The aim of this work was to analyze the performance of a wastewater system for Cr(VI) and sulfate compounds reduction via mathematical modeling. The considered process is coupled to chemical reactors to achieve its tasks. The first stage of the considered process is a biological sulfate-reducing reactor, by which sulfate compounds can be reduced to biogenic sulfide; then, in the second stage, the above-mentioned biogenic sulfide is fed to a second reactor in which the Cr(VI) is reduced, allowing high Cr(VI) concentration removal. The kinetic model of the biological sulfate-reducing process and the Cr(VI) reduction via biogenic sulfide reactions were experimentally corroborated and employed as a benchmarck for the wastewater process analysis via numerical simulations to achieve several feasible operation conditions, under the system’s constraints. The mathematical model was extended to a continuous operation, where numerical experiments were carried out predicting an excellent removal of 99% of Cr(VI) and 75% of sulfate compounds.

This study deals with the problem of estimating the amount of biomass and lactic acid concentration in a lactic acid production process. A continuous stirred tank bioreactor was used for the culture of Lactobacillus helveticus . A nonlinear sliding mode observer is proposed and designed, which gives an estimate of both the biomass and lactic acid concentrations as a function of glucose uptake from the culture medium. Numerical results are given to illustrate the effectiveness of the proposed observer against a standard sliding-mode observer. It was found that the proposed observer worked very well for the benchmark bioreactor model. Also, the numerical results indicated that the proposed estimation methodology was robust to the uncertainties associated with un-modelled dynamics. These new sensing technologies, when coupled to software models, improve performance for smart process control, monitoring, and prediction.

Distribution, eco-climatic characterisation, and potential growing regions of Annona cherimola Mill. (Annonaceae) in Mexico.

This work focuses on the design of different closed-loop control schemes based on nonlinear controller. A simulated two-stage reactor system (TSRS) was used to remove sulfate and hexavalent chromium (Cr(VI)). 24 Desulfovibrio alaskensis 6SR cells were anerobically grown in the first-stage reactor (biological rector BR), and then feeding to a second-stage reactor (chemical reactor, CR) where chemically Cr(VI) reduction occurred with biosulfide. In the last 20 years, it has been demonstrated that complete Cr(VI) removal was achieved in the CR and sulfate removal from 3500 to 500 mg L^-1 and was achieved in BR and lactate consumption from 5000 to almost 8000 mg L^-1 under appropriate conditions. To illustrate the influence of the consumed sulfate in order to produced sulfide by D. alaskensis 6SR in the BR and Cr(VI) reduction with biosulfide in the CR, a mathematical model was developedt by incorporating lactate oxidation and sulfide production kinetic and Cr(VI) reduction into the mass balance relationship of BR and CR, respectively, for an RS. Analysis of lactate, sulfate, and Cr(VI) concentration in SR using both model simulation and experimental data indicated that the rate of sulfide production is function of lactate/sulfate relation and that the Cr(VI) reduction decreased with the depletion of the sulfide concentration in BR. Finally, a nonlinear controller was proposed in order to regulate the dynamic behavior of the BR for biosulfide production and regulate the dynamic behavior of the CR for Cr(VI) reduction. Numerical experiments were carried out in order to show the satisfactory performance of the proposed controller.