Vânia M. J. Santiago

Phylogenetic and functional diversity of metagenomic libraries of phenol degrading sludge from petroleum refinery wastewater treatment system

In petrochemical refinery wastewater treatment plants (WWTP), different concentrations of pollutant compounds are received daily in the influent stream, including significant amounts of phenolic compounds, creating propitious conditions for the development of particular microorganisms that can rapidly adapt to such environment. In the present work, the microbial sludge from a refinery WWTP was enriched for phenol, cloned into fosmid vectors and pyrosequenced. The fosmid libraries yielded 13,200 clones and a comprehensive bioinformatic analysis of the sequence data set revealed a complex and diverse bacterial community in the phenol degrading sludge. The phylogenetic analyses using MEGAN in combination with RDP classifier showed a massive predominance of Proteobacteria, represented mostly by the genera Diaphorobacter, Pseudomonas, Thauera and Comamonas. The functional classification of phenol degrading sludge sequence data set generated by MG-RAST showed the wide metabolic diversity of the microbial sludge, with a high percentage of genes involved in the aerobic and anaerobic degradation of phenol and derivatives. In addition, genes related to the metabolism of many other organic and xenobiotic compounds, such as toluene, biphenyl, naphthalene and benzoate, were found. Results gathered herein demonstrated that the phenol degrading sludge has complex phylogenetic and functional diversities, showing the potential of such community to degrade several pollutant compounds. This microbiota is likely to represent a rich resource of versatile and unknown enzymes which may be exploited for biotechnological processes such as bioremediation.

Identification of Genes and Pathways Related to Phenol Degradation in Metagenomic Libraries from Petroleum Refinery Wastewater

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.

Long-term evaluation of different strategies of cationic polyelectrolyte dosage to control fouling in a membrane bioreactor treating refinery effluent.

ABSTRACT 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 MBRs overall pollutant removal performance.

Ageing effect on chlorinated polyethylene membrane of an MBR caused by chemical cleaning procedures

AbstractThe membrane lifetime has a strong influence on the competitiveness and sustainability of Membrane bioreactor (MBR) technology. Membrane replacement is highly expensive operational cost of MBR plants, besides generating residues that have been disposed at municipal landfills or incinerated. Chemical cleaning has been deemed to be one of the most significant factors that shortens membrane lifetime. Chemical cleaning is required to keep the operational flux that is likely to be shortened due to irreversible membrane fouling. This work was aimed to evaluate the influence of chemical agents on chlorinated polyethylene polymeric membrane. Two cleaning procedures were evaluated, namely, (1) cleaning with citric acid followed by sodium hypochlorite (NaOCl) and (2) oxalic acid followed by sodium hypochlorite. After each cleaning cycle, it was determined the membrane permeability. The membranes were also characterized by surface analysis using a scanning electron microscope, thermal resistance by thermogra...

The application of filterability as a parameter to evaluate the biological sludge quality in an MBR treating refinery effluent

AbstractMembrane bioreactors (MBR) have been extensively employed at industrial effluent treatment plants; however the membrane fouling has restrained its more extensive application. Filterability is an important parameter to evaluate sludge properties and the potentiality of membrane fouling in MBR, nevertheless the lack of standardization of its assessment method has made it difficult to understand its actual role on MBR performance and compare its results. In this context, this work aims to compare three filterability assessment methods described in the literature (TTF, FT, and SFI) regarding its capability to sense sludge quality variation and reproducibility, and evaluate the application of this parameter as a tool to monitor and control fouling in MBR treating petroleum refinery effluents. This study showed that, among the methods evaluated, time to filter was the most effective to assess the filterability, both in terms of its capability to sense sludge quality variation and reproducibility. The re...

Evaluation of the efficiency of deterioration of aromatic hydrocarbons by bacteria from wastewater treatment plant of oil refinery

Three bacterial strains were isolated from the activated sludge system of petroleum refinery wastewater, identified by partial sequencing of 16S rDNA, and classified as Acinetobacter genomospecies 3, Bacillus pumilus, and Bacillus flexus. The degradation efficiency of aromatic hydrocarbons was evaluated by gas chromatography with a flame ionization detector. In a mineral medium containing anthracene and phenanthrene and the consortium of microorganisms, the removal efficiency was 96% and 99%, respectively, after 30 days. The good rate of hydrocarbon degradation proves the operational efficiency of the microbial consortium in treating effluents containing these compounds.

Electrodialysis Treatment of Refinery Wastewater

Water is fundamental in the oil refining process, with on average 0.9 m3 water being consumed per m3 of oil processed. Water is used in the oil refining process for steam generation, cooling systems, potabilization, fire fighting, the removal of contaminants and services in general. Industries are having difficulties in obtaining water due to the growing scarcity and pollution of water, with increasing treatment costs as a consequence, which limits increases in productivity. It has therefore become necessary that industries implant a water management system, including its rationalization with process modification, choosing the best treatment method for discharge or reuse. For many industries, management systems and water reuse may be an important factor contributing to their survival. The wastewater generated in refineries is sent to a treatment plant, to reach the necessary quality for discharge. The composition of the wastewater varies greatly and depends on the complexity of the refining process. The reuse requires additional treatment processes and the selection of the method will depend on the characteristics of the wastewater and on the required water quality. Wastewater treatment processes using membranes are being increasingly used because of their high efficiency, small installation area, low consumption of chemicals and increased automation. Among the different membrane processes, electrodialysis has been increasingly employed in the industry for partial desalination aiming water reuse. In refineries, the electrodialysis reversal process is not yet widely used, but it has great growth potential. The evaluation of the pilots and industrial units in operation have shown the advantages over similar desalination processes, such as greater robustness, operational reliability and simplicity and less necessity of wastewater pre-treatment. This chapter will present an overview of the use of electrodialysis for water reuse in refineries.