Andrés Donoso-Bravo

• PhD
• CEO Founder at Modela

Anaerobic digestion plays a crucial role in the transition toward a circular economy. Incorporating system supervision through mathematical modelling can enhance control and resilience. This study aims to assess the impact of scheduled digester maintenance on the effectiveness of modelling as a tool for monitoring and control. Data from a pilot-sca...

Accurately characterizing the substrate used in anaerobic digestion is crucial for predicting the biogas plant's performance. This issue makes particularly challenging the application of modeling in codigestion plants. In this work, a novel methodology called substrate prediction module (SPM) has been developed and tested, using virtual codigestion...

Microalgae-bacteria consortia are considered a promising alternative for wastewater treatment. Photosynthesis performed by microalgae induces a self-oxygenation of the culture, eliminating the requirements for mechanical aeration. However, systems have limitations, such as high hydraulic retention times and difficulties associated with effluent cla...

Kinetics and CFD modeling is widely used for the study of biological treatment systems. This work reviews publications from 2006 to 2023 and compares the strategies applied to integrate the fluid dynamics and kinetics modeling. The identified strategies are grouped into three categories: a) the CFD coupled with the kinetics: mostly prohibitive in t...

Although computational fluid dynamics (CFD) modelling has been applied to study bioprocesses where mechanical mixing and aerations are key, the effect of having a free surface has usually been ignored. This work studies a mixing tank for bioprocess applications to analyze the impact that the assumption of a flat liquid level has upon the modelling...

The use of microalgae-bacteria consortia (MBC) for wastewater treatment have received increasing attention because of its high capacity for nutrients and organic matter removal, using sunlight as an energy source, through self-sufficient oxygen production provided by photosynthesis. This review addresses the research hotspots and main challenges of...

Modelling in anaerobic digestion will play a crucial role as a tool for smart monitoring and supervision of the process performance and stability. By far, the Anaerobic Digestion Model No. 1 (ADM1) has been the most recognized and exploited model to represent this process. This study aims to propose simple extensions for the ADM1 model to tackle so...

The olive alperujo (OA) corresponds to the solid waste generated in the olive oil extraction process using the two-phase centrifugation method. OA is produced in large quantities (800 kg OA/ton olives processed) and is characterized by its high moisture content, organic matter, and low pH. In Chile, the olive oil industry is recent, and one of its...

The culture medium in many fermentations is a non-Newtonian fluid. In bacterial alginate batch production, the broth becomes more pseudoplastic as the alginate concentration increases, which impairs the mixing process. This work characterizes the effect of the interaction between changing broth rheology and impeller mixing on a bioreactor fluid dyn...

The proliferation of microalgae, also known as microalgal bloom or Harmful Algae Bloom (HAB), is a damaging phenomenon for the correct functioning of salmon farming systems worldwide. Several anti-HAB systems have been developed and are currently being evaluated. One type of system is based on air diffusion from below the ocean surface where the fi...

Co-digestion of thermally pretreated sewage sludge with food waste is an innovative strategy that could improve the balance and availability of nutrients needed to increase the efficiency of anaerobic digestion in terms of biogas production. In this context, the aim of this research was to evaluate the impact of different proportions of sewage slud...

This paper reports a computational modelling study of a mixing tank for bioprocess applications. A dual impeller mixer containing several probes is used with a mixing speed of 400 rpm. The single‐phase transient model is validated against experimental measurements using torque and velocity profiles as the validation variables. A complete workflow i...

The potential for obtaining renewable energy from organic substrates such as food waste (FW) and biowaste has generated increasing interest in the anaerobic digestion process. Kinetic models are used to analyse the impact of different parameters on biological processes and thus, to optimize them to achieve and to increase the quality and quantity o...

Computational fluid dynamic (CFD) has been increasingly exploited for the design and optimization of (bio)chemical processes. Validation is a crucial part of any modeling application. In CFD, when validation is done, complex and expensive techniques are normally employed. The aim of this study was to test the capability of the CFD model to represen...

Mathematical models are tools that allow the prediction and control of the anaerobic digestion (AD) process, ensuring process stability and maximizing methane production. In this study, the AD of food waste (FW) was evaluated in single-stage and two-stage semicontinuous configurations, with the following organic loading rates (OLR: kgVS⋅m − 3 ⋅d −...

This paper presents a computational study of the static cooling of a catalytic converter with a monolith system. Under conditions without gas flow, the converter cools by convection and radiation to the surroundings. Internally, heat transfer occurs by conduction, natural convection and radiation. The monolith has a high initial temperature and is...

The aim of this study is to test the capability of the anaerobic digestion model n1 (ADM1) to reproduce data from full-scale digesters operated in a wastewater resource recovery facility (WRRF) where both thermal hydrolysis and codigestion with industrial waste are carried out. Furthermore, the potential uses of the model in a WRRF are also describ...

Most articles that report fitted parameters for kinetic models do not include meaningful statistical information. This study demonstrates the importance of reporting a complete statistical analysis and shows a methodology to perform it, using functionalities implemented in computational tools. As an example, alginate production is studied in a batc...

During mathematical representation of microbial cultures, it is normally assumed that changes in the environment produce instantaneous effects on growth. However, reports are available indicating that sometimes this may not be the case. This work studied the existence of delays on the response of a population of microalgae when subjected to changes...

In this study, beverage wastewater (BW) and extended aeration sewage sludge were assessed as co-substrates with both mixed sludge and thermally hydrolyzed sludge as substrates in an anaerobic codigestion (AcoD) process. The methodology is an integrated methodology that comprises a batch test (BMP) and semicontinuous reactor along with microbial div...

Anaerobic mono-digestion and co-digestion are nowadays widely used in wastewater treatment plants (WWTP). However, the data processing of the conventional biochemical potential test (BMP) carried out to assess potential substrates should be enhanced to reduce the uncertainty of the results. In this study, two methodologies aiming to improve the dat...

The present work compares two types of configurations for a two-reaction (acidogenesis and methanogenesis) anaerobic digestion model. These configurations are as follows: (i) a single bioreactor, where the acidogenesis and methanogenesis reactions occur inside and, (ii) two bioreactors connected sequentially, where each reaction occurs separately i...

Microaeration can be used to cost-effectively remove in-situ H2S from the biogas generated in anaerobic digesters. This study is aimed at developing and validating an extension of the Anaerobic Digestion Model n°1 capable of incorporating the main phenomena which occurs during microaeration. This innovative model was implemented and tested with dat...

An important variability in the experimental results in anaerobic digestion lab test has been reported. This study presents a meta-analysis coupled with multivariate analysis aiming to assess the impact of this experimental variability in batch and continuous operation at mesophilic and thermophilic anaerobic digestion of waste activated sludge. An...

Nowadays, thanks to the enhancement in computational power and software development, advanced mathematical modelling based on computational fluid dynamics (CFD) allows us to represent almost any system. Anaerobic bioreactors correspond to a complex biosystem where multiple reactions, in parallel and/or in series, take place. Besides this biological...

This study shows the implementation of the Anaerobic Digestion Model (ADM1) in an anaerobic plug-flow reactor (PFR) with two approaches based on the use of consecutive continuous stirred tank reactors (CSTR) connected in serie for considering non-ideal mixing. The two-region (TR) model splits each CSTR into two regions, while the particulate retent...

The high cost of axenic microalgae cultivation in photobioreactors limits nowadays the potential uses of microalgal biomass as a feedstock for the production of biodiesel or bioethanol. In this context, microalgae-based wastewater treatment (WWT) has emerged as the leading method of cultivation for supplying microalgae at low cost and low environme...

The production of renewable energy in the form of methane from the anaerobic digestion (AD) of food waste (FW) varies depending on factors such as the quantity and quality of the inoculum. This research evaluated the influence of trace elements (Ca, K, Fe, Zn, Al, Mg, Co, Ni, and Mo) present in inoculum from different sources (wastewater treatment...

La Digestión Anaerobia (DA) de los residuos de alimentos (RA), además de reducir los riesgos a la salud humana y elambiente, permite aumentar la vida útil de los rellenos sanitarios y principalmente es una estrategia para la generaciónde un tipo de energía renovable como el metano. Los modelos cinéticos permiten determinar la influencia de losfacto...

Anaerobic Digestion (AD) of food waste (FW) reduces risks to human health and environment, also increases the life of landfills, and mainly is an important strategy to produce energy renewable as methane. Kinetic models can determine the influence of the factors that affect the process of AD and predicts more precisely methane production in order t...

Traditional models describing microorganisms growth assume that changes in the environmental conditions generate immediate responses in microbial population. However, reports are available indicating that in some cases this may not be the case. The existence of a delayed inhibition response (DIR) was studied, exposing a microalgae culture to inhibi...

Odor emissions from wastewater treatment facilities have paid attention during the last decade. These emissions usually are treated as stationary emissions or variable based on emission factors. This general approach does not include biological activity to explain the influence of process variations such as organic load or inorganic hydrogen sulfid...

Se realizaron simulaciones de la operación de un digestor anaerobio de lodos, utilizando el modelo ADM1 para la simular al reactor, aplicando una variación aleatoria de las concentraciones de sustratos de la digestión presentes en los lodos. Se estableció que, a partir del seguimiento de las trayectorias transitorias de dos variables de la operació...

Background: Industrial wastewaters with a high content of nitrogen are a relevant environmental problem. Currently, treatments to remove nitrogen are not efficient, so is necessary to develop alternative methods. The objective of this study is to investigate a consortium of microalgae — nitrifying, that due to the symbiosis between them could be an...

Anaerobic digestion is a consolidated technology for effective waste (water) treatment and biogas production. Despite many reported studies, the complex dynamic behaviour of the process is not completely understood, hindering its full exploitation. In particular, process start-up is delicate and disturbances can deviate the process from its expecte...

Forward osmosis (FO) is a concentration process based on the natural phenomena of osmosis. It is nowadays considered a breakthrough technology that can be potentially used for concentrating suspensions and solutions, including wastes such as sewage. The diluted nature of sewage restricts the treatment technologies that can be applied. Then, sewage...

The conventional application of thermal pretreatment of sewage sludge has been to apply it prior to the anaerobic digestion. In this study, the thermal treatment of the digestate was assessed at lab-scale under several temperature and time conditions. Biochemical methane potential (BMP) tests were set up to evaluate the methane production kinetic b...

Swine slurry is generated in large quantities and anaerobic digestion may represent an appropriate process to both treat and revalue this waste as an energy source. Pretreatment processes aim to increase the anaerobic biodegradability of a specific waste. In this study, steam explosion and weak thermal-alkali pretreatments are evaluated. The first...

Anaerobic digestion is a consolidated bioprocess which can be further enhanced by incorporating an upstream pretreatment unit. The olive oil production produces a large amount of solid waste which needs to be properly managed and disposed. Three different pretreatment techniques were evaluated in regard to their impact on the anaerobic biodegradabi...

In this study the development and implementation of automated pilot plant as well as the preliminary sequential runs of the digester on the degradation of organic solid waste are presented. This was inoculated with anaerobic sludge from a waste water treatment plant and conditioned for degradation of fruits and vegetables. Productivity averages of...

The generation of organic waste associated with aquaculture fish processing has increased significantly in recent decades. The objective of this study is to evaluate the anaerobic biodegradability of several fish processing fractions, as well as water treatment sludge, for tilapia and sturgeon species cultured in recirculated aquaculture systems. A...

This paper shows the results of a computational study relating to the calculation of heat and mass transfer coefficients in the entry region of a circular duct. Laminar flow with temperature dependent physical properties is used. The results are compared with the classical results obtained for a fluid with constant physical properties. It is seen t...

We propose a simple model of landfill and study a minimal time control problem where the re-circulation leachate is the manipulated variable. We propose a scheme to construct the optimal strategy by dividing the state space into three subsets ℰ0, 𝒵1 and the complementary. On ℰ0 and 𝒵1, the optimal control is constant until reaching target, while it...

Abstract Two-phase anaerobic systems are being increasingly implemented for the treatment of both sewage sludge and organic fraction of municipal solid waste. Despite the good amount of mathematical models in anaerobic digestion, few have been applied in two phase systems. In this study, a three-reaction mechanistic model has been developed, implem...

Biogas produced during the anaerobic degradation of the organic matter from waste and wastewater has become an important source of renewable energy. Mathematical modeling can help to predict and control the system behavior in order to assure process stability and biogas production maximization. The identifiability of anaerobic digestion models pres...

Nuisance odors generation from waste and wastewater treatment plants are a cause of public discomfort and complaints. This situation impairs the air quality and represents a growing social and public health problem, especially in developing countries. Several modeling approaches have been developed and successfully implemented in the frame of a was...

Molecular biology techniques provide valuable insights in the investigation of microbial dynamics and evolution. Denaturing gradient gel electrophoresis (DGGE) analysis is one of the most popular methods which have been used in bioprocess assessment. Most of the anaerobic digestion models consider several microbial populations as state variables. H...

This literature review provides a comprehensive overview of the research published in 2012 concerning anaerobic processes and their role in wastewater treatment technologies. Included in this review is a discussion on the characterization, development and optimization of novel approaches for waste treatment. The scope of this year's anaerobic proce...

Phenol is a common wastewater contaminant from various industrial processes, including petrochemical refineries and chemical compounds production. Due to its toxicity to microbial activity, it can affect the efficiency of biological wastewater treatment processes. In this study, the efficiency of an Anaerobic Sequencing Batch Reactor (ASBR) fed wit...

Several mathematical models have been developed in anaerobic digestion systems and a variety of methods have been used for parameter estimation and model validation. However, structural and parametric identifiability questions are relatively seldom addressed in the reported AD modeling studies. This paper presents a 3-step procedure for the reliabl...

The biochemical methane potential of steam exploded wheat straw was evaluated in a pilot plant under different temperature-time combinations. The optimum was obtained for 1min and 220°C thermal pretreatment (3.5 severity factor), resulting in a 20% increase in methane production respect non-treated straw. For more severe treatments the biodegradabi...

Anaerobic co-digestion of grease trap and sewage sludge from a wastewater treatment plant is evaluated. Enzyme-lipase application, both addition and dosage, are evaluated by fitting the methane production of biochemical potential tests with the first order model. The enzyme addition effect, at 2,5 and 10% of grease trap (%GTVS(FED)(-1)) and the enz...

Improving anaerobic digestion of sewage sludge through pretreatment techniques is a suitable solution for better sludge management. In this sense, modeling may present itself as an important tool to assess and predict process performance and pretreatment effects. In this study, the feasibility of using biochemical methane potential (BMP) tests data...

The objective of this study was to evaluate the production of hydrogen in a two-stage CSTR system – both reactors having the same volume – and compare its performance with a conventional one-stage process. The lab-scale two-stage and one-stage systems were operated at five pHs and five hydraulic retention time (HRTs). The maximum volumetric hydroge...

Temperature is an important environmental variable that can strongly affect the performance of anaerobic reactors working at ambient temperatures. This study presents a mechanistic mathematical model which depends in an explicit way on the operating temperature. The cardinal temperature model function is proposed to describe the temperature depende...

In this study, the problem of developing simple dynamic models of an anaerobic digestion process is tackled using an identification procedure which proceeds in several consecutive steps. Starting from sets of experimental data describing the time evolution of several key component concentrations, i.e. biomass(es), substrates and products, the minim...

Molecular biology techniques provide valuable insights in the investigation of microbial dynamics and evolution. Denaturing gradient gel electrophoresis (DGGE) analysis is one of the most popular methods which have been used in bioprocess assessment. Most of the anaerobic digestion models consider several microbial populations as state variables. H...

This study presents an evaluation of the hydrolytic activity of a continuous thermophilic anaerobic reactor in long-term operation. The hydrolytic coefficient was estimated by fitting a three-reaction model of the anaerobic digestion process with experimental data obtained from a pilot thermophilic digester operated for about 2 years. The model fit...

The rate-limiting step concept has been widely used in anaerobic digestion processes as well as in many different biological processes. Sometimes it is described as part of the study introduction, but many times is used to support the specific objectives of the work. However, there is no clear consensus of how to define this step or how to determin...

This study presents and discusses the usefulness of mathematical models and simulation tools to describe the dynamic behaviour of advanced wastewater treatment plants taking into account technical, environmental, energetic and economical aspects. The main challenge of this work is to compare by simulation different conventional and advanced WWTPs c...

The start-up and activation of a nitrifying rotating biological contactor (RBC) and its performance inside a culture tank of rainbow trout were studied. First, in a lab-scale operation, the system was fed with a synthetic medium containing a high ammonia concentration (567 mg NH(4)(+)-N L(-1)) and operated at a high hydraulic retention time (HRT) (...

Anaerobic digestion enables waste (water) treatment and energy production in the form of biogas. The successful implementation of this process has lead to an increasing interest worldwide. However, anaerobic digestion is a complex biological process, where hundreds of microbial populations are involved, and whose start-up and operation are delicate...

Limited oxygen supply to sludge digesters has shown to be an effective method to eliminate hydrogen sulfide from the biogas produced during anaerobic digestion but uneven results have been found in terms of the effect on the degradation of complex organic matter. In this study, the effect that the limited oxygen supply provoked on the "anaerobic" d...

A start-up strategy was presented and evaluated to obtain a well-established biofilm in a gas lift-reactor capable both for the removal of organic matter and sulphate. Pumice stone was used as material support. The influence of shear forces, given by the biogas recirculation, the effect of the COD/SO(4)(-2) ratio and the OLRs increase were evaluate...

This paper evaluates the number and stability of steady states of a two-population model, describing the anaerobic degradation of solid organic waste. Analytical conditions are provided, which define in the input space regions characterized either by a different number or change of stability of steady states. The qualitative results do not depend o...

In this study a novel and practical procedure was developed, that involves: initial methane production rate measurement in batch tests, kinetic parameters determination and modeling application in a continuous digester. The procedure was evaluated with three experimental conditions: raw sludge as substrate incubated at 35 °C and 55 °C and thermal p...

Laboratory and pilot-scale experiments were carried out in order to evaluate the influence of thermal pre-treatment time on waste-activated sludge properties and anaerobic biodegradability. Six experimental conditions were analyzed from 0 to 30 min of hydrolysis time. Solubilization of macromolecular compounds, changes in the main sludge properties...

Sewage sludge is usually degraded by means of anaerobic digestion in order to produce biogas and stabilized sludge. Several reactor configurations have been implemented or studied intending to optimize the process; however, there is a lack of reliable mathematical models that can be used for this purpose. This paper deals with that issue by using a...

The effect of thermal and sonication pre-treatment on the anaerobic degradation of sewage sludge was evaluated through the calculation of performance parameters by using three simplified mathematical models and one kinetic model. The Modified Gompertz equation, the Logistic function, Reaction Curve and First-Order models were all used with experime...

The use of ultrasound as pre-treatment to improve anaerobic digestion of secondary sludge has been established as a promising technology. There are great differences between lab scale and full-scale devices, regarding the relationship between the disintegration achieved and the energy supplied. Based on economic aspects, most of the full-scale plan...

In this work, an anaerobic sequencing batch reactor (ASBR) was operated for 8 months to treat low strength sewage with high suspended organic matter content. Three phases of operation with increasing organic loading rates (OLR) were performed: 0.4 kg COD/m 3 x d (phase I), 0 .8 kg COD/m 3 x d (phase II) and 1.2 kg COD/m 3 x d (phase III). Adequate...

In this work, an anaerobic sequencing batch reactor (ASBR) was operated for 8 months to treat low strength sewage with high suspended organic matter content. Three phases of operation with increasing organic loading rates (OLR) were performed: 0.4 kg COD/m3 x d (phase I), 0 .8 kg COD/m3 x d (phase II) and 1.2 kg COD/m3 x d (phase III). Adequate sta...

The effect of temperature on the kinetic parameters involved in the main reactions of the anaerobic digestion process was studied. Batch tests with starch, glucose and acetic acid as substrates for hydrolysis, acidogenesis and methanogenesis, respectively, were performed in a temperature range between 15 and 45 degrees C. First order kinetics was a...

The anaerobic treatment of phenolic wastewater has demonstrated to be a suitable biological system, for that reason, a large number of systems have been implemented in a lab/pilot scale, several industrial plants have also been developed. Despite of this, there is a lack of modeling applications within these systems. In order to enhance the anaerob...

The goal of this study was to assess the effect of different modes of operation and configurations of Anaerobic Sequencing Batch Reactors (ASBRs) treating phenolic wastewater. Several lab-scale reactors were used in the mesophilic range. The reactors were fed with synthetic wastewater with a COD of 5 g/L using phenol as a carbon source (variable co...

The results of a two-phase anaerobic system using anaerobic sequencing batch reactors (ASBRs), treating low-strength wastewater (COD ∼ 500 mg/L) with a high fraction of particulate organic matter (70%, COD basis), are presented. Two reactors in series were used; the first one was hydrolytic–acidogenic, while the second one was methanogenic. This co...