Surface-modified Carriers Research Articles

Simultaneous removal of refractory organic pollutants and nitrogen using electron shuttle suspended biofilm carriers in an integrated hydrolysis/acidification-anoxic/aerobic process

Azo dyes wastewater contains refractory pollutant and nitrogen, which threatens human health and ecological environment when discharged into environment directly. Electron shuttle (ES) is able to participate in the extracellular electron transfer, and thus enhances the removal efficiency of refractory pollutant. However, the continuous dosing of soluble ES would rise operation cost and cause contamination inevitably. In this study, a type of insoluble ES (carbonylated graphene oxide (C-GO)) was developed and melt blended into polyethylene (PE) to prepare novel C-GO-modified suspended carriers. Compared to those of conventional carrier (31.60%), the surface active sites of novel C-GO-modified carrier increased to 52.95%. An integrated hydrolysis/acidification (HA, filled with C-GO-modified carrier) - anoxic/aerobic (AO, filled with clinoptilolite-modified carrier) process was applied to remove azo dye acid red B (ARB) and nitrogen simultaneously. ARB removal efficiency was significantly improved in the reactor filled with C-GO-modified carriers (HA2) compared to the reactor filled with conventional PE carriers (HA1) or activated sludge (HA0). Total nitrogen (TN) removal efficiency of the proposed process increased by 25.95–32.64% compared to the reactor filled with activated sludge. Moreover, the intermediates of ARB were identified by liquid chromatograph-mass spectrometer (LC-MS), and the degradation pathway of ARB through ES was proposed. C-GO-modified carriers induced ARB-removal-related bacterial enrichment (such as Chloroflexi, Lactivibrio, Longilinea, Bacteroidales and Anaerolineaceae). Besides, the relative abundance of denitrifiers and nitrifiers in the AO reactor filled with clinoptilolite-modified carrier was increased by 11.60% compared with activated sludge. Copy numbers of genes related to membrane transport, carbon/energy metabolism and nitrogen metabolism increased significantly on the surface-modified carriers. This study proposed an efficient approach for simultaneous azo dyes and nitrogen removal, showing potential in actual application.

Step-feed sequence batch reactor filled with surface-modified carriers can enhance nitrogen removal from low C/N ratio wastewater

It is difficult to achieve efficient nitrogen removal from low C/N ratio wastewater if there is no extra carbon source addition. In this study, integrated floating-film activated sludge (IFFAS) process filled with surface-modified carriers (rough, hydrophilic and positive-charged surface) was employed to enhance nitrogen removal performance. By applying step-feed sequence batch reactor strategy, high total nitrogen (TN) removal loading of 0.062 ± 0.010 kg/(m3∙d) could be achieved under the inflow flow ratio of 2:1:1 without external carbon source when treating low C/N ratio wastewater (C/N ratio: 3.5). In comparison, TN removal loading was only 0.031 ± 0.010 kg/(m3∙d) in activated sludge, and 0.057 ± 0.014 kg/(m3∙d) in IFFAS filled with conventional carrier system. The step-feed sequence batch reactor strategy resulted in complete utilization of influent carbon source for denitrification. The low C/N ratio also promoted microbial by-products production that enhanced nitrogen removal. Meanwhile, surface-modified carriers induced the mixed distribution of nitrifiers and denitrifiers. This study proposed a low-cost and efficient approach for nitrogen removal from low C/N ratio wastewater, showing potential in actual application.

Enhancing the formation of simultaneous nitrification and denitrification (SND) biofilm and nitrogen removal performance using two-units IFFAS process filled with surface-modified carriers

Moving-bed biofilm reactor (MBBR) and integrated floating-film activated sludge (IFFAS) are considered as well-established technologies for simultaneous nitrification and denitrification (SND). However, SND biofilm formation and nutrient removal performance are generally limited by the innate physico-chemical properties of conventional suspended carriers and/or insufficient carbon source available for denitrification. In this study, novel surface-modified carriers were developed via introducing mixed functional materials (natural zeolite, cationic polyquaternium-10, insoluble biodegradable organic polybutylene succinate/bamboo powder) into polyethylene. The modified carrier revealed enhanced hydrophilicity, positive surface charge, higher surface free energy and carbon source slow release capacity. Biofilm growth feature showed that the surface-modification resulted in more biofilm formation and more polysaccharide and protein in extracellular polymeric substances (EPS), which was structural and functional beneficial for substrate capture, transfer and intercellular interactions between nitrifiers and denitrifiers. IFFAS reactor filled with novel modified carriers was upgraded by dividing into two vertical units, where alternate feeding and aeration was conducted to create an anoxic unit to enhance the utilization of influent carbon source for denitrification as well as an aerobic unit to strengthen nitrification. The two-units IFFAS reactor exhibited highly efficient SND performance with TN removal efficiency of 59.9–65.9%, increased by 12.3–13.5% compared with control group. This study proposed an approach towards enhancement of functional biofilm formation and SND performance, and had fascinating potential in actual applications.

Enhanced simultaneous nitrification and denitrification via adding N-acyl-homoserine lactones (AHLs) in integrated floating fixed-film activated sludge process

• Efficient SND was achieved by adding exogenous AHLs at low C/N ratio. • AHLs rose polysaccharide content of EPS and improved biofilm structure and function. • AHLs enhanced the abundance of mixtrophic denitrifying genera participated in QS. • We proposed the mechanism of enhanced SND via exogenous AHLs in IFFAS process. Nitrogen removal from wastewater under low carbon/nitrogen (C/N) ratio and low dissolved oxygen (DO) level via simultaneous nitrification and denitrification (SND) can reduce energy consumption and exogenous carbon source, however, the stressful conditions would impair nitrogen removal performance. In this study, integrated floating fixed-film activated sludge (IFFAS) filled with novel surface-modified carriers was adopted and exogenous N-acyl-homoserine lactones (AHLs) were introduced to enhance SND. Results showed that efficient SND performance was achieved at low C/N ratio of 4 and DO concentration of 0.8 mg/L. AHLs could raise polysaccharide contents of extracellular polymeric substances (EPS) remarkably, which strengthened bacterial adhesion and provided structural and functional benefits to resource capture, digestive capacity and intercellular interactions. Bacterial community analysis indicated AHLs could enhance the abundance of mixtrophic denitrifying genera that participated in quorum sensing on carriers, such as anoxic denitrifiers ( Flavobacterium , relative abundance 12.7 %), aerobic denitrifiers ( Zooglaea , relative abundance 16.9 %) and autotrophic denitrifiers ( Silanimonas , relative abundance 5.2 %). The efficient SND was mainly attributed to the structural/compositional-improved biofilm and coexistence of enriched mixtrophic nitrogen-removal microorganisms caused by AHLs. This study inspired a feasible strategy towards synchronous enhancement of biofilm structure and SND performance at low C/N ratio and low DO level through exogenous AHLs.

Anammox attachment and biofilm development on surface-modified carriers with planktonic- and biofilm-based inoculation

This study investigates the kinetics, attachment, biofilm development and anammox bacteria enrichment of a novel detached anammox biofilm inoculation method on non-modified virgin MBBR carriers and pre-seeded denitrifying carriers. The study compares these results to the more common use of attached anammox carriers for anammox MBBR inoculation. The anammox bacteria specific attachment-growth rates for virgin carriers inoculated with detached anammox biofilm mass were 38.1% greater for the first 25 days, leading to approximately 30% less time required to achieve complete biofilm coverage than those measured in attached biofilm carrier inoculated systems during the attachment and early biofilm growth stages. The biofilm thickness increase rate was also 52.3% higher for virgin carriers with detached biofilm inoculum. Further, inoculation using pre-seeded denitrifying carriers compared to virgin carriers demonstrated a 13.8% preferential increase in anammox bacteria specific attachment-growth rate and a corresponding 47.2% higher NH4+-N removal rate at the time of biofilm maturation.

Development of an Innovative, Carrier-Based Dry Powder Inhalation Formulation Containing Spray-Dried Meloxicam Potassium to Improve the In Vitro and In Silico Aerodynamic Properties.

Most of the marketed dry powder inhalation (DPI) products are traditional, carrier-based formulations with low drug concentrations deposited in the lung. However, due to their advantageous properties, their development has become justified. In our present work, we developed an innovative, carrier-based DPI system, which is an interactive physical blend of a surface-modified carrier and a spray-dried drug with suitable shape and size for pulmonary application. Meloxicam potassium, a nonsteroidal anti-inflammatory drug (NSAID), was used as an active ingredient due to its local anti-inflammatory effect and ability to decrease the progression of cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). The results of the in vitro and in silico investigations showed high lung deposition in the case of this new formulation, confirming that the interparticle interactions were changed favorably.

Simultaneous nitrification and denitrification in continuous flow MBBR with novel surface-modified carriers

ABSTRACT Moving-Bed Biofilm Reactor (MBBR) process is an ideal preference for simultaneous nitrification and denitrification (SND) attributing to the longer sludge age and aerobic/anoxic microenvironment along biofilm. However, conventional carriers generally exhibit negative charge and surface hydrophobicity, which are unbeneficial for biofilm formation. In this study, novel surface-modified carriers with favourable hydrophilicity (surface contact angle dropped to 60.2 ± 2.3°) and positive surface charge (+11.7 ± 1.1 mV, pH 7.0) were prepared via polymer blending and implemented for SND in continuous flow MBBR system. Results indicated SND started up quickly with more biomass in MBBR filled with surface-modified carriers. At the operation condition of low dissolved oxygen level (0.75 ± 0.25 mg/L), pH of 7.5 ± 0.5, 23 ± 2°C and C/N ratio of 7, COD, NH4 +-N and TN removal efficiencies were 90.5%, 88.6% and 76.6% respectively in MBBR filled with surface-modified carriers, which ensured the effluent met the first grade A of the Discharge Standard of China. On the contrary, COD, NH4 +-N and TN removal efficiencies were 89.7%, 82.3% and 60.4% respectively in the control reactors filled with conventional polyethylene carriers. The worse performance of the control reactor was mainly attributed to the less biomass and lower functional bacteria abundance developed on conventional carriers. Moreover, novel carriers provided a favourable niche for more types of functional bacteria, of which autotrophic nitrification, anoxic denitrification, heterotrophic nitrification and aerobic denitrification co-existed and participated in nitrogen removal.

Simultaneous nitrification and denitrification process using novel surface-modified suspended carriers for the treatment of real domestic wastewater

Moving-bed biofilm reactor (MBBR) is a well-established technology for simultaneous nitrification and denitrification (SND). In MBBR, biofilm development and pollutant removal performance are strictly governed by the physico-chemical properties of the carriers. In this study, novel surface-modified carriers with enhanced hydrophilicity (surface contact angle of 60.2 ± 2.3°) and positively-charged surfaces (+11.7 ± 1.1 mV, pH 7.0) had been prepared successfully via polymer blending, and they had also been implemented in SND system for the treatment of real domestic wastewater. Results showed that accelerated startup of SND with more biomass on the carriers was observed in MBBR system filled with surface-modified carriers. At low DO level (0.6–0.8 mg L−1) and low C/N ratio (≤5), highly efficient organics removal and SND performance could be achieved with COD removal, TN removal and SND efficiencies of 79.3–85.7%, 62.0–75.9% and 58.5–71.8%, respectively. The efficient performance of SND in MBBR system filled with surface-modified carriers was mainly attributed to the coexistence of enriched mixtrophic nitrifiers and denitrifiers like autotrophic nitrifers (Nitrosomonas, Nitrospira, Nitrobacter), heterotrophic nitrifers (Rudaea), aerobicdenitrifiers (Dokdonella, Terrimonas), anoxic denitrifiers (Gemmobacter, Ottowia, Methyloversatilis, Thermomonas) and N2O producer (Mesorhizobium).

Characterizing the Surface Roughness Length Scales of Lactose Carrier Particles in Dry Powder Inhalers.

Surface roughness is well recognized as a critical physical property of particulate systems, particularly in relation to adhesion, friction, and flow. An example is the surface property of carrier particles in carrier-based dry powder inhaler (DPI) formulations. The numerical characterization of roughness remains rather unsatisfactory due to the lack of spatial (or length scale) information about surface features when a common amplitude parameter such as average roughness ( Ra) is used. An analysis of the roughness of lactose carrier particles at three different length scales, designed for specificity to the study of interactive mixtures in DPI, was explored in this study. Three Ra parameters were used to represent the microscale, intermediate scale, and macroscale roughness of six types of surface-modified carriers. Coating of micronized lactose fines on coarse carrier particles increased their microroughness from 389 to 639 nm while the macroroughness was not affected. Roller compaction at higher roll forces led to very effective surface roughening, particularly at longer length scales. Changes in Ra parameters corroborated the visual observations of particles under the scanning electron microscope. Roughness at the intermediate scale showed the best correlation with the fine particle fraction (FPF) of DPI formulations. From the range of 250 to 650 nm, every 100 nm increase in the intermediate roughness led to ∼8% increase in the FPF. However, the effect of surface roughness was greatly diminished when fine lactose (median size, 9 μm) of comparable amounts to the micronized drug were added to the formulation. The combination of roughness parameters at various length scales provided much discriminatory surface information, which then revealed the "quality" of roughness necessary for improving DPI performance.

Immobilization of starch-converting enzymes on surface-modified carriers using single and co-immobilized systems: properties and application to starch hydrolysis

Starch-converting enzymes, α-amylase and glucoamylase, were immobilized on surface-modified carriers using a co-immobilized as well as a single system. Hydrophilic silica gel and DEAE-cellulose entrapped in alginate beads were selected as the most effective carriers. The hydrophilic and the hydrophobic characteristics of carriers were made by polyethylimine-coating and silanization, respectively, and confirmed by contact angle measurements. All co-enzymes immobilized on hydrophilic carriers exhibited the highest activities in each modulation. The lower K m values (0.102 mg/ml for hydrophilic silica gel and 0.099 mg/ml for DEAE-cellulose entrapped in beads) than that of native enzyme (0.199 mg/ml) represented the higher affinity of immobilized enzymes to substrates. When performing the hydrolysis of starch, the shifts of optimum temperature from 50 to 60 °C (or activation energy) and pH from 5.0 to 5.5 after immobilization were due to covalent bond formation and polyionic characteristics of carriers, respectively. The co-enzymes immobilized on hydrophilic silica gel and DEAE-cellulose entrapped in alginate beads exhibited 92.3 and 88.9% of the remaining activity even after 10 times of reuse.