scholarly journals Defining the effect of the chemical concentration and solution pH on membrane chemical cleaning process

2019 ◽  
Vol 109 ◽  
pp. 00061
Author(s):  
Mykola Nechytailo ◽  
Olena Nahorna ◽  
Yevhenii Kosiuk
Keyword(s):  
Suspended Solids ◽  
Membrane Surface ◽  
Metal Salts ◽  
Chemical Concentration ◽  
Solution Ph ◽  
Chemical Cleaning ◽  
Negative Factor ◽  
Gel Layer ◽  
Chemical Washing ◽  
Active Substances

In the process of treating natural water from surface sources, precipitated substances are tend to be deposited on the ultrafiltration membrane, either as suspended solids or as gel structures, formed by humic substances with metal salts. Hydraulic washes are unable to remove gelled structures from the surface of the membranes. Consequently, the phenomenon of gelation on the surface of the membrane causes gradual decrease in productivity, which is a negative factor. Chemical washing of membranes is generally used to remove the gel layer from the membrane surface. In this paper, the range of compositions which effectively remove complex contaminants is proposed, and also the efficacy of both pH and changes in the concentration of active substances on the process of washing the membrane are analyzed.

Membrane separation of produced water

1996 ◽  
Vol 34 (9) ◽  
pp. 239-246 ◽  
Author(s):  
T. Bilstad ◽  
E. Espedal
Keyword(s):  
North Sea ◽  
Suspended Solids ◽  
Produced Water ◽  
Synergistic Effects ◽  
Membrane Surface ◽  
Volume Reduction ◽  
Chemical Cleaning ◽  
The North ◽  
Environmental Controls ◽  
The North Sea

Each time regulatory agencies initiate more stringent environmental controls, treatment technologies are refined to meet the updated standards. Centrifuges and hydrocyclones are, by and large, producing satisfactory effluents for meeting current quality requirements for the offshore petroleum industries. The European standard for effluent from onshore petroleum activities, however, requires less than 5 mg/l total hydrocarbons (HC) and less than 10 mg/l suspended solids. Such low concentrations are out of reach for the above classical separation processes. The amount of produced water in the North Sea is projected to increase by a factor of 6 from 1990 to the year 2000; from 16 to 90 million cubic meters each year. Produced water is the predominant source for oil discharges. The synergistic effects of chemicals, oil and dissolved components in the produced water effluent are given increased attention, with expectations of tougher effluent criteria. Microfiltration (MF) and ultrafiltration (UF) pilot trials with produced water from the Snorre field in the North Sea showed that UF, but not MF, could meet more stringent effluent standards for total HC, suspended solids and dissolved constituents. Total HC in the produced water was typically 50 mg/l and was reduced to 2 mg/l in the UF permeate (96% removal). The aromatics benzene, toluene and xylene (BTX) were similarly reduced by 54% and the heavy metals copper (Cu) and zinc (Zn) by 95%. UF trials were performed with organic tubular membranes with typical transmembrane pressures between 6 and 10 bars. The feed velocities through the tubes were between 2 and 4 m/s. Flux varied from 140 to 550 l/m2/h (lmh) at a produced water temperature of 60°C and membrane molecular weight cut-off between 100,000 and 200,000 daltons. By recirculating UF retentate as membrane feed, a volume reduction (VR) of 24 was obtained in the trials; i.e., 96% permeate recovery. The limited volume of produced water available in the feed tank negated further volume reduction. Full-scale design is based on permeate recovery of 99%. No irreversible fouling of the membrane surface was experienced. The cleanwater flux was restored after chemical cleaning. The alkaline detergent Ultrasil 11 was chosen as the optimal cleaning agent.

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.

Orange juice ultrafiltration: characterisation of deposit layers and membrane surfaces after fouling and cleaning

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Nurul Hainiza Abd-Razak ◽  
Y. M. John Chew ◽  
Michael R. Bird
Keyword(s):  
Shear Stress ◽  
Orange Juice ◽  
Surface Coverage ◽  
Fluid Shear Stress ◽  
Membrane Surface ◽  
Regenerated Cellulose ◽  
Fluid Shear ◽  
Chemical Cleaning ◽  
Membrane Area ◽  
Software Analysis

Abstract The influence of feed condition and membrane cleaning during the ultrafiltration (UF) of orange juice for phytosterol separation was investigated. UF was performed using regenerated cellulose acetate (RCA) membranes at different molecular weight cut-off (MWCO) values with a 336 cm2 membrane area and a range of temperatures (10–40 °C) and different feed volumes (3–9 L). Fluid dynamic gauging (FDG) was applied to assess the fouling and cleaning behaviours of RCA membranes fouled by orange juice and cleaned using P3-Ultrasil 11 over two complete cycles. During the FDG testing, fouling layers were removed by fluid shear stress caused by suction flow. The cleanability was characterised by using ImageJ software analysis. A Liebermann-Buchard-based method was used to quantify the phytosterol content. The results show that RCA 10 kDa filters exhibited the best separation of phytosterols from protein in orange juice at 20 °C using 3 L feed with a selectivity factor of 17. Membranes that were fouled after two cycles showed higher surface coverage compared to one fouling cycle. The surface coverage decreased with increasing fluid shear stress from 0 to 3.9 Pa. FDG achieved 80–95% removal at 3.9 Pa for all RCA membranes. Chemical cleaning using P3-Ultrasil 11 altered both the membrane surface hydrophobicity and roughness. These results show that the fouling layer on RCA membranes can be removed by fluid shear stress without affecting the membrane surface modification caused by chemical cleaning.

scholarly journals Microbial Flocculants as an Alternative to Synthetic Polymers for Wastewater Treatment: A Review

Symmetry ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 556 ◽  
Author(s):  
Faouzi Ben Rebah ◽  
Wissem Mnif ◽  
Saifeldin M. Siddeeg
Keyword(s):  
Heavy Metals ◽  
Wastewater Treatment ◽  
Suspended Solids ◽  
Specific Resistance ◽  
Oxygen Demand ◽  
Synthetic Polymers ◽  
Operating Parameters ◽  
Flocculating Activity ◽  
Microbial Strains ◽  
Active Substances

Microorganisms such as bacteria, fungi, and microalgae have been used to produce bioflocculants with various structures. These polymers are active substances that are biodegradable, environmentally harmless, and have flocculation characteristics. Most of the developed microbial bioflocculants displayed significant flocculating activity (FA > 70–90%) depending on the strain used and on the operating parameters. These biopolymers have been investigated and successfully used for wastewater depollution in the laboratory. In various cases, selected efficient microbial flocculants could reduce significantly suspended solids (SS), turbidity, chemical oxygen demand (COD), total nitrogen (Nt), dye, and heavy metals, with removal percentages exceeding 90% depending on the bioflocculating materials and on the wastewater characteristics. Moreover, bioflocculants showed acceptable results for sludge conditioning (accepted levels of dry solids, specific resistance to filtration, moisture, etc.) compared to chemicals. This paper explores various bioflocculants produced by numerous microbial strains. Their production procedures and flocculating performance will be included. Furthermore, their efficiency in the depollution of wastewater will be discussed.

Nanofiltration performance of lead solutions: effects of solution pH and ionic strength

2010 ◽  
Vol 10 (2) ◽  
pp. 193-200 ◽  
Author(s):  
Wuthikorn Saikaew ◽  
Supatpong Mattaraj ◽  
Ratana Jiraratananon
Keyword(s):  
Ionic Strength ◽  
Membrane Surface ◽  
Aromatic Polyamide ◽  
Solution Chemistry ◽  
Lead Ion ◽  
Solution Ph ◽  
Dead End ◽  
Flux Decline ◽  
Charged Membrane ◽  
Double Layer Thickness

Nanofiltration performance (i.e. rejection and flux decline) of lead solutions was investigated using a dead-end test cell at room temperature. An aromatic polyamide NF-90 membrane was chosen to determine the impacts of solution chemistry. The experimental results revealed that solution flux decline was dependent on solution pH, ionic strength, and type of lead solutions. Solution flux conducted with different types of lead solutions (i.e. PbCl2 and Pb(NO3)2) decreased with increased solution pH. Solutions having high pH exhibited greater flux decline than those having low solution pH, while lead ion rejections were relatively high. Increased ionic strengths resulted in a greater flux decline, while lead ion rejections decreased with decreasing solution pH and increasing ionic strengths. Such results were related to low solution pH, suggesting an increase in fixed charge of proton (H+), decreasing electrical double layer thickness within membrane, thus allowing increased lead concentration passing through the membrane surface. Solution flux and rejection decreased further at higher ionic strengths, which caused a reduced negatively charged membrane, and thus decreased rejections. It was also found that lead ion for PbCl2 solution exhibited higher rejections than that of Pb(NO3)2 solution.

scholarly journals Stimulatory effects on bacteria induced by chemical cleaning cause severe biofouling of membranes

2020 ◽  
Vol 10 (1) ◽  
pp. 82-94
Author(s):  
Xueye Wang ◽  
Jinxing Ma ◽  
Zhichao Wu ◽  
Zhiwei Wang
Keyword(s):  
Membrane Surface ◽  
Oxygen Species ◽  
Cleaning Efficiency ◽  
Chemical Cleaning ◽  
Physiological Mechanisms ◽  
Homoserine Lactones ◽  
Membrane Surfaces ◽  
Enhanced Production ◽  
Membrane Biofouling ◽  
Microbial Regrowth

Abstract Chemical cleaning with hypochlorite is routinely used in membrane-based processes. However, a high-transient cleaning efficiency does not guarantee a low biofouling rate when filtration is restarted, with the physiological mechanisms largely remaining unknown. Herein, we investigated the microbial regrowth and surface colonization on membrane surfaces after NaOCl cleaning had been completed. Results of this study showed that the regrowth of model bacteria, Pseudomonas aeruginosa, was initially subject to inhibition due to the damage of key enzymes' activity and the accumulation of intracellular reactive oxygen species although the oxidative stress induced by NaOCl had been removed. However, with the resuscitation ongoing, the stimulatory effects became obvious, which was associated with the enhanced production of N-acyl homoserine lactones and the secretion of eDNA that ultimately led to more severe biofouling on the membrane surface. This study elucidates the inhibition–stimulation mechanisms involved in biofilm reformation (membrane biofouling) after membrane chemical cleaning, which is of particular significance to the improvement of cleaning efficiency and application of membrane technologies.

scholarly journals Biomass Characteristics and Their Effect on Membrane Bioreactor Fouling

Molecules ◽  
2019 ◽  
Vol 24 (16) ◽  
pp. 2867 ◽  
Author(s):  
Petros K. Gkotsis ◽  
Anastasios I. Zouboulis
Keyword(s):  
Membrane Fouling ◽  
Membrane Bioreactor ◽  
Suspended Solids ◽  
Extracellular Polymeric Substances ◽  
Membrane Surface ◽  
Membrane Resistance ◽  
Soluble Microbial Products ◽  
Gelling Properties ◽  
Microbial Products ◽  
Soluble Part

Biomass characteristics are regarded as particularly influential for fouling in Membrane Bio-Reactors (MBRs). They primarily include the Mixed Liquor Suspended Solids (MLSS), the colloids and the Extracellular Polymeric Substances (EPS). Among them, the soluble part of EPS, which is also known as Soluble Microbial Products (SMP), is the most significant foulant, i.e., it is principally responsible for membrane fouling and affects all fundamental fouling indices, such as the Trans-Membrane Pressure (TMP) and the membrane resistance and permeability. Recent research in the field of MBRs, tends to consider the carbohydrate fraction of SMP (SMPc) the most important characteristic for fouling, mainly due to the hydrophilic and gelling properties, which are exhibited by polysaccharides and allow them to be easily attached on the membrane surface. Other wastewater and biomass characteristics, which affect indirectly membrane fouling, include temperature, viscosity, dissolved oxygen (DO), foaming, hydrophobicity and surface charge. The main methods employed for the characterization and assessment of biomass quality, in terms of filterability and fouling potential, can be divided into direct (such as FDT, SFI, TTF100, MFI, DFCM) or indirect (such as CST, TOC, PSA, RH) methods, and they are shortly presented in this review.

Replacement of Secondary Clarification by Membrane Separation—Results with Tubular, Plate and Hollow Fibre Modules

1999 ◽  
Vol 40 (4-5) ◽  
pp. 311-320 ◽  
Author(s):  
Berthold Günder ◽  
Karlheinz Krauth
Keyword(s):  
Activated Sludge ◽  
Suspended Solids ◽  
Membrane Separation ◽  
Membrane Surface ◽  
Hollow Fibre ◽  
Stable Operation ◽  
Membrane Systems ◽  
Process Technology ◽  
Mixed Liquor ◽  
Activated Sludge Processes

Membrane separation systems can replace the final clarification step to separate mixed liquor suspended solids (MLSS) in the activated sludge processes. Mixed liquor suspended solids concentrations as high as 20 g/l can be obtained compared with the typical 3-4 g/l for conventional activated sludge/secondary clarifier systems. This leads to much smaller reactor volumes. In addition, excellent, solids free effluent qualities can be achieved with this process technology. This paper reports about the parallel investigation of three membrane systems installed within or outside bioreactors of 7 to 9 m3 volume and flow rates from 1 to 3 m3/h. The different membrane modules were investigated: plate module (80 m2 membrane surface), hollow fibre module (80 m2) and tubular module (45 m2). At MLSS concentrations up to 25 g/l and water temperatures from 10 to 25°C a stable operation of the membrane systems was achieved for a period of more than one year. The energy consumption was approximately 1.5 kWh/m3 for the plate and hollow fibre and 3.0 kWh/m3 for the tubular module system.

Impact of chemical cleaning and air-sparging on the critical and sustainable flux in a flat sheet membrane bioreactor for municipal wastewater treatment

2008 ◽  
Vol 57 (12) ◽  
pp. 1873-1879 ◽  
Author(s):  
G. Guglielmi ◽  
D. Chiarani ◽  
D. P. Saroj ◽  
G. Andreottola
Keyword(s):  
Membrane Bioreactor ◽  
Municipal Wastewater ◽  
Membrane Surface ◽  
Municipal Wastewater Treatment ◽  
Chemical Cleaning ◽  
Critical Flux ◽  
Submerged Membrane Bioreactor ◽  
Flat Sheet ◽  
Exponential Trend ◽  
Flat Sheet Membrane

The paper discusses the experimental optimisation of both chemical and mechanical cleaning procedures for a flat-sheet submerged membrane bioreactor fed with municipal wastewater. Fouling was evaluated by means of the critical flux concept, which was experimentally measured by short-term flux-stepping tests. By keeping constant most important parameters of the biological process (MLSS, sludge age), two different chemical cleaning protocols (2,000 mg L−1 NaOCl and 200 mg L−1 NaOCl) were applied with different frequency and, after approximately 9 months of operation, the criticality threshold was determined under different values of SADm (specific aeration demand per unit of membrane surface area). The weaker and more frequent chemical cleaning regime (200 mg L−1, monthly) proved much more effective than the stronger and less frequent strategy (2,000 mg L−1, once every three months). The improvement of performances was quantified by two TMP-based parameters, the fouling rate and the ΔTMP (difference between TMP values during the increasing and decreasing phase of hysteresis). The best performing configuration was then checked over a longer period by running four long-term trials showing an exponential trend of the sub-critical fouling rate with the imposed flux.

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