A hybrid cascade control scheme for the VFA and COD regulation in two-stage anaerobic digestion processes

[Display omitted] •The regulation of VFA and COD concentrations in two-stage AD processes is analyzed.•On-line conductivity measurements allows the VFA regulation in the acidogenic phase.•A daily off-line measurement ensures the COD regulation of methanogenic phase.•The controller was tested experim...

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Bibliographic Details
Published in:Bioresource technology 2016-10, Vol.218, p.1195-1202
Main Authors: Méndez-Acosta, H.O., Campos-Rodríguez, A., González-Álvarez, V., García-Sandoval, J.P., Snell-Castro, R., Latrille, E.
Format: Article
Language:English
Subjects:
Anaerobiosis
Biological Oxygen Demand Analysis
Bioreactors - microbiology
Cascade control
Continuous and discrete measurements
Environmental Sciences
Fatty Acids, Volatile - analysis
Fatty Acids, Volatile - chemistry
Life Sciences
Methane - analysis
Tequila vinasses
Two-stage anaerobic digestion
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Summary:[Display omitted] •The regulation of VFA and COD concentrations in two-stage AD processes is analyzed.•On-line conductivity measurements allows the VFA regulation in the acidogenic phase.•A daily off-line measurement ensures the COD regulation of methanogenic phase.•The controller was tested experimentally during 110days with excellent results.•The controller favors the microbial abundance and diversity toward methane production. A hybrid (continuous–discrete) cascade control is proposed to regulate both, volatile fatty acids (VFA) and chemical oxygen demand (COD) concentrations in two-stage (acidogenic-methanogenic) anaerobic digestion (TSAD) processes. The outer loop is a discrete controller that regulates the COD concentration of the methanogenic bioreactor by using a daily off-line measurement and that modifies the set-point tracked by inner loop, which manipulates the dilution rate to regulate the VFA concentration of the acidogenic bioreactor, estimated by continuous on-line conductivity measurements, avoiding acidification. The experimental validation was conducted in a TSAD process for the treatment of tequila vinasses during 110days. Results showed that the proposed cascade control scheme was able to achieve the VFA and COD regulation by using conventional measurements under different set-point values in spite of adverse common scenarios in full-scale anaerobic digestion processes. Microbial composition analysis showed that the controller also favors the abundance and diversity toward methane production.
ISSN:0960-8524
1873-2976
DOI:10.1016/j.biortech.2016.07.076