Anaerobic Dynamic Membrane Bioreactor Research Articles

Characteristics and role of dynamic membrane layer in anaerobic membrane bioreactors.

A submerged anaerobic dynamic membrane bioreactor (AnDMBR) was operated for treatment of concentrated wastewater. The dynamic membrane (DM) or cake layer was characterized on its physicochemical and biological composition and the role of the DM layer in treatment and filtration performances was assessed. The results showed that the DM layer had an important role in organic matter removal. Both organic and inorganic materials, such as sludge particles, soluble microbial products (SMP), extracellular polymeric substances (EPS), and Ca, N, P, Mg precipitations contributed to the DM layer formation. Thus, effective retention of very small particles by the DM layer was achieved. The DM layer had higher microbial diversity and different microbial population composition in comparison to the bulk sludge. Overall, this study provided a better understanding about the DM layer structure in AnDMBRs, which might lead to increased applicability of this promising technology for the treatment of concentrated wastewaters.

Dynamic Membrane Formation in Anaerobic Dynamic Membrane Bioreactors: Role of Extracellular Polymeric Substances.

Dynamic membrane (DM) formation in dynamic membrane bioreactors plays an important role in achieving efficient solid-liquid separation. In order to study the contribution of extracellular polymeric substances (EPS) to DM formation in anaerobic dynamic membrane bioreactor (AnDMBR) processes, EPS extraction from and re-addition to bulk sludge were carried out in short-term filtration tests. DM formation behaviors could be well simulated by cake filtration model, and sludge with EPS re-addition showed the highest resistance coefficient, followed by sludge after EPS extraction. The DM layers exhibited a higher resistance and a lower porosity for the sludge sample after EPS extraction and for the sludge with EPS re-addition. Particle size of sludge flocs decreased after EPS extraction, and changed little with EPS re-addition, which was confirmed by interaction energy analysis. Further investigations by confocal laser scanning microscopy (CLSM) analysis and batch tests suggested that the removal of in-situ EPS stimulated release of soluble EPS, and re-added EPS were present as soluble EPS rather than bound EPS, which thus improved the formation of DM. The present work revealed the role of EPS in anaerobic DM formation, and could facilitate the operation of AnDMBR processes.

Anaerobic dynamic membrane bioreactor for wastewater treatment at ambient temperature

A bench-scale dynamic membrane (DM) bioreactor was operated to evaluate the anaerobic treatment of a synthetic municipal wastewater at ambient temperature. The DM was developed over a large pore size (200μm) mesh in order to improve sludge filterability and reduce energy consumption. The system achieved average organic removals higher than 80% and 90% for total COD and filtered COD, respectively. Results also demonstrated that the biofilm, which the DM is made of, played a significant part in obtaining the overall organic removal efficiency. The large pore size of the mesh allowed for high membrane fluxes (approximately 15–20Lm−2h−1) applying low TMP (usually lower than 50–100mbar). Fluxes higher than 20Lm−2h−1 produced low solid removal efficiency indicating deterioration of the DM. COD mass balance suggests that the low hydraulic retention times applied to the system caused methane loss through the effluent due to oversaturation.

An anaerobic dynamic membrane bioreactor (AnDMBR) for landfill leachate treatment: Performance and microbial community identification

In this study, a pilot-scale anaerobic dynamic membrane bioreactor was operated for 142days for treating landfill leachate. Under stable operation, average COD removal efficiency of 62.2% was achieved when the reactor was fed with the raw leachate containing total ammonium concentration above 3000mg/L and COD above 13,000mg/L. The methane content in the biogas was in the range of 70-90%, and the average methane yield was 0.34L/g CODremoved at the organic loading rate of 4.87kg COD/(m(3)d). Pyrosequencing analyses indicated that during the operation the archaeal community was relatively stable while obvious changes took place in the bacterial community. Alkaliphilus, Petrimonas, Fastidiosipila and vadinBC27 were the abundant fermentation bacteria in bacterial communities. Moreover, phylum TM6 gradually became the most dominant bacterial community and reached the highest relative abundance of 32.9% as the operation elapsed. In archaeal communities, genus Methanosarcina was identified as the dominant methanogen.

Applicability of dynamic membrane technology in anaerobic membrane bioreactors

This study investigated the applicability of dynamic membrane technology in anaerobic membrane bioreactors for the treatment of high strength wastewaters. A monofilament woven fabric was used as support material for dynamic membrane formation. An anaerobic dynamic membrane bioreactor (AnDMBR) was operated under a variety of operational conditions, including different sludge retention times (SRTs) of 20 and 40 days in order to determine the effect of SRT on both biological performance and dynamic membrane filtration characteristics. High COD removal efficiencies exceeding 99% were achieved during the operation at both SRTs. Higher filtration resistances were measured during the operation at SRT of 40 days in comparison to SRT of 20 days, applying a stable flux of 2.6 L/m2 h. The higher filtration resistances coincided with lower extracellular polymeric substances concentration in the bulk sludge at SRT of 40 days, likely resulting in a decreased particle flocculation. Results showed that dynamic membrane technology achieved a stable and high quality permeate and AnDMBRs can be used as a reliable and satisfactory technology for treatment of high strength wastewaters.

Microbial communities in an anaerobic dynamic membrane bioreactor (AnDMBR) for municipal wastewater treatment: Comparison of bulk sludge and cake layer

454 high-throughput pyrosequencing was employed to investigate microbial communities in bulk sludge (BS) and cake layer (CL) in an anaerobic dynamic membrane bioreactor (AnDMBR). Pyrosequencing produced 7402 and 7026 high-quality V1–V3 tags of the 16S rRNA-gene for the BS and CL samples, and the number of total OTUs estimated by Chao1 was 2906 (BS) and 2532 (CL) at a 3% distance. Phylogenetic spectrum and Venn diagrams revealed that the bacterial phyla in the two samples were nearly identical, and that the predominant microorganisms of them exhibited a high homology. Nevertheless, population distribution was different between them. Proteobacteria were the most dominant in the BS, while Bacteroidetes, Firmicutes and Spirochaetes were highly enriched in the CL, accounting for 57.6% of the total microbes. The main microbial groups in the CL were highly functionally organized. Bacteroides, Clostridia and Delta-proteobacteria were likely the pioneers for surface colonization on membranes in the AnDMBR.

Membrane fouling in an anaerobic dynamic membrane bioreactor (AnDMBR) for municipal wastewater treatment: Characteristics of membrane foulants and bulk sludge

An anaerobic dynamic membrane bioreactor (AnDMBR) treating municipal wastewater with a high flux of 65 L/(m 2 h) was operated for 11 months. Organic and inorganic membrane foulants and bulk sludge characteristics were investigated using particle size distribution analyzer, three-dimensional excitation–emission matrix fluorescence spectroscopy and X-ray fluorescence analysis. The fouling layers exhibited a double-layered structure, i.e., a loosely bound outer layer and a tightly bound internal layer. Besides that, there were foulants in membrane chambers due to the imperfect interception effect of solid particles by the dynamic membranes. Compared with the bulk sludge, membrane foulants in the internal layer and in the membrane chamber were found to have more fine particles. The Dacron mesh with large pore size could not achieve a good rejection of soluble macromolecules, which led to low soluble microbial products and extracellular polymeric substances contents in the membrane fouling layers but high contents in the foulants in membrane chambers. Microorganism activity and abundance analyses showed that the membrane foulants had some different communities and lower activities compared with the bulk sludge, which was attributed to the suppressed mass transfer in the foulants.

Formation of dynamic membrane in an anaerobic membrane bioreactor for municipal wastewater treatment

An anaerobic dynamic membrane bioreactor with a high flux of 65 L/(m 2 h) was used to treat municipal wastewater. Particle size distribution, scanning electron microscopy, gel filtration chromatography (GFC), and three-dimensional excitation–emission matrix (EEM) were used to investigate the components of the cake layer formed on the membrane surface and the interception effect of the dynamic membrane. Test results showed that the dynamic membrane was formed by suspended solids (SS) in the settling zone and the soluble contents such as soluble microbial products (SMP) and extracellular polymeric substances (EPS). According to the index of SS/cake volume, the formation of dynamic membrane can be divided into three stages, i.e., the formation of separation layer, the stable growth stage, and the fouling stage. The accumulation rates of SS, SMP and EPS were of some differences at each stage. The secondary membrane was not entirely formed until the 7th day, and the dynamic membrane demonstrated a weak interception effect of dissolved organic matters after the 20th day. From EEM and GFC analyses of SMP in the cake layer, it was found that the fluorescence intensity ratio of Peak B/Peak A in the EEM fluorescence spectra had a similar changing tendency with large molecules of MW > 5000 kDa. They both increased with operation time before the 20th day, probably due to the soluble by-products secreted by the microorganism in the cake layer.