Effect of temperature on extracellular organic matter (EOM) of Chlorella pyrenoidosa and effect of EOM on irreversible membrane fouling

Compensatory growth of Microcystis aeruginosa after copper stress and the characteristics of algal extracellular organic matter (EOM)

Cyanobacterial blooms can impair drinking water quality due to the concomitant extracellular organic matter (EOM). As copper is often applied as an algicide, cyanobacteria may experience copper stress. However, it remains uncertain whether algal growth compensation occurs and how EOM characteristics change in response to copper stress. This study investigated the changes in growth conditions, photosynthetic capacity, and EOM characteristics of M. aeruginosa under copper stress. In all copper treatments, M. aeruginosa experienced a growth inhibition stage followed by a growth compensation stage. Notably, although chlorophyll-a fluorescence parameters dropped to zero immediately following high-intensity copper stress (0.2 and 0.5 mg/L), they later recovered to levels exceeding those of the control, indicating that photosystem II was not destroyed by copper stress. Copper stress influenced the dissolved organic carbon (DOC) content, polysaccharides, proteins, excitation-emission matrix spectra, hydrophobicity, and molecular weight (MW) distribution of EOM, with the effects varying based on stress intensity and growth stage. Principal component analysis revealed a correlation between the chlorophyll-a fluorescence parameters and EOM characteristics. These results imply that copper may not be an ideal algicide. Further research is needed to explore the dynamic response of EOM characteristics to environmental stress.

Nano-clay modified membranes: A promising green strategy for microalgal antifouling filtration

Membrane fouling is a major challenge which limits the sustainable application of membrane filtration-based microalgal harvesting at industrial level. Membrane fouling leads to increased operational and maintenance costs and represents a major obstacle to microalgal downstream processing. Nano-clays are promising naturally occurring nanoparticles in membrane fabrication due to their low-cost, facile preparation, and their superior properties in terms of surface hydrophilicity, mechanical stability, and resistance against chemicals. The membrane surface modification using nano-clays is a sustainable promising approach to improve membranes mechanical properties and their fouling resistance. However, the positive effects of nano-clay particles on membrane fouling are often limited by aggregation and poor adhesion to the base polymeric matrix. This review surveys the recent efforts to achieve anti-fouling behavior using membrane surface modification with nano-clay fillers. Further, strategies to achieve a better incorporation of nano-clay in the polymer matrix of the membrane are summarised, and the factors that govern the membrane fouling, stability, adhesion, agglomeration and leaching are discussed in depth.

Effects of the nutrient inhibition on the yield of DBPFPs by Microcystis aeruginosa

The yield of three disinfection byproduct formation potentials (DBPFPs), including trichloromethane, dichloroacetic acid and trichloroacetic acid formation potential (TCMFP, DCAAFP and TCAAFP), by Microcystis aeruginosa under the nitrate and phosphate inhibition conditions was investigated. The results showed that excessive nitrate could inhibit the growth of M. aeruginosa, but the concentration of DBPFPs in the five fractions of algal metabolites, including hydrophilic extracellular organic matter (EOM), hydrophobic EOM, hydrophilic intracellular organic matter, hydrophobic intracellular organic matter and cell debris, only decreased slightly. Accordingly, the productivity of DBPFPs by M. aeruginosa increased by approximately 40% under the nitrate inhibition condition and the increased productivity of DBPFPs mainly came from EOM. The phosphate inhibition also performed a similar pattern with a lesser extent. The nutrient inhibition did not change the proportion of these three DPBFPs, and TCMFP accounted for approximately 87% of the total DBPFPs. The inhibition could promote M. aeruginosa to secrete more metabolites. However, the cyanobacteria tended to secrete more DBPFPs under the nitrate inhibition condition, which resulted in an increased specific DBPFP, while they tended to secrete more non-DBPFPs under the phosphate inhibition condition, which resulted in a decreased specific DBPFP.

Comprehensive analysis of the combined flocculation and filtration process for microalgae harvesting at various operating parameters

The combined process of flocculation and filtration can improve algae harvesting performance by combining the benefits of both and overcoming the drawbacks. The entire process was thoroughly examined in this study, considering technical and economic feasibility under a variety of operating situations. Dead-end filtration was performed to evaluate the harvesting performance, the removal of extracellular organic matter and the changes of flocs. Cross-flow filtration was then carried out to explore the effect of operating parameters on permeate flux and assess the technical and economic feasibility. The optimum operating condition was to use 5 mg/L cationic polyacrylamide with 25 μm pore size and 0.1 m/s cross-flow velocity, under which a high harvesting efficiency of 95.2 %, a high average permeate flux of 55.5 m³/(m² h) and a volumetric reduction factor of 118.9 were achieved. Algal floc analysis revealed that flocs formed by ferric chloride and polyaluminium sulfate tended to partially deconstruct into smaller pieces during the filtration process. In contrast, flocs formed by cationic polyacrylamide tended to aggregate into bigger flocs, which, when paired with the effect of flocculant dosage and membrane pore size, could explain the difference in filtration performance and membrane permeance. No negative effect on downstream technology was observed for the combined process. A significantly lowered estimated total cost of 0.139 $/kg under optimum operating condition was obtained compared to filtration without flocculation assisted (0.206 $/kg).

Investigation of membrane fouling and mechanism induced by extracellular organic matter during long-term exposure to pharmaceuticals and personal care products

This study investigated ultrafiltration membrane fouling by extracellular organic matter (EOM) and the mechanism operating during long-term exposure to pharmaceuticals and personal care products. The results indicated that carbamazepine and diclofenac in algal-laden water altered the filtration flux and membrane fouling by EOM. Exposure to low-concentration carbamazepine (0.25 μg/L) improved the filtration flux and the total (R_tot) and reversible fouling resistance (R_c), whereas the filtration flux and R_tot and R_c were reduced when EOM was used during long-term exposure to high carbamazepine concentrations (>1 μg/L). Both R_tot and R_c were increased when algae were exposed to 0.25 μg/L diclofenac, whereas the filtration flux and R_tot and R_c were alleviated when algae were exposed to >1 μg/L diclofenac. Moreover, carbamazepine and diclofenac (0.25 μg/L - 1000 μg/L) in water enhanced the irreversible fouling resistance (R_b) when ultrafiltration was used to treat algal-laden waters. The mechanism indicated that membrane fouling induced by standard blocking was transformed to complete blocking when EOM was exposed to high levels of carbamazepine (>0.25 μg/L) in the initial filtration process, whereas cake layer formation played an important role during the later filtration process; with low carbamazepine levels (0.25 μg/L), standard blocking of EOM was dominant during the entire filtration process. The membrane fouling mechanism also changed when algal-laden waters were exposed to diclofenac, the membrane fouling was transformed from complete blocking to standard blocking when DFC was present in the initial filtration process, whereas cake layer formation exerted an important role during the late filtration process. This research provides important information on the long-term risks caused by pharmaceutical and personal care products and potential threats to membrane treatment.

Performance of gravity-driven membrane systems for algal water treatment: Effects of temperature and membrane properties

Gravity-driven membrane (GDM) systems are promising for algal water treatment. However, the algae-bacteria interaction in the biofilm on the membrane, which is highly dependent on temperature and membrane properties, is still unclear. Therefore, this study investigated the effect of temperature on the performance of GDM systems during the filtration of algae-rich water for 50 days using two types of membranes. The results suggested that the combined effect of the microbial growth (controlled by temperature) and organic rejection (related to membrane properties) determined the membrane biofilm structure and its hydraulic resistance. Increasing the temperature from 10 to 35 °C gradually improved the foulant removal by both polyvinylidene fluoride (PVDF²⁰⁰) and polyvinyl chloride (PVC^0.01) membranes, corresponding to different microbial activities. The lowest removal observed at 10 °C was attributed to the algal cell rupture and limited bacteria growth. At 25 °C, the stimulated algae population was mainly responsible for nutrient removal, meanwhile the oxygenic environment encouraged the proliferation of heterotrophic bacteria for the organic removal. At a higher temperature of 35 °C, both the nutrient and organic removal were dominated by denitrification, accompanied by a strong increase in biological activity. Although PVDF²⁰⁰ membranes had 10 times higher initial fluxes than PVC^0.01 membranes, they obtained comparable final fluxes. Unlike PVDF²⁰⁰ membranes exhibited the highest final flux at 10 °C (3.64 L/m²/h), the PVC^0.01 membrane permeability increased in the order: 10 °C (1.58 L/m²/h) < 25 °C (2.20 L/m²/h) < 35 °C (4.00 L/m²/h). This is mainly because the PVDF²⁰⁰ membrane fouling was dominated by microbial biomass, while PVC^0.01 membranes with smaller pores and higher hydrophilicity were more sensitive to changes in microbial metabolites. This study links temperature, membrane properties and biofilm physiology, with practical relevance for the hydraulic performance of GDM systems, hopefully leading to their wider application in algal water treatment.

Optimization of Air Flotation and the Combination of Air Flotation and Membrane Filtration in Microalgae Harvesting

On account of its small size and poor sedimentation performance, microalgae harvesting is restricted from a wider application. Air flotation is an efficient and fast solid–liquid separation technology, which has the potential to overcome the impediments of microalgae harvesting. In this study, factors influencing microalgae harvesting by air flotation were investigated. The results illustrated that bound extracellular organic matter (bEOM) had a greater effect on microalgae harvesting by air flotation, compared with dissolved extracellular organic matter (dEOM). Microalgae harvesting by air flotation in different growth stages proceeded, and the effect of air flotation in the heterotrophic stage was better than the autotrophic stage. The molecular weight distributions demonstrated that after air flotation, the proportion of high MW substance increased, while the proportion of low MW substance decreased, regardless of whether dEOM or bEOM. Membrane filtration was carried out for the algal solutions before and after air flotation. The membrane of pre-flotation algal solution had a higher critical flux of 51 L/m2·h than that of no-pre-flotation (24 L/m2·h), and, thus, pre-flotation had an active effect on membrane filtration in microalgae harvesting. Moreover, the combination of air flotation and membrane filtration provided an efficient technology for microalgae harvesting.

Electro-Fenton improving fouling mitigation and microalgae harvesting performance in a novel membrane photobioreactor

An innovative electro-Fenton enhanced membrane photobioreactor with satisfactory membrane fouling mitigation was constructed for microalgae harvesting. The porous carbon and carbon nanotubes hollow fiber membranes (PC-CHFMs) were used as the separation unit and cathode, simultaneously. H₂O₂ was generated by cathode reducing O₂ in-situ, which would further produce •OH as the main oxidant by coupling H₂O₂ with Fe²⁺. The •OH could deeply remove the extracellular organic matter (EOM) deposited on the membrane surface or inside the pores. Experimental results showed that the permeate flux recovery rates of PC-CHFMs by electro-Fenton at the 18th, 29th and 41st day were 100%, 100% and 98.3%, respectively. The corresponding recovery rates by chemical cleaning at the same time were 99.8%, 81.7% and 54.4%. The stable and high permeate flux of PC-CHFMs made a great contribution to the microalgae harvesting efficiency, where the concentration factor could be 4.8 times higher than that of the control group. Filtrating superiority of PC-CHFMs was becoming more prominent with the extension of operating time. In addition, the removal efficiency of NH₄⁺-N and TP in wastewater was approximately 100% at stable culture period.

Component structure and characteristic analysis of cyanobacterial organic matters

The characteristic analysis of cyanobacterial organic matters is an important premise of cyanobacterial organic pollution control. This paper investigated the component structure characteristics of algal organic matters (AOM) secreted and released by cyanobacteria in laboratory culture and actual Taihu Lake environment by spectroscopic quantitative and qualitative methods. Results showed that the secretion amount of AOM was mainly 4-6 μg COD/10⁶ cells during the growth period of Microcystis aeruginosa, and the content ratio of extracellular organic matters (EOM) to intracellular organic matters (IOM) gradually increased from 0.83 in adaptation and logarithmic period to 3.33 in stable and decay period. The secretion of IOM showed a decrease trend, which indicated the decrease of its synthesis or the gradual infiltration and loss caused by cell membrane damage. From the component characteristics, the EOM had lower SUVA value and higher proportion of small molecular substances with molecular weight <3 kDa, indicating its more difficult to separate from water than IOM. Compared with the laboratory culture environment, the actual Taihu Lake resulted in more obvious characteristic heterogeneity of cyanobacteria EOM and IOM.

Membrane Fouling in Algal Separation Processes: A Review of Influencing Factors and Mechanisms

The use of algal biotechnologies in the production of biofuels, food, and valuable products has gained momentum in recent years, owing to its distinctive rapid growth and compatibility to be coupled to wastewater treatment in membrane photobioreactors. However, membrane fouling is considered a main drawback that offsets the benefits of algal applications by heavily impacting the operation cost. Several fouling control strategies have been proposed, addressing aspects related to characteristics in the feed water and membranes, operational conditions, and biomass properties. However, the lack of understanding of the mechanisms behind algal biofouling and control challenges the development of cost-effective strategies needed for the long-term operation of membrane photobioreactors. This paper reviews the progress on algal membrane fouling and control strategies. Herein, we summarize information in the composition and characteristics of algal foulants, namely algal organic matter, cells, and transparent exopolymer particles; and review their dynamic responses to modifications in the feedwater, membrane surface, hydrodynamics, and cleaning methods. This review comparatively analyzes (i) efficiency in fouling control or mitigation, (ii) advantages and drawbacks, (iii) technological performance, and (iv) challenges and knowledge gaps. Ultimately, the article provides a primary reference of algal biofouling in membrane-based applications.

Harvesting of Microcystis flos-aquae using chitosan coagulation: Influence of proton-active functional groups originating from extracellular and intracellular organic matter

Algogenic organic matter (AOM) produced by Microcystis cells inhibits coagulation harvesting; however, the harvesting inhibitory mechanisms at the functional groups level remain to be determined. This study fractionated extracellular organic matter (EOM) and intercellular organic matter (IOM) from Microcystis flos-aquae into five different hydrophilic and hydrophobic fractions and investigated their inhibition of chitosan coagulation harvesting. The proton-active functional groups in the inhibitory fractions were further analysed by potentiometric titration, and the interaction between these functional groups and chitosan was elucidated. The results showed that the harvesting inhibition of M. flos-aquae cells was dominated by HPI in AOM due to its high charge density, which resulted in greater consumption of coagulant. Potentiometric titration results suggested that the proton-active functional groups of both HPI_EOM and HPI_IOM consist mainly of phosphodiester, carboxylic, phosphoryl and amine/hydroxyl functional groups, and the harvesting inhibition of HPI on M. flos-aquae cells at pH 6.5 was mainly due to the deprotonation of phosphodiester and carboxylic functional groups. Moreover, carboxylic functional groups with stronger polarity could enhance the intermolecular interaction between HPI and chitosan more effectively than phosphodiester at pH 6.5. Preventing the deprotonation of carboxylic functional groups by adjusting the pH to 4.3 could effectively alleviate the harvesting inhibition caused by HPI. These findings revealed the inhibition mechanism of AOM on the coagulation harvesting of M. flos-aquae cells from the perspective of deprotonation of proton-active functional groups, which may provide important insights for assessing the role of AOM in the coagulation harvesting of Microcystis cells.

Application of coagulation-ultrafiltration-nanofiltration in a pilot study for Tai Lake water treatment

In this study, the inline coagulation was combined with ultrafiltration and nanofiltration (UF-NF) in a pilot study for Tai Lake water treatment. The results showed that the combination process was very effective for Tai Lake water treatment in terms of organic removal and membrane fouling control. With inline coagulation, no irreversible membrane fouling was observed for either UF or NF at fluxes of 65-90 and 22-26 L/(m²  hr), respectively. The membrane foulants were analyzed, and the results indicated that the low molecular weight fractions in the feed were main membrane fouling contributors for both UF and NF, where hydrophilic substances and proteins, as well as neutral substances and humic acids with polycarboxyl groups, contributed significantly to UF and NF membrane fouling, respectively. Compared with direct UF-NF filtration without coagulation, the coagulants could aggregate organic micromolecules for cake formation. With inline coagulation, the moving flocs could generate shear stress to scrub the membrane surface for fouling control of UF. Moreover, with inline coagulation, the organics removal efficiency could be further increased by 10%-20%. With NF, the permeate had a TOC concentration of less than 0.5 mg/L, satisfying the drinking water quality. Therefore, the coagulation-UF-NF is very useful for Tai Lake water treatment. PRACTITIONER POINTS: Inline coagulation-UF-NF for Tai Lake Water treatment is implemented. Inline coagulation can aggregate hydrophilic substances to reduce membrane fouling. Moving flocs produce shear stress for fouling control of UF-NF. Superior quality of permeate is achieved with the combined coagulation-UF-NF process.

A review of membrane fouling and its control in algal-related membrane processes

Membrane technologies have received much attention in microalgae biorefinery for nutrients removal from wastewater, carbon dioxide abatement from the air as well as the production of value-added products and biofuel in recent years. This paper provides a state-of-the-art review on membrane fouling issues and its control in membrane photobioreactors (MPBRs) and other algal-related membrane processes (harvesting, dewatering, and biofuel production). The mechanisms of membrane fouling and factors affecting membrane fouling in algal-related membrane processes are systematically reviewed. Also, strategies to control membrane fouling in algal-related membrane processes are summarized and discussed. Finally, the gaps, challenges, and opportunities in membrane fouling control in algal-related membrane technologies are identified and discussed.

Response of methanotrophic activity to extracellular polymeric substance production and its influencing factors

The accumulation of extracellular polymeric substance (EPS) is speculated to be related with the decrease of CH₄ oxidation rate after a peak in long-term laboratory landfill covers and biofilters. However, few data have been reported about EPS production of methanotrophs and its feedback effects on methanotrophic activity. In this study, Methylosinus sporium was used asa model methanotroph to investigate EPS production and its influencing factors during CH₄ oxidation. The results showed that methanotrophs could secret EPS into the habits during CH₄ oxidation and had a negative feedback effect on CH₄ oxidation. The EPS amount fitted well with the CH₄ oxidation activity with the exponential model. The environmental factors such as pH, temperature, CH₄, O₂, NO₃^--N and NH₄⁺-N could affect the EPS production of methanotrophs. When pH, temperature, CH₄, O₂ and N concentrations (including NO₃^--N and NH₄⁺-N) were 6.5-7.5, 30-40°C, 10-15%, 10% and 20-140mgL^-1, respectively, the high cell growth rate and CH₄ oxidation activity of Methylosinus sporium occurred in the media with the low EPS production, which was beneficial to sustainable and efficient CH₄ oxidation. In practice, O₂-limited condition such as the O₂ concentration of 10% might be a good way to control EPS production and enhance CH₄ oxidation to mitigate CH₄ emission from landfills.

Interactions of specific extracellular organic matter and polyaluminum chloride and their roles in the algae-polluted water treatment

Extracellular organic matter (EOM) is ubiquitous in the algae-polluted water and has a significant impact on the human health and drinking water treatment. We investigate the different characteristics of dissolved extracellular organic matter (dEOM) and bound extracellular organic matter (bEOM) recovered from the various growth period of Microcystis aeruginosa and the interactions of them and polyaluminum chloride (PACl). The roles of the different EOM in the algae-polluted water treatment are also discussed. The functional groups of aromatic, OH, NH, CN and NO in bEOM possessing the stronger interaction with hydroxyl aluminum compared with dEOM is responsible for bEOM and algae removal. Some low molecular weight (MW) organic components and protein-like substances in bEOM are most easily removed. And dEOM weakly reacts with PACl or inhibits coagulation, especially dEOM with the high MW organic components. The main coagulation mechanisms of bEOM are the generation of insoluble Al-bEOM through complexation, the bridge of AlO₄Al₁₂(OH)₂₄(H₂O)₁₂⁷⁺ (Al₁₃), the adsorption of Al(OH)_3(am) and the entrapment of flocs. The adsorption of Al₁₃ and Al(OH)_3(am) mainly contribute to dEOM removal. It is also recommended to treat the algae with dEOM and bEOM at the initial stage.

The filtration and fouling performance of membranes with different pore sizes in algae harvesting

In this study, ultrafiltration membranes with three different pore sizes were applied for algae harvesting to investigate filtration performance. The critical fluxes (J_C) increased as the pore size increased, and the J_C of 0.03-, 0.05- and 0.1-μm membranes were 20.0, 25.0 and 42.0Lm^-2h^-1, respectively. During continuous filtration, 0.7J_C was selected as the operation flux and the 0.1-μm membrane had the highest initial flux and final flux. It also had the highest flux decline rate, and therefore, the 0.1-μm membrane was more appropriate for algae separation compared to the 0.03- and 0.05-μm membrane. The mechanism by which pore size influenced filtration performance and membrane fouling was presented from the viewpoint of permeate drag force (F_D). A lower F_D retarded the velocity of algae cells towards the membrane, which could decelerate the deposition of particles on the membrane and thus reduce the membrane fouling rate. As the pore size increased, the membrane hydraulic resistance (R_m) decreased, which led to a decrease of F_D.

Unique characteristics of algal dissolved organic matter and their association with membrane fouling behavior: a review

Over the last several decades, the frequent occurrence of algal bloom in drinking water supplies, driven by increasing anthropogenic input and climate change, has posed serious problems for membrane filtration processes, resulting in reduced membrane permeability and increased energy consumption. It is essential to comprehensively understand the characteristics of algal dissolved organic matter (DOM) and the subsequent effects on the filtration processes for better insight into membrane fouling mitigation. Many studies have revealed that algal DOM has displayed unique characteristics distinguished from other sources of DOM with respect to the chemical composition, the structures, and the molecular weight distributions. Algal DOM is considered to be a major obstacle in understanding membrane fouling due to its complicated interactions among dissimilar algal DOM constituents as well as between algal DOM and membrane material matrices. The present review article summarizes (1) recent characterizing methods for algal DOM, (2) environmental factors affecting the characteristics of algal DOM, (3) the discrepancies between algal DOM and other sources of aquatic DOM, particularly terrestrial sources, and (4) potential fouling effects of algal DOM on membrane filtration processes and their associations with algal DOM characteristics. A broad understanding of algal DOM-driven membrane fouling can lead to breakthroughs in efficient membrane filtration processes to treat algal bloom water sources.

Impact of algal organic matter released from Microcystis aeruginosa and Chlorella sp. on the fouling of a ceramic microfiltration membrane

Algal blooms lead to the secretion of algal organic matter (AOM) from different algal species into water treatment systems, and there is very limited information regarding the impact of AOM from different species on the fouling of ceramic microfiltration (MF) membranes. The impact of soluble AOM released from Microcystis aeruginosa and Chlorella sp. separately and together in feedwater on the fouling of a tubular ceramic microfiltration membrane (alumina, 0.1 μm) was studied at lab scale. Multi-cycle MF tests operated in constant pressure mode showed that the AOM (3 mg DOC L(-1)) extracted from the cultures of the two algae in early log phase of growth (12 days) resulted in less flux decline compared with the AOM from stationary phase (35 days), due to the latter containing significantly greater amounts of high fouling potential components (protein and humic-like substances). The AOM released from Chlorella sp. at stationary phase led to considerably greater flux decline and irreversible fouling resistance compared with that from M. aeruginosa. The mixture of the AOM (1:1, 3 mg DOC L(-1)) from the two algal species showed more similar flux decline and irreversible fouling resistance to the AOM from M. aeruginosa than Chlorella sp. This was due to the characteristics of the AOM mixture being more similar to those for M. aeruginosa than Chlorella sp. The extent of the flux decline for the AOM mixture after conventional coagulation with aluminium chlorohydrate or alum was reduced by 70%.

Construction and application of the Synechocystis sp. PCC6803-ftnA in microbial contamination control in a coupled cultivation and wastewater treatment

Inspired by iron fertilization experiments in HNLC (high-nitrate, low-chlorophyll) sea areas, we proposed the use of iron-rich engineered microalgae for microbial contaminant control in iron-free culture media. Based on the genome sequence and natural transformation system of Synechocystis sp. PCC6803, ftnA (encoding ferritin) was selected as our target gene and was cloned into wild-type Synechocystis sp. PCC6803. Tests at the molecular level confirmed the successful construction of the engineered Synechocystis sp. PCC6803-ftnA. After Fe(3+)-EDTA pulsing, the intracellular iron content of Synechocystis sp. PCC6803-ftnA was significantly enhanced, and the algae was used in the microbial contamination control system. In the coupled Synechocystis sp. PCC6803-ftnA production and municipal wastewater (MW, including Scenedesmus obliquus and Bacillus) treatment, Synechocystis sp. PCC6803-ftnA accounted for all of the microbial activity and significantly increased from 70% of the microbial community to 95%. These results revealed that while the stored iron in the Synechocystis sp. PCC6803-ftnA cells was used for growth and reproduction of this microalga in the MW, the growth of other microbes was inhibited because of the iron limitation, and these results provide a new method for microbial contamination control during a coupling process.

Comparison of axial vibration membrane and submerged aeration membrane in microalgae harvesting

The submerged aeration membrane (SAM) system and axial vibration membrane (AVM) system can mitigate membrane fouling. In this study, both systems were investigated to compare the performance of filtration and the membrane fouling in algae filtration. In 5-h filtration, the transmembrane pressure (TMP) of SAM reached to 70.0 kPa, while there was almost no increase in TMP for AVM. After continuous filtration, it could be found that there was hardly any algae cells on the membrane of AVM (0.11 g/m(2)), which was about 32.4 times less than that of SAM (3.56 g/m(2)). Compared with the SAM system, AVM had a lesser membrane fouling, regardless of the reversible fouling or irreversible fouling. By SEM, FTIR and EEM, it could be found there was less irreversible extracellular organic matter (EOM) on the membrane of AVM. By MW distribution, it could be observed that less EOM with high-MW adhered to membrane of AVM.

Microfiltration process for surface water treatment: irreversible fouling identification and chemical cleaning

Irreversible fouling before (left) and after (right) chemical cleaning.