Risks of using EDTA as an agent for trace metals dosing in anaerobic digestion of olive mill solid waste

ABSTRACT

Low concentrations of trace elements in many organic wastes recommend their supplementation in order to avoid potential limitations. Different chelating agents have been used to ensure an adequate trace metal pool in the soluble fraction, by forming dissolved complexes. Ethylenediaminetetraacetic acid (EDTA) is probably the most common, although several negative effects could be associated with its usage. Biomethane potential tests were performed using Olive Mill Solid Waste as the substrate, supplementing different combinations of Fe, Co, Ni, Ba, always under the presence of EDTA. Results show that Ni and Co slightly recovered biodegradability. However, Ba supplementation resulted in worsening the methane yield coefficient in all cases. High concentration of EDTA led to decrease in the activity of anaerobic digestion. High availability of EDTA induces the capture of trace metals like Co or Ni, key trace metals for anaerobic biomass activity. While supplementing trace metals, the addition of Ba and/or EDTA must be carefully considered.

KEYWORDS:

• Ethylenediaminetetraacetic acid
• metal affinity
• methane production rate
• microbial activity
• olive mill solid waste
• trace metal supplementation

ORCID

A. Serrano http://orcid.org/0000-0002-4615-5038

F. Pinto-Ibieta http://orcid.org/0000-0001-6005-886X

A.F.M. Braga http://orcid.org/0000-0003-3464-2469

D. Jeison http://orcid.org/0000-0002-2234-8257

R. Borja http://orcid.org/0000-0002-3699-7223

F.G. Fermoso http://orcid.org/0000-0002-2586-007X

Additional information

Funding

The authors are very grateful to the Spanish Ministry of Economy and Competitiveness (Secretaria de Estado de Investigación, Desarrollo e Innovación) for funding this research through Project [CTM2014-55095-R]. The authors would also like to thank the Marie Curie’s International Research Staff Exchange Scheme (IRSES) ‘Renewable energy production through microalgae cultivation: closing material cycles’ [PIRSES-GA-2011-295165], Seventh Framework Programme; and to the Brasilian Conselho Nacional de Desenvolvimento Científico e Tecnológico [CNPq – Process: 301020/2014-0] for providing financial support. David Jeison wishes to thank the support provided by the CRHIAM Centre [CONICYT/FONDAP/15130015]; Comisión Nacional de Investigación Científica y Tecnológica; Secretaría de Estado de Investigación, Desarrollo e Innovación.