyric acid was the main metabolite generated, with maximum concentrations of 2.2, 1.8 and 2.2 g L -1 for C1, C2 and C3, respectively. The decrease in hydrogen production was accompanied by the production of methane, acetic acid and hydrogen sulfide in the three tests, probably related to hydrogenotrophic methanogenesis, homoacetogenesis and sulfidogenesis, respectively. The phylogenetic characterization of the bacterial community was performed by cloning and sequencing analysis. The microorganisms identified in the consortium were similar (> 95%) to Clostridium sp., Klebsiella sp., Routella sp. and Desulfovibrio sp. These genera were associated with hydrogen production, degradation of cellulosic substrates, and/or hydrogen-consuming microorganisms.

ABSTRACT This study evaluates the influence of initial nitrogen concentration, temperature and stirring speed on specific anammox activity (SAA). The biomass was tested in single batch reactors with different initial nitrogen concentrations (Assay 1) ranging from 60 to 140 mg Ntotal/L in equimolar ratio (NO2--N/NH4+-N) and in another test to 67.3 mg NH4+-N/L and 92.2 mg NO2--N/L (close to anammox stoichiometric ratio). The anammox biomass was also tested in single batch at different temperatures (from 20 to 37° C) to determine the short-term effects on SAA (Assay 2). In the third assay the stirring speed ranged from 50 to 150 rpm in a sequencing batch reactor (SBR) at 37 ºC. SAA was affected by the stoichiometric molar ratio but not by equimolar initial concentrations. The maximum specific anammox activities were 26.2 mg NH4+-N/g VSS.h in the single batch reactor at 37 ºC with NO2--N/NH4+-N stoichiometric ratio and 33.5 mg NH4+-N/g VSS.h in the SBR at 37 ºC and 50 rpm. The NO2--N/NH4+-N molar ratio affected specific anammox activity, and SAA showed to be more hindered by low increases of stirring speed than reported in the literature.

The objective of this study was to evaluate the degradation of Linear Alkylbenzene Sulfonate (LAS) in anaerobic sequencing batch reactor (ASBR) under denitrifying conditions using swine sludge as inoculum. The reactor was operated for 104 days with synthetic substrate containing nitrate, and LAS was added later (22 mg/L). Considering the added mass of the LAS, the adsorbed mass in the sludge and discarded along with the effluent, degradation of the surfactant at the end of operation was 87%, removal of chemical oxygen demand was 86% and nitrate was 98%. The bacterial community was evaluated by cutting the bands and sequencing of polymerase chain reaction (PCR) fragments and denaturing gradient gel electrophoresis (DGGE). The sequences obtained were related to the phylum Proteobacteria and the alpha-and beta-proteobacteria classes, these bacteria were probably involved in the degradation of LAS. The efficiently degraded LAS in the reactor was operated in batch sequences in denitrifying conditions.

The aim of this work was to identify groups of microorganisms that are capable of degrading organic matter utilizing sulfate as an electron acceptor. The assay applied for this purpose consisted of running batch reactors and monitoring lactate consumption, sulfate reduction and sulfide production. A portion of the lactate added to the batch reactors was consumed, and the remainder was converted into acetic, propionic and butyric acid after 111 hours of operation These results indicate the presence of sulfate-reducing bacteria (SRB) catalyzing both complete and incomplete oxidation of organic substrates. The sulfate removal efficiency was 49.5% after 1335 hours of operation under an initial sulfate concentration of 1123 mg/L. The SRB concentrations determined by the most probable number (MPN) method were 9.0x10(7) cells/mL at the beginning of the assay and 8.0x10(5) cells/mL after 738 hours of operation.

In this work, the biological denitrification associated with anoxic oxidation of methane and the microbial diversity involved were studied. Kinetic tests for nitrate (NO3-) and nitrite (NO2-) removal and methane uptake were carried out in 100 mL batch reactors incubated in a shaker (40 rpm) at 30 ºC. Denitrificant/methanotrophic biomass was taken from a laboratory scale reactor fed with synthetic nitrified substrates (40 mgN L-1 of NO3- and subsequently NO2-) and methane as carbon source. Results obtained from nitrate removal followed a first order reaction, presenting a kinetic apparent constant (kNO3)) of 0.0577±0.0057d-1. Two notable points of the denitrification rate (0.12gNO3--N g-1 AVS d-1 and 0.07gNO3--N g-1 AVS d-1) were observed in the beginning and on the seventh day of operation. When nitrite was added as an electron acceptor, denitrification rates were improved, presenting an apparent kinetic constant (kNO2) of 0.0722±0.0044d-1, a maximum denitrification rate of 0.6gNO2--N g-1AVS d-1, and minimum denitrification rate of 0.1gNO2--N g-1AVS d-1 at the beginning and end of the test, respectively. Endogenous material supporting denitrification and methane concentration dissolved in the substrate was discarded from the control experiments in the absence of methane and seed, respectively. Methylomonas sp. was identified in the reactors fed with nitrate and nitrite as well as uncultured bacterium.

Reator anaeróbio horizontal de leito fixo (RAHLF), preenchido com espumas de poliuretano, foi usado para tratar benzeno em solução etanólica, sob condições sulfetogênicas. Benzeno foi adicionado em concentração inicial de 2,0 mg.l-1, seguido de aumentos que variaram até 10 mg.l-1. O etanol foi adicionado em concentrações de 170 mg.l-1 a 980 mg.l-1. Soluções de sulfato ferroso e sulfato de sódio foram usadas, nas concentrações de 91 e 550 mg.l-1, respectivamente. O reator foi operado a 30 (± 2) ºC com tempo de detenção hidráulica de 12 h. A remoção da matéria orgânica foi próxima a 90% com taxa máxima de degradação de benzeno de 0,07 mg benzeno.mg-1SSV.d-1. O presente trabalho corrobora os dados obtidos por Cattony et al (2005), na medida em que torna mais consistente a proposta do uso de unidades compactas de RAHLF, para a biorremediação in situ de compostos aromáticos.

In this study it is reported the operation of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor under sulfate-reducing condition which was also exposed to different amounts of ethanol and benzene. The HAIB reactor comprised of an immobilized biomass on polyurethane foam and ferrous and sodium sulfate solutions were used (91 and 550 mg.l-1, respectively), to promote a sulfate-reducing environment. Benzene was added at an initial concentration of 2.0 mg.l-1 followed by an increased to 9 e 10 mg.l-1, respectively. Ethanol was added at an initial concentration of 170 mg.l-1 followed by an increased range of 960 mg.l-1. The reactor was operated at 30 (± 2) ºC with hydraulic detention time of 12 h. Organic matter removal efficiency of 90% with a maximum benzene degradation rate of 0.07 mg benzene.mg-1VSS.d-1. Thus, this work corroborate the data obtained for Cattony et al (2005) and also demonstrate that compact units of HAIB reactors, under sulfate reducing conditions, are a potential alternative for in situ aromatic compounds bioremediation.

Avaliou-se o desempenho de dois reatores anaeróbios operados em bateladas seqüenciais (1,2 m³) diferenciados pelo tipo de imobilização de biomassa, na forma de suporte inerte e de biomassa granular no tratamento de esgoto sanitário do Campus da USP de São Carlos. O monitoramento ao longo de 70 dias de operação revelou similaridade no comportamento das configurações ensaiadas, que apresentaram eficiências médias de remoção de DQO e sólidos suspensos ao redor de 60% e 75%, respectivamente. Por meio de técnicas de biologia molecular constatou-se diferenças na comunidade bacteriana nos reatores no 35º e 70º dias de operação, indicando que a imobilização de biomassa selecionou populações bacterianas diferentemente. Em relação ao domínio Archaea houve maior similaridade, provavelmente, pelo fato desses microrganismos utilizarem substratos específicos ao final do processo anaeróbio.

The performances of two anaerobic sequencing batch reactors (1.2 m³) containing biomass immobilized in inert support and as granular sludge in the treatment of domestic sewage from the Campus of São Carlos-University of São Paulo were evaluated. The experimental phase lasted seventy days. During this period, the reactors presented quite similar performances in respect to COD and total suspended solids removal, achieving average efficiencies of approximately 60% and 75%, respectively. The analysis using molecular biology techniques on biomass samples taken at 35th and 70th showed differences in the bacterial community in the reactors indicating that the type of biomass immobilization selected the populations differently. A higher similarity was found for the Archaea domain probably because these microorganisms utilize specific substrates formed at the end of the anaerobic process.