RESUMO
This study aims to evaluate membrane bioreactor (MBR) performance in a pilot scale to treat petroleum refinery effluent, and has been primarily focused on (1) investigation of dynamics of organic matter removal; (2) characterization of membrane fouling under real hazardous events; (3) evaluation of the effect of fouling on membrane lifetime; and (4) estimate the membrane lifetime. The results have shown that the MBR was able to effectively reduce COD, NH3-N, turbidity, color, phenol and toxicity, and bring them to the levels required to meet disposal and non-potable water reuse standards. The FTIR results showed that organic matter was removed by biological oxidation and/or retained by adsorption in the biological sludge, or retention in the UF membrane, and that SMP was produced during the treatment. In terms of membrane permeability, the results showed that soluble fraction of mixed liquor contributed significantly to membrane fouling. And finally, considering the concept of lifetime based on permeability decline, a membrane lifetime of 7 years is expected.
Assuntos
Reatores Biológicos , Resíduos Industriais , Membranas Artificiais , Compostos Orgânicos/isolamento & purificação , Petróleo/análise , Poluentes Químicos da Água/isolamento & purificação , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
In this article, the long-term use of cationic polyelectrolyte to improve the sludge filterability and to control membrane fouling in bioreactor membrane while treating refinery effluents have been evaluated in pilot scale. Corrective and preventive cationic polyelectrolyte dosages have been added to the membrane bioreactor (MBR) to evaluate the membrane fouling mitigation in both strategies. The results have confirmed that the use of the Membrane performance enhancer (MPE) increased the sludge filterability and reduced the membrane fouling. During the monitoring period, stress events occurred due to the increase in oil and grease and phenol concentrations in the MBR feeds. The preventive use of cationic polyelectrolyte allowed for a more effective and stable sludge filterability, with lower cationic polyelectrolyte consumption and without decreasing MBR's overall pollutant removal performance.
Assuntos
Reatores Biológicos , Membranas Artificiais , Poliaminas , Eliminação de Resíduos Líquidos/instrumentação , Biopolímeros/análise , Carbono/análise , Filtração/instrumentação , Floculação , Resíduos Industriais , Indústria de Petróleo e Gás , Polieletrólitos , Esgotos , Eliminação de Resíduos Líquidos/métodos , Poluentes da Água/análiseRESUMO
Two fosmid libraries, totaling 13,200 clones, were obtained from bioreactor sludge of petroleum refinery wastewater treatment system. The library screening based on PCR and biological activity assays revealed more than 400 positive clones for phenol degradation. From these, 100 clones were randomly selected for pyrosequencing in order to evaluate the genetic potential of the microorganisms present in wastewater treatment plant for biodegradation, focusing mainly on novel genes and pathways of phenol and aromatic compound degradation. The sequence analysis of selected clones yielded 129,635 reads at an estimated 17-fold coverage. The phylogenetic analysis showed Burkholderiales and Rhodocyclales as the most abundant orders among the selected fosmid clones. The MG-RAST analysis revealed a broad metabolic profile with important functions for wastewater treatment, including metabolism of aromatic compounds, nitrogen, sulphur and phosphorus. The predicted 2,276 proteins included phenol hydroxylases and cathecol 2,3- dioxygenases, involved in the catabolism of aromatic compounds, such as phenol, byphenol, benzoate and phenylpropanoid. The sequencing of one fosmid insert of 33 kb unraveled the gene that permitted the host, Escherichia coli EPI300, to grow in the presence of aromatic compounds. Additionally, the comparison of the whole fosmid sequence against bacterial genomes deposited in GenBank showed that about 90% of sequence showed no identity to known sequences of Proteobacteria deposited in the NCBI database. This study surveyed the functional potential of fosmid clones for aromatic compound degradation and contributed to our knowledge of the biodegradative capacity and pathways of microbial assemblages present in refinery wastewater treatment system.
Assuntos
Biodegradação Ambiental , Biblioteca Gênica , Metagenômica , Petróleo , Fenol/metabolismo , Esgotos/microbiologia , Reatores Biológicos/microbiologia , Catecol 2,3-Dioxigenase/genética , Catecol 2,3-Dioxigenase/metabolismo , Clonagem Molecular , Mapeamento de Sequências Contíguas , DNA Bacteriano/genética , Genoma Bacteriano , Oxigenases de Função Mista/genética , Oxigenases de Função Mista/metabolismo , Anotação de Sequência Molecular , Dados de Sequência Molecular , Fases de Leitura Aberta , Filogenia , Águas Residuárias/microbiologiaRESUMO
Bacterial diversity of two distinct wastewater treatment systems, conventional activated sludge (CAS) and membrane bioreactor (MBR), of petroleum refineries were investigated through 16S rRNA gene libraries. Sequencing and phylogenetic analysis showed that the bacterial community composition of sludge samples was distinct between the two wastewater treatment systems. MBR clones belonged predominantly to Class Betaproteobacteria, represented mainly by genera Thiobacillus and Thauera, whereas CAS clones were mostly related to Class Alphaproteobacteria, represented by uncultured bacteria related to Order Parvularculales. Richness estimators ACE and Chao revealed that the diversity observed in both libraries at the species level is an underestimate of the total bacterial diversity present in the environment and further sampling would yield an increased observed diversity. Shannon and Simpson diversity indices were different between the libraries and revealed greater bacterial diversity for the MBR library, considering an evolutionary distance of 0.03. LIBSHUFF analyses revealed that MBR and CAS communities were significantly different at the 95% confidence level (P< or =0.05) for distances 0< or =D< or =0.20. This work described, qualitatively and quantitatively, the structure of bacterial communities in industrial-scale MBR and CAS processes of the wastewater treatment system from petroleum refineries and demonstrated clearly differentiated communities responsible for the stable performance of wastewater treatment plants.
Assuntos
Reatores Biológicos/microbiologia , Proteobactérias/genética , Esgotos/microbiologia , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/metabolismo , Sequência de Bases , Biodegradação Ambiental , DNA Bacteriano/química , DNA Bacteriano/genética , Indústrias Extrativas e de Processamento , Variação Genética , Resíduos Industriais , Dados de Sequência Molecular , Petróleo , Filogenia , Reação em Cadeia da Polimerase , Proteobactérias/isolamento & purificação , Proteobactérias/metabolismo , RNA Ribossômico 16S/química , RNA Ribossômico 16S/genética , Alinhamento de SequênciaRESUMO
The phenolic compounds are a major contaminant class often found in industrial wastewaters and the biological treatment is an alternative tool commonly employed for their removal. In this sense, monitoring microbial community dynamics is crucial for a successful wastewater treatment. This work aimed to monitor the structure and activity of the bacterial community during the operation of a laboratory-scale continuous submerged membrane bioreactor (SMBR), using PCR and RT-PCR followed by Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rRNA libraries. Multivariate analyses carried out using DGGE profiles showed significant changes in the total and metabolically active dominant community members during the 4-week treatment period, explained mainly by phenol and ammonium input. Gene libraries were assembled using 16S rDNA and 16S rRNA PCR products from the fourth week of treatment. Sequencing and phylogenetic analyses of clones from 16S rDNA library revealed a high diversity of taxa for the total bacterial community, with predominance of Thauera genus (ca. 50%). On the other hand, a lower diversity was found for metabolically active bacteria, which were mostly represented by members of Betaproteobacteria (Thauera and Comamonas), suggesting that these groups have a relevant role in the phenol degradation during the final phase of the SMBR operation.