Bacteria help to treat water used by oil refineries

Microorganisms identified by researchers are able to eliminate toxic contaminants found in industrial wastewater; findings from the study were presented at the Brazil-U.K. Frontiers of Engineering meeting.

By Elton Alisson, in Jarinu

Agência FAPESP – Oil refineries use large amounts of water in an industrial process called catalytic cracking, which is designed to increase the yield of products such as gasoline and liquid petroleum gas (LPG) by converting heavy fractions from oil distillation to lighter fractions for commercial use.

Given their high concentration of toxic contaminants such as phenols, sulfide and hydrocyanic gases, in addition to ammonia, mercaptans and hydrocarbons, this industrial wastewater – called “acid water” – cannot be sent directly for treatment, but instead must be stored by the refineries to remove ammonia and sulfides before disposal.

“Concentrations of toxic contaminants in this industrial wastewater can range from 100 to 1,000 parts per million (ppm). If this effluent was sent directly to a treatment pond, it could cause major environmental problems,” said Elen Aquino Perpetuo, a professor at the Institute of the Sea at the Federal University of São Paulo (Unifesp), in comments to Agência FAPESP.

In collaboration with colleagues from the Center for Environmental Research and Training (CEPEMA) – a cooperative center for environmental engineering funded by FAPESP – the researcher found a more practical solution for treating this industrial wastewater.

The scientists identified two types of bacteria – Achromobacter sp. and Pandoraea sp. – capable of reducing the concentration of contamination by “acid water” to acceptable levels, allowing its release into the environment or its reuse in industrial processes at refineries.

Several of the findings of the project were presented at the Brazil-U.K. Frontiers of Engineering meeting, held November 6-8, 2014, in Jarinu, in inland São Paulo (Brazil). This meeting was organized by the Royal Academy of Engineering of the United Kingdom in collaboration with FAPESP.

The event brought together 63 young researchers from various areas of engineering – 33 from Brazil and 30 from the United Kingdom – working at universities, research institutions and companies such as Shell, Foster Wheeler and Petrobras.

“The bacteria are able to remove all of the contaminants from the refinery wastewater,” said Perpetuo, who received FAPESP scholarships to pursue her master’s degree and PhD as well as to conduct post-doctoral research.

According to the professor, the two types of bacteria were isolated from the air and discovered inadvertently when she worked as a researcher at CEPEMA in Cubatão, near a Petrobras refinery.

By leaving a phenol solution of 500 ppm exposed in an open-air processing area of CEPEMA, the researchers realized that several days later, the solution became cloudy, which is a sign of cell growth.

“Because phenol was the only source of carbon in the solution, we realized that microorganisms were degrading the compound,” Perpetuo said. “Then, we began to isolate the bacteria and inoculate them with different concentrations of pollutants to determine which better resisted the presence of phenols. We determined that Achromobacter sp. and Pandoraea sp. were the most efficient in degrading the compound.”

Degrading phenol

To test the effectiveness of the bacteria in degrading the phenols, the researchers conducted two different experiments. In the first experiment, performed in bioreactors, they added 100 milliliters (ml) of Achromobacter sp. biomass to 500 ml of “acid water” and kept the bacteria in the solution for 82 hours.

In the second experiment, they kept strains of Pandoraea sp. in a solution of “acid water” in an Erlenmeyer flask (a glass flask) for 96 hours, under stirring and at a controlled temperature.

To turn the “acid water” treated with the bacteria into a clear solution, they used a concentration of 6 grams/liter (g/L) of activated coal, similar to that found in domestic water filters.

The results of the experiments indicated that the bacteria were capable of degrading the phenols and compounds such as o-cresol and m-cresol found in the solutions at concentrations of 500 ppm.

The Achromobacter sp. bacteria, however, were the most efficient and proved capable of degrading phenols at a concentration of up to 2 g/L of solution.

“Up to that point, no bacteria had been identified to have such a high a capacity in real [not synthetic] wastewater. Those reported in the scientific literature have the capacity to degrade concentrations of up to 200 or 300 ppm of synthetic wastewater, such as water added to phenol, with no contaminants mixed in,” said Perpetuo.

Through doctoral research carried out with a scholarship from FAPESP, the researchers analyzed the proteome (the set of proteins) of the bacteria to identify the enzymes involved in the microorganisms’ capacity to degrade phenols.

The findings of the analysis were published in the journal Current Proteomics and demonstrated that the microorganisms have enzymes that present a wide range of expression when exposed to phenol.

“We think that the Achromobacter sp. could be a new species of bacteria. That is why we have already requested the sequencing of its whole genome,” Perpetuo said.

Large-scale application

According to the professor, one possible way to use the bacteria to treat “acid water” would be to apply the biofilm of the microorganisms to biological cylinders, similar to water wheels, that would be partially immersed because bacteria need aeration and that would spin on the surface of a wastewater storage tank.

Spinning the cylinders would allow the bacteria to alternately have contact with the wastewater, degrading the toxic contaminants, and remain exposed to the air.

“We developed a prototype biological cylinder for a one-liter tank in an open environment, and it worked. We don’t think that it will be hard to make one on a much larger scale,” she said.

According to Perpetuo and the other experts present at the Jarinu event, bioremediation, which is the use of microorganisms to change the biology of undesirable chemical products by immobilizing metals or modifying the properties of the materials to enhance the use of resources such as water and soil, is considered to be one of the most cost-effective solutions for cleaning polluted water and soils.

With new genetic sequencing techniques, the field has begun to expand in recent years, said Andrew Singer, a researcher at the Center for Ecology and Hydrology at the U.K.’s Natural Environment Research Council (NERC).

“Modern molecular microbiology has developed at such a rapid pace in recent years that it has allowed us not only to identify isolated microbes and their genetic activity but also to do a quick survey of an entire environment to determine the species of microorganisms present and estimate its size and activity,” Singer said during a lecture at the event.

Research collaboration

The Brazil-U.K. Frontiers of Engineering event was aimed at allowing the participants to meet other outstanding researchers in different fields and from other places to develop a multidisciplinary perspective on engineering. The event also sought to promote the establishment of multinational networks of collaborative research.

“The idea was to create a space for discussion during the meeting where young researchers from universities and research institutions as well as from companies could talk about topics that will have economic and social impacts in the future,” explained Euclides de Mesquita Neto, a professor at the School of Mechanical Engineering (FEM) of the University of Campinas (Unicamp) and one of the event’s coordinators.

“The topics that we selected for discussion at this event were Oil and Gas, Smart Grids, Big Data in Healthcare, and Bioremediation,” said Mesquita Neto, who is a member of the FAPESP Area Panel Committee on Engineering.

During the three-day event, 16 oral presentations and poster sessions were delivered on the four topics.

The article “Proteome analysis of phenol-degrading Achromobacter sp. strain C-1, isolated from an industrial area” (doi: 10.2174/1570164611209040007) by Gracioso and colleagues can be read by subscribers to the journal Current Proteomics at benthamscience.com/journal/abstracts.php?journalID=cp&articleID=107135.