A. Paulo

Photocatalytic and combined anaerobic–photocatalytic treatment of textile dyes

A photocatalytic process based on immobilized titanium dioxide was used to treat crude solutions of azo, anthraquinone and phthalocyanine textile dyes. In addition, the process was applied to the treat autoxidized chemically reduced azo dyes, i.e. representatives of recalcitrant dye residues after biological sequential anaerobic-aerobic treatment. Photocatalysis was able to remove more than 90% color from crude as well as autoxidized chemically reduced dye solutions. UV-absorbance and COD were also removed but to a lower extent (50% in average). The end products of photocatalytic treatment were not toxic toward methanogenic bacteria. The results demonstrate that photocatalysis can be used as a pre- or post-treatment method to biological anaerobic treatment of dye-containing textile wastewater.

Microbial remediation of organometals and oil hydrocarbons in the marine environment

Marine environments are exposed to pollution that mostly results from human activities. Organometals and oil hydrocarbons are among the most hazardous pollutants. In surface waters and along the water column, these compounds are more easily degraded than in sediments, especially under anoxic conditions, where they are highly persistent. Due to their negative impact in living organisms, decontamination of polluted marine sites with minimum collateral impacts is imperative. Bioremediation strategies, benefiting from the ability of aerobic and anaerobic microorganisms to degrade organometals or oil hydrocarbons to simpler and less toxic derivatives, represent an alternative to traditional physicochemical decontamination methods. Different bioremediation strategies have been applied in marine environments, including monitored natural recovery, biostimulation, bioaugmentation and phytoremediation. Individual microbial agents or mixed microbial consortia able to remediate these pollutants in marine environments have been identified, and the most relevant mechanisms of biodegradation of pollutants are characterised.

Enhancement of methane production from 1-hexadecene by additional electron donors

1‐Hexadecene‐contaminated wastewater is produced in oil refineries and can be treated in methanogenic bioreactors, although generally at low conversion rates. In this study, a microbial culture able to degrade 1‐hexadecene was enriched, and different stimulation strategies were tested for enhancing 1‐hexadecene conversion to methane. Seven and three times faster methane production was obtained in cultures stimulated with yeast extract or lactate, respectively, while cultures amended with crotonate lost the ability to degrade 1‐hexadecene. Methane production from 1‐hexadecene was not enhanced by the addition of extra hydrogenotrophic methanogens. Bacteria closely related to Syntrophus and Smithella were detected in 1‐hexadecene‐degrading cultures, but not in the ones amended with crotonate, which suggests the involvement of these bacteria in 1‐hexadecene degradation. Genes coding for alkylsuccinate synthase alpha‐subunit were detected in cultures degrading 1‐hexadecene, indicating that hydrocarbon activation may occur by fumarate addition. These findings are novel and show that methane production from 1‐hexadecene is improved by the addition of yeast extract or lactate. These extra electron donors may be considered as a potential bioremediation strategy of oil‐contaminated sites with bioenergy generation through methane production.