Iván Moreno-Andrade

Microbial communities from 20 different hydrogen-producing reactors studied by 454 pyrosequencing

To provide new insight into the dark fermentation process, a multi-lateral study was performed to study the microbiology of 20 different lab-scale bioreactors operated in four different countries (Brazil, Chile, Mexico, and Uruguay). Samples (29) were collected from bioreactors with different configurations, operation conditions, and performances. The microbial communities were analyzed using 16S rRNA genes 454 pyrosequencing. The results showed notably uneven communities with a high predominance of a particular genus. The phylum Firmicutes predominated in most of the samples, but the phyla Thermotogae or Proteobacteria dominated in a few samples. Genera from three physiological groups were detected: high-yield hydrogen producers (Clostridium, Kosmotoga, Enterobacter), fermenters with low-hydrogen yield (mostly from Veillonelaceae), and competitors (Lactobacillus). Inocula, reactor configurations, and substrates influence the microbial communities. This is the first joint effort that evaluates hydrogen-producing reactors and operational conditions from different countries and contributes to understand the dark fermentation process.

Biohydrogen production from industrial wastewaters

The feasibility of producing hydrogen from various industrial wastes, such as vinasses (sugar and tequila industries), and raw and physicochemical-treated wastewater from the plastic industry and toilet aircraft wastewater, was evaluated. The results showed that the tequila vinasses presented the maximum hydrogen generation potential, followed by the raw plastic industry wastewater, aircraft wastewater, and physicochemical-treated wastewater from the plastic industry and sugar vinasses, respectively. The hydrogen production from the aircraft wastewater was increased by the adaptation of the microorganisms in the anaerobic sequencing batch reactor.

Microrespirometric determination of the effectiveness factor and biodegradation kinetics of aerobic granules degrading 4-chlorophenol as the sole carbon source

In this study, a microrespirometric method was used, i.e., pulse respirometry in microreactors, to characterize mass transfer and biodegradation kinetics in aerobic granules. The experimental model was an aerobic granular sludge in a sequencing batch reactor (SBR) degrading synthetic wastewater containing 4-chlorophenol as the sole carbon source. After 15 days of acclimation, the SBR process degraded 4-chlorophenol at a removal rate of up to 0.9kg CODm(-3)d(-1), and the degradation kinetics were well described by the Haldane model. The microrespirometric method consisted of injecting pulses of 4-chlorophenol into the 24 wells of a microreactor system containing the SBR samples. From the respirograms obtained, the following five kinetic parameters were successfully determined during reactor operation: (i) Maximum specific oxygen uptake rate, (ii) substrate affinity constant, (iii) substrate inhibition constant, (iv) maximum specific growth rate, and (v) cell growth yield. Microrespirometry tests using granules and disaggregated granules allowed for the determination of apparent and intrinsic parameters, which in turn enabled the determination of the effectiveness factor of the granular sludge. It was concluded that this new high-throughput method has the potential to elucidate the complex biological and physicochemical processes of aerobic granular biosystems.

Experiments for modelling the biodegradation of wastewater in sequencing batch reactors

Three types of wastewater were considered: typical municipal wastewater and the effluent of a dairy industry, both polluted with organic carbon and nitrogen, and wastewater typical of a chemical industry, containing toxic or recalcitrant compounds (4-chlorophenol). Sequencing batch reactors (SBRs) were considered. Process experiments were performed to provide experimental data for parameter identification of the dynamical models of the SBRs. The processes were instrumented with sensors to measure O2, NH3, T, pH, OUR, and other off line measurements (e.g.: NO2 − and NO3 −, COD, phenol concentration, microbiological counts and activities) in order to study more accurately the behaviour of the biomasses. However, the general idea is to design a system with a minimal number of sensors.

Membrane biofouling mechanism in an aerobic granular reactor degrading 4-chlorophenol

The membrane fouling of an aerobic granular reactor coupled with a submerged membrane in a sequencing batch reactor (SBR) was evaluated. The fouling analysis was performed by applying microscopy techniques to determine the morphology and structure of the fouling layer on a polyvinylidene fluoride membrane. It was found that the main cause of fouling was the polysaccharide adsorption on the membrane surface, followed by the growth of microorganisms to form a biofilm.

Biodegradation of 4-methylaniline in a sequencing batch reactor

The biodegradation of the aromatic amine 4-methylaniline (4MA) using an aerobic sequencing batch reactor was evaluated. The specific degradation rate showed an exponential increase during the acclimation of the microorganisms reaching a maximal value of 34 mg 4MA/VSS/h. After the acclimation, the process showed a stable operation. A high similarity index was observed, indicating a low variation in the population diversity. During this period, the physicochemical parameters demonstrated a stable operation of the reactor.

Acclimatization model of an aerobic bioreactor for the treatment of toxic wastewater

This work proposes a mathematical model for the acclimatization process of a bioreactor treating toxic wastewater. Experimental data was used to identify the changing kinetic parameters of the model as acclimatization progresses. It was found that only one key parameter, the specific biomass growth rate function, changed during the acclimatization process. Therefore, an acclimatization model was proposed to explain the changes of this parameter.

ACCLIMATION MODEL OF AN AEROBIC BIOREACTOR FOR THE TREATMENT OF TOXIC WASTEWATER

Abstract The optimal automation of the acclimation process of a biorreactor, for treating toxicant wastewaters, may be possible if a sound mathematical model is developed in order to cope with the instrumentation limitations that exist nowadays. This work presents a first step in creating such a model. Experimental data was used to identify the changing kinetic parameters of the model as acclimation progresses. It was found that only one key parameter changed during the acclimation process. Then an acclimation model, i.e. a model of such a parameter progression in time, as a function of the total substrate treated, is proposed.

CONTROL STRATEGIES FOR TREATING TOXIC WASTEWATER USING BIOREACTORS

Abstract Different control strategies are compared, in regard to issues associated to biomass inhibition when treating toxic wastewater, to operate sequencing batch bioreactors. In particular the problem of time optimal operation and also the problem of handling sudden unknown toxicant peak concentrations are addressed. Because of the application characteristics it is not feasible, nowadays, to measure all of the important variables, thus little information is available online for controlling the process. One of the alternatives presented, the Event-Driven Time Optimal Control, offers to solve all problems, using only the practically available variables, even if uncertainties are present in the mathematical model of the bioreactor.

Greywater treatment in an aerobic SBR: sludge structure and kinetics

In order to have an efficient operation, sequencing batch reactors (SBR) must support granular biomass with high conversion rates, settling properties, and be able to deal with the inherent variability of the composition of real wastewaters. In this study, the effect of the influent composition and the specific organic loading rate (Bx) on the granulation process was evaluated in two SBRs, fed with greywater (GW) and a synthetic medium (SM). The feeding with SM led to the formation of compact granular biomass, with a sludge volume index (SVI) of 22.4 mL g-1, and a zone settling velocity (ZSV) of 13.1 m h-1. In contrast, feeding with GW induced the formation of filamentous granules, with lower settling properties (SVI = 165 mL g-1 and ZSV = 10 m h-1), when the system was operated at high Bx (4.4 kg COD kg VSS-1 d-1). However, the reduction of the average Bx to 2 kg COD kg VSS-1 d-1 induced an improvement in the morphology and properties of the granules (SVI = 98 mL g-1 and ZSV = 13 m h-1). Furthermore, the kinetic analysis indicated that granules cultivated with SM were formed by fast growing microorganisms with a high cell yield, whereas those cultivated in GW presented a much lower cell yield.