RESUMO
The measurement of sludge bioavailability and biodegradability is important to assess the sludge potential as a source of carbon and energy during its biological stabilization. As the majority of biological sludge (secondary sludge) consists of biomass, an increase in sludge bioavailability can be achieved by using different techniques for cell lysis, which is aimed at releasing intracellular organics into the bulk solution and enhancing hydrolysis of particulate organic matter. This paper reviews the main methodologies currently used for cell lysis, which include thermal, ultrasonic and chemical techniques and a combination of these, as well as the analytical procedures that can be employed to assess the degree of lysis and sludge solubilization. In addition, this paper also discusses common techniques that can be used for measuring the biodegradability of sludge under aerobic and anaerobic conditions.
Assuntos
Biodegradação Ambiental , Esgotos , Eliminação de Resíduos Líquidos/métodos , SolubilidadeRESUMO
This paper discusses the results of pentachlorophenol (PCP) anaerobic biodegradation in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor operated under methanogenic and halophylic conditions. The system was inoculated with autochthonous microorganisms taken from a site in the Santos-São Vicente Estuary (state of São Paulo, Brazil) severely contaminated with PCP, phenolic compounds, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and heavy metals. The inoculum was previously enriched for methanogenesis activity by changing glucose concentrations and under halophylic condition. PCP was added to the HAIB reactor as sodium salt (NaPCP) at an initial concentration of 5 mg l(-1) and increased to 13, 15, and 21 mg l(-1). Organic matter removal efficiency ranged from 77 to 100%. PCP removal efficiency was 100%. Denaturing gradient gel electrophoresis profile showed changes in the structure of Bacteria domain, which was associated with NaPCP and glucose amendments. The diversity of Archaea remained unaltered during the different phases. Scanning electron microscope examinations showed that cells morphologically resembling Methanosarcina and Methanosaeta predominated in the biofilm. These cells were detected by fluorescence in situ hybridization with the Methanosarcinales (MSMX860) specific probe. The results are of great importance in planning the estuary's restoration by using anaerobic technology and autochthonous microorganisms for bioremediation.
Assuntos
Reatores Biológicos/microbiologia , Sedimentos Geológicos/microbiologia , Pentaclorofenol/metabolismo , Microbiologia da Água , Anaerobiose , Bactérias/genética , Bactérias/metabolismo , Bactérias/ultraestrutura , Biodegradação Ambiental , Biofilmes/crescimento & desenvolvimento , Biomassa , Brasil , Eletroforese/métodos , Hibridização in Situ Fluorescente , Methanosarcina/genética , Methanosarcina/metabolismo , Methanosarcina/ultraestrutura , Microscopia Eletrônica de Varredura , Pentaclorofenol/química , RNA Ribossômico 16S/genéticaRESUMO
We used in situ hybridization with fluorescently labeled rRNA-targeted oligonucleotide probes concurrently with microscopic examinations and methane measurements to characterize the microbial community of an anaerobic hybrid reactor treating pentachlorophenol (PCP) with a mixture of fatty acids (propionic, butyric, acetic and lactic) and methanol. Archaeal cells detected with probe ARC915 prevailed in anaerobic granular sludge without and with the addition of PCP in a range of 2.0 to 21.0 mg/L to the reactor. This group accounted for 81 and 90% of the DAPI-stained cells before and after the addition of 21 mg/L of PCP, respectively. In these conditions, cells detected with the Methanosarcinales specific probe (MSMX860) were the only methanogenic Archaea found and accounted for 59 to 87.6% of the DAPI-stained cells. No cells were detected by the Methanomicrobiales (MG1200), Methanobacteriaceae (MB1174) and Methanococcaceae (MC1109) specific probes. Bacterial cells detected with probe EUB338 were found in very low numbers, which ranged from 5.7 to 1.0% of the DAPI-stained cells. This finding agrees with the scanning electron microscope examinations, in which cells morphologically resembling Methanosaeta and Methanosarcina were predominantly observed in the granular sludge. Results contributed to the investigation of the importance of the methanogens during PCP degradation.
Assuntos
Reatores Biológicos , Poluentes Ambientais/metabolismo , Methanobacteriaceae/fisiologia , Pentaclorofenol/metabolismo , Biomassa , DNA Bacteriano/análise , Hibridização in Situ Fluorescente , Methanobacteriaceae/genética , Sondas de Oligonucleotídeos , Dinâmica Populacional , RNA RibossômicoRESUMO
In this study we investigated the development of anaerobic biofilms in differential reactors and suspension cultures in batch reactors under thermophilic (55 degrees C) conditions. FISH, SEM, chemical and chromatographic analysis were used. The differential reactors reached 99.6%, 92.3% and 6.7% of acetic acid, COD and sulfate removal efficiencies, respectively, after 166 h of incubation time. The batch reactor reached 95.6% and 31.8% of acetic acid and sulfate removal efficiencies after 675 h, respectively. FISH results showed that bacterial cells rather than archaeal cells dominated biofilms. These cells, detected with the Bacteria specific probe (EUB338), accounted for 61.1% (+/-3.6) of the DAPI-stained cells and resembled acetate-oxidizing rods and Desulfotomaculum morphologies. Archaeal cells, which hybridized to the Archaea specific probe (ARC915), were also detected in biofilm but they accounted for 36.7% (+/-2.9) of the DAPI-stained cells. These cells were similar to Methanosaeta-like and hydrogenotrophic methanogen rods. In the suspension culture, archaeal cells (58.0%+/-3.8) morphologically similar to Methanosarcina and hydrogenotrophic methanogen rods were predominant over bacterial cells (41.0%+/-4.5), which resembled acetate-oxidizing rods and Desulfotomaculum morphologies. The percentage of sulfate-reducing bacteria cells (SRB) ranged from 12.2% (+/-2.5) to 21.7% (+/-2.8) in the biofilms and from 13.3% (+/-3.6) to 21.7% (+/-4.3) of the DAPI stained cells in suspension culture.
Assuntos
Archaea , Bactérias Anaeróbias , Reatores Biológicos , Euryarchaeota , Biofilmes , Hibridização in Situ Fluorescente , Microscopia Eletrônica de Varredura , Dinâmica Populacional , TemperaturaRESUMO
The present research aimed at evaluating pentachlorophenol (PCP) degradation in a hybrid reactor supplied with a mixture of fatty acids (propionic, butyric, acetic and lactic) and methanol. The performance of the reactor is remarkably stable and efficient during PCP additions at range of 2.0 to 21.0 mg/L. The reduction of chemical oxygen demand (COD) was around 97% and methane was found to be 88% in the biogas production. The efficiency of volatile fatty acids breakdown was 93%, 64% and 74% respectively for butyric, propionic and acetic. PCP total removal of more than 99% was reached by granular sludge activities formed during 21 months of reactor operation. Methanogenic microorganisms predominance was noticed with 10(5) to 10(6) cells/mL during enumeration on methanol or lactate added to sulfate culture media. The removal rate was 1.07 mg PCP.g-1 VS.d-1 during the highest PCP concentration addition.