Polyurethane Foam Carriers Research Articles

A novel method for immobilizing anammox bacteria in polyurethane foam carriers through dewatering

Biomass immobilization is an effective method for retaining the slow-growing anammox bacteria in reactors. A novel method for rapidly immobilizing anammox bacteria in polyurethane foam carriers through dewatering was proposed in this study. The polyurethane foam carriers sucked anammox sludge and then naturally dewatered for 12 h. 83.12 ± 3.24 % of the sucked sludge was retained within carriers under shear conditions. The specific anammox activity of the anammox bacteria retained in the carriers was lost by 19.95 ± 1.37 % during the dewatering process. This immobilization of anammox bacteria through dewatering process was mainly attributed to the cross-linking of alginate-like exopolysaccharides with Ca2+ and the network structure of polyurethane foam carrier. This dewatering immobilization provides an easy and low-cost method for the rapid immobilization of slow-growing anammox bacteria.

Bioinspired Self‐Supporting Phthalocyanine@ZnIn2S4 Foam for Photocatalytic CO2 Reduction Under Visible Light Irradiation

Molecular catalysis for photocatalytic CO2 reduction (PCR) has recently attracted much attention, whereas its scaled practical application is usually limited by the difficulty of recycling and its photochemical instability in homogeneous solutions. Immobilization of molecular catalysts on solid matrices, that is, covalent bonds or noncovalent interactions, provides a great blueprint to tackle this issue. Herein, a bioinspired self‐supporting phthalocyanine@ZnIn2S4 (Pc@ZnIn2S4) foam by growing ZnIn2S4 nanosheets on the commercialized polyurethane foam (PF) followed by loading amino‐modified cobalt phthalocyanine (CoPc–NH2) is developed. The self‐supporting Pc@ZnIn2S4 PF carrier can be directly taken out of the reaction system for the next reaction cycle without any other procedures. The optimized Pc@ZnIn2S4 PF demonstrates superior PCR efficiency under visible light (λ = 420 nm), achieving 474.65 μmol CO g−1 catalyst after 8 h. The superior PCR performance is attributed to the elevated light‐harvesting ability induced by the porous foam structure and the enhanced charge separation efficiency facilitated by the dimension‐matched interface between ZnIn2S4 and Pc. The special design of the immobilization molecular catalyst on solid supporters presented herein develops an efficient strategy for solar‐driven energy conversion.

Simultaneous supplementation of magnetite and polyurethane foam carrier can reach a Pareto-optimal point to alleviate ammonia inhibition during anaerobic digestion

Material addition is a potential method to alleviate ammonia inhibition in the anaerobic digestion process. In this study, seven materials were selected to examine their impact on methane production (MP). In the batch experiment, the reactors with “Magnetite + foam carrier” exhibited nearly a 56% increase in maximum MP rate. Different strategies of magnetite and foam carrier addition were further explored in semi-continuous experiment. Adding two materials together (simultaneous supplementation) resulted in almost 60% increase in MP, 28–41% higher than when supplemented separately. Simultaneous supplementation of the two materials was considered as the Pareto-optimal solution for MP maximization. The acetogenic and methanogenic activities analyses revealed that foam carrier addition accelerated propionate transformation (from propionate to acetate or valerate) while magnetite addition intensified the methanogenesis step. Direct interspecies electron transfer (DIET) was strengthened with over 50% enrichment in DIET-related bacteria. The Anaerobic Digestion Model No.1 was modified with the development of liquid metabolite and biofilm, result in a goodness-of-fit of R2 > 0.96.16sRNA gene sequencing demonstrated that the microbes in the biofilm had kinetic advantages over those in the liquid phase, coupled with higher km and lower Ks values, which contributed to the enhanced MP.

Evaluation and mechanism investigation of the effect of polyurethane foam carrier on improving settleability of activated sludge

Evaluation and mechanism investigation of the effect of polyurethane foam carrier on improving settleability of activated sludge

Effects of polyurethane foam carrier addition on anoxic/aerobic membrane bioreactor (A/O-MBR) for coal gasification wastewater (CGW) treatment: Performance and microbial community structure

Coal gasification wastewater (CGW) is a typical toxic and refractory industrial wastewater with abundant phenols contained. Two identical anoxic/aerobic membrane bioreactors (with (R2) and without (R1) polyurethane (PU) foam) were carried out in parallel to investigate the role of PU foam addition in enhancing pollutants removal in CGW. Results showed that both systems exhibited effective removal of chemical oxygen demand (>93%) and total phenols (>97%) but poor ammonia nitrogen removal (<35%) constrained by ammonia oxidation process. GC–MS analysis revealed that aromatic and other refractory intermediates were dramatically reduced in R2. Moreover, the PU addition had negligible influence on the total soluble microbial products and extracellular polymeric substances contents but significantly alleviated membrane fouling with the operating time 33% prolonged. Microbial community revealed that Flavobacterium, Holophaga, and Geobacter were enriched on PU. Influent type might be a main driver for microbial community succession.

Immobilization of Cells on Polyurethane Foam.

In this chapter, protocols and details for the immobilization of a model cell onto polyurethane foam carriers are provided in order to facilitate the use of such systems in laboratory or industrial reactors. Polyurethane foam has recently acquired great relevance as a carrier for its good mechanical properties, high porosity, and large adsorption surface. In addition, it has a very low commercial cost. Two different immobilization protocols have been described, differing in the flow regime or the possibilities for the reactor: immobilization in a stirred tank reactor working in a discontinuous regime (by cycles) and immobilization in a packed column working in continuous operation mode. Protocols for carrier sterilization, analytical methodology, and immobilization are described.

Heterogeneous biocatalyst: Polyurethane foam coating technique with co-immobilized lipase for bio-flavor production

Bio-flavor is produced from the esterification reaction including free fatty acids and citronellol. Free fatty acids (lauric C12) can be obtained from the hydrolysis of coconut oil substrate. Both of these reactions use heterogeneous polyurethane foam (PUF) matrix catalysts which immobilize the lipase enzyme. PUF is used as an immobilized matrix, because it has characteristics as open cell, rigid, high porosity, consists of of the ether-, carbamate-, amide-groups, so it has the ability to absorb water-oil. PUF has been modified its surface structure by co-immobilized lipase coating technique to make it more hydrophobic/oleofilic. Co immobilized consists of a mixture of gelatine, lechitin, polyethylene glycol (PEG), MgCl2. The aim of this research is to compare the immobilization technique of lipase Mucor miehei using different carriers, that are zeolite, alginate and polyurethane foam (PUF) to produce bio-flavor at mild condition. Each of that was through the mechanism of adsorption, entrapment and covalent binding process. The research was done in specific condition and all of the carriers has gone through the esterification process using different mole ratio of FFA and citronellol. Optimum result of bio-flavor conversion was obtained at the temperature of 40°C, highest thermal stability of 90% and the ability for reusage 4 times on PUF carrier. This results have proven to be cheaper on cost and environmentally friendly.

Hydrophilization of Polyurethane Foam Carriers in MBBR with Hyperbranched Polymeric Diazonium Salts

In recent years, there has been a considerable research interest in moving-bed biofilm reactor(MBBR) for its efficiency and stability. This work proposes a new way to modify the hydrophilicity of polyurethane foam(PU) carriers via the layer-by-layer self-assembly of hyperbranched polymeric diazonium salt(M-HB-DAS) and poly(sodium-p-styrenesulfonate)(PSS). Modified carriers showed very good adsorption for microbes according to the results of scanning electron microscope(SEM). Biochemical experiments on wastewater treatment confirm that the modified PU carriers can improve the removal rate of chemical oxygen demand(COD).

Production of a potential liquid plant bio-stimulant by immobilized Piriformospora indica in repeated-batch fermentation process

Piriformospora indica, a mycorrhizal-like fungus able to establish associations with roots of a wide range of plants, supporting plant nutrition and increasing plant resistance and tolerance to stress, was shown to solubilise phosphate applied in the form of animal bone char (HABO) in fermentation systems. The process of P solubilisation was caused most likely by proton extrusion and medium pH lowering. The fungal mycelium was successfully immobilized/retained in a polyurethane foam carrier. Further employment of the immobilized mycelium in repeated-batch fermentation process resulted in at least 5 cycles of P solubilization. The concentration of soluble P increased during the experiment with 1.0 and 3.0 g HABO l−1 and at the end of the 5th batch cycle reached 40.8 and 120 mg l−1, respectively. The resulting final liquid product, without or with solubilized phosphate, was found to significantly increase plant growth and P plant uptake. It can be used as a biostimulant containing microbial plant growth-promoting substances and soluble P derived from renewable sources (HABO) thus supporting the development of sustainable agro-ecosystems.

The effect of dissolved oxygen concentration (DO) on oxygen diffusion and bacterial community structure in moving bed sequencing batch reactor (MBSBR)

The effect of dissolved oxygen concentration (DO) on simultaneous nitrification and denitrification was studied in a moving bed sequencing batch reactor (MBSBR) by microelectrode measurements and by real-time PCR. In this system, the biofilm grew on polyurethane foam carriers used to treat municipal sewage at five DO concentrations (1.5, 2.5, 3.5, 4.5 and 5.5 mg/L). The results indicated that the MBSBR exhibited good removal of chemical oxygen demand (92.43%) and nitrogen (83.73%) when DO concentration was 2.5 mg/L. Increasing the oxygen concentration in the reactor was inhibitory to denitrification. Microelectrode measurements showed that the thickness of oxygen penetration increased from 1.2 to 2.6 mm when the DO concentration (from 1.5 mg/L to 5.5 mg/L) in the system increased. Oxygen diffusion was not significantly limited by the boundary layer surrounding the carrier and had the largest slope when DO concentration was 2.5 mg/L. The real-time PCR analysis indicated that the amount of the ammonia-oxidizing bacteria and nitrite-oxidizing bacteria increased slowly as DO concentration increased. The proportions of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, as a percentage of the total bacteria, were low with average values of 0.063% and 0.67%, respectively. When the DO concentration was 2.5 mg/L, oxygen diffusion was optimal and ensured the optimal bacterial community structure and activity; under these conditions, the MBSBR was efficient for total inorganic nitrogen removal. Changing the DO concentration could alter the aerobic zone and the bacterial community structure in the biofilm, directly influencing the simultaneous nitrification and denitrification activity in MBSBRs.

Modification of polyurethane foam carriers and application in a moving bed biofilm reactor

In this study hydrophilic cationic modified polyurethane foam (MPUF) carriers were developed to achieve faster water immersion and increased affinity for biofilm attachment in a moving bed biofilm reactor compared with generally used polyurethane foam (PUF) carriers. Biofilm was more susceptible to attachment to MPUF carrier than to PUF carrier. At the steady state of reactor operation, the amount of biofilm attached to MPUF carriers was 1.3 times more than that to PUF carriers. Phylogenetic analysis using 454-pyrosequencing revealed that biofilms attached to MPUF carrier displayed more complex community diversity, with higher Ace, Chao1 and Shannon indices and a lower Simpson index.

Simultaneous removal of Pb(II) and chemical oxygen demand from aqueous solution using immobilized microorganisms on polyurethane foam carrier

We studied the simultaneous removal of Pb(II) and chemical oxygen demand (COD) from synthetic solutions using immobilized microorganism. The immobilized microorganisms on polyurethane foam (IPUF) were successfully prepared by cultivating the microbe B350 in a mixture of culture medium and polyurethane foam (PUF). The adsorption of Pb(II) ion from aqueous solutions onto PUF and IPUF was studied by batch adsorption. IPUF exhibited high Pb(II) removal efficiency. When 0.12 g of IPUF was used to treat 50 mL of 20 mg/L P(I) solution at pH 7.0 and 25 degrees C for 120 mins, the removal ratio was 80%. The biosorption kinetics could be described by the pseudo-second-order model, and the adsorption isotherms could be described by Langmuir and Freundlich equations. In addition, for synthetic wastewater containing Pb(lI) and C6H12O6, the removal ratios of Pb(II) and COD after being treated by IPUF for 8 hours were 92.0% and 84.2%, respectively. The removal ratio of COD clearly decreased with the increase of Pb(II) concentration, meaning that Pb(lI) was toxic to the mobilized microorganisms and lower Pb(II) concentration was preferred.

Effects of packing rates of cubic-shaped polyurethane foam carriers on the microbial community and the removal of organics and nitrogen in moving bed biofilm reactors

The effects of packing rates (20%, 30%, and 40%) of polyurethane foam (PUF) to the removal of organics and nitrogen were investigated by continuously feeding artificial sewage in three aerobic moving bed biofilm reactors. The results indicated that the packing rate of the PUF carriers had little influence on the COD removal efficiency (81% on average). However, ammonium removal was affected by the packing rates, which was presumably due to the different relative abundances of nitrifying bacteria. A high ammonium removal efficiency of 96.3% at a hydraulic retention time of 5h was achieved in 40% packing rate reactor, compared with 37.4% in 20% packing rate. Microprofiles of dissolved oxygen and nitrate revealed that dense biofilm limits the DO transfer distance and nitrate diffusion. Pyrosequencing analysis of the biofilm showed that Proteobacteria, Bacteroidetes and Verrucomicrobia were the three most abundant phyla, but the proportions of the microbial community varied with the packing rate of the PUF carriers.

Microbial activity and community structure in a lake sediment used for psychrophilic anaerobic wastewater treatment

The aim of the study was to investigate the feasibility of a continuous reactor for psychrophilic anaerobic wastewater treatment by using the sludge from cold natural environment. Six sludge samples (S1-S6) were collected from different cold natural locations to select sludge with high anaerobic microbial activity under low temperatures. After a 225-day incubation, the maximum specific methane production rate of a waterfowl lake sediment (S1) at 15°C (70·5mLCH(4) gVSS(-1) day(-1)) was much higher than all other samples. S1 was thus chosen as the seed sludge for the reactor treating synthetic brewery wastewater at 15°C, by immobilizing the micro-organisms on polyurethane foam carriers. The chemical oxygen demand (COD) removal efficiency reached over 80% after 240-day operation at an organic loading rate of 5·3kg m(-3) day(-1), and significant enrichment of biomass was observed. Clone libraries of the microbial communities in the inoculum had high diversities for both archaea and bacteria. Along with a decrease in microbial community diversities, the dominant bacteria (79·5%) at the end of the operation represented the phylum Firmicutes, while the dominant archaeon (41·5%) showed a similarity of 98% with the psychrotolerant methanogen Methanosarcina lacustris. The possibility of using anaerobic micro-organisms from cold environments in anaerobic wastewater treatment under psychrophilic conditions is supported by these findings. This study enriches the theory on microbial community and the application on anaerobic treatment of sludge from cold natural environments.

Decolourization of a textile-reactive dye with Phanerochaete chrysosporium incubated in different ways under non-sterile conditions

Most studies on decolourization of reactive dye with Phanerochaete chrysosporium have been performed under sterile conditions. In this paper, Phanerochaete chrysosporium, suspended in liquid medium, immobilized on nylon nets, and immobilized on polyurethane foams were studied to decolorize a textile-reactive dye in agitated liquid incubation under non-sterile conditions. The results showed that the decolourization against reactive brilliant red K-2BP by mycelia pellets in suspended cultures, the fungi immobilized on nylon nets and immobilized on polyurethane foams were 0%, 52% and 95%, respectively. The suspended incubation system and the system with nylon nets were contaminated with yeasts, which deteriorated the decolourization effects. The three-dimensional reticular structure of polyurethane foam was benefit to Phanerochaete chrysosporium growth in spreading mycelia taking nutrients and oxygen effectively. The foam could quickly absorb liquid medium into its holes, leaving much less nutrients to support the growth of single cell micro-organisms such as yeast in liquid. The micro-environment existed in polyurethane foam was close to the wild growth conditions of white rot fungus in nature. In conclusion, immobilized culture with polyurethane foam carriers is advantaged to reduce the colonization of other micro-organisms, and makes Phanerochaete chrysosporium possess higher decolorizing ability under non-sterile conditions.

Effective microbial degradation of organochlorines in fluidised bed reactor

The aerobic microbial treatment of a groundwater contaminated with several organic compounds was investigated. This microbial process was combined with posttreatment by activated carbon. Mixed cultures were immobilised on polyurethane foam carrier material in a fluidised bed reactor. The main contaminants benzene and chlorobenzene were almost completely eliminated. Elimination rates remained high even at hydraulic retention times of about two hours. A complete elimination of the haloorganic compounds resistant to microbial degradation was achieved by subsequent adsorption on activated carbon. On the basis of the elimination rates and hydraulic retention times, established by these investigations, a technical scale plant combining microbial degradation and polishing adsorption can be designed. Due to the high degree of microbial mineralisation the presented process offers economic advantages over conventional methods. The quantity of residual waste products for disposal is also minimised.

Modelling denitrification in a moving bed of porous carriers from a low-loaded wastewater treatment plant

A model was developed to describe hydrolysis in a moving bed with polyurethane foam carriers under anoxic conditions. It is formulated as a two-box model and structured into bulk and carrier compartments linked by mass transfer processes for solutes and particles. The biological processes consist of the anoxic growth and decay of heterotrophic organisms and hydrolysis of the slowly biodegradable substrate. Kinetic and stoichiometric parameters are taken from Activated Sludge Model No. 2 (Henze et al., 1995). Parameter estimations based on 24 batch experiments resulted in anoxic hydrolysis rates of 3.9 d−1 (at 20°C) and 2.6 d−1 (at 10°C). The mass transfer coefficient for solutes was determined from the mixing of an inert tracer to be 0.3 m d−1. Measurements of the enzymatic activity of α-, β-glucosidase and esterases confirmed that 90% of the activity involves the carriers. In conjunction with the finding that the absorption capacity of the carriers for slowly biodegradable substrate is high, it can be concluded that the hydrolysis takes place principally within the carriers.

Modelling denitrification in a moving bed of porous carriers from a low-loaded wastewater treatment plant

A model was developed to describe hydrolysis in a moving bed with polyurethane foam carriers under anoxic conditions. It is formulated as a two-box model and structured into bulk and carrier compartments linked by mass transfer processes for solutes and particles. The biological processes consist of the anoxic growth and decay of heterotrophic organisms and hydrolysis of the slowly biodegradable substrate. Kinetic and stotchtometrtc parameters are taken from Activated Sludge Model No. 2 (Henze et al, 1995). Parameter estimations based on 24 batch experiments resulted in anoxic hydrolysis rates of 3.9 d−1 (at 20°C) and 2.6 d−1 (at 10°C).The mass transfer coefficient for solutes was determined from the mixing of an inert tracer to be 0.3 m d−1. Measurements of the enzymatic activity of α-, β-glucosidase and esterases confirmed that 90% of the activity involves the carriers. In conjunction with the finding that the absorption capacity of the carriers for slowly biodegradable substrate is high, it can be concluded that the hydrolysis takes place principally within the carriers.

Continuous semi‐solid cultivation for the production of cellulase by Trichoderma reesei mutants using a polyurethane foam carrier and a liquid medium

AbstractThe production of cellulase was investigated in semi‐solid state culture using the immobilized mycelium of Trichoderma reesei mutants on polyurethane foam impregnated with lactose medium. An extremely high value of about 2.6 FPU/ml was reached after the cultivation of T. reesei D‐78085 on a 0.5% lactose medium in continuous culture at a pH medium of 4.0 when a bioreactor with vertical polyurethane foam plates was used. The enzyme yield on lactose was 520 FPU/g of lactose metabolized in comparison with 160 FPU/g using a stirred tank bioreactor.

ImmobilizedAspergillus terreus in itaconic acid production from glucose

The production of itaconic acid by immobilizedAspergillus terreus TKK 200-5-1 was studied both in shake flask cultures, and in continuous column bioreactors. The effect of glucose and ammonium nitrate concentrations, and of pH were examined using a statistical experimental plan. The highest itaconic acid product concentration could be reached at the highest investigated glucose concentration of 150 g/l and the highest initial pH of 3.75, in the absence of ammonium nitrate. In a continuous packed bed column system operated fro 4.5 months itaconic acid was obtained at a productivity of 328 mg/d per gram of polyurethane foam carrier.