Biomass Attachment Research Articles

Operating diagram of a flocculation model in the chemostat

The objective of this study is to analyze a model of the chemostat involving the attachment and detachment dynamics of planktonic and aggregated biomass in the presence of a single resource. Considering the mortality of species, we give a complete analysis for the existence and local stability of all steady states for general monotonic growth rates. The model exhibits a rich set of behaviors with a multiplicity of coexistence steady states, bi-stability, and occurrence of stable limit cycles. Moreover, we determine the operating diagram which depicts the asymptotic behavior of the system with respect to control parameters. It shows the emergence of a bi-stability region through a saddle-node bifurcation and the occurrence of coexistence region through a transcritical bifurcation. Finally, we illustrate the importance of the mortality on the destabilization of the microbial ecosystem by promoting the washout of species. L'objectif de cette étude est d'analyser un modèle du chémostat impliquant la dynamique d'attachement et de détachement de la biomasse planctonique et agrégée en présence d'une seule ressource. En considérant la mortalité des espèces, nous donnons une analyse complète de l'existence et de la stabilité locale de tous les équilibres pour des taux de croissance monotones. Le modèle pré-sente un ensemble riche de comportements avec multiplicité d'équilibres de coexistence, bi-stabilité et apparition des cycles limites stables. De plus, nous déterminons le diagramme opératoire qui dé-crit le comportement asymptotique du système par rapport aux paramètres de contrôle. Il montre l'émergence d'une région de bi-stabilité via une bifurcation noeud col et l'occurrence d'une région de coexistence via une bifurcation transcritique. Enfin, nous illustrons l'importance de la mortalité sur la déstabilisation de l'écosystème microbien en favorisant le lessivage des espèces.

Immobilization of sulfate and thiosulfate-reducing biomass on sand under haloalkaline conditions

Biological sulfate and thiosulfate reduction under haloalkaline conditions can be applied to treat waste streams from biodesulfurization systems. However, the lack of microbial aggregation under haloalkaline conditions limits the volumetric rates of sulfate and thiosulfate reducing bioreactors. As biomass retention in haloalkaline bioreactors has not been studied before, sand was chosen as a biomass carrier material to increase cell retention and consequently raise the volumetric rates. The results showed that ~10 fold higher biomass concentrations could be achieved with sand, compared to previous studies without carrier addition. The volumetric rates of sulfate/thiosulfate reduction increased approximately 4.5 times. Biomass attachment to the sand was restricted to cavities within the sand particles. Acetate produced by acetogenic bacteria from H2 and CO2 was used as carbon source for biomass growth, while formate that was also produced from H2 and CO2 enhanced sulfate reduction. The microbial community composition was analyzed by 16S rRNA gene amplicon sequencing, and Tindallia related bacteria were probably responsible for formate formation from hydrogen. The community attached to the sand particles was similar to the suspended fraction, but the relative abundance of sequences most closely related to Desulfohalobiaceae was much higher in the attached fraction compared to the suspended fraction (30% and 13%, respectively). The results indicated that even though the biomass attachment to sand was poor, it still increased the biomass concentration and consequently the sulfate and thiosulfate reduction volumetric rates.

A value-added insight of reusing microplastic waste: Carrier particle in fluidized bed bioreactor for simultaneous carbon and nitrogen removal from septic wastewater

Turning microplastic litter into reusable products is a resource-saving and eco-friendly strategy of disposing of plastic pollution. This work realized a value-added insight of reusing microplastic waste by processing the recycled microplastic items with clay waste into composite particle (CP). Furthermore, the systematic evaluation of CP particle was carried out in a Liquid-solid fluidized bed bioreactor (LSFBBR-CP) treating septic sewage with low COD to nitrogen ratio (C/N ≤3). The commercial inorganic particle, bioceramsite (BC), was tested in the LSFBBR-BC for comparison. During the 257-day stepwise operation, two LSFBBRs constantly achieved effluent of TCOD <45 mg L−1 and low observed sludge yield (Yobs ≤0.067 g VSS g-1 COD). Comparatively, the lower fluidization velocity for the CP particles (ul, 0.67-1.20 cm s-1) not only contributed to high biomass attachment (17.2 mg VSS g-1 CP particles) but also favored nitrifiers (Nitrosomonas, Nitrosospira, Nitrobacter and Nitrospira) enrichment. Additionally, the LSFBBR-CP outperformed the LSFBBR-BC in energy conservation by consuming 41.1–47.4% less energy for fluidization, due to the lower ul. Contrary to BC particles’ attrition regarding to particle size decrease and surface chemicals loss, the CP particles exhibited superiority in physio-chemical stability. Those comparative advantages confirmed that the CP could be a promising alternative for BC as a carrier particle in LSFBBR, suggesting that turning microplastic litter into reusable carrier particle for FBBRs is feasible.

A sustainable bio-carrier medium for wastewater treatment: Modified basalt fiber

Bio-carrier plays important roles in the performance of biological contact oxidation reactors for wastewater treatment. Most of the conventional bio-carriers are polymeric. Developing more sustainable materials is necessary to reduce the overconsumption of petrochemicals and second pollution after disposal. This work studied the inorganic basalt fiber (BF) fabricated from nature basalt rock as a green and sustainable bio-carrier medium for wastewater treatment. To improve the bio-affinity, the silica-based BF was modified with a hydrophilic cationic polymer (hexadecyl trimethyl ammonium chloride, CTAC). The modified basalt fiber (MBF) showed a more hydrophilic and positively charged surface. The bio-affinity of BF and MBF bio-carriers were evaluated in Bacillus subtilis adhesion and activated sludge immobilization tests. The influence of CTAC coating on the initial adhesion of bacteria and subsequent biomass immobilization was investigated. The results showed that MBF bio-carriers had higher biomass attachment capacity and microorganism diversity with shorter biofilm formation time. The reported MBF provided an environmental-friendly, sustainable and economical alternative to conventional bio-carriers for wastewater treatment.

Reuse of spent resin for aqueous nitrate removal through bio-regeneration

Some commercial products of anion exchange resins have been used in removing aqueous nitrate, but their application has been limited by the spent resins and the brine-waste. In this work, the regeneration of nitrate-laden resin using denitrifying bacteria was investigated for the reuse of the spent resin without brine-waste discharge. The results indicate that the bio-regeneration contains two mainly processes of chemical regeneration (ion exchange) and bio-degradation (denitrification), in which the denitrification related to the inoculum amount was the limiting factor of bio-regeneration. The bio-regeneration time was reduced to about 4.0 h with increasing inoculum amount to 2.2 g VSS/L. It also reduced from more than 50.0 h–4.0 h with the decreasing resin amount from 5.0 g to 0.2 g in the saturation of 35.5 mg/g, and reduced from 12.0 h to 3.0 h with the resin saturation from 27.4 mg/g to 2.70 mg/g in the resin amount of 0.2 g under the inoculum amount of 2.8 g VSS/L. The comparation of bio-degradation rate between data with different resin amount and data with different resin saturation suggested that the spent resin with a high degree of saturation is favorable to bio-regeneration. The bio-regenerated resin can be reused with 11.6% of capacity loss in the initial 5 cycles and gradually reach a stable reusability. This decrease was attributed to the adsorption of protein-like substances onto resin rather than biomass attachment onto resin. This study proposes the reuse of spent resin by bio-regeneration in a reuse mode for the aqueous nitrate removal, with at least 87.5% reduction on the production of waste water from bio-regeneration process.

Cassava Wastewater Treatment in Fixed-Bed Reactors: Organic Matter Removal and Biogas Production

The process of cassava starch extraction is associated with the generation of a large volume of liquid wastes from root washing and starch extraction (5 to 7 L.kg-1root). In this context, the objective of this study was to evaluate the treatment of cassava starch wastewater in a horizontal anaerobic fixed bed reactor to the removal of organic matter and generation of biogas. For this purpose, two fixed bed reactors filled with two different types of support materials were used: bamboo rings and flexible PVC rings. The reactors were constructed in polyvinyl chloride (PVC) with 90 cm length and 15 cm diameter. The working volume of R1 (bamboo as support material) and R2 (PVC as support material) were 6.0 and 8.0 L, respectively. In the operation of the reactors, 13 assays (A1 to A13) were carried out with an increase in the organic loading rate (OLR: 1.7 to 15.0 g COD.L-1.d-1) and a decrease in the hydraulic retention time (HRT: 4.0 to 0.8 days). Biogas production followed a similar pattern in both reactors. The highest biogas productions of 1.5 L.L-1.d-1 (R1) and 1.1 L.L-1.d-1 (R2) were verified in the assay 6 in which were applied highest affluent concentration (15,122 mg.L-1), intermediates organic loading rate (5.6 g.L-1.d-1) and hydraulic retention time (2.7 d). The removal of COD increased with the increase of OLR resulting in COD removal values of up to 99%. Total solids removal efficiencies of 79 and 87% were achieved in R1 and R2, respectively. In both reactors, the contact surface of bamboo (132 m2.m-3) and PVC (191 m2.m-3) supported biomass attachment even in highest OLR (15 g.L-1.d-1) and low HRT (0.8 d). The both support material provided conditions to the reactors withstand the variations and reestablish the equilibrium after possible hydraulic and load shocks, constituting a robust system for the treatment of cassava starch wastewater. In these conditions the COD and solids removal remained satisfactory. After a 450-day reactor running, no changes were observed in the composition and structure of the support material, an indication that bamboo and PVC are possible cheap and efficient alternatives for biomass immobilization.

Production of 1,3-propanediol from pure and crude glycerol using a UASB reactor with attached biomass in silicone support

The 1,3-propanediol (1,3-PDO) yield and productivity from glycerol were studied over a 155-day period. A UASB reactor that also contained silicone support for biomass attachment was used to evaluate the optimal operational conditions and microbiota development. The highest average 1,3-PDO yield was 0.54 and 0.48 mol.mol-gly−1 when reactor pH was 5.0–5.5 and the applied loading rate was 18 and 20 g-gly.L−1.d−1 using the pure and crude substrate, respectively. The productivity was close to 7.5 g.L−1.d−1 for both substrates; therefore, the direct use of crude glycerol can be valorized in practice. Clostridium was the predominant genus for 1,3-PDO production and C. pasteurianum was dominant in the biofilm. Using crude glycerol, C. beijerinckii dropped strongly; some Clostridium population was then replaced by Klebsiella pneumoniae and Lactobacillus spp. The good process performance and the advances in the microbiota knowledge are steps forward to obtain a more cost-effective system in practice.

Microbial characteristics of nitrifiers, denitrifiers and anammox bacteria on different support media to treat space mission wastewater

Biomass attachment and growth are important factors for the startup and stability of fixed-film biological reactors being proposed to recycle wastewater for potable water use in manned space activity. Eight different biofilm support media commonly used in wastewater treatment plants, aquaculture, and aquariums were compared for their relative ability to support attachment and growth of nitrifiers, denitrifiers, and anaerobic ammonia oxidizing (anammox) bacteria biomass. Accumulated total biomass was determined by comparing dry weight of each media before and after culturing of biomass. Fluorescence In-Situ Hybridization (FISH) analysis was used to quantify the proportion and relative activity of each organism group on each media. Measurements of dry biomass normalized to several media properties showed polyether polyurethane foam to have the highest extent of specific biomass attachment and colonization. Six of the eight media were able to sustain a population of anammox bacteria that was more abundant than the other cohorts.

ZnO superhydrophobic coating via convenient spraying and its biofouling resistance

The attachment of microbial biomass on solid surfaces, also referred to as biofouling, is a universal phenomenon that occurs in natural and engineering systems. However, traditional antibiofouling surfaces based on either the release of biocidal compounds or surface chemical/physical design have some drawbacks, such as the high cost, the complicated process, the low accuracy, and the limitation to achieve coatings over large area. Herein, to overcome these problems, a superhydrophobic coating is fabricated via spraying the mixture of hydrophobized zinc oxide nanoparticles and epoxy resin. The zinc oxide nanoparticles form a multiscale roughness, and the epoxy resin promotes the robustness of the coating. The so‐formed superhydrophobic coating resists the attachment of protein, bacteria, and marine algae. It is expected that the so‐developed superhydrophobic coating can be applied in the fields of biomedical instruments, antimicrobial material, marine platform, and ships.

A simple model of biofilm growth in a porous medium that accounts for detachment and attachment of suspended biomass and their contribution to substrate degradation

We derive a macroscopic model for biofilm formation in a porous medium reactor to investigate the role of suspended bacteria on reactor performance. The starting point is the mesoscopic one-dimensional Wanner–Gujer biofilm model. The following processes are included: hydrodynamics and transport of substrate in the reactor, biofilm and suspended bacteria growth in the pore space, attachment of suspended cells to the biofilm, and detachment of biofilm cells. The mesoscopic equations are up-scaled from the biofilm scale to the reactor scale, yielding a stiff system of balance laws, which we study numerically. We find that suspended bacteria and attachment can have a significant effect on biofilm reactor performance.

Optimization of polyurethane foam cube in enhancing the attachment of microalgae biomass

Attachment of microalgae biomass to polyurethane foam material is believed could reduce the cost and time needed for harvesting process in making it reliable to be used in industry for biodiesel production. This paper aim to optimize the usage of polyurethane for higher attachment of microalgae biomass yield in term of it sizes and packing volume. The investigation revealed that 1.0 cm 3 polyurethane foam yield highest attached biomass (0.812 g) and it has best performance compared to 0.125 cm 3 , 8 cm 3 and 27 cm 3 with attached biomass yield 0.666 g, 0.546 g, and 0.368 g respectively. For packing volume, 6% is the best since has highest attached microalgae biomass with yield 0.753 g, compared with 2%, 4%, 8% and 10% with yield 0.426 g, 0.577 g, 0.687 g and 0.644 g attached biomass respectively. Keywords : microalgae; chlorella vulgaris, polyurethane; attached biomass.

Attachment of anaerobic ammonium-oxidizing bacteria to augmented carrier material

ABSTRACTThe formation of stable and highly active anammox biofilm is a lengthy process leading to long start-up times of deammonifying reactors of several months or more. This study aims to provide a quick solution to the problem of long start-up periods by pretreating the surface of carrier material. Two different techniques were investigated. The first one focused on growing a layer of heterotrophic biofilm on the surface of the plastic carriers prior to inoculation with anammox biomass. Specific anammox activity increased by almost 400% as compared to seed values and was equal to 250 mg NH4-N/gVSS/L•d. In the second technique, the carrier material was coated with a layer of granular-activated carbon to provide a higher surface area. The anammox activity increased by approximately 50%. In comparison, the control reactor did not develop any biofilm and no anammox activity was detected. Rapid attachment of the anammox biomass was achieved in a reactor with media that had a predeveloped layer of a biofilm. In a way, this approach is analogous to a primer or an undercoat that is put on materials before painting to ensure better adhesion of paint to the surface, hence the suggested name – bioprimer.

Computational investigation of the flow field contribution to improve electricity generation in granular activated carbon-assisted microbial fuel cells

Abstract Microbial fuel cells (MFCs) offer an alternative approach to treat wastewater with less energy input and direct electricity generation. To optimize MFC anodic performance, adding granular activated carbon (GAC) has been proved to be an effective way, most likely due to the enlarged electrode surface for biomass attachment and improved mixing of the flow field. The impact of a flow field on the current enhancement within a porous anode medium (e.g., GAC) has not been well understood before, and thus is investigated in this study by using mathematical modeling of the multi-order Butler-Volmer equation with computational fluid dynamics (CFD) techniques. By comparing three different CFD cases (without GAC, with GAC as a nonreactive porous medium, and with GAC as a reactive porous medium), it is demonstrated that adding GAC contributes to a uniform flow field and a total current enhancement of 17%, a factor that cannot be neglected in MFC design. However, in an actual MFC operation, this percentage could be even higher because of the microbial competition and energy loss issues within a porous medium. The results of the present study are expected to help with formulating strategies to optimize MFC with a better flow pattern design.

Anti-biofilm and sporicidal activity of peptides based on wheat puroindoline and barley hordoindoline proteins

The broad-spectrum activity of antimicrobial peptides (AMPs) and low probability of development of host resistance make them excellent candidates as novel bio-control agents. A number of AMPs are found to be cationic, and a small proportion of these are tryptophan-rich. The puroindolines (PIN) are small, basic proteins found in wheat grains with proposed roles in biotic defence of seeds and seedlings. Synthetic peptides based on their unique tryptophan-rich domain (TRD) display antimicrobial properties. Bacterial endospores and biofilms are highly resistant cells, with significant implications in both medical and food industries. In this study, the cationic PIN TRD-based peptides PuroA (FPVTWRWWKWWKG-NH2 ) and Pina-M (FSVTWRWWKWWKG-NH2 ) and the related barley hordoindoline (HIN) based Hina (FPVTWRWWTWWKG-NH2 ) were tested for effects on planktonic cells and biofilms of the common human pathogens including Pseudomonas aeruginosa, Listeria monocytogenes and the non-pathogenic Listeria innocua. All peptides showed significant bactericidal activity. Further, PuroA and Pina-M at 2 × MIC prevented initial biomass attachment by 85-90% and inhibited >90% of 6-h preformed biofilms of all three organisms. However Hina, with a substitution of Lys-9 with uncharged Thr, particularly inhibited Listeria biofilms. The PIN based peptides were also tested against vegetative cells and endospores of Bacillus subtilis. The results provided evidence that these tryptophan-rich peptides could kill B. subtilis even in sporulated state, reducing the number of viable spores by 4 log units. The treated spores appeared withered under scanning electron microscopy. The results establish the potential of these tryptophan-rich peptides in controlling persistent pathogens of relevance to food industries and human health. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

Nutrients removal enhancement using a modified rotating activated bacillus contactor (RABC) process

This study was performed to develop a new process technology for advanced wastewater treatment using a modified Rotating Activated Bacillus Contactor (RABC) process that adopts anoxic-oxic suspended biomass tanks to enhance nutrients removal. A modified lab-scale RABC process was applied to examine its applicability and to obtain the design factors for the optimum operation of the system. The modified RABC process showed a little more stable and high nutrients removal efficiency than the prototype RABC process: about 70% of nitrogen and 55% of phosphorous removal when the low organic loading (influent COD 200mg/L). However, the processing efficiency of nutrients removal rates was enhanced to great extent when high organic loading: nitrogen 90% and phosphorous 85% (influent COD 500mg/L). High organic loading stimulated extremely good biomass attachment on the reticular carrier RABC stage and the excellent nutrients removal, nevertheless with almost no offensive odor.

An Integrated Attached Growth Bioreactor for the Treatment of Wastewater

An integrated attached growth bioreactor was evaluated in this study for the removal of organic matter (COD). The bioreactor integrated the aerobic tank, anoxic tank and the secondary clarifier in a single unit. An attached growth media was submerged into the aerobic tank to improve the growth of biomass while bio-balls were submerged into the anoxic tank. Synthetic wastewater simulating medium and high strength domestic wastewater were pumped into the reactor for biodegradation. Hydraulic Retention Time (HRT) was varied in the range 12 and 7.2 days. Influent COD was introduced in two phases. Phase 1 consists of COD 400 mg/L whereas phase 2 consists of COD 650 mg/L. In phase 1, steady state was attained from day 18 until day 26. Effluent concentrations of COD were approximately 9 mg/L at HRT of 12 days. The effluent COD concentration increased (16 mg/L) when COD concentration was increased to 650 mg/L at HRT of 12 days. Effluent COD decreased from 19-9 mg/L when HRT was increased from 7.2-12 days. The effluent COD obtained in this study was below the Malaysia Department of Environment (DOE) guideline limit Standard A (120 mg/L). Residual ammonia, nitrate and total suspended solids were also monitored at steady state. Results show a 97, 87 and 97%, respectively removals for ammonia, nitrate and TSS, respectively. The attached growth media in the aerobic and anoxic tanks provided a large surface area for the attachment of biomass. The bioreactor performance shows it can serve as an alternative footprint for the treatment of wastewater.

Advances in biofouling mitigation: A review

ABSTRACTThe attachment of microbial biomass on solid surfaces is a universal phenomenon that occurs in natural and engineering systems and is responsible for various types of biofouling. Biological fouling, also referred to as biofouling, remains one of the most critical problems toward the durable application of materials. The eradication of this problem using sustainable and environmentally friendly techniques is still of critical importance and is therefore receiving significant interest from researchers worldwide. The authors start with a definition of processes that lead to biofouling and their relevance to various industrial applications. The most relevant findings from past research are presented and particular emphasis is focused on present research, where recent developments in surface modification receive specific attention.

Evaluation of different support materials used with a photo-fermentative consortium for hydrogen production

Three different support materials were evaluated for immobilization of a consortium of purple non-sulfur bacteria producing hydrogen gas. The inoculum was obtained from a bioelectrochemical system, and it was subsequently enriched. Molecular analysis showed that the consortium was mainly composed of Rhodopseudomonas palustris. The tested materials included acrylic rods, high-density polyethylene cylinders and luffa (dispersed fibers and cubes). The hydrogen production, using volatile fatty acids as the substrate, was evaluated in continuously illuminated reactors (7 klux) at 32 °C. The hydrogen production rate observed was between 14 and 20 mL H2/g VS/h. Dispersed luffa fibers showed the highest amount of immobilized biomass (19.6 ± 1.5 mg VS/cm3) followed by luffa in cubes, high-density polyethylene cylinders, and acrylic bars. The dispersed luffa fibers allowed for a better light distribution and contact with the media than the luffa in cubes. There was no significant difference in hydrogen production among the three support materials (luffa, acrylic bars or polyethylene) when the same amount of immobilized biomass was used. The luffa in fibers was the most suitable support for the purple non-sulfur consortium because of the highest area/volume ratio, biomass attachment as well as the adequate light distribution.

A fungal biofilm reactor based on metal structured packing improves the quality of a Gla::GFP fusion protein produced by Aspergillus oryzae

Fungal biofilm is known to promote the excretion of secondary metabolites in accordance with solid-state-related physiological mechanisms. This work is based on the comparative analysis of classical submerged fermentation with a fungal biofilm reactor for the production of a Gla::green fluorescent protein (GFP) fusion protein by Aspergillus oryzae. The biofilm reactor comprises a metal structured packing allowing the attachment of the fungal biomass. Since the production of the target protein is under the control of the promoter glaB, specifically induced in solid-state fermentation, the biofilm mode of culture is expected to enhance the global productivity. Although production of the target protein was enhanced by using the biofilm mode of culture, we also found that fusion protein production is also significant when the submerged mode of culture is used. This result is related to high shear stress leading to biomass autolysis and leakage of intracellular fusion protein into the extracellular medium. Moreover, 2-D gel electrophoresis highlights the preservation of fusion protein integrity produced in biofilm conditions. Two fungal biofilm reactor designs were then investigated further, i.e. with full immersion of the packing or with medium recirculation on the packing, and the scale-up potentialities were evaluated. In this context, it has been shown that full immersion of the metal packing in the liquid medium during cultivation allows for a uniform colonization of the packing by the fungal biomass and leads to a better quality of the fusion protein.

Mesophilic hydrogen production in acidogenic packed-bed reactors (APBR) using raw sugarcane vinasse as substrate: Influence of support materials

Bio-hydrogen production from sugarcane vinasse in anaerobic up-flow packed-bed reactors (APBR) was evaluated. Four types of support materials, expanded clay (EC), charcoal (Ch), porous ceramic (PC), and low-density polyethylene (LDP) were tested as support for biomass attachment. APBR (working volume – 2.3 L) were operated in parallel at a hydraulic retention time of 24 h, an organic loading rate of 36.2 kg-COD m−3 d−1, at 25 °C. Maximum volumetric hydrogen production values of 509.5, 404, 81.4 and 10.3 mL-H2 d−1 L−1reactor and maximum yields of 3.2, 2.6, 0.4 and 0.05 mol-H2 mol−1 carbohydrates total, were observed during the monitoring of the reactors filled with LDP, EC, Ch and PC, respectively. Thus, indicating the strong influence of the support material on H2 production. LDP was the most appropriate material for hydrogen production among the materials evaluated. 16S rRNA gene by Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis and scanning electron microscopy confirmed the selection of different microbial populations. 454-pyrosequencing performed on samples from APBR filled with LDP revealed the presence of hydrogen-producing organisms (Clostridium and Pectinatus), lactic acid bacteria and non-fermentative organisms.