Carlos Pelayo-Ortiz

Software sensors for highly uncertain WWTPs: a new approach based on interval observers

This paper presents the practical implementation of a new robust interval observer on a 1 m3 continuous fixed bed anaerobic reactor used for the treatment of industrial wine distillery wastewater. This interval observer is able to generate guaranteed intervals for the unmeasured variables (i.e. acidogenic and methanogenic bacteria, alkalinity and chemical oxygen demand) from few on-line measurements (i.e. input liquid flow rate, CO2 gaseous flow rate, volatile fatty acids and total inorganic carbon). The main advantage of this approach is its independance with respect to disturbances and uncertainty in the initial conditions, in the kinetics and, last but not least, in the process inputs.

Bagasse hydrolyzates from Agave tequilana as substrates for succinic acid production by Actinobacillus succinogenes in batch and repeated batch reactor.

The aim of this work was to obtain fermentable sugars by enzymatic or acid hydrolyses of Agave tequilana Weber bagasse in order to produce succinic acid with Actinobacillus succinogenes. Hydrolyses were carried out with mineral acids (sulfuric and hydrochloric acids) or a commercial cellulolytic enzyme, and were optimized statistically by a response surface methodology, having as factors the concentration of acid/enzyme and time of hydrolysis. The concentration of sugars obtained at optimal conditions for each hydrolysis were 21.7, 22.4y 19.8g/L for H2SO4, HCl and the enzymatic preparation respectively. Concerning succinic acid production, the enzymatic hydrolyzates resulted in the highest yield (0.446g/g) and productivity (0.57g/Lh) using A. succinogenes in a batch reactor system. Repeated batch fermentation with immobilized A. succinogenes in agar and with the enzymatic hydrolyzates resulted in a maximum concentration of succinic acid of 33.6g/L from 87.2g/L monosaccharides after 5 cycles in 40h, obtaining a productivity of 1.32g/Lh.

Immobilization of Actinobacillus succinogenes by adhesion or entrapment for the production of succinic acid

The production of succinic acid was studied with entrapped and adsorbed Actinobacillus succinogenes. The adsorption of fermentation products (organic acids in the concentration range of 1-20 g/L) on different supports was evaluated. It was found that succinic acid was adsorbed in small quantities on diatomite and zeolite (12.6 mg/g support). The highest production of succinic acid was achieved with A. succinogenes entrapped in agar beads. Batch fermentations with immobilized cells were carried out with glucose concentrations ranging from 20 to 80 g/L. Succinic acid (43.4 g/L) was obtained from 78.3g/L glucose, and a high productivity (2.83 g/Lh) was obtained with a glucose concentration of 37.6g/L. For repeated batch fermentations (5 cycles in 72 h) with immobilized cells in agar, the total glucose consumed was 147.55 g/L, while the production of succinic acid was 107 g/L. Immobilized cells reduced significantly the fermentation time, yield, productivity and final concentration of succinic acid.

Robust Interval-Based SISO Regulation of an Anaerobic Reactor

Abstract A robust regulation law is proposed for the stabilization of an anaerobic digester for the treatment of organic highly loaded wastewater. This process exhibits a highly nonlinear dynamic behavior. In addition, it must work under an uncertain environment with the presence of unknown inputs. Supporting some structural and operational conditions, this regulation law exponentially stabilizes the regulated variable around its nominal value in the presence of uncertainties and input disturbances. Simulations are carried out handling operational conditions close to those used in a real plant.

Robust Interval-Based SISO Regulation of a Highly Uncertain Anaerobic Digester

Abstract A robust regulation law is proposed for the stabilization of an anaerobic digester for the treatment of organic wastewater. This process exhibits a highly nonlinear dynamic behavior with poorly known parameters. In addition, it must work under an uncertain environment with the presence of unknown inputs. Supporting some structural and operational conditions, this regulation law exponentially stabilizes the regulated variable around its nominal value in the presence of uncertainty and input disturbances. Simulations are carried out handling operational conditions close to those used in a real plant.

Interval-Based Diagnosis of Biological Systems - Application to an Anaerobic Digestion Pilot Plant

Abstract Anaerobic digestion is a highly nonlinear time-varying process used for biological wastewater treatment which is subject to large disturbances of both influent concentrations and flow rates. These perturbations can lead to the crash of the digester and thus, the dynamics of the main state variables - including biomass - must be closely monitored to use this information in the design and implementation of advanced control schemes. However, such processes still suffer From a lack of reliable and cheap sensors. As a consequence, efficient monitoring, control and decision support systems are needed in order to insure the correct process operation. Particularly, there is an increasing interest on the proposal of Fault Detection and Isolation (FDI) and Fault Detection and Analysis (FDA) integrated systems. In this paper, we propose the use of interval observers in order to detect and isolate sensor faults as well as input changes in biological systems that are not observable. This approach is experimentally implemented on a 1 m 3 pilot scale anaerobic digestion continuous process.

Regulation of Volatile Fatty Acids and Total Alkalinity in Anaerobic Digesters

Abstract This paper deals with the simultaneous regulation of volatile fatty acids (VFAs) and total alkalinity (TA) in anaerobic digesters. The control scheme is conformed by an output feedback control and an extended Luenberger observer used to estimate the uncertainties associated to the controlled states ( i.e. , kinetics terms and inlet composition). The inlet flow rate is used to regulate the VFAs concentration, whereas an alkali solution is added directly to the digester for the regulation of the TA concentration. The control scheme is evaluated via numerical simulations under different operating conditions. Results show that the control law is capable to regulate the VFAs and TA despite of load disturbances, uncertainties in the kinetics terms, noisy measurements and control inputs restrictions.