Chairat Siripatana

Analysis and extension of Gompertz-type and Monod-type equations for estimation of design parameters from batch anaerobic digestion experiments

Gompertz equation, particularly its modified form is widely used to describe growth and product formation data for various types of dynamically biological systems. In anaerobic digestion, it becomes a fashion to use it as an empirical representation of biogas/methane/hydrogen accumulation data although its physical meaning is sometimes obscured. This work outlines the use of Gompertz-type model and its related extensions in more systematic and meaningful manners. Firstly these time-derivative rate equations were reformulated using unstructured reasoning which considered the effects of growth associated product formation and two forms of time-rate derivatives: Schnute postulate and Power law extension. The analysis revealed that this class of models predict non-zero product formation at zero time. Thus we propose their corrected forms to be used for meaningful parameter estimation. Secondly, we compiled currently available solutions for most popular Monod-type models for batch digestion. Some solutions wer...

Effect of dilution and ash supplement on the bio-methane potential of palm oil mill effluent (POME)

This study aimed to evaluate the bio-methane potential of POME at different dilutions (100, 80, 60, 40, and 20 percent of initial POME) and different pH dues to different levels of ash supplement. Five different amounts of ash were added to digesters (0, 2, 4, 6, and 8 grams of ash were added to 170 ml of POME respectively). The digesters were operated in batch anaerobic digestion systems at room temperature (28-30 °C) and the experiments were performed in duplicate manner. The results showed that POME without dilution gave highest cumulative biogas (950 ml). However, 80% dilution from original POME gave the highest methane yield (45.83 mL CH4/ gCODadded or 103.13 mL CH4/ gCODremoved). Finally, the results of experiment 2, this adding ash into POME increased pH as well as enhanced the biogas production. It was found that adding ash at the ash:POME ratio of 2 g: 170 ml gave the highest both the cumulative biogas and methane yield (1,520 mL and 218.79 mL CH4/ gCODremoved respectively). The addition of ash i...

Astaxanthin production from sewage of traditional Thai rice vermicelli

This research aimed to investigate an optimal condition for astaxanthin production by Phaffia rhodozyma TISTR 5730 in two different media: synthetic YM medium and the medium added with coconut water and diluted with sewage from Thai traditional rice vermicelli plant (coconut water: sewage of 1:0, 1:1, 1:3 and 1:5 ration respectively). The basic medium formulation was composed of 10 g/L glucose, 3 g/L yeast extract, 0.1 g/L K2HPO4 , 0.01 g/L NaCl , 0.01 g/L MgSO4 and 0.01 g/L CaCl2 with initial pH 5.5. The cultures were cultivated on 200 rpm shaking bath at 50 C for 120 hr. It was found that P. rhodozyma TISTR 5370 grew optimally when cultivated in a mixture of coconut water and Thai rice vermicelli sewage (ratio of 1:3), with growth of 3.23 g dry biomass/L and specific astaxanthin production of 680 μg/g dry cell respectively. When fan palm sugar was added to increase reducing sugar from 10 to 15, 20 and 25 g/L, it was demonstrated that the 15 g/L formulation produced highest both dry cell weight (9.66 g/L) and astaxanthin (810 μg/g dry cell weight). Furthermore, when 0.5, 1.0 and 1.5 g/L citric acid was added as supplement, it was found that 1.0-g/L citric acid formulation gave the best result: 10.30 g/L dried cell weight and 930 μg/g dry cell weight astaxanthin. This study provides a promising alternative method of sewage reduction and valorization of wastewater from Thai traditional rice vermicelli plant.

A generalized volumetric dispersion model for a class of two-phase separation/reaction: finite difference solutions

This article explores a volumetric approach in formulating differential equations for a class of engineering flow problems involving component transfer within or between two phases. In contrast to conventional formulation which is based on linear velocities, this work proposed a slightly different approach based on volumetric flow-rate which is essentially constant in many industrial processes. In effect, many multi-dimensional flow problems found industrially can be simplified into multi-component or multi-phase but one-dimensional flow problems. The formulation is largely generic, covering counter-current, concurrent or batch, fixed and fluidized bed arrangement. It was also intended to use for start-up, shut-down, control and steady state simulation. Since many realistic and industrial operation are dynamic with variable velocity and porosity in relation to position, analytical solutions are rare and limited to only very simple cases. Thus we also provide a numerical solution using Crank-Nicolson finite difference scheme. This solution is inherently stable as tested against a few cases published in the literature. However, it is anticipated that, for unconfined flow or non-constant flow-rate, traditional formulation should be applied.

Mathematical Simulation of Solid-Liquid Diffusion in Continuous Countercurrrent Extraction Process, Part II - Modeling Verification and Its Application

In this work, a backmixing-diffusion model was developed for continuous countercurrent extraction process. Various parameters/factors influenced the extraction were investigated for juice extraction. Important parameters/factors studied were solid to liquid ratio, solid retention time, extraction temperature, external resistance to mass transfer, size and shape of solid materials and degree of backmixing for solid and liquid phase. For juice extraction from pineapple, apple and pear, it was found that the backmixing-diffusion concept can be used through the whole range of operation time. The model could predict the concentration profile well for both unsteady state period and steady state one. The simulation was successful for juice extraction process.