Bioaugmentation of an anaerobic sequencing batch biofilm reactor (AnSBBR) with immobilized sulphate reducing bacteria (SRB) for the treatment of sulphate bearing chemical wastewater

Application of nanoparticles to increase biological hydrogen production: the difference in metabolic pathways in batch and continuous reactors

An alternative to improve the production of biorefinery products, such as biohydrogen (H2) and volatile fatty acids (VFA), is the combination of nanotechnology and biological processes. In order to compare the use of both processes in two different reactor configurations, batch reactors and continuous anaerobic fluidized bed reactors (AFBR) were studied under the same conditions (37°C, pH 6.8, Clostridium butyricum as an inoculum and glucose as a substrate) to evaluate the influence of zero valence iron and nickel nanoparticles (NPs) on H2 and VFA production. There was a shift in the production of acetic and butyric acids to produce mainly valeric acid when NPs were added in batch reactors. Meanwhile, in AFBR the change was from lactic acid to butyric and acetic acids with the addition of NPs. It showed that the effect of NPs on the fermentation process was different when the configuration of batch and continuous reactors was compared. The H2 yield in both reactor configurations increased with the addition of NPs. In batch reactors from 6.6 to 8.0 mmol H2 g-1 of COD and in AFBR from 4.9 to 6.2 mmol of H2 g-1 of COD. Therefore, given the simplicity and low cost of the synthesis of metallic NPs, it is a promising additive to optimize the fermentation process in different reactor configurations.

Controllable and biocompatible 3D bioprinting technology for microorganisms: Fundamental, environmental applications and challenges

3D bioprinting is a new 3D manufacturing technology, that can be used to accurately distribute and load microorganisms to form microbial active materials with multiple complex functions. Based on the 3D printing of human cells in tissue engineering, 3D bioprinting technology has been developed. Although 3D bioprinting technology is still immature, it shows great potential in the environmental field. Due to the precise programming control and multi-printing pathway, 3D bioprinting technology provides a high-throughput method based on micron-level patterning for a wide range of environmental microbiological engineering applications, which makes it an on-demand, multi-functional manufacturing technology. To date, 3D bioprinting technology has been employed in microbial fuel cells, biofilm material preparation, microbial catalysts and 4D bioprinting with time dimension functions. Nevertheless, current 3D bioprinting technology faces technical challenges in improving the mechanical properties of materials, developing specific bioinks to adapt to different strains, and exploring 4D bioprinting for intelligent applications. Hence, this review systematically analyzes the basic technical principles of 3D bioprinting, bioinks materials and their applications in the environmental field, and proposes the challenges and future prospects of 3D bioprinting in the environmental field. Combined with the current development of microbial enhancement technology in the environmental field, 3D bioprinting will be developed into an enabling platform for multifunctional microorganisms and facilitate greater control of in situ directional reactions.

Magnetite Alters the Metabolic Interaction between Methanogens and Sulfate-Reducing Bacteria

It is known that the presence of sulfate decreases the methane yield in the anaerobic digestion systems. Sulfate-reducing bacteria can convert sulfate to hydrogen sulfide competing with methanogens for substrates such as H2 and acetate. The present work aims to elucidate the microbial interactions in biogas production and assess the effectiveness of electron-conductive materials in restoring methane production after exposure to high sulfate concentrations. The addition of magnetite led to a higher methane content in the biogas and a sharp decrease in the level of hydrogen sulfide, indicating its beneficial effects. Furthermore, the rate of volatile fatty acid consumption increased, especially for butyrate, propionate, and acetate. Genome-centric metagenomics was performed to explore the main microbial interactions. The interaction between methanogens and sulfate-reducing bacteria was found to be both competitive and cooperative, depending on the methanogenic class. Microbial species assigned to the Methanosarcina genus increased in relative abundance after magnetite addition together with the butyrate oxidizing syntrophic partners, in particular belonging to the Syntrophomonas genus. Additionally, Ruminococcus sp. DTU98 and other species assigned to the Chloroflexi phylum were positively correlated to the presence of sulfate-reducing bacteria, suggesting DIET-based interactions. In conclusion, this study provides new insights into the application of magnetite to enhance the anaerobic digestion performance by removing hydrogen sulfide, fostering DIET-based syntrophic microbial interactions, and unraveling the intricate interplay of competitive and cooperative interactions between methanogens and sulfate-reducing bacteria, influenced by the specific methanogenic group.

Treatment of Organic and Sulfate/Sulfide Contaminated Wastewater and Bioelectricity Generation by Sulfate-Reducing Bioreactor Coupling with Sulfide-Oxidizing Fuel Cell

A wastewater treatment system has been established based on sulfate-reducing and sulfide-oxidizing processes for treating organic wastewater containing high sulfate/sulfide. The influence of COD/SO42- ratio and hydraulic retention time (HRT) on removal efficiencies of sulfate, COD, sulfide and electricity generation was investigated. The continuous operation of the treatment system was carried out for 63 days with the optimum COD/SO42- ratio and HRT. The result showed that the COD and sulfate removal efficiencies were stable, reaching 94.8 ± 0.6 and 93.0 ± 1.3% during the operation. A power density level of 18.0 ± 1.6 mW/m2 was obtained with a sulfide removal efficiency of 93.0 ± 1.2%. However, the sulfide removal efficiency and power density decreased gradually after 45 days. The results from scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX) show that sulfur accumulated on the anode, which could explain the decline in sulfide oxidation and electricity generation. This study provides a promising treatment system to scale up for its actual applications in this type of wastewater.

Bimetallic core-shell nanoparticle arrays at liquid-liquid interface for the degradation and monitoring of dye pollutants in situ by surface-enhanced Raman spectroscopy

In situ monitoring of chemical reactions has attracted great attention in many fields. Herein, we successfully in situ track the degradation reaction process of a dye pollutant, methylene blue (MB), on the liquid-liquid interface (LLI) of bimetallic gold core-silver shell nanoparticles (Au@AgNPs) by surface-enhanced Raman spectroscopy (SERS). The optimized LLI bimetallic array of Au₅₀@Ag₁₀NPs exhibits ultrahigh SERS enhancement and excellent catalytic activity. Results evidenced a detection limit of MB down to 1 ppb, and the degradation rate of Au@AgNPs was as high as 85.2% in 30 s, relying on the excellent self-healing properties of nanoarrays. Furthermore, as a practical SERS analyzer, the LLI bimetallic array was used to detect trace amounts of other harmful dyes, including Rhodamine 6G (R6G) and crystal violet (CV) in pure or complex media. Our LLI bimetallic array exhibits a new orientation for monitoring catalytic reactions involving highly toxic, hazardous, or costly targets in food security fields in the future.

Anaerobic biofilm enriched with an ammonia tolerant methanogenic consortium to improve wastewater treatment in the fishing industry

The digestion efficiency of liquid industrial wastes increases when using bioreactors colonized by microbial biofilms. High concentrations of proteins derived from the fish processing industry lead to the production of ammonia, which inhibits methane production. Two bioreactors were constructed to compare methanogenic activity: one enriched with mMPA (methylaminotrofic methane production archaea) consortia (control bioreactor), and the second with NH₃ tolerant consortia (treatment bioreactor). Ammonia tolerant activity was assessed by applying an ammonia shock (755 mg NH₃/L). Methane production, consumption of total organic carbon (TOC) and the taxonomic composition of bacteria and archaea was evaluated using 16S rDNA in the acclimatization, ammonia shock, and recovery phases.The ammonia shock significantly affected both methane production and the consumption of TOC in the control reactor (p < 0.05) and taxonomical composition of the microbial consortia (OTU). These values remained constant in the treatment reactor. The analysis of biofilm composition showed a predominance of Methanosarcinaceae (Methanomethylovorans sp., and probably two different species of Methanosarcina sp.) in bioreactors. These results demonstrate that using acclimated biofilms enriched with ammonia tolerant methanogens control the inhibitory effect of ammonia on methanogenesis.

Performance of microbial community dominated by Bacillus spp. in acid mine drainage remediation systems: A focus on the high removal efficiency of SO4 2-, Al3+, Cd2+, Cu2+, Mn2+, Pb2+, and Sr2

A consortium of microbial community was used for the treatment of acid mine drainage wastewater laden with sulphate and heavy metals. The wastewater was treated in an anaerobic continuously stirred tank bioreactor. The microbial community activity increased the pH from 5.6 to 6.5, and improved sulphate removal up to 85% from an initial sulphate concentration of 8080 mg SO42−/L in a continuous mode, following enrichment for 21 d. The maximum heavy metal removal percentage was observed for Cd (98%), Al (97%), Mn (95%), Pb (94%), Sr (94%) and Cu (91%). The microbial community showed synergy between strictly anaerobic and facultative Firmicutes sp., which were responsible for the bioreactor performance. The biochemical reaction indicated the microbial community has a wider range of substrates dominated by metallo-aminopeptidases.

Over-sulfated soils and sediments treatment: A brief discussion on performance disparities of biological and non-biological methods throughout the literature

High sulfate concentrations in industrial effluents as well as solid materials (excavated soils, dredged sediments, etc.) are a major hindrance for circular economy outlooks. SO₄^2- acceptability standards are indeed increasingly restrictive, given the potential outcomes for public health and ecosystems. This literature review deals with the treatment pathways relying on precipitation, adsorption and microbial redox principles. Although satisfactory removal performances can be achieved with each of them, significant yield differences are displayed throughout the bibliography. The challenge here was to identify the parameters leading to this variability and to assess their impact. The precipitation pathway is based on the formation of two main minerals (ettringite and barite). It can lead to total sulfate removal but can also be limited by aqueous wastes chemistry. Stabilizer kinetics of formation and equilibrium are highly constrained by background properties such as pH, Eh, SO₄^2- saturation state and inhibiting metal occurrences. Regarding the adsorption route, sorbents' intrinsic features such as the q_max parameter govern removal yields. Concerning the microbial pathway, the chemical oxygen demand/SO₄^2- ratio and the hydraulic retention time, which are classically evoked as yield variation factors, appear here to be weakly influential. The effect of these parameters seems to be overridden by the influence of electron donors, which constitute a first order factor of variability. A second order variability can be read according to the nature of these electron donors. Approaches using simple monomers (ethanol lactates, etc.) perform better than those using predominantly ligneous organic matter.

Optimising Brewery-Wastewater-Supported Acid Mine Drainage Treatment vis-à-vis Response Surface Methodology and Artificial Neural Network

This study investigated the use of brewing wastewater (BW) as the primary carbon source in the Postgate medium for the optimisation of sulphate reduction in acid mine drainage (AMD). The results showed that the sulphate-reducing bacteria (SRB) consortium was able to utilise BW for sulphate reduction. The response surface methodology (RSM)/Box–Behnken design optimum conditions found for sulphate reduction were a pH of 6.99, COD/SO42− of 2.87, and BW concentration of 200.24 mg/L with predicted sulphate reduction of 91.58%. Furthermore, by using an artificial neural network (ANN), a multilayer full feedforward (MFFF) connection with an incremental backpropagation network and hyperbolic tangent as the transfer function gave the best predictive model for sulphate reduction. The ANN optimum conditions were a pH of 6.99, COD/SO42− of 0.50, and BW concentration of 200.31 mg/L with predicted sulphate reduction of 89.56%. The coefficient of determination (R2) and absolute average deviation (AAD) were estimated as 0.97 and 0.046, respectively, for RSM and 0.99 and 0.011, respectively, for ANN. Consequently, ANN was a better predictor than RSM. This study revealed that the exclusive use of BW without supplementation with refined carbon sources in the Postgate medium is feasible and could ensure the economic sustainability of biological sulphate reduction in the South African environment, or in any semi-arid country with significant brewing activity and AMD challenges.

Xanthan gum as a carrier for bacterial cell entrapment: Developing a novel immobilised biocatalyst

Xanthan gum (XAN) is a widely used polysaccharide in various industries. Because of its unique properties, in this study, an attempt was made to adopt the procedure of xanthan gum cross-linking for the entrapment of bacterial cells that are able to biodegrade naproxen. The developed procedure proved to be completely neutral for Bacillus thuringiensis B1(2015b) cells, which demonstrated a survival rate of 99%. A negative impact of entrapment was noted for strain Planococcus sp. S5, which showed a survival rate in the 93-51% range. To achieve good mechanical properties of the composites, they were additionally hardened using polydopamine (PDA). XAN/PDA composites revealed a high stability in a wide range of pH, and their sorption capacity included both cationic and anionic molecules. Analysis of the survival rate during storage at 4 °C in 0.9% NaCl showed that, after 35 days, 98-99% of B1(2015b) and 47% of S5 cells entrapped in XAN/PDA remained alive. This study also presents the results of naproxen biodegradation conducted using XAN/PDA/B1(2015b) in a trickling filter with autochthonous microflora. Hence, owing to the significant acceleration of drug biodegradation (1 mg/L in 14 days) and the chemical oxygen demand removal, the entrapped B1(2015b) cells in XAN/PDA composites showed a promising potential in bioremediation studies and industrial applications.

A new strategy to recover from volatile fatty acid inhibition in anaerobic digestion by photosynthetic bacteria

The accumulation of volatile fatty acids (VFAs) can decrease reactor pH and inhibit methane-producing process. For the first time, photosynthetic bacteria (PSB) were used to recover from VFAs inhibition (pH 6.0) of an anaerobic digestion system. After adding PSB for 12 days with and without light condition, the methane content recovered from 33.3% to 60.5% and from 32.1% to 59.3%, respectively; the pH increased to 7.1 and 6.8, respectively, the system alkalinity rapidly increased to 2238 and 1921 mg/L, respectively; the sCOD decreased from 5600 to 995 mg/L and from 5575 to 2025 mg/L, respectively; and the contents of formic acid, acetic acid, propionic acid and total VFA were greatly reduced. Microbial analysis found that PSB bioaugmentation could maintain microbial diversity of the system. PSB bioaugmentation could effectively relieve acids accumulation and stimulate methane production especially under light condition. It is also found that light could accelerate recovery with or without bioaugmentation.

Immobilized-microbial bioaugmentation protects aerobic denitrification from heavy metal shock in an activated-sludge reactor

The inhibition of denitrification by heavy metals is a problem in nitrogen wastewater treatment, but the solutions are rarely studied. In this study, Pseudomonas brassicacearum LZ-4, immobilized in sodium alginate-kaolin, was applied in an activated-sludge reactor to protect denitrifiers from hexavalent chromium (Cr(VI)). Q-PCR result showed that the strain LZ-4 was incorporated into activated sludge under the help of immobilization. In the non-bioaugmentation system, the removal efficiency of nitrate was decreased by 86.07% by 30 mg/L Cr(VI). Whereas, denitrification was protected and 95% of nitrate was removed continuously in immobilized-cell bioaugmentation system. Miseq sequencing data showed that bioaugmentation decreased the impact of Cr(VI) on microbial communities and increased the abundance of denitrifiers. Based on the results of biomass and extracellular polymers, activated sludge was protected from Cr(VI) toxicity. This discovery will provide a feasible technique for nitrogen wastewater treatment in the presence of distressing heavy metals.

Enhanced anaerobic performance and SMD process in treatment of sulfate and organic S-rich TMBA manufacturing wastewater by micro-electric field-zero valent iron-UASB

This study focused on investigating reactor performance, simultaneous methanogeneis and denitrifiction (SMD) process for treatment of a sulfate plus organic sulfur - rich 3,4,5-Triethoxybenzaldehyde (TMBA) manufacturing wastewater with variable COD/TSO₄^2- (total sulfate) ratio by micro-electric field- zero-valent-iron (ZVI) UASB for 390 days. The initial COD/TSO₄^2- was set as 1.42, 0.9 and 0.5, respectively by manually introducing sulfate. The experimental results indicated that micro-electric field- zero-valent-iron UASB was an attractive integrated option for satisfactory COD removal, nitrate reduction and a reasonable methane yield rate even at COD/TSO₄^2- as low as 0.9. Further declining the COD/TSO₄^2- to 0.5 can result in a moderate inhibition of SMD process. The behavior of organic S release was not inhibited over the entire experimental period. Thus, surprisingly, sulfate concentration in the effluent was always higher than that in the influent. In comparison with sludge sample at Day-1, sludge at Day-390 was characterized with high abundant Tissierella Soehngenia, Anaerolinaceae and Brevundimonas diminuta, which played critical role in promising performance in COD abatement. The relatively low abundance of sulfate reducing bacteria (SRB) such as Desulfobulbus and Desulfomicrobium can explain the lower sulfate reduction efficiency in term of high concentration of sulfate plus released from organic S-rich compounds.

Removal of sulfamethoxazole (SMX) in sulfate-reducing flocculent and granular sludge systems

This study investigated sulfamethoxazole (SMX) removal and fate in sulfate-reducing up-flow sludge bed (SRUSB) reactors inoculated with sulfate-reducing bacteria (SRB) granules and flocs. The resilience of SRB granules and flocs against varying pHs and hydraulic retention times (HRTs) was also examined. SRB granules and flocs efficiently removed SMX from wastewater, which was significantly higher than the aerobic sludge. SRB granules achieved significantly (p < 0.05) higher SMX removal (∼13.3 μg/g suspended solids (SS)-d) than the SRB flocs (∼11.2 μg/g SS-d) during 150-day of SRUSB reactors operation. The SMX removal by both granules and flocs was mainly attributed to biodegradation. Sorption also contributed to SMX removal, in which aromatic protein-like substances of extracellular polymeric substances played important role in SMX removal. In addition, SRB granules showed higher resilience than SRB flocs against varying pHs and HRTs. Thus, SRB-mediated biological process, especially SRB granules, could be a promising biotechnology to remove SMX from wastewaters.

Bioaugmentation strategy for enhancing anaerobic digestion of high C/N ratio feedstock with methanogenic enrichment culture

To investigate whether bioaugmentation could improve the digestion performance of high C/N ratio feedstock without co-digestion with nitrogen-rich substrate, different forms of enriched methanogenic culture were introduced to the continuous feed digesters. The performance efficiency of bioaugmentation on digestion improvement was compared. The effect of bioaugmentation on microbial community composition was revealed as well. Results demonstrated that routine bioaugmentation with liquid culture (containing the microbes and the medium remains) showed the best performance, with the organic loading rate (OLR), methane percentage, volumetric methane production (VMP) and volatile solid methane production (VSMP) higher at 1.0 g L^-1 d^-1, 24%, 0.22 L L^-1 d^-1 and 0.23 L g^-1 VS d^-1 respectively, compared to the non-bioaugmentation control. Whole genome pyrosequencing analysis suggested that consecutive microbial consortium addition could reconstruct the methanogens community by increasing the populations of acetoclastic methanogens Methanothrix, which could accelerate the degradation of acetate and methane production.

Induced bioelectrochemical metabolism for bioremediation of petroleum refinery wastewater: Optimization of applied potential and flow of wastewater

Hybrid based bioelectrochemical system (BES) configured with embedded anode and cathode electrodes in soil was tested for the bioelectrochemical degradation of petroleum refinery wastewater (PRW). Four applied potentials were studied to optimize under batch mode operation, among which 2 V resulted in higher COD degradation (69.2%) and power density (725 mW/m²) during 7 days of operation. Further studies with continuous mode of operation at optimized potential (2 V) showed that hydraulic retention time (HRT) of 19 h achieved the highest COD removal (37%) and highest power density (561 mW/m²). BES function with respect to treatment efficiencies of other pollutants of PRW was also identified with respect to oil and grease (batch mode, 91%; continuous mode, 34%), total dissolved salts (batch mode, 53%; continuous mode, 24%) and sulfates (batch mode, 59%; continuous mode, 42%). Soil microenvironment in association with BES forms complex processes, providing suitable conditions for efficient treatment of PRW.

Sulfamethoxazole degradation in anaerobic sulfate-reducing bacteria sludge system

Sulfamethoxazole (SMX) is one of the most commonly used antibiotics. SMX degradation in sulfate-reducing bacteria (SRB) sludge systems has not been reported so far. This research investigated the SMX degradation using SRB sludge in a sulfate-reducing up-flow sludge bed reactor. Moreover, the mechanisms and kinetics of SMX removal were also investigated using SRB sludge via a series of batch experiments. The results showed that SMX removal was characterized by a rapid sorption onto SRB sludge, and desorption from SRB sludge to aqueous phase until achieving equilibrium, and then followed by slow biodegradation. Biodegradation was the dominant route for SMX removal. The sorption process conformed well to a pseudo-second-order kinetic model, meaning that the sorption occurred primarily via a chemical sorption process. The removal of SMX followed the pseudo-zero-order kinetic model with a specific removal rate of 13.2 ± 0.1 μg/L/d at initial SMX concentration 100 μg/L in batch tests. Based on the analysis of metabolites, most of the SMX biotransformation products' structures altered in the isoxazole ring, which were significantly different from that produced by aerobic and anaerobic sludge systems. Thus, SRB sludge system could play an important role in SMX biodegradation, especially in Sulfate-reduction Autotrophic denitrification and Nitrification Integrated (SANI) process for sewage treatment.

Spatial impacts of inorganic ligand availability and localized microbial community structure on mitigation of zinc laden mine water in sulfate-reducing bioreactors

Sulfate-reducing bioreactors (SRBRs) represent a passive, sustainable, and long-term option for mitigating mining influenced water (MIW) during release. Here we investigate spatial zinc precipitation profiles as influenced by substrate differentiation, inorganic ligand availability (inorganic carbon and sulfide), and microbial community structure in pilot-scale SRBR columns fed with sulfate and zinc-rich MIW. Through a combination of aqueous sampling, geochemical digests, electron microscopy and energy-dispersive x-ray spectroscopy, we were able to delineate zones of enhanced zinc removal, identify precipitates of varying stability, and discern the temporal and spatial evolution of zinc, sulfur, and calcium associations. These geochemical insights revealed spatially variable immobilization regimes between SRBR columns that could be further contrasted as a function of labile (alfalfa-dominated) versus recalcitrant (woodchip-dominated) solid-phase substrate content. Both column subsets exhibited initial zinc removal as carbonates; however precipitation in association with labile substrates was more pronounced and dominated by metal-sulfide formation in the upper portions of the down flow columns with micrographs visually suggestive of sphalerite (ZnS). In contrast, a more diffuse and lower mass of zinc precipitation in the presence of gypsum-like precipitates occurred within the more recalcitrant column systems. While removal and sulfide-associated precipitation were spatially variable, whole bacterial community structure (ANOSIM) and diversity estimates were comparatively homogeneous. However, two phyla exhibited a potentially selective relationship with a significant positive correlation between the ratio of Firmicutes to Bacteroidetes and sulfide-bound zinc. Collectively these biogeochemical insights indicate that depths of maximal zinc sulfide precipitation are temporally dynamic, influenced by substrate composition and broaden our understanding of bio-immobilized zinc species, microbial interactions and potential operational and monitoring tools in these types of passive bioreactors.

The performance efficiency of bioaugmentation to prevent anaerobic digestion failure from ammonia and propionate inhibition

This study aims to investigate the effect of bioaugmentation with enriched methanogenic propionate degrading microbial consortia on propionate fermentation under ammonia stress from total ammonia nitrogen concentration (TAN) of 3.0gNL^-1. Results demonstrated that bioaugmentation could prevent unstable digestion against further deterioration. After 45days of 1dosage (0.3g dry cell weight L^-1d^-1, DCW L^-1d^-1) of bioaugmentation, the average volumetric methane production (VMP), methane recovery rate and propionic acid (HPr) degradation rate was enhanced by 70mLL^-1d^-1, 21% and 51%, respectively. In contrast, the non-bioaugmentation reactor almost failed. Routine addition of a double dosage (0.6g DCW L^-1d^-1) of bioaugmentation culture was able to effectively recover the failing digester. The results of FISH suggested that the populations of Methanosaetaceae increased significantly, which could be a main contributor for the positive effect on methane production.

Enhanced biological stabilization of heavy metals in sediment using immobilized sulfate reducing bacteria beads with inner cohesive nutrient

A series of experiments were conducted for treating heavy metals contaminated sediments sampled from Xiangjiang River, which combined polyvinyl alcohol (PVA) and immobilized sulfate reducing bacteria (SRB) into beads. The sodium lactate was served as the inner cohesive nutrient. Coupling the activity of the SRB with PVA, along with the porous structure and huge specific surface area, provided a convenient channel for the transmission of matter and protected the cells against the toxicity of metals. This paper systematically investigated the stability of Cu, Zn, Pb and Cd and its mechanisms. The results revealed the performance of leaching toxicity was lower and the removal efficiencies of Cu, Zn, Pb and Cd were 76.3%, 95.6%, 100% and 91.2%, respectively. Recycling experiments showed the beads could be reused 5 times with superbly efficiency. These results were also confirmed by continuous extraction at the optimal conditions. Furthermore, X-ray diffraction (XRD) and energy-dispersive spectra (EDS) analysis indicated the heavy metals could be transformed into stable crystal texture. The stabilization of heavy metals was attributed to the carbonyl and acyl amino groups. Results presented that immobilized bacteria with inner nutrient were potentially and practically applied to multi-heavy-metal-contamination sediment.

The effect of acidic pH and presence of metals as parameters in establishing a sulfidogenic process in anaerobic reactor

The successful use of anaerobic reactors for bioremediation of acid mine drainage has been shown in systems with neutral pH. However, the choice of an efficient and suitable process for such wastewater must consider the capability of operating at acidic pH and in the presence of metals. This work studies the performance of an anaerobic batch reactor, under conditions of varying initial pH for its efficiencies in sulfate removal and metal precipitation from synthetic acid mine drainage. The chemical oxygen demand/sulfate (COD/SO4(2-)) ratio used was 1.00, with ethanol chosen as the only energy and carbon source. The initial pH of the synthetic drainage was progressively set from 7.0 to 4.0 to make it as close as possible to that of real acid mine drainage. Metals were also added starting with iron, zinc, and finally copper. The effectiveness of sulfate and COD removal from the synthetic acid mine drainage increased as the initial pH was reduced. The sulfate removal increased from 38.5 ± 3.7% to 52.2 ± 3%, while the removal of organic matter started at 91.7 ± 2.4% and ended at 99 ± 1%. These results indicate that the sulfate reducing bacteria (SRB) community adapted to lower pH values. The metal removal observed was 88 ± 7% for iron, 98.0 ± 0.5% for zinc and 99 ± 1% for copper. At this stage, an increase in the sulfate removal was observed, which reaches up to 82.2 ± 5.8%. The kinetic parameters for sulfate removal were 0.22 ± 0.04 h(-1) with Fe, 0.26 ± 0.04 h(-1) with Fe and Zn and 0.44 ± 0.04 h(-1) with Fe, Zn, and Cu.

Bioaugmentation and its application in wastewater treatment: A review

Bioaugmentation (the process of adding selected strains/mixed cultures to wastewater reactors to improve the catabolism of specific compounds, e.g. refractory organics, or overall COD) is a promising technique to solve practical problems in wastewater treatment plants, and enhance removal efficiency. The potential of this option can now be enhanced in order to take advantage of important advances in the fields of microbial ecology, molecular biology, immobilization techniques and advanced bioreactor design. Reports on bioaugmentation in WWT show the difficulties in evaluating the potential parameters involved, leading frequently to inconclusive outcomes. Many studies have been carried out on the basis of trial-and-error approaches, and it has been reported that reactors bioaugmented with pure cultures often fail to perform as well as the pure cultures under laboratory conditions. As an interesting technical challenge, the feasibility of bioaugmentation should ultimately be assessed by data from field implementation, and this review highlights several promising areas to explore in the future.

Bioaugmentation of potent acidogenic isolates: a strategy for enhancing biohydrogen production at elevated organic load

The efficiency of bioaugmentation strategy for enhancing biohydrogenesis at elevated organic load was successfully evaluated by augmenting native acidogenic microflora with three acidogenic bacterial isolates viz., Bacillus subtilis, Pseudomonas stutzeri and Lysinibacillus fusiformis related to phyla Firmicutes and Proteobacteria separately. Hydrogen production ceased at 50g COD/l operation due to feed-back inhibition. B. subtilis augmented system showed higher H2 production followed by L. fusiformis, P. stutzeri and control operations, indicating the efficacy of Firmicutes as bioaugmentation biocatalyst. Higher VFA production with acetic acid as a major fraction was specifically observed with B. subtilis augmented system. Shift in metabolic pathway towards acidogenesis favoured higher H2 production. FISH analysis confirmed survivability and persistence of augmented strains apart from improvement in process performance. Bio-electrochemical analysis depicted specific changes in the metabolic activity after augmentation which also facilitated enhanced electron transfer. P. stutzeri augmented system documented relatively higher COD removal.

Relative effect of bioaugmentation with electrochemically active and non-active bacteria on bioelectrogenesis in microbial fuel cell

Bioelectrogenic activity of microbial fuel cells (MFC) augmented with electrochemically active bacteria (EAB, Pseudomonas aeruginosa) and non-EAB (Escherichia coli) as biocatalysts was investigated. Anodic microflora augmented with P. aeruginosa (AMFCP) yielded higher electrogenic activity (418 mV; 3.87 mA) than E. coli (AMFCE; 254 mV; 1.67 mA) and non-augmented native microflora (MFCC; 235 mV; 1.37 mA). Higher redox currents along with lower Tafel-slopes were observed with AMFCP operation compared to AMFCE and MFCC due to manifestation of bioaugmentation thereby minimizing the losses. A fourfold and twofold increase in capacitance and exchange current was observed with AMFCP and AMFCE operation respectively, when compared to MFCC. Tracking of augmented biocatalyst by fluorescent in situ hybridization (FISH) with defined probes documented the survivability of Pseudomonas sp. in higher numbers than Enterobacteriaceae. Study corroborated enhanced electron transfer capability of mixed consortia owing to the synergistic interaction with EAB due to augmentation.

Optimisation of single-phase dry-thermophilic anaerobic digestion under high organic loading rates of industrial municipal solid waste: population dynamics

Different high feed organic loading rates (OLRs) (from 5.7 g to 46.0 g TVS/l/d) or hydraulic retention times (HRTs) (from 15 d to 2 d) in single-phase dry-thermophilic anaerobic digestion (AD) of organic fraction municipal solid waste (OFMSW) were investigated. The specific gas production (SGP) values (0.25-0.53 m(3)/kg TVS) and the percentages of Eubacteria, Archaea, H2-utilising methanogens (HUMs) and acetate-utilising methanogens (AUMs) were stable within the ranges 80.2-91.1%, 12.4-18.5%, 4.4-9.8% and 5.5-10.9%, respectively. A HUM/AUM ratio greater than 0.7 seems to be necessary to maintain very low partial pressures of H2 required for dry AD process. Increasing OLR resulted in an increase in all the populations, except for propionate-utilising acetogens (PUAs). Optimal conditions were obtained at 3d HRT (OLR=30.7 g TVS/l/d), which is lower than the doubling time of acetogens and methanogens. The methane production (MP) was clearly higher than those reported in AD of OFMSW.

Biodegradation of industrial-strength 2,4-dichlorophenoxyacetic acid wastewaters in the presence of glucose in aerobic and anaerobic sequencing batch reactors

This research explored the biodegradability of 2,4-dichlorophenoxyacetic acid (2,4-D) in two laboratory-scale sequencing batch reactors (SBRs) that operated under aerobic and anaerobic conditions. The potential limit of 2,4-D degradation was investigated at a hydraulic retention time of 48 h, using glucose as a supplemental substrate and increasing feed concentrations of 2,4-D; namely 100 to 700 mg/L (i.e. industrial strength) for the aerobic system and 100 to 300 mg/L for the anaerobic SBR. The results revealed that 100 mg/L of 2,4-D was completely degraded following an acclimation period of 29 d (aerobic SBR) and 70 d (anaerobic SBR). The aerobic system achieved total 2,4-D removal at feed concentrations up to 600 mg/L which appeared to be a practical limit, since a further increase to 700 mg/L impaired glucose degradation while 2,4-D biodegradation was non-existent. In all cases, glucose was consumed before the onset of 2,4-D degradation. In the anaerobic SBR, 2,4-D degradation was limited to 120 mg/L.

Study of Biodegradable Polyurethane Foam as Carriers for Low C/N Ratio Wastewater

In this study, the performance of nitrification and denitrification were investigated in a sequencing batch biofilm reactor (SBBR) with biodegradable polyurethane foam. The study aimed at solving the shortage of carbon sources for denitrification treating wastewater with a low C/N ratio. Ammonium, nitrite, nitrate, pH and Dissolved oxygen (DO) were carried out to monitor the process of nitrification-denitrification in every cycle. The results showed that Total nitrogen (TN) removal efficiency of 67.5% was achieved during a monitoring period of three months. The SBBR showed good behavior in terms of total nitrogen removal as the biodegradable polymer was an effective substrate providing reducing power for denitrification. According to scanning electron microscope, the biofilm from the inside of the Polyurethane (PU) carriers comprised predominately of small rod-shaped and spherical clusters were dominant, while clusters of filamentous form and few long rod shaped were observed on the surface. The used PU carriers after being washed with distilled water were found some cavities due to corrosion by microorganisms.

An eco-friendly treatment of tannery wastewater using bioaugmentation with a novel microbial consortium

A novel microbial consortium (BM-S-1) enriched from natural soils was successfully used to treat tannery wastewater from leather manufacturing industries in Korea on a pilot scale. The objective of this study was to determine whether augmentation with a novel microbial consortium BM-S-1could successfully treat the recalcitrant wastewater without chemical pre-treatment in a tannery wastewater treatment system. Chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were monitored for water quality. The microbial population dynamics were analyzed using pyrosequencing, and denitrifying bacteria were quantified using real-time PCR (RT-PCR). The removal efficiencies for COD, TN and TP were greater than 91%, 79%, and 90%, respectively. The dominant phyla in the buffering tank (B), primary aeration (PA), secondary aeration (SA) and sludge digestion tank (SD) were Proteobacteria, Firmicutes, Bacteroidetes, Planctomycetes and Deinococcus-Thermus. Cluster analysis based on the UniFrac distance of the species in the different stages showed that the PA is similar to the SA, whereas the B is similar to the SD. qPCR of the nosZ genes showed the highest abundance of denitrifiers in B, which was increased 734-fold compared to the influent (I). It was hypothesized that anaerobic denitrifiers and the diverse microbial community may play important roles in the biological treatment of tannery wastewater. This technology may also contribute to the full-scale treatment of industrial wastewater containing food processing wastewater and marine sediment with high organic content.

Bioaugmentation for treating transient or continuous p-nitrophenol shock loads in an aerobic sequencing batch reactor

Bioaugmentation with an enriched microbial population was applied in an aerobic sequencing batch reactor (SBR) receiving transient or continuous shock loads of p-nitrophenol (PNP). The effect of the amount of biomass added for bioaugmentation was assessed by using two different dosages (2% or 5% w/w of the total biomass in the seeded SBR). In both cases, total PNP removal was achieved during the transient PNP shock load occurring after bioaugmentation. However, after a long PNP starvation period the only experiment still showing total PNP removal during a second PNP shock load was the one where a dosage of 5% w/w was applied. The results suggested that the dosage is a key factor for the implementation of a successful bioaugmentation strategy. In addition, the performance of a bioaugmented SBR receiving a continuous PNP shock load was enhanced when compared to a non-bioaugmented SBR.

Implications of volatile fatty acid profile on the metabolic pathway during continuous sulfate reduction

Volatile fatty acid (VFA) profile is an important parameter in anaerobic reactors because it enables the assessment of metabolic pathways. Volatile fatty acids were monitored during sulfate reduction in a UASB (upflow anaerobic sludge blanket) reactor treating 2g/L sulfate concentration and with the organic loading increasing from 3.5 kg COD/m(3)d to 5.9 kg COD/m(3)d, for a 1-day residence time. In the absence of recirculation, the best outcome (65% reduction) was noticed with the lowest organic loading (3.55 kg/m(3)d). When recirculation was applied, sulfate reduction yields increased to 89%, corresponding to a sulfate removal rate of 1.94 kg SO(4)(2-)/m(3)d. The reactor performance was discussed in relation to microbial diversity and metabolic pathways. At high organic loading, two metabolic pathways account for lactate degradation: (i) lactate is oxidized to acetate and carbon dioxide by the incomplete-oxidizer SRB (sulfate-reducing bacteria) Desulfomonas, Desulfovibrio, Desulfolobus, Desulfobulbus and Desulfotomaculum spp.; (ii) lactate is converted to acetate by fermenting bacteria such as Clostridium sp. High propionate concentrations imply that there are low sulfate reduction efficiencies.

Effect of COD/SO4(2-) ratio on anaerobic treatment of landfill leachate during the start-up period

This study investigates the performance of an anaerobic baffled reactor (ABR) during the start-up period of raw young landfill leachate treatment at two chemical oxygen demand (COD) to SO4(2-) ratios of 20 and 4. The reactor was operated at ambient temperature and low organic loading rates (0.52, 0.76 and 1.05 kg COD/m3 per day). During the study, sulfate-reducing bacteria (SRB) activity increased at the lower ratio of COD/SO4(2-) producing higher levels of sulfide and alkalinity. The dissolved sulfide concentration reached an inhibitory level above 250 mg/L, which caused a sharp reduction in the total COD removal efficiency from 77-80% to 32%. Total volatile fatty acid (TVFA) production proceeded at a constant level despite increased organic loading. As the effluent total and organic COD concentrations increased, the inhibitory effect of the inborn sulfide was correlated to the limitation experienced in the hydrolysis/acidogenesis stages, and thus VFA production and organic matter removal.

Anaerobic treatment of sulfate-rich wastewater in an anaerobic sequential batch reactor (AnSBR) using butanol as the carbon source

Biological sulfate reduction was studied in a laboratory-scale anaerobic sequential batch reactor (14 L) containing mineral coal for biomass attachment. The reactor was fed industrial wastewater with increasingly high sulfate concentrations to establish its application limits. Special attention was paid to the use of butanol in the sulfate reduction that originated from melamine resin production. This product was used as the main organic amendment to support the biological process. The reactor was operated for 65 cycles (48 h each) at sulfate loading rates ranging from 2.2 to 23.8 g SO(4)(2-)/cycle, which corresponds to sulfate concentrations of 0.25, 0.5, 1.0, 2.0 and 3.0 g SO(4)(2-) L(-1). The sulfate removal efficiency reached 99% at concentrations of 0.25, 0.5 and 1.0 g SO(4)(2-) L(-1). At higher sulfate concentrations (2.0 and 3.0 g SO(4)(2-) L(-1)), the sulfate conversion remained in the range of 71-95%. The results demonstrate the potential applicability of butanol as the carbon source for the biological treatment of sulfate in an anaerobic batch reactor.

Isolation and bioaugmentation of an estradiol-degrading bacterium and its integration into a mature biofilm

Bioaugmentation can alter the potential activity as well as the composition of the naturally occurring microbial biota during bioremediation of a contaminated site. The focus of the current study is the pollutant 17β-estradiol (E2), which can cause endocrine effects and is potentially harmful to aquatic biota and to public health. The community composition and function of biofilms, originating from a wetland system, as affected by augmentation of an estradiol-degrading bacterium (EDB-LI1) under different conditions, were investigated. EDB-LI1 inoculation into biofilm from two wetland ponds representing early and advanced water treatment stages, respectively, yielded three significant observations, as follows: (i) EDB-LI1, enriched from a biofilm of a constructed wetland wastewater treatment system, was detected (by quantitative PCR [qPCR] analysis) in this environment in the augmented biofilm only; (ii) the augmented biofilm acquired the ability to remove estradiol; and (iii) the bacterial community composition (analyzed by PCR-denaturing gradient gel electrophoresis [DGGE]) of the augmented biofilm differed from that of the control biofilm. Furthermore, EDB-LI1 bioaugmentation showed a higher level of removal of estradiol with biofilms that originated from the advanced-treatment-stage wetland pond than those from the early-treatment-stage pond. Hence, the bioaugmentation efficiency of EDB-LI1 depends on both the quality of the feed water and the microbial community composition in the pond.

Bioaugmentation of a biological contact oxidation ditch with indigenous nitrifying bacteria for in situ remediation of nitrogen-rich stream water

In this study, specialized bacteria were domesticated and cultivated with polluted stream water. The bioaugmentation of specialized bacteria would significantly enhance the removal efficiency of TN and NH4+-N from 25.9% to 50.3%, and from 34.5% to 60.1%, respectively. Concomitant increases in the number of microbial communities and the proportion of nitrifying bacteria were also identified by the most probable number (MPN) method. PCR-DGGE profiles revealed that the bacterial community could be successfully enriched and the ammonia-oxidizing bacteria communities were shown predominant by the species of Nitrosomonas. The biological contact oxidation ditch (BCOD) system augmented with specialized bacteria can be a viable alternative for treating polluted stream water to achieve improved nitrogen removal.

Interaction effects of organic load and cycle time in an AsBr applied to a personal care industry wastewater treatment

A mechanically stirred anaerobic sequencing batch reactor (ASBR) containing granular biomass was applied to the treatment of a wastewater simulating the effluent from a personal care industry. The ASBR was operated with cycle lengths (t(C)) of 8, 12 and 24 h and applied volumetric organic loads (AVOL) of 0.75, 0.50 and 0.25 gCOD/L.d, treating 2.0 L liquid medium per cycle. Stirring frequency was 150 rpm and the reactor was kept in an isothermal chamber at 30 °C. Increase in t(C) resulted in efficiency increase at constant AVOL, reaching 77% at t(C) of 24 h versus 69% at t(C) of 8 h. However, efficiency decreased when AVOL decreased as a function of increasing t(C), due to the lack of substrate in the reaction medium. Moreover, replacing part of the wastewater by a chemically balanced synthetic one did not yield the expected effect and system efficiency dropped.

Influence of feed time and sulfate load on the organic and sulfate removal in an ASBR

The removal of sulfate and organic matter was assessed in an ASBR, which treated wastewater containing 500 mg CODL(-1) (3 g CODL(-1)d(-1)) in 8h-cycles at 30 degrees C. The wastewater was enriched with sulfate at [COD/SO(4)(2-)] ratios of 1.34, 0.67 and 0.34 (8.8,4.5 and 2.2 gSO(4)(2-)L(-1)d(-1)). For each COD/[SO(4)(2-)] ratio fill times used were: 10 min (batch), 3 and 6h (fed-batch), achieving sulfate reduction of 30%, 72% and 72% (COD/[SO(4)(2-)] of 1.34); 25%, 58% and 55% (COD/[SO(4)(2-)] of 0.67) and 23%, 37% and 27% (COD/[SO(4)(2-)] of 0.34), respectively, and organic matter removal of 87%, 68% and 80% (COD/[SO(4)(2-)] of 1.34); 78%, 75% and 69% (COD/[SO(4)(2-)] of 0.67) and 85%, 84% and 83% (COD/[SO(4)(2-)] of 0.34), respectively. The results showed that fed-batch operation improved sulfate reduction, whereas organic matter removals were similar for batch and fed-batch operation. In addition, increase in sulfate loading in the fed-batch operation improved organic matter removal.

Methane production from oleate: assessing the bioaugmentation potential of Syntrophomonas zehnderi

The potential for improving long-chain fatty acids (LCFA) conversion to methane was evaluated by bioaugmenting a non-acclimated anaerobic granular sludge with Syntrophomonas zehnderi. Batch bioaugmentation assays were performed with and without the solid microcarrier sepiolite, using 1 mM oleate as sole carbon and energy source. When S. zehnderi was added to the anaerobic sludge methane production from oleate was faster. High methane yields, i.e. 89 ± 5% and 72 ± 1%, were observed in bioaugmented assays in the absence and presence of sepiolite, respectively. Sepiolite stimulated a faster methane production from oleate and prevented the accumulation of acetate. Acetoclastic activity was affected by oleate in the absence of sepiolite, where methane production rate was 26% lower than in assays with microcarrier.

Effect of impeller type and agitation on the performance of pilot scale ASBR and AnSBBR applied to sanitary wastewater treatment

The objective of this work was to assess the effect of agitation rate and impeller type in two mechanically stirred sequencing batch reactors: one containing granulated biomass (denominated ASBR) and the other immobilized biomass on polyurethane foam (denominated AnSBBR). Each configuration, with total volume of 1 m(3), treated 0.65 m(3) sanitary wastewater at ambient temperature in 8-h cycles. Three impeller types were assessed for each reactor configuration: flat-blade turbine impeller, 45 degrees -inclined-blade turbine impeller and helix impeller, as well as two agitation rates: 40 and 80 rpm, resulting in a combination of six experimental conditions. In addition, the ASBR was also operated at 20 rpm with a flat-blade turbine impeller and the AnSBBR was operated with a draft tube and helix impeller at 80 and 120 rpm. To quantify how impeller type and agitation rate relate to substrate consumption rate, results obtained during monitoring at the end of the cycle, as well as the time profiles during a cycle were analyzed. Increasing agitation rate from 40 rpm to 80 rpm in the AnSBBR improved substrate consumption rate whereas in the ASBR this increase destabilized the system, likely due to granule rupture caused by the higher agitation. The AnSBBR showed highest solids and substrate removal, highest kinetic constant and highest alkalinity production when using a helix impeller, 80 rpm, and no draft tube. The best condition for the ASBR was achieved with a flat-blade turbine impeller at 20 rpm. The presence of the draft tube in the AnSBBR did not show significant improvement in reactor efficiency. Furthermore, power consumption studies in these pilot scale reactors showed that power transfer required to improve mass transfer might be technically and economically feasible.

Evaluation of performance and community dynamics of microorganisms during treatment of distillery spent wash in a three stage bioreactor

The ability of Emericella nidulans var. lata, Neurospora intermedia and Bacillus sp. to treat distillery spent wash in a three stage bioreactor was investigated. Process parameters were optimized in shake flask cultures with the individual strains before treatment of the effluent in a 15-l bioreactor. Treatment was first carried out by the fungi followed by bacteria. The treated effluent showed significant reduction in color (82%) and COD (93%) after 30 h. Metabolites formed after degradation of complex polymers in distillery effluent were assayed by gas chromatography-mass spectroscopy and included furan, simple acid types and organic compounds. Denaturing gradient gel electrophoresis of 16S rDNA and 18S rDNA sequences amplified from DNA isolated from the reactor communities indicated the presence of other organisms besides those introduced initially. The microbial communities were able to carry out bioremediation of distillery effluent and produce discharge that conforms to safety standards.

Bioaugmentation with the nicotine-degrading bacterium Pseudomonas sp. HF-1 in a sequencing batch reactor treating tobacco wastewater: degradation study and analysis of its mechanisms

The highly effective nicotine-degrading bacterium Pseudomonas sp. HF-1 was augmented in an SBR system that is used to treat tobacco wastewater. Compared to the non-bioaugmented (non-BA) system, the bioaugmented (BA) system exhibited considerably stronger pollution disposal abilities, with 100% nicotine degradation and more than 84% chemical oxygen demand (COD) removal within 12h. Nicotine degradation had a significant effect on COD removal in SBRs (r=0.928, p<0.01). The mechanisms of bioaugmentation were systematically investigated using a combination of polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) and a toxicity assay (protein carbonyl (PC) and DNA-protein crosslinking (DPC)). DGGE fingerprint profiles showed that the number of bands and the Shannon-Wiener index decreased at a nicotine load of 250mg/L compared to a 40-130mg/L nicotine load in the non-BA system. However, a stepwise increase in the Shannon-Wiener index was found during all periods in the BA system. A comparison of sequences excised from DGGE gels demonstrated significant differences in the dominant microbial species between the two SBRs. This result suggested that bioaugmentation of strain HF-1 could select cooperators for treating complicated tobacco wastewater. The PC content and the DPC coefficient increased significantly at levels higher than 80mg/L in the non-BA system; nevertheless, no increase was observed in the BA system during the stepwise nicotine load. This indicated that bioaugmentation of strain HF-1 resulted in the maintenance of high treatment activity by minimizing the nicotine toxicity for other microbes in the BA system. In conclusion, the rapid nicotine degradation of strain HF-1 performed a vital function in SBR by influencing the microbial community structure, dynamics and activity of the activated sludge system.

Effect of amended soil and hydraulic load on enhanced biological nitrogen removal in lab-scale SWIS

To characterize the effect of amended soil on nitrogen removal in subsurface wastewater infiltration system (SWIS), culture, grass carbon, and zeolite were mixed to produce microbial inoculums, and then the optimal microbial inoculums, nutrient substance, cinder, and original soil were mixed to produce the soils through bioaugmentation. Results indicate that the microbial inoculums (culture+50% grass carbon+50% zeolite) and the amended soil (12.5% microbial inoculums+25% nutrient substrate+12.5% cinder+50% original soil) have the optimal biogenic stimulating properties, and the adsorption capacity of the amended soil are 1.216 mg-Pg(-1) and 0.495 mg-Ng(-1). The laboratory soil column experiment indicates that the efficient mode of nitrogen removal in lab-scale SWIS is adsorption-nitrification-denitrification and the nitrification/denitrification can be enhanced by the application of the amended soil. On average, the SWIS filled with amended soil converts 85% of ammonia nitrogen (NH(4)(+)-N) to NO(x)(-)-N and removes 49.8-60.6% of total nitrogen (TN), while the system filled with original soil removes 80% of NH(4)(+)-N and 31.3-43.2% of TN at 4-8 cm day(-1). Two systems are overloads at 10 cm day(-1). It is concluded that the microbial activities and nitrogen removal efficiencies are improved in SWIS after bioaugmentation.

Bioaugmentation of microbial communities in laboratory and pilot scale sequencing batch biofilm reactors using the TOL plasmid

The aim of this study was to investigate the effectiveness of bioaugmentation and transfer of plasmid pWWO (TOL plasmid) to mixed microbial populations in pilot and laboratory scale sequencing batch biofilm reactors (SBBRs) treating synthetic wastewater containing benzyl alcohol (BA) as a model xenobiotic. The plasmid donor was a Pseudomonas putida strain chromosomally tagged with the gene for the red fluorescent protein carrying a green fluorescent protein labeled TOL plasmid, which confers degradation capacity for several compounds including toluene and BA. In the pilot scale SBBR donor cells were disappeared 84 h after inoculation while transconjugants were not detected at all. In contrast, both donor and transconjugant cells were detected in the laboratory scale reactor where the ratio of transconjugants to donors fluctuated between 1.9 x 10(-1) and 8.9 x 10(-1) during an experimental period of 32 days. BA degradation rate was enhanced after donor inoculation from 0.98 mg BA/min prior to inoculation to 1.9 mg BA/min on the seventeenth day of operation. Survival of a bioaugmented strain, conjugative plasmid transfer and enhanced BA degradation was demonstrated in the laboratory scale SBBR but not in the pilot scale SBBR.