RESUMO
Recent papers have confirmed current environmental pollution and the continuous release of polychlorinated biphenyls (PCBs) despite the prohibition of its manufacture worldwide. As the dehalogenating microorganisms are able to remove halogens from various analogous compounds, the characterization of PCB metabolisms can improve the degradation of similar compounds. Thus, this study extensively evaluated the microbial community developed in methanogenic and iron-reducing reactors. The horizontal-flow anaerobic reactor (HAIB) with real waste of Aroclor (1 mL L-1) was fed with mineral medium, ethanol, and sodium formate. Bacteria belonging to Thermotogaceae (Thermotogae), Geobacteraceae, Chloroflexi, Proteobacteria, and Firmicutes (Clostridium) were identified in the HAIB reactor. Bacteria belonging to the Chloroflexi, Firmicutes, and Geobacteraceae are associated with the degradation of hydrocarbons and could be related to the Aroclor waste in this paper. Furthermore, 5.26 × 1012 cells gTVS-1 of iron-reducing bacteria were quantified by the most probable number method in the HAIB reactor, suggesting that this group has an important role in aromatic degradation. Moreover, the evaluation of methanogenic and iron-reducing microorganisms in batch reactors with Aroclor 1260 was performed and the biomass growth was not affected by the addition of PCB. The methane production reached 0.38 µmol CH4 gTVS-1 and the iron reduction attained 90% in batch reactors. Through microbial analyses from HAIB and batch reactors, lower diversity was evidenced in the presence of PCB. This paper indicates the relevant role of iron-reducing organisms and Chloroflexi, Geobacteraceae, and Firmicutes group in PCB metabolism.
Assuntos
Reatores Biológicos/microbiologia , Ferro/metabolismo , Metanol/metabolismo , Bifenilos Policlorados/metabolismo , Chloroflexi/metabolismo , Firmicutes/metabolismo , Proteobactérias/metabolismoRESUMO
Linear alkylbenzene sulfonate (LAS) is an anionic surfactant used in cleaning products, which is usually found in wastewaters. Despite the greater LAS removal rate related to a lower concentrations of volatile fatty acids (VFA), the influence of different ranges of VFA on LAS degradation is not known. LAS degradation was evaluated in upflow anaerobic sludge blanket (UASB) and expanded granular sludge bed (EGSB) reactors at different ranges of VFA concentrations. The reactors were fed with a synthetic wastewater containing LAS (14 mg/L). A greater LAS removal rate (40-80%) was related to the lower and narrower range of acetic acid concentration (1-22 mg/L) in the EGSB reactor. In the UASB reactor, the acetic acid concentrations presented a wider range (2-45 mg/L), and some low LAS removal rates (around 20-25%) were observed even at low acetic acid concentrations (<10 mg/L). The high recirculation rate in the EGSB reactor improved substrate-biomass contact, which resulted in a narrower range of VFA and greater LAS removal rate.
Assuntos
Ácidos Alcanossulfônicos/metabolismo , Ácidos Graxos Voláteis/química , Eliminação de Resíduos Líquidos/métodos , Ácido Acético/química , Ácidos Alcanossulfônicos/química , Anaerobiose , Análise da Demanda Biológica de Oxigênio , Biomassa , Reatores Biológicos , Detergentes/química , Detergentes/metabolismo , Esgotos , Fatores de Tempo , Eliminação de Resíduos Líquidos/instrumentação , Águas Residuárias/químicaRESUMO
The effect of a lipase-rich enzyme preparation produced by the fungus Penicillium sp. on solid-state fermentation was evaluated in two anaerobic bioreactors (up-flow anaerobic sludge blanket (UASB) and horizontal-flow anaerobic immobilized biomass (HAIB)) treating dairy wastewater with 1200 mg oil and grease/L. The oil and grease hydrolysis step was carried out with 0.1% (w/v) of the solid enzymatic preparation at 30 degrees C for 24 h. This resulted in a final concentration of free acids eight times higher than the initial value. The bioreactors operated at 30 degrees C with hydraulic retention times of 12 h (HAIB) and 20 h (UASB) for a period of 430 days, and had high chemical oxygen demand (COD) removal efficiencies (around 90%) when fed with pre-hydrolyzed wastewater. There was, however, an increase in the effluent oil and grease concentration (from values as low as 17 mg/L to values above 150 mg/L in the UASB bioreactor, and from 38-242 mg/L in the HAIB bioreactor), and oil and grease accumulation in the biomass throughout the operational period (the oil and grease content reached 1.7 times that found in the inoculum of the UASB bioreactor). The HAIB bioreactor gave better results because the support for biomass immobilization acted as a filter, retaining oil and grease at the entry of the bioreactor. The molecular analysis of the Bacteria and Archaea domains revealed significant differences in the microbial profiles in experiments conducted with and without the pre-hydrolysis step. The differences observed in the overall parameters could be related to the microbial diversity of the anaerobic sludge.
Assuntos
Reatores Biológicos/microbiologia , Indústria de Laticínios , Lipase/metabolismo , Consórcios Microbianos , Águas Residuárias/microbiologia , Anaerobiose , Bactérias/genética , Análise da Demanda Biológica de Oxigênio , Biomassa , Ácidos Graxos Voláteis/análise , Concentração de Íons de Hidrogênio , Hidrólise , Methanobacterium/genética , Methanobacterium/isolamento & purificação , Methanosarcinales/genética , Methanosarcinales/isolamento & purificação , Óleos/metabolismo , Penicillium/enzimologia , FilogeniaRESUMO
Degradation of linear alkylbenzene sulfonate (LAS) in UASB reactors was optimized by varying the bioavailability of LAS based on the concentration of biomass in the system (1.3-16 g TS/L), the hydraulic retention time (HRT), which was operated at 6, 35 or 80 h, and the concentration of co-substrates as specific organic loading rates (SOLR) ranging from 0.03-0.18 g COD/g TVS.d. The highest degradation rate of LAS (76%) was related to the lowest SOLR (0.03 g COD/g TVS.d). Variation of the HRT between 6 and 80 h resulted in degradation rates of LAS ranging from 18% to 55%. Variation in the bioavailability of LAS resulted in discrete changes in the degradation rates (ranging from 37-53%). According to the DGGE profiles, the archaeal communities exhibited greater changes than the bacterial communities, especially in biomass samples that were obtained from the phase separator. The parameters that exhibited more influence on LAS degradation were the SOLR followed by the HRT.