Trace metal supplementation in wastewater sludge digesters

Ishaq, Farryad (2012). Trace metal supplementation in wastewater sludge digesters. University of Birmingham. Ph.D.

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Abstract

Multiple studies have shown the importance of transition metals for the microorganisms involved in anaerobic digestion. Deficiencies in metals can translate into suboptimal digester performances and therefore where present an opportunity to stimulate anaerobic digestion exists. Previous supplementation studies that have used EDTA complexed metals have shown conflicting results.

Assays supplemented with cobalt-EDTA on its own consistently responded to a level equal to or higher than that from assays supplemented with a combination of metals. The results seemingly indicate that cobalt was the most commonly deficient metal in the sludge digesters. However this study has raised questions about the bioavailability of other metals as EDTA chelates, particularly nickel-EDTA. Differing levels of bioavailability for different EDTA complex metals explain how conflicting results for EDTA complexed metals can exist. Metal deficiencies were present 69% of the time in the wastewater sludge digesters samples. Given the questions raised about the bioavailability of metal-EDTA chelates the prevalence of deficiencies was likely to have been higher. At a site specific level it was found that a lower than expected Vmax for a given sites acetoclastic methanogen population corresponded with a positive response from supplementation and therefore it can act as an indicator of metal requirement.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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