scholarly journals Characteristics of membrane fouling by consecutive chemical cleaning in pressurized ultrafiltration as pre-treatment of seawater desalination

Desalination ◽  
2015 ◽  
Vol 369 ◽  
pp. 51-61 ◽  
Author(s):  
Yun Chul Woo ◽  
Jeong Jun Lee ◽  
Leonard D. Tijing ◽  
Ho Kyong Shon ◽  
Minwei Yao ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Seawater Desalination ◽  
Chemical Cleaning ◽  
Pre Treatment

A study on membrane fouling due to algal deposition

2000 ◽  
Vol 41 (10-11) ◽  
pp. 327-335 ◽  
Author(s):  
S. Babel ◽  
S. Takizawa
Keyword(s):  
Organic Matter ◽  
Membrane Fouling ◽  
Cell Lysis ◽  
Chemical Cleaning ◽  
Membrane Cleaning ◽  
Treatment Techniques ◽  
Ozone Pretreatment ◽  
Extensive Cell ◽  
Pre Treatment ◽  
Physical And Chemical

Batch filtration experiments in dead-end mode were carried out to investigate the membrane fouling phenomenon due to Chlorella deposition and to analyse the effectiveness of pretreatment techniques to control membrane fouling. Experiments were also conducted to identify efficient and effective physical and chemical methods for cleaning the membrane. For both cellulose acetate and PVDF membranes, the effect of algal concentration was found similar. Initially when the deposition was less, the flux was high and the resistance was very low or negligible. As the deposition increased, the resistance increased exponentially. With further increase in deposition, the resistance increases linearly at a constant rate. Among the three pre-treatment techniques studied, coagulation with alum and ozonation were effective in controlling the fouling of membrane. Chlorine pretreatment was not effective in reducing the algal cake resistance because it brought about an extensive cell lysis. Photographs taken by Scanning Electron Microscope (SEM) showed damage to the cell surface architecture and release of organic matter to the medium after chlorination. Ozone pretreatment was more effective than chlorine in disintegrating only the extracelluar organic matter (EOM) without causing cell lysis, thus bringing down the algal cake resistance. Cleaning experiments after algal filtration without pre-treatment showed that physical cleaning was less effective than chemical cleaning. All four chemicals tested for membrane cleaning could reduce the cake resistance by more than 99%.

Understanding membrane fouling in ultrafiltration of WWTP-effluent

2000 ◽  
Vol 41 (10-11) ◽  
pp. 345-353 ◽  
Author(s):  
J.H. Roorda ◽  
J.H. van der Graaf
Keyword(s):  
Membrane Fouling ◽  
Waste Water Treatment ◽  
Rapid Decrease ◽  
Short Term ◽  
Chemical Cleaning ◽  
Water Treatment Plants ◽  
Wwtp Effluent ◽  
Pre Treatment ◽  
Cleaning Methods

The application of ultrafiltration to effluent of waste water treatment plants (WWTP-effluent) is getting increasing attention. However, many experiments show a rapid decrease in flux urging frequent and intensive cleaning. In order to understand the mechanisms of the occurring fouling process, various filtration and cleaning experiments were performed, giving information about the filterability of the feedwater (F) and the reversibility of the occurring fouling layer (R). Short-term fluxes are mainly determined by the filterability, while both the filterability and the reversibility greatly affect long-term fluxes. The objective of this research is to measure the filterability of WWTP-effluent and the reversibility of the occurring fouling layer in ultrafiltration of wwtp-effluent with and without pre-treatment. The results of the filtration experiments show a rapid decrease of flux resulting in a low value for the filterability, which also decreases during progressing filtration. The filterability is mainly related to the volume of treated water. Pre-treatment of the WWTP-effluent by in-line coagulation or by deep-bed filtration has little influence on the filterability. However, results on the reversibility show an improvement of the reversibility by pre-treatment. Both filterability of the WWTP-effluent and reversibility of the fouling layer are found to be independent of the applied flux. As to the applied cleaning methods, the back flush is far more effective than the forward flush even if combined with air. In all experiments the remaining fouling layer still has to be removed by an intensive chemical cleaning. This research indicates the very importance of reducing the formation of an irreversible, non-removable fouling layer.

Effect of pre-coagulation on mitigating irreversible fouling during ultrafiltration of a surface water

2005 ◽  
Vol 51 (6-7) ◽  
pp. 93-100 ◽  
Author(s):  
K. Kimura ◽  
Y. Hane ◽  
Y. Watanabe
Keyword(s):  
Molecular Weight ◽  
Surface Water ◽  
Water Purification ◽  
Membrane Fouling ◽  
Pilot Scale ◽  
Organic Substances ◽  
Chemical Cleaning ◽  
Membrane Unit ◽  
Pre Treatment ◽  
Purification Plant

Membrane fouling can be divided into two types: reversible fouling and irreversible fouling. The former can be easily canceled by physical cleaning (e.g., backwashing) while the latter needs chemical cleaning to be mitigated. For more efficient use of membranes, the control of irreversible membrane fouling is of importance. In this study, the effectiveness of pre-coagulation/sedimentation on irreversible membrane fouling was investigated, based on the pilot-scale operation of the membrane unit installed at an existing water purification plant. The membrane employed was a low-pressure ultrafiltration (UF) membrane made of polysulfone and having a molecular weight cut-off of 750,000 daltons. Although pre-coagulation/sedimentation significantly mitigated membrane fouling mainly through the reduction of reversible membrane fouling, the degree of irreversible fouling was not reduced by the pre-treatment. This was because the irreversible fouling observed during this study was mainly attributed to polysaccharides/protein like fractions of organic substances that cannot be efficiently removed by coagulation/sedimentation. Aluminium used as coagulant was thought to cause irreversible fouling to some extent but did not in the pilot operation, which could probable be explained by the fact that coagulation was conducted at relatively high pH (7.0) in this study.

Low-pressure membrane filtration with unconventional coagulation regimes

2005 ◽  
Vol 5 (5) ◽  
pp. 1-8 ◽  
Author(s):  
K.Y. Choi ◽  
B.A. Dempsey
Keyword(s):  
Activated Carbon ◽  
Membrane Filtration ◽  
Membrane Surface ◽  
Cross Flow ◽  
Chemical Cleaning ◽  
Sand Filters ◽  
Charge Neutralization ◽  
Floc Size ◽  
Filtration System ◽  
Pre Treatment

The objective of the research was to evaluate in-line coagulation to improve performance during ultrafiltration (UF). In-line coagulation means use of coagulants without removal of coagulated solids prior to UF. Performance was evaluated by removal of contaminants (water quality) and by resistance to filtration and recovery of flux after hydraulic or chemical cleaning (water production). We hypothesized that coagulation conditions inappropriate for conventional treatment, in particular under-dosing conditions that produce particles that neither settle nor are removed in rapid sand filters, would be effective for in-line coagulation prior to UF. A variety of pre-treatment processes for UF have been investigated including coagulation, powdered activated carbon (PAC) or granular activated carbon (GAC), adsorption on iron oxides or other pre-formed settleable solid phases, or ozonation. Coagulation pre-treatment is often used for removal of fouling substances prior to NF or RO. It has been reported that effective conventional coagulation conditions produced larger particles and this reduced fouling during membrane filtration by reducing adsorption in membrane pores, increasing cake porosity, and increasing transport of foulants away from the membrane surface. However, aggregates produced under sweep floc conditions were more compressible than for charge neutralization conditions, resulting in compaction when the membrane filtration system was pressurized. It was known that the coagulated suspension under either charge-neutralization or sweep floc condition showed similar steady-state flux under the cross-flow microfiltration mode. Another report on the concept of critical floc size suggested that flocs need to reach a certain critical size before MF, otherwise membranes can be irreversibly clogged by the coagulant solids. The authors were motivated to study the effect of various coagulation conditions on the performance of a membrane filtration system.

A rapid small scale evaluation of ultrafiltration performance for surface water treatment at Alcantarilha's water treatment works (Algarve, Portugal)

2004 ◽  
Vol 4 (5-6) ◽  
pp. 199-206
Author(s):  
M. Ribau Teixeira ◽  
H. Lucas ◽  
M.J. Rosa
Keyword(s):  
Water Treatment ◽  
Membrane Fouling ◽  
Conventional Treatment ◽  
Apparent Molecular Weight ◽  
Small Scale ◽  
Hydraulic Permeability ◽  
Scale Evaluation ◽  
Surface Water Treatment ◽  
Drinking Water Production ◽  
Pre Treatment

A rapid small-scale evaluation of ultrafiltration (UF) performance with and without physical–chemical pre-treatment was performed to up-grade the conventional treatment used for drinking water production in Alcantarilha's water treatment works, Algarve, Portugal. Direct UF and pre-ozonation/coagulation/flocculation/sedimentation/UF (O/C/F/S/UF) were evaluated using polysulphone membranes of different apparent molecular weight cut-off (MWCO) (15–47 kDa). The results indicated that (i) UF is an effective barrier against microorganisms, including virus larger than 80 nm; (ii) for surface waters with low to moderate SUVA values, direct UF performance is equivalent or better than the conventional treatment in terms of residual turbidity, while UV254 nm and TOC residuals require the use of O/C/F/S/UF; (iii) the permeate quality improves with the membrane apparent MWCO decrease, especially for the direct UF, although the conventional treatment performance is never reached using UF; (iv) membrane fouling and adsorption phenomena are more severe in direct UF than in O/C/F/S/UF sequence (pre-ozonation decreases the membrane foulants by decreasing their hydrophobicity) and these phenomena increase with the membrane hydraulic permeability and, particularly, with the membrane apparent MWCO.

scholarly journals Removal Characteristics of N-Nitrosamines and Their Precursors by Pilot-Scale Integrated Membrane Systems for Water Reuse

2018 ◽  
Vol 15 (9) ◽  
pp. 1960 ◽  
Author(s):  
Haruka Takeuchi ◽  
Naoyuki Yamashita ◽  
Norihide Nakada ◽  
Hiroaki Tanaka
Keyword(s):  
Membrane Fouling ◽  
Water Reuse ◽  
Pilot Scale ◽  
Feed Water ◽  
Water Reclamation ◽  
Size Distributions ◽  
Membrane Systems ◽  
Chemical Cleaning ◽  
Ro Membrane ◽  
Feed Water Temperature

This study investigated the removal characteristics of N-Nitrosamines and their precursors at three pilot-scale water reclamation plants. These plants applies different integrated membrane systems: (1) microfiltration (MF)/nanofiltration (NF)/reverse osmosis (RO) membrane; (2) sand filtration/three-stage RO; and (3) ultrafiltration (UF)/NF and UF/RO. Variable removal of N-Nitrosodimethylamine (NDMA) by the RO processes could be attributed to membrane fouling and the feed water temperature. The effect of membrane fouling on N-Nitrosamine removal was extensively evaluated at one of the plants by conducting one month of operation and chemical cleaning of the RO element. Membrane fouling enhanced N-Nitrosamine removal by the pilot-scale RO process. This finding contributes to better understanding of the variable removal of NDMA by RO processes. This study also investigated the removal characteristics of N-Nitrosamine precursors. The NF and RO processes greatly reduced NDMA formation potential (FP), but the UF process had little effect. The contributions of MF, NF, and RO processes for reducing FPs of NDMA, N-Nitrosopyrrolidine and N-Nitrosodiethylamine were different, suggesting different size distributions of their precursors.

Characteristics of coagulation-flocculation of humic acid with effective performance of polymeric flocculant and inorganic coagulant

2003 ◽  
Vol 47 (1) ◽  
pp. 89-95 ◽  
Author(s):  
J. Yu ◽  
D.D. Sun ◽  
J.H. Tay
Keyword(s):  
Humic Acid ◽  
Membrane Fouling ◽  
Membrane Filtration ◽  
Molecular Size ◽  
Aluminium Sulphate ◽  
Fouling Control ◽  
Effective Performance ◽  
Water And Wastewater ◽  
Pre Treatment ◽  
Flocculation Process

Ferric chloride and aluminium sulphate as coagulants and positive charged flocculants PDDMAC ((PDDMAC = poly (diallyldimethylammonium chloride) were used for pre-treatment of water and wastewater for removing humic substance prior to RO membrane filtration. It was found that a combination of flocculant and coagulant enhanced the coagulation-flocculation process and humic acid removal. The optimum conditions of coagulation-flocculation were established in reference to the ratio of humic acid and coagulant. Zeta potential and the ratio of E4/E6 were investigated to explore the possible micro-mechanisms of coagulation-flocculation. The ratios of E4/E6 show the molecular size variations using different coagulants and flocculants, which are expected to benefit membrane-fouling control.

scholarly journals Optimization of In Situ Backwashing Frequency for Stable Operation of Anaerobic Ceramic Membrane Bioreactor

Processes ◽  
2020 ◽  
Vol 8 (5) ◽  
pp. 545 ◽  
Author(s):  
Rathmalgodage Thejani Nilusha ◽  
Tuo Wang ◽  
Hongyan Wang ◽  
Dawei Yu ◽  
Junya Zhang ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Membrane Filtration ◽  
Membrane Bioreactor ◽  
Ceramic Membrane ◽  
Pure Water ◽  
Ex Situ ◽  
Stable Operation ◽  
Chemical Cleaning ◽  
Cake Layer

The cost-effective and stable operation of an anaerobic ceramic membrane bioreactor (AnCMBR) depends on operational strategies to minimize membrane fouling. A novel strategy for backwashing, filtration and relaxation was optimized for stable operation of a side stream tubular AnCMBR treating domestic wastewater at the ambient temperature. Two in situ backwashing schemes (once a day at 60 s/day, and twice a day at 60 s × 2/day) maintaining 55 min filtration and 5 min relaxation as a constant were compared. A flux level over 70% of the initial membrane flux was stabilized by in situ permeate backwashing irrespective of its frequency. The in situ backwashing by permeate once a day was better for energy saving, stable membrane filtration and less permeate consumption. Ex situ chemical cleaning after 60 days’ operation was carried out using pure water, sodium hypochlorite (NaOCl), and citric acid as the order. The dominant cake layer was effectively reduced by in situ backwashing, and the major organic foulants were fulvic acid-like substances and humic acid-like substances. Proteobacteria, Firmucutes, Epsilonbacteria and Bacteroides were the major microbes attached to the ceramic membrane fouling layer which were effectively removed by NaOCl.

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