Integrated adsorption and biological removal of the emerging contaminants ibuprofen, naproxen, atrazine, diazinon, and carbaryl in a horizontal tubular bioreactor.

Groundwater and surface water bodies may have contaminants from urban, industrial, or agricultural wastewater, including emerging contaminants (ECs) or micropollutants (MPs). Frequently, they are not efficiently removed by microbial action due to their minimal concentration in water and the low microbiota affinity for complex compounds. This work developed a process allowing the adsorption of contaminants and their simultaneous biodegradation using horizontal tubular fixed-bed biofilm reactors (HTR). Each HTR has two zones: an equalizer-aerator of the incoming liquid flow and a fixed bed zone. This zone was packed with a mixed support material consisting of granular bio-activated carbon (Bio-GAC) and porous material that increases the bed permeability, thus decreasing the pressure drop. Five microbial communities were acclimated and immobilized in granular activated carbon (GAC) to obtain different specialized Bio-GAC particles able to remove the micropollutants ibuprofen, naproxen, atrazine, carbaryl, and diazinon. The Bio-GAC particles were transferred to HTRs continuously run in microaerophilia at several MPs loading rates. Under these conditions, the removal efficiencies of MPs, except atrazine and carbaryl, were around 100.

Xylose-glucose co-fermentation to ethanol by Escherichia coli strain MS04 using single- and two-stage continuous cultures under micro-aerated conditions.

BACKGROUND: Simultaneous co-fermentation of mixed sugars is an important feature to consider in the production of ethanol from lignocellulosic biomass hydrolysates because it enhances the overall ethanol yield and volumetric productivity during fermentation. Continuous cultures can be used during ethanol production from lignocellulosic hydrolysates to prevent catabolite repression by glucose on other sugars, such as xylose, and thus promote the simultaneous and total consumption of sugars and reduce fermentation time. The use of single- and two-stage continuous cultures under micro-aerated conditions for simultaneous consumption of xylose and glucose, and fermentation to ethanol by ethanologenic Escherichia coli strain MS04 was studied. Mineral medium supplemented with glucose, xylose and sodium acetate, was used to compare continuous cultures performance to batch cultures. RESULTS: Single-stage continuous cultures under micro-aerated conditions allowed the total co-consumption of a mixture of glucose and xylose (7.5 and 42.5 g/L, respectively) in mineral medium, with steady state ethanol production of 18 g/L, and a volumetric ethanol productivity of 0.9 g/L h, when low dilution rates (0.05 h-1) were used. However, the volumetric productivity was lower than the batch process under similar conditions (1.3 g/L h). Conversely, micro-aerated two-stage continuous culture enhanced the volumetric productivity up to 1.6 g/L h at a dilution rate of 0.15 h-1, with a total consumption of sugars and a slight reduction of the overall ethanol yield. CONCLUSIONS: The total and simultaneous consumption of glucose and xylose by the ethanologenic E. coli strain MS04 was accomplished by using two-stage continuous culture under micro-aerated conditions with an increase in the volumetric ethanol productivity of 23% and 78% when compared to batch and single-stage continuous cultures, respectively. Multi-stage continuous cultivation can be used to promote the simultaneous consumption of all sugars contained in biomass hydrolysates, and thus increase the volumetric ethanol productivity of the fermentation process.

Simulation and experimental validation of a gradient feeding system for fast assessment of the kinetic behavior of a microbial consortium in a tubular biofilm reactor.

This study deals with the mathematical simulation and experimental validation of a gradient system for the gradual change of the imidacloprid loading rate to a tubular biofilm reactor (TBR). The strategy was used for fast studies of the kinetic and stoichiometric impact caused by the increase in the pesticide loading rate in a TBR, running in plug flow regime. Seemingly, this strategy has never been used for biokinetic and stoichiometric studies in biofilm reactors. For this purpose, a mathematical model describing the substrate transient behavior Sg(t) in a concentration gradient generator system using variable volume tanks is proposed. A second model, representing the temporary variation in the loading rate of imidacloprid to an aerated equalizer tank preceding the packed zone of the TBR, is also presented. Both models were experimentally confirmed. After the treatment of the experimental data, the kinetic and stoichiometric changes occurring in the TBR, caused by the gradual increase in the imidacloprid loading rate, were readily evaluated. Although the structure of the microbial community, at the phylum level, showed similar behavior along the tubular reactor, the stress produced by the gradual increase in imidacloprid concentration had functional consequences on the mixed microbial populations which were reflected on the stoichiometric and kinetic parameters. After increasing more than five times the imidacloprid loading rate to the TBR, the imidacloprid removal efficiency decayed about 40%, and the microbial-specific removal rate of the insecticide showed a decrease of about 30%.

Kinetics of carbendazim degradation in a horizontal tubular biofilm reactor.

The fungicide carbendazim is an ecotoxic agent affecting aquatic biota. Due to its suspected hormone-disrupting effects, it is considered a "priority hazard substance" by the Water Framework Directive of the European Commission, and its degradation is of major concern. In this work, a horizontal tubular biofilm reactor (HTBR) operating in plug-flow regime was used to study the kinetics of carbendazim removal by an acclimated microbial consortium. The reactor was operated in steady state continuous culture at eight different carbendazim loading rates. The concentrations of the fungicide were determined at several distances of the HTBR. At the loading rates tested, the highest instantaneous removal rates were observed in the first section of the tubular biofilm reactor. No evidence of inhibition of the catabolic activity of the microbial community was found. Strains of the genera Flectobacillus, Klebsiella, Stenotrophomonas, and Flavobacterium were identified in the biofilm; the last three degrade carbendazim in axenic culture.

Effect of herbicide adjuvants on the biodegradation rate of the methylthiotriazine herbicide prometryn.

A microbial community, selected by its ability to degrade triazinic herbicides was acclimatized by successive transfers in batch cultures. Initially, its ability to degrade prometryn, was evaluated using free cells or cells attached to fragments of a porous support. As carbon, nitrogen and sulfur sources, prometryn, (98.8 % purity), or Gesagard, a herbicide formulation containing 44.5 % prometryn and 65.5 % of adjuvants, were used. In batch cultures, a considerable delay in the degradation of prometryn, presumptively caused by the elevated concentration of inhibitory adjuvants, occurred. When pure prometryn was used, volumetric removal rates remarkably higher than those obtained with the herbicide formulation were estimated by fitting the raw experimental data to sigmoidal decay models, and differentiating them. When the microbial consortium was immobilized in a continuously operated biofilm reactor, the negative effect of adjuvants on the rate and removal efficiency of prometryn could not be detected. Using the herbicide formulation, the consortium showed volumetric removal rates greater than 20 g m(-3) h(-1), with prometryn removal efficiencies of 100 %. The predominant bacterial strains isolated from the microbial consortium were Microbacterium sp., Enterobacter sp., Acinetobacter sp., and Flavobacterium sp. Finally, by comparison of the prometryn removal rates with others reported in the literature, it can be concluded that the use of microbial consortia immobilized in a biofilm reactor operated in continuous regime offer better results than batch cultures of pure microbial strains.

Biohydrogen, biomethane and bioelectricity as crucial components of biorefinery of organic wastes: a review.

Biohydrogen is a sustainable form of energy as it can be produced from organic waste through fermentation processes involving dark fermentation and photofermentation. Very often biohydrogen is included as a part of biorefinery approaches, which reclaim organic wastes that are abundant sources of renewable and low cost substrate that can be efficiently fermented by microorganisms. The aim of this work was to critically assess selected bioenergy alternatives from organic solid waste, such as biohydrogen and bioelectricity, to evaluate their relative advantages and disadvantages in the context of biorefineries, and finally to indicate the trends for future research and development. Biorefining is the sustainable processing of biomass into a spectrum of marketable products, which means: energy, materials, chemicals, food and feed. Dark fermentation of organic wastes could be the beach-head of complete biorefineries that generate biohydrogen as a first step and could significantly influence the future of solid waste management. Series systems show a better efficiency than one-stage process regarding substrate conversion to hydrogen and bioenergy. The dark fermentation also produces fermented by-products (fatty acids and solvents), so there is an opportunity for further combining with other processes that yield more bioenergy. Photoheterotrophic fermentation is one of them: photosynthetic heterotrophs, such as non-sulfur purple bacteria, can thrive on the simple organic substances produced in dark fermentation and light, to give more H2. Effluents from photoheterotrophic fermentation and digestates can be processed in microbial fuel cells for bioelectricity production and methanogenic digestion for methane generation, thus integrating a diverse block of bioenergies. Several digestates from bioenergies could be used for bioproducts generation, such as cellulolytic enzymes and saccharification processes, leading to ethanol fermentation (another bioenergy), thus completing the inverse cascade. Finally, biohydrogen, biomethane and bioelectricity could contribute to significant improvements for solid organic waste management in agricultural regions, as well as in urban areas.

Dynamic and structural response of a multispecies biofilm to environmental perturbations induced by the continuous increase of benzimidazole fungicides in a permeable reactive biobarrier.

Purpose: This work explores the dynamics of spatiotemporal changes in the taxonomic structure of biofilms and the degradation kinetics of three imidazole group compounds: carbendazim (CBZ), methyl thiophanate (MT), and benomyl (BN) by a multispecies microbial community attached to a fixed bed horizontal tubular reactor (HTR). This bioreactor mimics a permeable reactive biobarrier, which helps prevent the contamination of water bodies by pesticides in agricultural wastewater. Methods: To rapidly quantify the microbial response to crescent loading rates of benzimidazole compounds, a gradient system was used to transiently raise the fungicide volumetric loading rates, measuring the structural and functional dynamics response of a microbial community in terms of the volumetric removal rates of the HTR entering pollutants. Results: The loading rate gradient of benzimidazole compounds severely impacts the spatiotemporal taxonomic structure of the HTR biofilm-forming microbial community. Notable differences with the original structure in HTR stable conditions can be noted after three historical contingencies (CBZ, MT, and BN gradient loading rates). It was evidenced that the microbial community did not return to the composition prior to environmental disturbances; however, the functional similarity of microbial communities after steady state reestablishment was observed. Conclusions: The usefulness of the method of gradual delivery of potentially toxic agents for a microbial community immobilized in a tubular biofilm reactor was shown since its functional and structural dynamics were quickly evaluated in response to fungicide composition and concentration changes. The rapid adjustment of the contaminants' removal rates indicates that even with changes in the taxonomic structure of a microbial community, its functional redundancy favors its adjustment to gradual environmental disturbances.

Biodegradation of the herbicide propanil, and its 3,4-dichloroaniline by-product in a continuously operated biofilm reactor.

The persistence of propanil in soil and aquatic environments along with the possible accumulation of toxic degradation products, such as chloroanilines, is of environmental concern. In this work, a continuous small-scale bioprocess to degrade the herbicide propanil, its main catabolic by-product, 3,4-dichloroaniline (3,4-DCA), and the herbicide adjuvants is carried out. A microbial consortium, constituted by nine bacterial genera, was selected. The isolated strains, identified by amplification and sequencing of their 16S rDNA, were: Acidovorax sp., Luteibacter (rhizovicinus), Xanthomonas sp., Flavobacterium sp., Variovorax sp., Acinetobacter (calcoaceticus), Pseudomonas sp., Rhodococcus sp., and Kocuria sp. The ability of the microbial consortium to degrade the herbicide was evaluated in a biofilm reactor at propanil loading rates ranging from 1.9 to 36.8 mg L(-1) h(-1). Complete removal of propanil, 3,4-DCA, chemical oxygen demand and total organic carbon was obtained at propanil loading rates up to 24.9 mg L(-1) h(-1). At higher loading rates, the removal efficiencies decayed. Four of the identified strains could grow individually in propanil, and 3,4-DCA: Pseudomonas sp., Acinetobacter calcoaceticus, Rhodococcus sp., and Xanthomonas sp. The Kokuria strain grew on 3,4-DCA, but not on propanil. The first three bacteria have been related to biodegradation of phenyl urea herbicides or chlorinated anilines. Although some strains of the genera Xanthomonas and Kocuria have a role in the biodegradation of several xenobiotic compounds, as far as we know, there are no reports about degradation of propanil by Xanthomonas or 3,4-DCA by Kocuria species.

Permeable reactive surface-biobarriers. Testing and evaluation of an ecotechnology for the removal of agrotoxic compounds carried by agricultural runoffs.

PURPOSE: The objective of the work is to determine the best operating conditions for variants of an ecological engineering tool (permeable reactive surface biobarrier -PRSB-) potentially useful for the protection of water resources, preventing the arrival of sediments and pesticides transported by runoffs and tile drainage from agricultural lands, to water bodies. METHODS: Four PRB-prototypes were constructed as fixed-bed horizontal channels packed with a porous material supporting an enriched microbial biofilm. Their dynamic and stoichiometric performance was evaluated in the presence or absence of granular activated carbon, with limiting or sufficient O2 supply. The removal of the pesticides and their leading catabolic derivatives were determined by HPLC. The most abundant cultivable microorganisms were isolated and identified by the sequencing of 16sDNA amplicons. RESULTS: The pollutant removal efficiencies obtained in the aerobic biobarriers or microaerophilia were similar. In addition, slight differences were observed in the presence of GAC as an adsorbent, meaning that the most economical and straightforward type of biobarrier was adequate to remove the pollutants studied. In addition, among the most abundant microorganisms isolated in the microbial biofilms colonizing the aerobic biobarriers, the microalgae Micractinium sp. showed the capacity to accumulate the insecticides permethrin and cypermethrin. CONCLUSIONS: The main observed role of Micractinium sp. in the aerobic barriers was the bioaccumulation of pyrethroids, meaning that biosorption is also a valuable removal mechanism operating in the aerobic PRBs. In this aspect, they behave analogously to subsurface constructed wetlands but, instead of superficial plant life, aerobic PRSBs host microalgae.

Degradation kinetics of carbendazim by Klebsiella oxytoca, Flavobacterium johnsoniae, and Stenotrophomonas maltophilia strains.

The fungicide carbendazim is an ecotoxic pollutant frequently found in water reservoirs. The ability of microorganisms to remove pollutants found in diverse environments, soil, water, or air is well documented. Although microbial communities have many advantages in bioremediation processes, in many cases, those with the desired capabilities may be slow-growing or have low pollutant degradation rates. In these cases, the manipulation of the microbial community through enrichment with specialized microbial strains showing high specific growth rates and high rates and efficiencies of pollutant degradation is desirable. In this work, bacteria of the genera Klebsiella, Flavobacterium, and Stenotrophomonas, isolated from the biofilm attached to the packed zones of a biofilm reactor, were able to grow individually in selective medium containing carbendazim. In the three bacteria studied, the mheI gene encoding the first enzyme involved in the degradation of the fungicide carbendazim was found. Studying the dynamics of growth and carbendazim degradation of the three bacteria, the effect of co-formulants was also evaluated. The pure compound and a commercial formulation of carbendazim were used as substrates. Finally, the study made it possible to define the biokinetic advantages of these strains for amendment of microbial communities.

Assembly of an atrazine catabolic operon and its introduction to Gram-negative hosts for robust and stable degradation of triazine herbicides.

In 1995, Pseudomonas sp. ADP, capable of metabolizing atrazine, was isolated from contaminated soil. Genes responsible for atrazine mineralization were found scattered in the 108.8 kb pADP-1 plasmid carried by this strain, some of them flanked by insertion sequences rendering them unstable. The goal of this work was to construct a transcriptional unit containing the atz operon in an easy to transfer manner, to be introduced and inherited stably by Gram-negative bacteria. atz genes were PCR amplified, joined into an operon and inserted onto the mobilizable plasmid pBAMD1-2. Primers were designed to add efficient transcription and translation signals. Plasmid bearing the atz operon was transferred to different Gram-negative strains by conjugation, which resulted in Tn5 transposase-mediated chromosomal insertion of the atz operon. To test the operon activity, atrazine degradation by transposants was assessed both colorimetrically and by high-performance liquid chromatography (HPLC). Transposants mineralized atrazine more efficiently than wild-type Pseudomonas sp. ADP and did not accumulate cyanuric acid. Atrazine degradation was not repressed by simple nitrogen sources. Genes conferring atrazine-mineralizing capacities were stable and had little or null effect on the fitness of different transposants. Introduction of catabolic operons in a stable fashion could be used to develop bacteria with better degrading capabilities useful in bioremediation.

The corrosion process caused by the activity of the anaerobic sporulated bacterium Clostridium celerecrescens on API XL 52 steel.

The microbial corrosion of oil and gas pipes is one of the problems occurring in the oil industry. Various mechanisms explaining microbial corrosion have been demonstrated. Commonly, biocorrosion is attributed to sulfate-reducing bacteria. Also, it has recently been reported that microbial species can connect their electron transport system to metal electrodes. In this research, two spore-forming bacteria isolated in different years from a gas pipeline were identified by biochemical techniques and by 16S rDNA amplification, sequencing, and comparison with the NCBI database. Isolates were also compared between them using molecular techniques as the restriction patterns, unique for 16S rDNA (ARDRA), and the profile of the amplified bit from the genomic DNA, using an unspecific primer (RAPD). The results obtained showed that both isolates corresponded to Clostridium celerecrescens with a 99% similarity according to the sequence reported on the NCBI database. Also, the ARDRA and RAPD electrophoretic profiles of both strains were identical, and no plasmids were found in the strains. Thus, it can be settled that this bacterium is persistent in the environment prevailing in gas pipelines. Also, it was demonstrated that the bacterial secretion of organic acids contributes to the pitting and general biocorrosion of API XL 52 steel. The rates of corrosion obtained, approximately after 40 days, were correlated with the presence and metabolic activity of C. celerecrescens on the metallic surfaces.

Biodegradation of a commercial mixture of the herbicides atrazine and S-metolachlor in a multi-channel packed biofilm reactor.

Atrazine and S-metolachlor are two of the most widely used herbicides for agricultural purposes; consequently, residues of both compounds and their metabolites had been detected in ground and superficial waters. Unlike atrazine, the complete degradation of metolachlor has not been achieved. Hence, the purpose of this research is to study the biodegradation of a commercial mixture of atrazine and S-metolachlor in a prototype of a multi-channel packed-bed-biofilm reactor (MC-PBR) designed with the aim of solving the problems of pressure drop and oxygen transfer, typically found on this type of bioreactors.Because the removal efficiency of the herbicides was increased when Candida tropicalis was added to the original microbial community isolated, the reactor was inoculated with this enriched community. The operational conditions tested in batch and continuous mode did not affect the removal efficiency of atrazine; however, this was not the case for S-metolachlor. The removal rates and efficiencies showed a notable variation along the MC-PBR operation.

Effect of propanil, linuron, and dicamba on the degradation kinetics of 2,4-dichlorophenoxyacetic acid by Burkholderia sp. A study by differential analysis of 2,4-dichlorophenoxyacetic acid degradation data.

The successive application of distinct pesticides, or mixtures of them, is a frequent practice that could adversely affect the microbial species inhabiting soil and aquatic ecosystems. The ability of soil or aquatic microbiota to degrade a pesticide could be affected by the presence of another. If the degradation rate of the first compound is inhibited, its dissipation half-life in the environment could be hazardously enlarged. Few studies have been made to quantify the impact on the biodegradation rate of pesticides in soils or water by the presence of other pesticides. In this work, a method for assessing the effect of a pesticide on the biodegradation rate of another, measuring its effect on the biodegradation kinetics of a single bacterial strain is presented. The mathematical analysis is a powerful tool to study the stoichiometry and kinetics of microbial processes, which was used to evaluate independently, in detail, the effect of three pesticides (propanil, linuron, and dicamba) on the biodegradation kinetics of 2,4-dichlorophenoxyacetic acid by a strain of Burkholderia sp. It was evidenced that linuron and dicamba caused a decay of more than 40% in the top instantaneous degradation rate of 2,4-dichlorophenoxyacetic acid, while propanil showed a minimal effect.

Lactic acid bacteria production from whey.

The main purpose of this work was to isolate and characterize lactic acid bacteria (LAB) strains to be used for biomass production using a whey-based medium supplemented with an ammonium salt and with very low levels of yeast extract (0.25 g/L). Five strains of LAB were isolated from naturally soured milk after enrichment in whey-based medium. One bacterial isolate, designated MNM2, exhibited a remarkable capability to utilize whey lactose and give a high biomass yield on lactose. This strain was identified as Lactobacillus casei by its 16S rDNA sequence. A kinetic study of cell growth, lactose consumption, and titratable acidity production of this bacterial strain was performed in a bioreactor. The biomass yield on lactose, the percentage of lactose consumption, and the maximum increase in cell mass obtained in the bioreactor were 0.165 g of biomass/g of lactose, 100%, and 2.0 g/L, respectively, which were 1.44, 1.11, and 2.35 times higher than those found in flask cultures. The results suggest that it is possible to produce LAB biomass from a whey-based medium supplemented with minimal amounts of yeast extract.

Biodegradation of the herbicide Diuron in a packed bed channel and a double biobarrier with distribution of oxygenated liquid by airlift devices: influence of oxygen limitation.

From agricultural soils, where the herbicide Diuron has been frequently applied, a microbial community capable of degrading Diuron and 3,4-dichloroaniline was obtained. The volumetric rates and degradation efficiencies of Diuron and 3,4-DCA were evaluated in two distinct biofilm reactors, which differ in their operating conditions. One is a horizontal fixed bed reactor; plug-flow operated (PF-PBC) with severe limitation of oxygen. In this reactor, the air was supplied to an equalizer reservoir at the start of the PF-PBC reactor. The other is a compartmentalized aerobic biobarrier with internal recirculation of liquid aerated through airlift devices (ALB), continuously or intermittently operated. Both reactors were inoculated with a microbial community capable of degrading Diuron, isolated from a sugarcane field. In the oxygen-limited PF-PBC reactor, 3,4-DCA accumulation was detected, mainly in the middle zone of the packed channel. On the contrary, in the fully aerobic ALB reactor, minimal accumulation of catabolic byproducts was detected, and high Diuron removal efficiencies and removal rates were obtained when it was continuously operated in steady-state conditions. Additionally, the influence of oxygen limitation on the kinetic behavior of the PF-PBC reactor was determined, and a method to estimate the local removal rates of Diuron RV,CD along the plug-flow channel is described. It was observed that the local values of the instantaneous removal rate of Diuron dCD/dt are high in the aerobic region of the PF-PBC reactor; but, suddenly decay in the reactor zones limited by dissolved oxygen.

Steady-state inhibition model for the biodegradation of sulfonated amines in a packed bed reactor.

Aromatic amines are important industrial products having in their molecular structure one or more aromatic rings. These are used as precursors for the synthesis of dyes, adhesives, pesticides, rubber, fertilizers and surfactants. The aromatic amines are common constituents of industrial effluents, generated mostly by the degradation of azo dyes. Several of them are a threat to human health because they can by toxic, allergenic, mutagenic or carcinogenic. The most common are benzenesulfonic amines, such as 4-ABS (4-aminobenzene sulfonic acid) and naphthalene sulfonic amines, such as 4-ANS (4-amino naphthalene sulfonic acid). Sometimes, the mixtures of toxic compounds are more toxic or inhibitory than the individual compounds, even for microorganisms capable of degrading them. Therefore, the aim of this study was to evaluate the degradation of the mixture 4-ANS plus 4-ABS by a bacterial community immobilized in fragments of volcanic stone, using a packed bed continuous reactor. In this reactor, the amines loading rates were varied from 5.5 up to 69 mg L(-1) h(-1). The removal of the amines was determined by high-performance liquid chromatography and chemical oxygen demand. With this information, we have studied the substrate inhibition of the removal rate of the aromatic amines during the degradation of the mixture of sulfonated aromatic amines by the immobilized microorganisms. Experimental results were fitted to parabolic, hyperbolic and linear inhibition models. The model that best characterizes the inhibition of the specific degradation rate in the biofilm reactor was a parabolic model with values of RXM=58.15±7.95 mg (10(9) cells h)(-1), Ks=0.73±0.31 mg L(-1), Sm=89.14±5.43 mg L(-1) and the exponent m=5. From the microbial community obtained, six cultivable bacterial strains were isolated and identified by sequencing their 16S rDNA genes. The strains belong to the genera Variovorax, Pseudomonas, Bacillus, Arthrobacter, Nocardioides and Microbacterium. This microbial consortium could use the mixture of aromatic amines as sources of carbon, nitrogen, energy and sulfur.

Biodegradation of a mixture of the herbicides ametryn, and 2,4-dichlorophenoxyacetic acid (2,4-D) in a compartmentalized biofilm reactor.

In this work, an efficient degradation process for the removal of 2,4-D and ametryn, together with organic and inorganic adjuvants used in the commercial formulations of both herbicides, was developed. Although both compounds are toxic for microbial communities, ametryn is markedly more toxic than 2,4-D. In spite of this, the microbial consortium used could resist loading rates up to 31.5 mg L(-1) d(-1) of ametryn, with removal efficiencies up to 97% for both herbicides. Thus, an alternative use of this consortium could be bioaugmentation, as a tool to protect the structure and function of an activated-sludge biota against ametryn or 2,4-D shock loads. The process was carried out in a lab-scale prototype of aerobic biobarrier constructed as a compartmentalized fixed film reactor with airlift recirculation of oxygenated liquid.

Treatment of mezcal vinasses: a review.

Mexican distilleries produce near eight million liters of mezcal per year, and generate about 90 million liters of mezcal vinasses (MV). This acidic liquid waste is very aggressive to the environment because of its high content of toxic and recalcitrant organic matter. As a result, treatment is necessary before discharge to water bodies. It is interesting, yet disturbing; verify that there is a significant gap on the treatment of MV. However, there is an abundant body of research on treatment of other recalcitrant toxic effluents that bear some similarity to MV, for example, wine vinasse, vinasses from the sugar industry, olive oil, and industrial pulp and paper wastewaters. The objective of this review is to critically organize the treatment alternatives of MV, assess their relative advantages and disadvantages, and finally detect the trends for future research and development. Experience with treatment of this set of residuals, indicates the following trends: (i) anaerobic digestion, complemented by oxidative chemical treatments (e.g. ozonation) are usually placed as pretreatments, (ii) aerobic treatment alone and combined with ozone which have been directed to remove phenolic compounds and color have been successfully applied, (iii) physico-chemical treatments such as Fenton, electro-oxidation, oxidants and so on., which are now mostly at lab scale stage, have demonstrated a significant removal of recalcitrant organic compounds, (iv) fungal pretreatment with chemical treatment followed by oxidative (O(3)) or anaerobic digestion, this combination seems to give attractive results, (v) vinasses can be co-composted with solid organic wastes, particularly with those from agricultural activities and agro-industies; in addition to soil amenders with fertilizing value to improve soil quality in typical arid lands where agave is cultivated, it seems to be a low cost technology very well suited for rural regions in underdeveloped countries where more sophisticated technologies are difficult to adopt, due to high costs and requirements of skilled personnel.