Sergio Revah | Universidad Autónoma Metropolitana-Cuajimalpa (original) (raw)

Papers by Sergio Revah

Enzyme and microbial technology, 2007

Higher solubility at alkaline conditions is very significant for an efficient treatment process o... more Higher solubility at alkaline conditions is very significant for an efficient treatment process of gaseous H 2 S (g) by reducing the gas-liquid transfer limitations. Nevertheless, the alkaline biodegradation process of H 2 S can be limited when sulfide concentrations are inhibitory. At alkaline conditions (pH > 9), the abiotic chemical sulfide oxidation can attain relatively high rates. A series of abiotic and biotic kinetic experiments of oxygen consumption were performed at pH 10. For the biological oxidation, an alkaliphilic sulfide oxidizing consortium (ASBC) isolated from a soda lake was used. The intermediates from the chemical sulfide oxidation in alkaline and aerobic conditions did not inhibit the activity of ASBC at six-fold concentration of that where H 2 S inhibition was detected (1.19 mM). Stoichiometries and kinetic expressions for the chemical sulfide oxidation to pentasulfide (S 5 2−) and its further oxidation to thiosulfate (S 2 O 3 2−) are proposed and validated with experimental data. The faster oxic chemical sulfide oxidation under alkaline conditions could be advantageous for the biological oxidation to sulfate by reducing the concentration of the inhibiting sulfide. These results suggest that the chemical and the biological oxidation processes can be segregated, allowing higher sulfide loading rates.

Journal of Hazardous Materials, Jun 1, 2011

The biodegradation of methane, a greenhouse gas, and the accumulation of poly-␤-hydroxybutyrate (... more The biodegradation of methane, a greenhouse gas, and the accumulation of poly-␤-hydroxybutyrate (PHB) were studied using a methanotrophic consortium and an isolated strain thereof. The specific rates for methane consumption were 100 and 17 mg CH 4 g −1 x h −1 for the isolate and the consortium, respectively. Also the effect of including 10% (v v −1) of silicone oil in a two-phase partitioning bioreactor (TPPB) was assayed for the elimination of 1% methane in air stream. TPPB allowed a 33-45% increase of methane elimination under growing conditions. Nitrogen limitation was assayed in bioreactors to promote PHB production. Under this condition, the specific methane degradation rate remained unchanged for the consortium and decreased to 36 mg CH 4 g −1 x h −1 for the isolated strain. The accumulated PHB in the reactor was 34% and 38% (w w −1) for the consortium and the isolate, respectively. The highest productivity was obtained in the TPPB and was 1.61 mg PHB g −1 x h −1. The CZ-2 isolate was identified as Methylobacterium organophilum, this is the first study that reports this species as being able to grow on methane and accumulate up to 57% (w w −1) of PHB under nitrogen limitation in microcosm experiments.

Water Science and Technology, Oct 1, 2012

The aim of this paper was to evaluate the performance of biotrickling filters (BTFs) for treating... more The aim of this paper was to evaluate the performance of biotrickling filters (BTFs) for treating low concentrations of dimethyl disulfide (DMDS), using different bacterial consortia adapted to consume reduced sulfur compounds under alkaline (pH ≈ 10) or neutral (pH ≈ 7) conditions. Solubility experiments indicated that the partition of DMDS in neutral and alkaline mineral media was similar to the value with distilled water. Respirometric assays showed that oxygen consumption was around ten times faster in the neutrophilic as compared with the alkaliphilic consortium. Batch experiments demonstrated that sulfate was the main product of the DMDS degradation. Two laboratory-scale BTFs were implemented for the continuous treatment of DMDS in both neutral and alkaline conditions. Elimination capacities of up to 17 and 24 g DMDS m À3 h À1 were achieved for the alkaliphilic and neutrophilic reactors with 100% removal efficiency after an initial adaptation and biomass build-up.

Journal of Chemical Technology & Biotechnology, Feb 1, 2009

BACKGROUND: Mathematical models describing the physical, chemical and biological processes that t... more BACKGROUND: Mathematical models describing the physical, chemical and biological processes that take place in bioremediation are necessary to design and optimise these technologies. This work models the effect of toluene as a gaseous cosubstrate in the degradation of phenanthrene in soil, considering the consumption of pollutants, the production of intermediate degradation compounds and mineralisation. The proposed model consists of a set of sequential reactions to convert phenanthrene to carbon dioxide and biomass with the production and consumption of phthalic acid, which is the main intermediate metabolite. RESULTS: The considerations of the model were supported by experimental data, and it was evaluated for phenanthrene degradation kinetics with previously reported packed column reactor experiments. The mathematical model proposed describes the mineralisation of phenanthrene accurately and also predicts a reduced accumulation of phthalic acid when toluene is added as cosubstrate. The model fits the experimental data of phenanthrene degradation when toluene is added but slightly overestimates the residual phenanthrene in the control case. CONCLUSION: The simplified model of sequential reactions represents the column experiments (P < 0.05) for phenanthrene degradation and mineralisation with toluene as cosubstrate, considerating the production and consumption of phthalic acid.

Journal of Hazardous Materials, 2017

h i g h l i g h t s • Biostimulation by cosubstrates addition enhanced the DDX degradation in soi... more h i g h l i g h t s • Biostimulation by cosubstrates addition enhanced the DDX degradation in soil. • Glycerol induced anoxic sulfidogenic process mediated by sulfate-reducing bacteria. • Toluene induced biotic degradation of DDX mediated by oxygenases as initial step. • Microbial community changes were observed after aerobic and anoxic treatments.

International Journal of Hydrogen Energy, Aug 1, 2015

ABSTRACT

Journal of Environmental Engineering, Mar 1, 2005

... The reactor had two sections, each packed with ceramic Raschig rings differing in water reten... more ... The reactor had two sections, each packed with ceramic Raschig rings differing in water retention capacity and internal porosity. ... The reactor had two sections, each packed with ceramic Raschigrings differing in water retention capacity and internal porosity. ...

Applied Microbiology and Biotechnology, Oct 8, 2016

The operation and performance of a biotrickling filter for methanol (MeOH) and hydrogen sulfide (... more The operation and performance of a biotrickling filter for methanol (MeOH) and hydrogen sulfide (H 2 S) removal at acid pH was studied. Excess biomass in the filter bed, causing performance loss and high pressure drop, was controlled by intermittent addition, of ozone (O 3) and hydrogen peroxide (H 2 O 2). The results showed that after adaptation to acid pH, the maximum elimination capacity (EC) reached for MeOH was 565 g m −3 h −1 (97 % RE). High MeOH loads resulted in increased biomass concentration within the support, triggering reductions in the removal efficiency (RE) for both compounds close to 50 %, and high pressure drop. At this stage, an inlet load of 150.2 ± 16.7 g m −3 h −1 of O 3 was fed by 38 days favoring biomass detachment, and EC recovery and lower pressure dropped with a maximum elimination capacity of 587 g m −3 h −1 (81 % RE) and 15.8 g m −3 h −1 (97 % RE) for MeOH and H 2 S, respectively. After O 3 addition, a rapid increase in biomass content and higher fluctuations in pressure drop were observed reducing the system performance. A second treatment with oxidants was implemented feeding a O 3 load of 4.8 ± 0.1 g m −3 h −1 for 7 days, followed by H 2 O 2 addition for 23 days, registering 607.5 g biomass L −1 packing before and 367.5 g biomass L −1 packing after the oxidant addition. PCR-DGGE analysis of different operating stages showed a clear change in the bacterial populations when O 3 was present while the fungal population was less affected. Keywords pH. Pressure drop. Ozone. H 2 O 2. Biotrickling filter. Biomass

Journal of Hazardous Materials, Apr 17, 2006

The stimulation of the microbial population by a more bioavailable supplementary carbon source an... more The stimulation of the microbial population by a more bioavailable supplementary carbon source and by a surfactant pretreatment was studied in petroleum hydrocarbon-polluted soils bioremediation. Two types of soils were used, Soil A which had been recently polluted and the aged Soil B. They contained 52.4 and 50.4 g of total petroleum hydrocarbons per kg of dry soil, respectively. The effect of passing a continuous small stream of air containing a low concentration of gaseous toluene through packed 0.5 l (∅ = 5.5 cm) columns was studied. For Soil A, after 62 days the THPs degradation was 28% higher in the toluene treated columns than in controls. In aged Soil B the effect of toluene was not significant, probably due to bioavailability limitations. With Soil B, the combined effect of toluene as cosubstrate and a surfactant pretreatment was studied and the hydrocarbons degradation was 29% higher in the toluene-amended columns than in the controls. Toluene removal was higher than 99% in all cases. Surfactant addition increased hydrocarbon degradation when toluene was also added suggesting that the biological reaction was the limiting process. The study shows the possibilities of using gaseous substrates, such as toluene, for the in situ or ex situ treatment of petroleum hydrocarbon-polluted soil in processes limited by the biological reaction. The main advantage of the treatment is that the compound can be easily and directly delivered to the polluted soil through the venting system.

The measurement of pressure drop (DP) across an aerated fermentation bed was used to follow Asper... more The measurement of pressure drop (DP) across an aerated fermentation bed was used to follow Aspergillus niger growth on Amberlite IRA-900, a synthetic resin, imbibed with a solution containing high concentrations of sucrose (Si=100, 200, 300 and 400 g l−1). The DP allowed monitoring the germination, vegetative growth, limitation and sporulation for the four concentrations studied A relation between the biomass and the relative intrinsic permeability established that the continuity of the gas phase was not broken and a regular mesh-like growth occurred Relative intrinsic permeability as low as 0.0125 occurred at biomass concentrations of 103 mg dry biomass (g dry support)−1 obtained with Si=400 g l−1. Under these conditions the mold occupies 34% of the free space. The DP measurement was used to follow growth on cane bagasse and wheat bran, in both cases, the four growth phases (germination, vegetative, substrate limitation, and sporulation) were monitored.

The Chemical Engineering Journal and The Biochemical Engineering Journal, Dec 1, 1995

A mathematical model for the growth of filamentous fungi, Aspergtllus nrger, on a packed-bed met?... more A mathematical model for the growth of filamentous fungi, Aspergtllus nrger, on a packed-bed met? support 1s proposed and venfied The model deals with vanables such as biomass, sugar, water, oxygen, carbon dloxlde and bulk temperature The model IS denved from kmetics and mass and energy balances and it describes the superficial colonization of A nlger on an mert support wltbm an elementary representative volume previously impregnated with culture medmm, the net water consumption, the evolution of gases and metabolic heat The model provides good predlctlve values for Qfferent culture media when substrate mhlbltlon (K, = 300 kg substrate rnw3 packed) IS consldered Increasing values of maintenance coefficient ((1 O-5 5) X 10e6 kg substrate (kg wet biomass)-' s-') and decreasing values of biomass yields are obtained when the mltlal sugar concentration increases Water and void spaces, at the end of the process, remained available up to 80 and 94% respectively of the mltlal condltlons The rate-lnmtmg step m mycehal growth seems to be sugar depletion which IS independent of mltlal sugar concentration The model could be a helpful tool m developing smtable bloreactor operating strategies for any other smular type of culture

Environmental Science & Technology, Jan 15, 2003

Chemical Engineering Journal, Feb 1, 2018

The limited gas-liquid mass transfer represents the main challenge in the operation of costeffect... more The limited gas-liquid mass transfer represents the main challenge in the operation of costeffective bioreactors devoted to the treatment of poorly soluble gas pollutants such as methane (CH 4). This study evaluates the influence of internal gas-recycling strategies on the enhancement of CH 4 abatement in a bubble column bioreactor inoculated with the methanotroph Methylocystis hirsuta. Maximum CH 4 removal efficiencies of 72.9 ± 0.5 % (corresponding to elimination capacities of 35.2 ± 0.4 g m-3 h-1) were recorded under process operation at an empty bed residence time of 30 min and 0.50 m 3 gas m-3 reactor min-1 of internal gas-recycling rate. The accumulation of poly-3-hydroxybutyrate (PHB) in M. hirsuta was evaluated batchwise under limitations of potassium, manganese, nitrogen, and nitrogen with excess of iron. Nitrogen starvation resulted in the highest PHB content (28 ± 1 %). Likewise, the implementation of sequential N starvation cycles in a continuous bubble column reactor operated at a gas residence time of 30 min and an internal gasrecycling rate of 0.50 m 3 gas m-3 reactor min-1 supported a PHB content of up to 34.6 ± 2.5 %, with a volumetric PHB productivity of 1.4 ± 0.4 kg m-3 d-1 and elimination capacities of 16.2 ± 9.5 g m-3 h-1 .

Fems Microbiology Letters, Dec 6, 2017

Microalgae are among the most productive biological systems for converting sunlight into chemical... more Microalgae are among the most productive biological systems for converting sunlight into chemical energy, which is used to capture and transform inorganic carbon into biomass. The efficiency of carbon dioxide capture depends on the cultivation system configuration (photobioreactors or open systems) and can vary according to the state of the algal physiology, the chemical composition of the nutrient medium, and environmental factors such as irradiance, temperature and pH. This mini-review is focused on some of the most important environmental factors determining photosynthetic activity, carbon dioxide biofixation, cell growth rate and biomass productivity by microalgae. These include carbon dioxide and O 2 concentrations, light intensity, cultivation temperature and nutrients. Finally, a review of the operation of microalgal cultivation systems outdoors is presented as an example of the impact of environmental conditions on biomass productivity and carbon dioxide fixation.

Biotechnology and Bioengineering, May 20, 2000

The effects of successive mixing (homogenization) of packing material (peat), with or without wat... more The effects of successive mixing (homogenization) of packing material (peat), with or without water addition, on the removal of toluene vapors in a biofilter were studied. Over a period of 50 days, an increase in the Elimination Capacity (EC) of approximately 240% was obtained by successive mixing and water additions. After each mixing, a high EC of toluene was maintained only for a short period of 3-4 days. After this time, decreased biofilter performance was observed, probably associated with the development of dried and/or clogged zones. In the long-term experiments, an attenuation of the EC recovery was observed after successive mixing. In this case, an increase of 110% over 4 months of experiment was obtained. The global reduction of EC over time could be explained by the colonization of the biofilter by filamentous fungi which was facilitated by the mixing of the packing material. The most frequently observed fungi were identified as Scedosporium sp. and Cladosporium sp.

Environmental Technology, Oct 1, 2004

The elemental sulfur formation by the partial oxidation of thiosulfate by both a sulfoxidizing co... more The elemental sulfur formation by the partial oxidation of thiosulfate by both a sulfoxidizing consortium and by Thiobacillus thioparus ATCC 23645 was studied under aerobic conditions in chemostat. Steady state was attained with essentially total conversion to sulfate when the dissolved oxygen concentration was 5 mgO2 l(-1) and below a dilution rate (D) of 3.0 d(-1)for the consortium and 0.9 d(-1) for T thioparus. The consortium formed elemental sulfur in steady state under oxygen limitation. Fifty percent of the theoretical elemental sulfur yield was obtained with a dissolved oxygen concentration of 0.2 mgO2 l(-1). Growth of T thioparus was negatively affected with a concentration below 1.9 mgO2 l(-1). Consortium yield from batch cultures was 2.1 g(-1) (protein) mol(-1) (thiosulfate), which was comparable with the values obtained in the chemostat at dilution rates of 0.4 d(-1) and 1.2 d(-1). The consortium showed a maximum degradation rate of 0.105 g(thiosulfate) g(-1) (protein) min(-1) and a saturation rate for S2O3(2-) of 1.9 mM.

Canadian Journal of Civil Engineering, Dec 1, 2009

Mathematical modeling in the biofiltration of volatile organic compounds is a valuable tool for p... more Mathematical modeling in the biofiltration of volatile organic compounds is a valuable tool for performance prediction and in scaling up. Majority of the published models include parameters obtained from fitting experimental data, thus masking their real influence as they are lumped generally. The present work aims to evaluate experimentally some of the most relevant parameters including kinetic constant, partition coefficient in the biofilm, biofilm thickness, superficial area, and effective diffusivity. For the fungal biofilm, all the parameters mentioned above were obtained experimentally; and for the bacterial biofilm, the biofilm thickness and some intrinsic parameters used to obtain the first-order kinetic constant were taken from the literature. These parameters were then incorporated in a mathematical model to describe the steady-state degradation of hexane in bacterial and fungal biofilters operating under continuous mode. Experimentally, the dimensionless partition coefficients (mG) indicated that hexane was 4 and 35 times more soluble in the bacterial (mG = 9.14) and fungal (mG = 0.88) biofilters, respectively, than in water (mG = 30.4). Comparison of model estimates with experimental concentration profiles of the pollutant along the height of the biofilters proves that the first-order limited by reaction model was appropriate to interpret the experimental results with a small error of ∼1%.

Biotechnology and Bioengineering, Nov 20, 1998

Biotechnological techniques, including biofilters and biotrickling filters are increasingly used ... more Biotechnological techniques, including biofilters and biotrickling filters are increasingly used to treat air polluted with VOCs (Volatile Organic Compounds). In this work, the start-up, the effect of the gaseous ammonia addition on the toluene removal rate, and the problems of the heat accumulation on the performance of a laboratory scale biofilter were studied. The packing material was sterilized peat enriched with a mineral medium and inoculated with an adapted consortium (two yeast and five bacteria). Start-up showed a short adaptation period and an increased toluene elimination capacity (EC) up to a maximum of 190 g/m3/h. This was related to increased CO2 outlet concentration and temperature gradients between the packed bed and the inlet (Tm-Tin). These events were associated with the growth of the microbial population. The biofilter EC decreased thereafter, to attain a steady state of 8 g/m3/h. At this point, gaseous ammonia was added. EC increased up to 80 g/m3/h, with simultaneous increases on the CO2 concentration and (Tm-Tin). Two weeks after the ammonia addition, the new steady state was 30 g/m3/h. In a second ammonia addition, the maximum EC attained was 40 g/m3/h, and the biofilter was in steady state at 25 g/m3/h. Carbon, heat, and water balances were made through 88 d of biofilter operation. Emitted CO2 was about 44.5% of the theoretical value relative to the total toluene oxidation, but accumulated carbon was found as biomass, easily biodegradable material, and carbonates. Heat and water balances showed strong variations depending on EC. For 88 d the total metabolic heat was -181.2 x 10(3) Kcal/m3, and water evaporation was found to be 56.5 kg/m3. Evidence of nitrogen limitation, drying, and heterogeneities were found in this study.

Biotechnology and Bioengineering, 2005

The removal of hydrophobic pollutants in biofilters is often limited by gas liquid mass transfer ... more The removal of hydrophobic pollutants in biofilters is often limited by gas liquid mass transfer to the biotic aqueous phase where biodegradation occurs. It has been proposed that the use of fungi may improve their removal efficiency. To confirm this, the uptake of hexane vapors was investigated in 2.6-L perlite-packed biofilters, inoculated with a mixed culture containing bacteria and fungi, which were operated under neutral or acid conditions. For a hexane inlet load of around 140 g.m À3 .h À1 , elimination capacities (EC) of 60 and 100 g.m À3 .h À1 were respectively reached with the neutral and acid systems. Increasing the inlet hexane load showed that the maximum EC obtained in the acid biofilter (150 g.m À3 .h À1) was twice greater than in the neutral filter. The addition of bacterial inhibitors had no significant effect on EC in the acid system. The biomass in the acid biofilter was 187 mg.g À1 dry perlite without an important pressure drop (26.5 mm of water.m À1 reactor). The greater efficiency obtained with the acid biofilter can be related to the hydrophobic aerial hyphae which are in direct contact with the gas and can absorb the hydrophobic compounds faster than the flat bacterial biofilms. Two fungi were isolated from the acid biofilter and were identified as Cladosporium and Fusarium spp. Hexane EC of 40 g.m À3 .h À1 for Cladosporium sp. and 50 g.m À3 .h À1 for Fusarium sp. were obtained in short time experiments in small biofilters (0.230 L). A biomass content around 30 mg.g À1 dry perlite showed the potential for hexane biofiltration of the strains.

Journal Of Environmental Science And Health, Part A, Jun 1, 2012

This article may be used for research, teaching, and private study purposes. Any substantial or s... more This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.