Suspended Carriers Research Articles

Performance of a suspended biofilter as a new bioreactor for removal of toluene

A suspended biofilter, as a new bioreactor, was constructed for removal of VOCs (volatile organic compounds). The biofilter bed (height of 30cm, diameter 16cm and working volume of 6.0L) was formed by applying suspended carrier with porous surface and the carrier itself has a density slightly lower than water. According to the results, it was found that the suspended biofilter was suitable to treat the toluene-contaminated stream. Since it could startup quickly, tolerate great transient shock loadings, and possess average removal efficiency higher than 90.2% in a toluene loading range of 11.0–58.5gm−3h−1. What is more, it also gained a maximum elimination capacity of 113.6gm−3h−1 at a toluene loading rate of 272.2gm−3h−1. The remarkable performance could be contributed to the rich bacterial communities for toluene degradation. A following 16S rRNA gene sequence analysis reveals that the communities contain high efficient toluene-degrading bacteria, i.e., Acinetobacter sp. Tol 5, Burkholderia, and Comamonadaceae. In addition, after a long-term operation of 141 days, no clogging was observed although there was a high biomass concentration in the biofilter bed. It demonstrated that this novel suspended biofilter overcome clogging and accumulation of biomass, which are the drawback of fixed biofilter.

Treatment of Coking Wastewater by a Submerged Membrane Bioreactor with Suspended Carriers

A renovated hybrid membrane bioreactor (HMBR) was investigated for its capability of coking wastewater treatment. The HMBR combined biofilm process and membrane filtration process. The system was efficient in degrading COD and phenol in coking wastewater and controlling membrane. It was found that the coking wastewater could be effectively treated with 88.6% of COD removal efficiency and 98.3% of phenol removal efficiency at hydraulic retention time (HRT) of 16 h. The removal efficiency of COD and phenol decreased gradually down to 83.2% and 97.7% when HRT decreased to 8 h. The long term experiments indicated that the degree of membrane fouling for HMBR was far lower than that for MBR. The scrubbing effect of suspended carrier in HMBR was observed to be capable of reducing the cake fouling of membrane. The operation time of HMBR was 8.4-fold longer than that with MBR.

Improved efficiency of reactor startup in biological aerated filter by poly(lactic acid)

The enhancement effect of polyethylene (PE) surfaces modified with poly(lactic acid) (PLA) on formation of nitrifying biofilms in biological aerated filter (BAF) was investigated in this study. X-ray photoelectron spectroscopy, scanning electron microscope, and protein absorption analysis revealed that modified PE surfaces produced active groups, including carboxyl (O═C─O), hydroxyl (C─OH), and carbonyl (C═O), increased surface roughness, and enhanced the adsorption of both the bovine serum albumin and fibrinogen. During the startup period of 33 days, the average removal rates of ammonia nitrogen (NH3-H) were 68 and 72% before and after modification which were 36 and 43% for total nitrogen, 47 and 45% for total organic carbon. The results of denaturing gradient gel electrophoresis experiments demonstrated that modified carriers adsorbed and gathered more species of bacteria on surfaces. Thus, surface modification of PE suspended carrier by PLA improved the efficiency of reactor startup for drinking water treatment.

Analysis of Biomass Characteristics in MBR and MB-MBR Systems Fed with Synthetic Wastewater: Influence of a Gradual Salinity Increase

The paper presents the results of a field gathering campaign carried out on two different pilot scale membrane bioreactor (MBR) systems, treating synthetic wastewater subject to a gradual increase of salinity. One was a conventional MBR system, while the other was a moving bed biofilm membrane bioreactor (MB-MBR), which combines suspended biomass and biofilm. Indeed, the presence of suspended carriers inside the bioreactor seems to give benefits due to the collisions between the circulating media and the membrane. The aim of the study was the comparison of two configurations in terms of biomass activity characterization and performance (pollutants removal and hydraulic behaviour). The results highlighted a significant biomass activity for both heterotrophic and autotrophic populations. Such behaviour was emphasized in MB-MBR system, likely due to the presence of biofilm attached on suspended sponge carriers, which is characterized by high retention times, thus improving through the “seeding” effect the nitrification ability of the whole system.

Accelerated start-up of moving bed biofilm reactor by using a novel suspended carrier with porous surface.

A novel suspended carrier with porous surface was firstly prepared by coating a sponge on the inside and outside of a hard polyethylene ring. Herein the effects of the sponge thickness (0, 2, 4, 6 mm) and pore size (17, 45, 85 pores per inch, ppi) on the performance of the start-up stage in moving bed biofilm reactor (MBBR) were investigated. The results indicated that the home-made carrier with the sponge thickness of 4 mm and the pore size of 45 ppi, defined as SC4-45, showed the best performance, which obtained high biomass concentration of 2,136.6 mg/L, oxygen uptake rate for COD of 150.1 mg O2/h and oxygen uptake rate for NH4(+)-N of 17.4 mg O2/h. The DGGE profiles of the biofilms obtained in SC4-45 and a commercial carrier showed a similar community as the Dice similarity coefficients between two samples was 0.72. Furthermore, 16S rRNA gene sequence analysis reveals dominance of Sphaerotilus sp. and Aeromonas sp. in the community of both samples. Moreover, for the MBBR based on SC4-45, COD and NH4(+)-N removal rates reached 99.5 ± 1.1 and 93.6 ± 2.3 % at the end of the start-up stage, much higher than those of the commercial carrier, 74.9 ± 2.7 and 40.0 ± 1.8 %, respectively. These indicated the novel carrier obtained a quick start-up.

Application of Immobilization Technology on Enhancing Hydrogen Production by Photosynthetic Bacteria

Hydrogen is a clean and effective energy. Development of hydrogen production technologies is one of the research focuses currently. Application of new-type technologies and materials on biological hydrogen producing is a research emphasis to enhance hydrogen production and promote its engineering application. The latest progress in research on photo fermentative hydrogen production by immobilized photosynthetic bacteria is reviewed. The fundamental of immobilization,progress of its application and impact factors on hydrogen production are summarized. Three immobilization methods including entrapment,suspended carrier and fixed biofilm are discussed in detail,mainly from the aspect of their effects on photo fermentative hydrogen production.New materials which have been worldwide utilized on immobilization are introduced. An outlook on research direction and focuses are also proposed.

Effect of Suspended Carriers on Extracellular Polymeric Substances in MBR

Suspended carriers were added into a submerged membrane bioreactor (SMBR) using polypropylene non-woven fabric (PP NWF) as membrane model to treat synthetic wastewater. The changes of EPSSEPSB and EPS in activated sludge mixing liquid of MBR and in sludge on membrane model surface were researched at different aeration rate. The results showed that adding suspended carriers in MBR can increase the concentration of EPSS and EPSB in activated sludge mixing liquid, but the effect on EPSS and EPSB in the sludge on membrane model surface is related to aeration rate. Adding suspended carriers can increase the concentration of EPSS and EPSB in the sludge on membrane model surface at 0.10m3/h of aeration rate; the concentration of EPSS and EPSB in the sludge with suspended carriers is reduced when aeration rate is increased to 0.25m3/h. The study on the effect of aeration rate on EPS in sludge mixing liquid of MBR and in sludge on membrane model surface showed that an optimized aeration rate exists if suspended carriers are added to control MBR membrane fouling. At the optimized aeration rate, membrane fouling can be mitigated and controled effectively.

Polyacrylamide Wastewater Treatment in a Nested Biofilm Airlift Suspension Reactor

Polyacrylamide has been widely used in tertiary oil recovery. Oilfield produced water in a large scale contain polyacrylamide, leading to oilfield environment pollution. In this paper, the nested loops biofilm airlift suspension reactor was used in polyacrylamide wastewater treatment. In the reactor, wastewater can alternately flow through the hypoxic environment fixed light carriers and aerobic environment suspended walnut shell biological carriers, achieving simultaneous removal of organic matter and nitrogen. The influencing factors on the organic compound degradation and denitrification performance were studied. Biological and hydrodynamic model of nitrogen and carbon removal was established. Also, the biological phase structure of the carrier biofilm was observed. The results show that polyacrylamide degradation and ammonia nitrogen removal rate are around 30% and 95%, respectively when the experimental hydraulic retention time is 24h. Due to poor denitrification efficiency; nitrate removal rate is only 20%. The carrier biofilm thickness is appropriate, and filamentous bacteria occupy the dominant position.

Suspended Carrier Used in Municipal Wastewater Treatment

In this study, suspended carrier bed process was applied to treat the effluent from the chemical-biological flocculation plant. The bio-startup characteristics and the mechanisms of biofilm maturation were investigated. Results showed that the NH3-N removal efficiency was higher than 80% after a 10d run, and the NH3-N concentration of effluent was lower than 5.0mg/L, which satisfies the needs of The Pollutants Discharge Standard for Municipal Wastewater Treatment Plants (Class I-A). In other words, the suspended carrier used here did a good job. The bed finished its bio-startup process with stable nitrification efficiency. The biofilm formed on the carriers wing plates, which was helpful for its adhesion and ageing biofilm to fall off. It was found through electron microscope observation and PCR-DGGE (Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis) that the biofilm which formed on the surface of the carrier contained plenty of microbes. The stability of the microbial system was efficient in stabilizing nitrification.

Research and Development of a New Nano-Attapulgite PVF Suspension Carrier in Wastewater Treatment

The optimum proportion and comprehensive performance as sewage treatment microbial carriers of a new type nanoattapulgite polyvinyl alcohol-formaldehyde suspended carrier (AT-PVF) was researched. The results show that when the polyvinyl alcohol (PVA) dosage is at the range of 10%-16%, H2SO4: PVA plays greatest impact on carrier performance, followed by CH2O: PVA and surfactant, PVA at last. Finally, a new formula of the AT-PVF carrier has been developed, which is showed as follows: PVA 13%, CH2O/PVA weight ratio=0.75, H2SO4/PVA weight ratio=1.0, surfactant 0.5%, AT 0.4%. Test results show that AT-PVF is superior to polyurethane carriers in physical, chemical and biochemical performance.

Successional development of biofilms in moving bed biofilm reactor (MBBR) systems treating municipal wastewater

Biofilm-based technologies, such as moving bed biofilm reactor (MBBR) systems, are widely used to treat wastewater. Biofilm development is important for MBBR systems as much of the microbial biomass is retained within reactors as biofilm on suspended carriers. Little is known about this process of biofilm development and the microorganisms upon which MBBRs rely. We documented successional changes in microbial communities as biofilms established in two full-scale MBBR systems treating municipal wastewater over two seasons. 16S rRNA gene-targeted pyrosequencing and clone libraries were used to describe microbial communities. These data indicate a successional process that commences with the establishment of an aerobic community dominated by Gammaproteobacteria (up to 52 % of sequences). Over time, this community shifts towards dominance by putatively anaerobic organisms including Deltaproteobacteria and Clostridiales. Significant differences were observed between the two wastewater treatment plants (WWTPs), mostly due to a large number of sequences (up to 55 %) representing Epsilonproteobacteria (mostly Arcobacter) at one site. Archaea in young biofilms included several lineages of Euryarchaeota and Crenarchaeota. In contrast, the mature biofilm consisted entirely of Methanosarcinaceae (Euryarchaeota). This study provides new insights into the community structure of developing biofilms at full-scale WWTPs and provides the basis for optimizing MBBR start-up and operational parameters.

悬浮填料对MBR中胞外聚合物的影响<br>Effect of Suspended Carriers on Extracellular Polymeric Substances in MBR

以聚丙烯无纺布为膜组件，向浸渍式膜生物反应器中投加悬浮填料处理人工废水。考察不同曝气量下MBR中污泥混合液以及膜组件表面污泥EPSS、EPSB和EPS的变化。结果表明，MBR中添加悬浮填料能增加污泥混合液中EPSS和EPSB的浓度，而对膜组件表面污泥中EPSS和EPSB影响，与曝气强度有关。在曝气量为0.10 m3/h时，添加悬浮填料能增加污泥中的EPSS和EPSB的浓度，当曝气量增大到0.25 m3/h时，添加悬浮填料的污泥中的EPSS和EPSB的浓度有所降低。曝气量对MBR污泥混合液及膜组件表面污泥EPS影响的研究结果表明，采用添加悬浮填料控制MBR膜污染时存在一个优化的曝气量，在此曝气量下，能实现有效地延缓和控制膜污染。 Suspended carriers were added into a submerged membrane bioreactor (SMBR) using polypropylene non- woven fabric (PP NWF) as membrane model to treat synthetic wastewater. The changes of EPSS, EPSB and EPS in activated sludge mixing liquid of MBR and in sludge on membrane model surface were researched at different aeration rate. The results showed that adding suspended carriers in MBR can increase the concentration of EPSS and EPSB in activated sludge mixing liquid, but the effect on EPSS and EPSB in the sludge on membrane model surface is related to aeration rate. Adding suspended carriers can increase the concentration of EPSS and EPSB in the sludge on membrane model surface at 0.10 m3/h of aeration rate; the concentration of EPSS and EPSB in the sludge with suspended carriers is reduced when aeration rate is increased to 0.25 m3/h. The study on the effect of aeration rate on EPS in sludge mixing liquid of MBR and in sludge on membrane model surface showed that an optimized aeration rate exists if suspended carriers are added to control MBR membrane fouling. At the optimized aeration rate, membrane fouling can be mitigated and controled effectively.

Study on the Contrast of Different Carriers on Degradation of Pollutants

In this literature, two phases of contrast experiments on the removal of COD and ammonia by different carriers were carried out. The results showed that the removal ability of COD by saran lock carriers was superior to other carriers. The removal ability of ammonia by saran lock carriers and spiral carriers were better in contrast with other carriers in two phases experiment respectively. Saran lock carriers were the best and suspended carriers were the worst in the carriers we tested considering the results of two phases of contrast experiments.

Microbial morphology and community structure in a suspended carrier biofilm reactor as a function of substrate loading rates

An aerobic suspended carrier biofilm reactor was efficient in simultaneous organic carbon and nitrogen removal, with COD removal efficiencies of 87.1–99.0% and simultaneous nitrification and denitrification (SND) efficiencies about 96.7-98.8%. The effects of substrate loading on microbial morphology and community structure were investigated by environmental scanning electron microscopy (ESEM), denaturing gel gradient electrophoresis (DGGE) and fluorescence in situ hybridization (FISH). Biofilms formed at different substrate loadings had different morphology and community structures. A higher substrate concentration resulted in denser and thinner biofilms, while a lower substrate concentration resulted in looser and thicker biofilms with significant presence of filamentous bacteria. Both sequence analysis of DGGE bands and FISH analysis indicated the dominance of β-Proteobacteria in the biofilm communities, especially Zoogloea. FISH analysis revealed that the relative abundance of β-proteobacteria ammonia oxidizing bacteria (AOB) was positively correlated with ammonium concentrations, whereas Nitrospira-like nitrite-oxidizing bacteria (NOB) were negatively affected by ammonia and nitrite concentrations. The presence of denitrifying bacteria, Hydrogenophaga spp.,Hyphomicrobium spp. and Rhizobium spp. suggested that not only the oxygen microgradients within the biofilm but also aerobic denitrifiers may be responsible for SND in the aerobic biofilm. Key words: Microbial community structure, microbial morphology, substrate loading, suspended carrier biofilm.

Performance of suspended and attached growth MBR systems in treating high strength synthetic wastewater

The performance of laboratory-scale attached growth (AG) and suspended growth (SG) membrane bioreactors (MBRs) was evaluated in treating synthetic wastewater simulating high strength domestic wastewater. This study investigated the influence of sponge suspended carriers in AG-MBR system, occupying 15% reactor volume, on the removal of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP), and compared it to that of SG-MBR. Results showed that the removal efficiencies of COD, TN and TP in AG-MBR were 98%, 89% and 58%, respectively as compared to 98%, 74% and 38%, respectively in SG-MBR. Improved TN removal in AG-MBR systems was primarily based on simultaneous nitrification and denitrification (SND) process. These results infer that the presence of small bio-particles having higher microbial activity and the growth of complex biomass captured within the suspended sponge carriers resulted in improved TN and TP removal in AG-MBR.

Measuring and modeling the oxygen profile in a nitrifying Moving Bed Biofilm Reactor

In this paper we determine the oxygen profile in a biofilm on suspended carriers in two ways: firstly by microelectrode measurements and secondly by a simple mathematical model. The Moving Bed Biofilm Reactor is well-established for wastewater treatment where bacteria grow as a biofilm on the protective surfaces of suspended carriers. The flat shaped BiofilmChip P was developed to allow good conditions for transport of substrates into the biofilm. The oxygen profile was measured in situ the nitrifying biofilm with a microelectrode and it was simulated with a one-dimensional mathematical model. We extended the model by adding a CSTR equation, to connect the reactor to the biofilm through the boundary conditions. We showed the dependence of the thickness of the mass transfer boundary layer on the bulk flow rate. Finally, we estimated the erosion parameter λ to increase the concordance between the measured and simulated profiles. This lead to a simple empirical relationship between λ and the flow rate. The data gathered by in situ microelectrode measurements can, together with the mathematical model, be used in predictive modeling and give more insight in the design of new carriers, with the ambition of making process operation more energy efficient.

Tracking composition and dynamics of nitrification and denitrification microbial community in a biofilm reactor by PCR-DGGE and combining FISH with flow cytometry

A compact suspended carrier biofilm reactor (SCBR) was operated at three different C/N ratios (C/N = 10:1, 5:1 and 3:1) with focus on reactor performance and microbial community composition of nitrifying and denitrifying bacteria. The process was capable of achieving over 90% removal of chemical oxygen demand (COD) and over 83.3% of simultaneous nitrification and denitrification (SND) efficiency. Denaturing gradient gel electrophoresis (DGGE) analysis showed that the diversity of ammonia-oxidizing bacteria (AOB) community decreased with inoculation sludge, C/N ratio 3:1, 10:1 and 5:1 in turn. Phylogenetics analysis indicated that there were three distinct groups of AOB in Betaproteobacteria subdivision, where Nitrosomonas were the dominant members in the biofilm. Fluorescence in situ hybridization-flow cytometry (FISH-FCM) results revealed that Alpha-, Beta- and Gamma-proteobacteria accounted for over 50% of all cells. Additionally, the clusters of Nitrosomonas, Nitrosospira, Nitrobacter, Nitrospira and AOB of Betaproteobacteria yielded a similar distribution pattern about 5–12% of all cells. Nested analysis of variance assay (ANOVA) demonstrated that the C/N ratio did not significantly affect the shift of populations in different groups of nitrifying and denitrifying bacteria detected by FISH-FCM.

Comparison between hybrid moving bed biofilm reactor and activated sludge system: a pilot plant experiment

The paper presents the comparison between the traditional activated sludge system (AS) and a hybrid moving bed biofilm reactor (HMBBR). In particular, an experimental campaign has been carried out at the WWTP in Palermo (Italy), on a pilot plant consisting of two pre-anoxic schemes. The aerated tank of the HMBBR line was filled with suspended carriers (AnoxKaldnes K1), with a 30% filling ratio. The hydraulic load of the HMBBR line was increased up to two times the AS one. Further, in order to distinguish the additional contribution of the attached biomass for the HMBBR system, in the two lines the Mixed Liquor Suspended Solids (MLSS) was maintained as equal as possible. The monitoring period lasted three months during which several parameters were monitored. The obtained results showed a good treatment ability of the HMBBR system, referring to the organic matter removal as well as to the ammonium removal. In particular, in spite of the increase of the hydraulic load for the HMBBR line, the two systems showed a similar performance in terms of both organic and nitrogen removal. The results demonstrate the higher treatment capacity of the HMBBR addressing such system as an effective technology for the upgrading of overloaded wastewater treatment plants.

Filtration characteristics of activated sludge in hybrid membrane bioreactor with porous suspended carriers (HMBR)

The suspended carriers were efficient in controlling membrane fouling in hybrid membrane bioreactor with porous suspended carriers (HMBR). The purpose of this study consisted in investigating the effect of suspended carriers on the sludge suspension, especially the filterability of sludge suspension. The filterability of sludge suspension in HMBR and general membrane bioreactor (MBR) were investigated and compared in parallel conditions by dead-end filtration for better evaluating the influence of suspended carriers on the sludge suspension. Several aspects of sludge suspension such as filtration resistance, specific cake resistance and particle size were discussed. During long-term operation the filtration resistances rose gradually in the early stage (about 100 days) and then increased rapidly, but there was a slight difference between MBR and HMBR with the prolongation of operation time. The granulometric analysis revealed that the mean particle size of sludge suspension of HMBR decreased more sharply than that of MBR, because the fluidized carriers in HMBR would impose shear stresses on sludge flocs and induce the destruction of the network of sludge zoogloea. Dead-end filtration experiments indicated that the resistance-increasing rates of three portions of sludge suspension were in the order of supernatant > dissolved organics > microbial flocs. In order to further understand the filterability of sludge suspension, the specific cake resistance (α or α.C) of sludge suspension and supernatant in HMBR and MBR were determined. During long-term operation the α and α.C increased with operation time. These results revealed that the suspended carriers in HMBR had appreciably negative effect on the biological characteristics and filterability of the sludge suspension, but they were efficient in controlling membrane fouling during continuous operation of HMBR.

Carrier effects on oxygen mass transfer behavior in a moving‐bed biofilm reactor

AbstractThis study investigates the carrier effects on the oxygen mass transfer behavior of a gas–liquid biofilm surface, and aims to provide evidence for parameter optimization in the practical operation of a moving‐bed biofilm reactor (MBBR) during the coking‐plant wastewater process. By using the dynamic oxygen dissolution method, the volumetric oxygen mass transfer coefficient KLa was measured by varying the suspended carrier stuffing rate and the intensity of aeration. Within the range of fluidizable flow rate, the efficiency of oxygen mass transfer increased with suspended carrier stuffing rate, and KLa reached its peak value when the stuffing rate was 40%. KLa has an increasing trend with an increase of the aeration intensity, but high aeration intensity was not favorable for reactor operation. Better oxygen mass transfer effect and higher oxygen transfer efficiency could be achieved when the aeration intensity was 0.3 m3 h−1 and the suspended carrier stuffing rate was 30–50%. The possible mechanisms that can account for carrier effects on oxygen mass transfer are the changes in the gas–liquid interfacial area. The ammonia nitrogen removal performance of the coking‐plant wastewater in MBBR was satisfied by using the above‐suggested conditions. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.