Instrumentation, Control and Automation in Anaerobic Digestion

Abstract

Anaerobic digestion (AD) is a biochemical process in nature. It has been used to decompose organic waste in order to reduce environmental pollution, and to destroy pathogenic microorganisms for the protection of human and animal health. The process itself produces methane, which can then be used as an energy source. The use of AD in an integrated resource recovery system is one of the most important ways of achieving economic and environmental benefits.



Owing to the fact that the successful anaerobic conversion of organic waste to biogas relies on a series of biochemical reactions carried out by different groups of anaerobic microorganisms that live interdependently, the process is often considered to be unstable and sensitive to environmental changes. Apart from the need to develop advanced bioreactors, close monitoring and control of the AD process has been recognized to be a necessary factor for ensuring reliable and stable operation and guarding the process against failure.



One objective of the work reported in the thesis has been to investigate new analytical methods for on-line monitoring of the AD process. More specifically, the emphasis has been very much on biosensor development for analysis of intermediate fermentation products from consecutive biochemical breakdown of organic polymers to methane and carbon dioxide, as monitored by means of short-term biochemical oxygen demand (BOD). In comparison with the conventional BOD 5-day test, the biosensor was capable of estimating the BOD value rapidly (i.e. within a minute) and of providing satisfying results regarding both precision and agreement with values obtained from the 5-day test. In order to make the sensor a suitable candidate for industrial application in the field, a novel design of BOD biosensor was developed to simplify construction of the sensor and renewal of the biochemical receptor. By using a mixed culture as the bio-receptor, the sensor design allows rapid and convenient renewal of the bio-receptor on a regular basis and on-line assay of a broad range of substrates.



Another aspect of the work was to investigate new control strategies for operating AD processes efficiently at high load. One successful implementation was a control system consisting of a cascade controller that was embedded into a rule-based supervisory system, based on a new principle of probing control. The control system was not only able to respond rapidly to process imbalance, but also to schedule control tasks according to different time scales. Good control performance was achieved during start-up and steady-state running operations, and also rejection of disturbances. The controller was capable of compensating for the negative effects of different types of underload and overload, as well as the temperature variability of the reactor. Furthermore, the control system attempted to steer the reactor load progressively to a maximum value while keeping the microbial ecosystem in balance. This control strategy can be considered to be an interesting and promising approach for achievement of an economically feasible anaerobic process.

• author: Liu, Jing
• supervisor: [unknown] [unknown]
• opponent: Dr Spanjers, Henri, LeAF - Lettinga Associates Foundation, The Netherlands.
• organization: Biotechnology
• publishing date: 2003
• type: Thesis
• publication status: published
• subject: Industrial Biotechnology
• keywords: Bioteknik, Biotechnology, ICA, automation, control, monitoring, biosensor, instrumentation, anaerobic digestion, biogas
• pages: 186 pages
• defense location: Lecture hall A, at the Center for Chemistry and Chemical Engineering, Sölvegatan 39, Lund Institute of Technology.
• defense date: 2003-12-05 13:15:00
• external identifiers: other:ISRN: LUTKDH/TKBT- -03/1070- -SE
• ISBN: 91-89627-17-2
• language: English
• LU publication?: yes
• additional info: Article: 1. Liu, J., Björnsson, L. and Mattiasson, B. (2000). Immobilised activated sludge based biosensor for BOD measurement. Biosensors & Bioelectrons 14(12), pp. 883-893. Article: 2. Liu, J., Olsson, G. and Mattiasson, B. (2003). Short-term BOD (BODst) as a parameter for on-line monitoring of biological treatment process, Part I: A novel design of BOD biosensor for easy renewal of bio-receptor. (submitted for publication) Article: 3. Liu, J., Olsson, G. and Mattiasson, B. (2003). Short-term BOD (BODst) as a parameter for on-line monitoring of biological treatment process, Part II: Instrumentation of integrated flow injection analysis (FIA) system for BODst estimation. (submitted for publication) Article: 4. Liu, J. and Mattiasson, B. (2002). Microbial BOD sensors for wastewater analysis. Water Research, 36(15), pp. 3786-3802. Article: 5. Liu, J., Olsson, G. and Mattiasson, B. (2003). A volumetric meter for monitoring of low gas flow rate from laboratory-scale biogas reactors. Sensors and Actuators B: Chemical, (in press). Article: 6. Liu, J., Olsson, G. and Mattiasson, B. (2003). Monitoring of two-stage anaerobic biodegradation using a BOD biosensor. Journal of Biotechnology,100(3), pp. 261-265. Article: 7. Liu, J., Olsson, G. and Mattiasson, B. (2003). On-line monitoring of a two-stage anaerobic digestion process using a BOD analyzer. (submitted for publication). Article: 8. Liu, J., Olsson, G. and Mattiasson, B. (2003). Advanced monitoring and control of an anaerobic up-flow fixed bed reactor for high loading rate operation and disturbances rejection. (submitted for publication)
• id: 3ee3a803-002a-4db6-9935-da3af97af873 (old id 466476)
• date added to LUP: 2016-04-04 11:28:06
• date last changed: 2018-11-21 21:05:02