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.

scholarly journals Improving chemical cleaning of fouled membranes in a drinking water treatment plant

2019 ◽  
Vol 19 (8) ◽  
pp. 2330-2337
Author(s):  
Susumu Hasegawa ◽  
Yasuhiro Tanaka ◽  
Naokazu Wake ◽  
Ryosuke Takagi ◽  
Hideto Matsuyama
Keyword(s):  
Drinking Water ◽  
Water Treatment ◽  
Humic Substances ◽  
Sodium Hypochlorite ◽  
Membrane Fouling ◽  
Treatment Plant ◽  
Drinking Water Treatment ◽  
Water Treatment Plant ◽  
Chemical Cleaning ◽  
Water Treatment Plants

Abstract Recently, membrane filtration systems have become increasingly common in drinking water treatment plants. In this industry, preventing membrane fouling is of utmost importance. Many studies on the relationship between raw water components and membrane fouling have been performed in laboratory conditions. However, very few studies have analyzed the components of foulants on the fouled membrane as operated in actual drinking water treatment plants. By analyzing these components in plant-conditions, membrane fouling will be more effectively prevented. In this study, we analyzed the components of foulants extracted with 0.1 N NaOH from a fouled membrane operated in a drinking water treatment plant in Japan. Our analysis revealed that the main foulants were humic substances. In order to dissolve the accumulated humic substances, additional chemical cleaning was attempted with 500 ppm sodium hypochlorite. As a result, it was found that humic substances were dissolved and filtration resistance significantly decreased. Additionally, the removal of inorganic foulants was also greater after chemical cleaning with 500 ppm sodium hypochlorite, as inorganic foulants trapped within humic substances were released to the membrane surface as hydroxides by the additional sodium hypochlorite cleaning and were dissolved by the periodic citric acid cleaning.

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

Implementing biofilm carriers into activated sludge process-15 years of experience

1998 ◽  
Vol 37 (9) ◽  
pp. 167-174 ◽  
Author(s):  
N. Müller
Keyword(s):  
Waste Water ◽  
Water Treatment ◽  
Nitrogen Removal ◽  
Waste Water Treatment ◽  
Fixed Bed ◽  
Activated Sludge Process ◽  
Water Treatment Plants ◽  
Biofilm Carriers ◽  
Practical Experiences

Seven full-scale hybrid systems have been operating in waste water treatment plants in Southern Germany since the early eighties. The aerobic submerged biofilm technology applied is known as Bio-2-Sludge process. The plants have originally been designed for carbon removal and were modified later on to allow nitrogen removal. For this purpose, the age of the operating sludge had to be raised. This was achieved without any addition of reactor volume by installation of submerged biofilm carriers. The use of the submerged, fixed bed devices results in a very efficient sludge, allowing MLSS of up to 11 g/l. Operational results show both a purification improvement of BOD and ammonia and the existence of simultaneous denitrification. Practical experiences of long-term operations are being reported.

scholarly journals The Effect of Different Cleaning Methods on Protein Deposition and Optical Characteristics of Orthokeratology Lenses

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4318
Author(s):  
Chen-Ying Su ◽  
Lung-Kun Yeh ◽  
Yi-Fei Tsao ◽  
Wen-Pin Lin ◽  
Chiun-Ho Hou ◽  
...  
Keyword(s):  
Optical Characteristics ◽  
Short Term ◽  
Protein Deposition ◽  
Tear Proteins ◽  
Cleaning Methods ◽  
Vitro Analysis ◽  
In Vitro Analysis ◽  
Myopia Control

Orthokeratology lenses are commonly used for myopia control, especially in children. Tear lipids and proteins are immediately adsorbed when the lens is put on the cornea, and protein deposition may cause discomfort or infection. Therefore, we established an in vitro protein deposition analysis by mimicking the current cleaning methods for orthokeratology lens wearers for both short-term and long-term period. The results showed that the amounts of tear proteins accumulated daily and achieved a balance after 14 days when the lens was rubbed to clean or not. Protein deposition also affected the optical characteristics of the lens regardless of cleaning methods. Our results provided an in vitro analysis for protein deposition on the lens, and they may provide a potential effective method for developing care solutions or methods that can more effectively remove tear components from orthokeratology lenses.

scholarly journals Direct-acting Antivirals in Kidney Transplant Patients: Successful Hepatitis C Treatment and Short Term Reduction in Urinary Protein/Creatinine Ratios

2017 ◽  
Vol 2 (3) ◽  
pp. 366 ◽  
Author(s):  
Michael R. Goetsch ◽  
Ashutosh Tamhane ◽  
Mohit Varshney ◽  
Anuj Kapil ◽  
Edgar T. Overton ◽  
...  
Keyword(s):  
Kidney Transplant ◽  
Post Treatment ◽  
Kidney Graft ◽  
Direct Acting Antivirals ◽  
Short Term ◽  
Transplant Patients ◽  
Kidney Transplant Patients ◽  
Pre Treatment ◽  
Direct Acting

Introduction: The role of Hepatitis C Virus (HCV) clearance in long-term kidney graft survival is unknown. In this study, we examined short-term trends of urinary protein/creatinine (P/C) ratios in a cohort of HCV-infected kidney transplant recipients with stable graft function and treated with direct-acting antivirals (DAAs).Methods: We conducted a retrospective study of 19 kidney transplant patients with chronic HCV infection treated with DAAs at the University of Alabama at Birmingham 1917 Viral Hepatitis Clinic between January 2013 and June 2016. Markers of glomerular damage were assessed using average protein/creatinine (P/C) ratios measured pre- and post-treatment. We also described treatment efficacy using sustained virologic response at 12 weeks post-HCV treatment (SVR12).Results: The median age of the 19 patients included was 59 years (Q1=58, Q3=64) at completion of treatment. Of these patients, 68% were African American, 32% were White and 63% were male. The median time between kidney transplant and initiation of DAA therapy was 2.25 years (Q1=0.79, Q3=3.79). Post-treatment P/C ratios (median=0.127, Q1=0.090, Q3=0.220) were significantly lower (p=0.01) than pre-treatment ratios (median=0.168, Q1=0.118, Q3=0.385). P/C ratios decreased in 14 of 19 patients (74%) with median change of -0.072 (median percent change= -40%). Post-treatment eGFRs (median=58.9, Q1=48.9, Q3=72.3) were not significantly different (p=0.82) than the pre-treatment values (median=57.0, Q1=48.8, Q3=67.8).Conclusions: In this preliminary study, there was a statistically significant decrease in P/C ratios associated with HCV clearance, suggesting a potential role for DAAs in improving kidney graft survival. Larger cohort studies will be needed to assess the clinical and long-term benefits of DAAs in this special population of HCV infected patients. 

The response of defoliated swards of subterranean clover to temperature

1976 ◽  
Vol 27 (5) ◽  
pp. 593 ◽  
Author(s):  
EAN Greenwood ◽  
BA Carbon ◽  
RC Rossiter ◽  
JD Beresford
Keyword(s):  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Carbon Dioxide Exchange ◽  
Short Term ◽  
Plant Parts ◽  
Pre Treatment ◽  
Reproductive Phases ◽  
Whole Life Cycle

The objective was to characterize the response of Trifolium subterraneum L. (cv. Daliak) swards to short-term and to long-term changes in temperature at several stages of plant growth. Short-term responses were studied with microswards growing in boxes in the open and defoliated every week to simulate heavy grazing. At seven stages, one subsample of boxes was harvested and three other subsamples were moved to controlled-temperature glasshouses and grown for 14 days at 10/5° (day/night), 17.5/12.5° and 25/20°C respectively, and then harvested. Dry weights and numbers of plant parts, and areas of leaves, height, light penetration and net carbon dioxide exchange of swards were measured. For long-term responses, young, defoliated microswards were transferred to the above temperatures for 9 weeks and cut weekly. On days 32 (pre-treatment harvest), 53, 74 and 95, tops and roots were harvested. The results support three generalizations. Firstly, severely defoliated subterranean clover pastures respond to temperature between 10/5° and 25/20° in a variety of ways over the whole life cycle. However, temperature is of greater importance as a determinant of dry weight of tops during the post-emergence and reproductive phases than it is during the preflowering phase. Secondly, total growth rate (TGR) after the first 8–10 weeks of growth does not increase at temperatures above 10/5°. And thirdly, even with moderately low LAI values of 1–4, temperatures of 25/20° can inhibit TGR after about 8 weeks of growth. The biological and agricultural implications are discussed.

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%.

Early glycaemic changes after initiation of oral antidiabetic medication and risk of major adverse cardiovascular events: results from a large primary care population of patients with type 2 diabetes

2020 ◽  
Author(s):  
Jonas Ghouse ◽  
Paul Blanche ◽  
Morten W Skov ◽  
Bent Lind ◽  
Allan Vaag ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Cardiovascular Events ◽  
Major Adverse Cardiovascular Events ◽  
Short Term ◽  
Oral Antidiabetic ◽  
Steep Decline ◽  
Pre Treatment ◽  
First Time

Abstract Aims To determine the risk of major adverse cardiovascular events (MACE) and death, associated with an early large and rapid decline in glycated haemoglobin (HbA1C) following first time initiation of an oral antidiabetic drug (OAD). Methods and results We included 10 518 primary care patients with type 2 diabetes, who initiated an OAD for the first time. For each individual, we measured a decline in HbA1C, as the difference between the pre-treatment HbA1C (within 3 months before OAD initiation) and the post-treatment HbA1C (within 1.5–4.5 months after OAD initiation), divided by the time between the two measurements. The decline was reported in mmol/mol change per 3 months in HbA1C and categorized by the median decline into levels of steep [≥9 mmol/mol (≥0.8%)] and flat decline [<9 mmol/mol per 3 months (<0.8%)]. Pre-treatment HbA1C was categorized by the median, into levels of low (48–62 mmol/mol) and high (>62 mmol/mol). Multiple Cox regression was used to study the effect of decline (steep vs. flat) on the outcome hazard rates separately for patients with low and high pre-treatment HbA1C. Analyses were adjusted for age, sex, traditional cardiovascular risk factors, severe comorbidities, and concomitant medication treatment. During a median follow-up time of 7.7 years, 1625 developed MACE and 2323 died. We found that a steep decline vs. a flat decline was significantly associated with a decreased hazard for MACE, both in individuals with high [hazard ratio (HR) 0.81; 95% confidence interval (CI) 0.69–0.94; P = 0.005] and low pre-treatment HbA1C (HR 0.79; 95% CI 0.66–0.96; P = 0.015). The hazard of MACE was more pronounced on the short-term vs. long-term in individuals with high pre-treatment HbA1C. We found no significant association between combinations of pre-treatment HbA1C and decline categories and hazard of all-cause mortality. However, a combination of a low pre-treatment HbA1C and steep decline was associated with increased 1-year mortality (HR 1.52; 95% CI 1.00–2.29; P = 0.048) and hypoglycaemia (HR 1.82; 95% CI 1.11–2.98; P = 0.017). Conclusion A combination of a high pre-treatment HbA1C and a steep decline in HbA1C was associated with a decreased short-term risk of MACE. A low pre-treatment HbA1C and a steep decline was associated with a long-term reduced risk of MACE, but a short-term increased risk of death and hypoglycaemia.

scholarly journals Capillary Nanofiltration under Anoxic Conditions as Post-Treatment after Bank Filtration

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1599 ◽  
Author(s):  
Jeannette Jährig ◽  
Leo Vredenbregt ◽  
Daniel Wicke ◽  
Ulf Miehe ◽  
Alexander Sperlich
Keyword(s):  
Organic Carbon ◽  
Membrane Fouling ◽  
Pilot Scale ◽  
Bank Filtration ◽  
Organic Micropollutants ◽  
Current Water ◽  
Pre Treatment ◽  
Iron And Manganese ◽  
Good Retention

Bank filtration schemes for the production of drinking water are increasingly affected by constituents such as sulphate and organic micropollutants (OMP) in the source water. Within the European project AquaNES, the combination of bank filtration followed by capillary nanofiltration (capNF) is being demonstrated as a potential solution for these challenges at pilot scale. As the bank filtration process reliably reduces total organic carbon and dissolved organic carbon (DOC), biopolymers, algae and particles, membrane fouling is reduced resulting in long term operational stability of capNF systems. Iron and manganese fouling could be reduced with the possibility of anoxic operation of capNF. With the newly developed membrane module HF-TNF a good retention of sulphate (67–71%), selected micropollutants (e.g., EDTA: 84–92%) and hardness (41–55%) was achieved together with further removal of DOC (82–87%). Fouling and scaling could be handled with a good cleaning concept with acid and caustic. With the combination of bank filtration and capNF a possibility for treatment of anoxic well water without further pre-treatment was demonstrated and retention of selected current water pollutants was shown.

scholarly journals Long-term effects of different cleaning methods on copolyester retainer properties

2018 ◽  
Vol 89 (2) ◽  
pp. 221-227 ◽  
Author(s):  
Emily Wible ◽  
Manika Agarwal ◽  
Sibel Altun ◽  
Tyler Ramir ◽  
Grace Viana ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Artificial Saliva ◽  
Flexural Modulus ◽  
Qualitative Difference ◽  
Light Transmittance ◽  
Qualitative Assessment ◽  
Long Term Effects ◽  
Chemical Cleaning ◽  
Cleaning Methods

ABSTRACT Objective: To evaluate light transmittance, surface roughness, and flexural modulus of copolyester retainer material after long-term exposure to different cleaning methods. Materials and Methods: Standardized copolyester retainer specimens (ACE) were subjected to seven chemical cleaning solutions for 6 months: Invisalign cleaning crystals, Retainer Brite, Polident, Listerine mouthwash, 2.5% acetic acid, 0.6% NaClO, and 3% H2O2. Seventy specimens (n = 10 per method, 50.8 mm × 12.7 mm × 1.0 mm) were exposed to the different solutions twice a week for 2 minutes or according to manufacturer's instructions and stored in artificial saliva at 37°C. Another group of specimens (n = 10) was brushed with a standardized toothbrushing machine for 2 minutes twice a week. At baseline and 6 months, light transmittance, surface roughness and flexural modulus of the specimens were quantified using spectrophotometry, profilometry, and three-point bend testing, respectively. Qualitative assessment was performed using scanning electron microscopy (SEM). Statistical analyses were accomplished at a significance level of .05. Results: The results indicated that light transmittance through the specimens decreased significantly from baseline for all cleaning methods at 6 months. Flexural modulus of the specimens decreased significantly for all cleaning methods except Invisalign crystals and Retainer Brite (P > .05). The Listerine group demonstrated the worst light transmittance change while H2O2 demonstrated the greatest change in flexural modulus of the specimens compared with other cleaning methods; however, no qualitative difference was observed using SEM analysis. Conclusions: The results suggest that different cleaning methods affect long-term physical properties of the ACE retainer material. At the present time, none of these cleaning methods is ideal for copolyester retainer material.

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