Tolerance of a sulfidogenic sludge to trichloroethylene at microcosms level as a basis for a long-term operation of reactors designed for its biodegradation

Abstract

Trichloroethylene (TCE) is known as a toxic organic compound found as a pollutant in water streams around the world. The ultimate goal of the present work was to determine the TCE concentration that would be feasible to biodegrade on a long-term basis by a sulfidogenic sludge while maintaining sulfate reducing activity (SRA). Microcosms were prepared with sulfidogenic sludge obtained from a stabilized sulfidogenic UASB and amended with different TCE concentrations (100–300 µM) and two different proportions of volatile fatty acids (VFA) acetate, propionate and butyrate at COD of 2.5:1:1 and 1:1:1, respectively to evaluate the tolerance of the sludge. The overall results suggested that the continuous exposure of the microorganisms to TCE leads to inhibition of SRA; nonetheless, the SRA can be recovered after adequate supplementation of carbon sources and sulfate. The most suitable TCE concentration to operate on a long-term basis while preserving SRA was 26–35 mg L^–1 (200–260 µM). A low level of expression of the mRNA of the sulfite reductase subunit alpha (dsrA) gene was obtained in the presence of the TCE and its intermediate products. This gene was associated to SRB belonging to the genera Desulfovibrio, Desulfosalsimonas, Desulfotomaculum, Desulfococcus, Desulfatiglans and Desulfomonas.

Keywords:

• Sulfidogenic sludge
• sulfate reduction
• hydrothermal vent sediments
• trichloroethylene biodegradation
• toxicity of trichloroethylene
• vinyl chloride biodegradation

Acknowledgment

Authors thank Diana Valeria Ruiz Hernández for her technical assistance in the lab.

Compliance with ethical standards

Conflict of interest

The authors declare that there are not conflicts of interest.

Additional information

Funding

The authors are grateful for the financial support provided by Secretaría de Investigación y Posgrado (SIP), Instituto Politécnico Nacional, grants 20170311 and 20180357 awarded to C. Guerrero-Barajas and 20170243 and 20180359 awarded to J. Jan-Roblero, the scholarship BEIFI granted to M. A. Santana-Santos.