Limiting factors for anaerobic digestion of olive mill wastewater blends under mesophilic and thermophilic conditions

Experimental trials of anaerobic digestion of olive mill wastewater (OMW) blended with other agro-industrial by-products were carried out to evaluate biogas production and sensitivity of the process to inhibiting compounds. Blends containing different percentages of OMW, digested liquid manure, and...

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Bibliographic Details
Published in:Journal of agricultural engineering (Pisa, Italy) Italy), 2018-02, Vol.49 (2), p.130-137
Main Authors: Zema, Demetrio Antonio, Zappia, Giovanni, Benalia, Souraya, Zimbalatti, Giuseppe, Perri, Enzo, Urso, Elena, Tamburino, Vincenzo, Bernardi, Bruno
Format: Article
Language:English
Subjects:
Agro-industrial by-product
Anaerobic conditions
Anaerobic digestion
Anaerobic processes
Biogas
Essential oils
Fatty acids
Food industries wastewaters
inhibiting compounds
Limiting factors
Liquid manure
methane yield
Microorganisms
Mixtures
Polyphenols
Refuse as fuel
Substrates
Thermophilic microorganisms
Toxicity
Volatile fatty acids
Wastewater
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Summary:Experimental trials of anaerobic digestion of olive mill wastewater (OMW) blended with other agro-industrial by-products were carried out to evaluate biogas production and sensitivity of the process to inhibiting compounds. Blends containing different percentages of OMW, digested liquid manure, and citrus peel were subjected to a batch anaerobic digestion process under both mesophilic and thermophilic conditions. The results showed that blends with percentages of OMW higher than 20% (v/v) had low methane yields due high concentrations of polyphenols (PPs) and/or volatile fatty acids (concentrations above 0.8 g kg–1 and 2.4 g L–1, respectively). The addition of other substrates such as citrus peel may have induced synergic inhibiting effects of PPs and essential oils (EO) on microbial growth. Thermophilic processes were more sensitive to these inhibiting compounds than mesophilic processes. The results of this study suggest that reducing PPs and EO concentrations in blends subject to anaerobic digestion below the inhibiting concentrations of 0.6 g L–1 and 0.5 g kg–1, respectively, is suitable. Additionally, it is advisable to maintain the volatile fatty acids content below 2 g L–1 to avoid its evident toxic effects on the growth of microorganisms in biochemical processes.
ISSN:1974-7071
2239-6268
DOI:10.4081/jae.2018.792