Combined air-water flush in dead-end ultrafiltration

2001 ◽  
Vol 1 (5-6) ◽  
pp. 393-402 ◽  
Author(s):  
J.Q.J.C. Verbeck ◽  
G.I.M. Worm ◽  
H. Futselaar ◽  
J.C. van Dijk
Keyword(s):  
Membrane Surface ◽  
Head Loss ◽  
Direct Result ◽  
Two Phase ◽  
Sand Filters ◽  
Membrane Pores ◽  
Dead End ◽  
Pre Treatment ◽  
A New Technique ◽  
Energy Dissipated

Dead-end ultrafiltration has proven itself as a technique for reclamation of backwash water of sand filters and as a pre-treatment step for spiral wound reverse osmosis. A direct result of dead-end filtration is a decreased flux caused by the accumulation of material in the membrane pores and on the membrane surface. Different cleaning techniques are used to remove this accumulated material. Recently a new technique has been introduced, the AirFlush. This technique makes use of air to create higher turbulence as compared to a water flush. At Delft University of Technology research has started into the fundamentals of the combined air- and water-flush. First a series of experiments has been carried out to determine the different flow patterns, followed by experiments to determine which air- and water-velocities give the best cleaning. Finally head loss experiments have been done to get information about the energy dissipated in the system. The results of the head loss experiments have been compared to the theoretical head loss calculated with the theory of heterogeneous two-phase flow.

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.

The role of microparticles in dead-end ultrafiltration of wwtp-effluent

2004 ◽  
Vol 50 (12) ◽  
pp. 87-94 ◽  
Author(s):  
J.H. Roorda ◽  
S. te Poele ◽  
J.H.J.M. van der Graaf
Keyword(s):  
Wastewater Treatment Plants ◽  
Pilot Scale ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Membrane Pores ◽  
Wwtp Effluent ◽  
Dead End ◽  
Minor Influence ◽  
Pre Treatment

Ultrafiltration is considered as an interesting polishing technique for effluent of wastewater treatment plants (wwtp-effluent). Results in pilot-scale experiments indicated that microparticles might dominate the filtration characteristics. In this article the results of investigations on the role of microparticles on the filterability of effluent is described. Calculation effects on particle size distributions of effluent showed that particles smaller than 2.0 μm predominantly influence the filterability of the wwtp-effluent. Additionally, experiments were performed on the filterability of size fractions of effluent. Effluent was fractionated with laboratory filters (pore diameter 5.0, 1.2, 0.45, 0.2 and 0.1 μm). The filterability of this pre-filtered effluent in applying ultrafiltration was evaluated by measurement of the SUR, a new parameter for measurement of the filterability of effluent. The results showed that filterability of the effluent was mainly influenced by 40% to 57% by the fraction larger than 0.1 μm and smaller than 0.2 μm, which is five to twenty times larger than the ultrafiltration membrane pores. Pre-treatment of the effluent by coagulation or sand filtration showed only minor influence on these results.

scholarly journals Air Backwash Efficiency on Organic Fouling of UF Membranes Applied to Shellfish Hatchery Effluents

Membranes ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 48 ◽  
Author(s):  
Clémence Cordier ◽  
Christophe Stavrakakis ◽  
Patrick Sauvade ◽  
Franz Coelho ◽  
Philippe Moulin
Keyword(s):  
Membrane Surface ◽  
Operating Conditions ◽  
Particle Removal ◽  
Two Phase ◽  
Significant Information ◽  
Dead End ◽  
Biodiversity Preservation ◽  
Organic Fouling ◽  
Uf Membranes ◽  
The Impact

Among all the techniques studied to overcome fouling generated in dead-end filtration, the injection of air during backwashes proved to be the most effective. Indeed, shear stress engendered by the two-phase flow enhanced particle removal on membrane surface. This work aims to study the injection of air to drain the membranes before backwash. Firstly, the efficiency of this backwash procedure was evaluated during the ultrafiltration of seawater on a semi industrial pilot plant using different operating conditions. Then, the treatment of seawater, doped with oyster gametes to simulate the filtration of shellfish hatchery effluents, was performed to confirm the hydraulic performance of the air backwash. Indeed, the release of gametes, expulsed by exotic bivalves in the natural environment, could be a risk for the biodiversity preservation. The impact of air backwash on the integrity of oocytes and spermatozoa was identified using flow cytometry and microscopic analyses. When oyster gametes were added, their retention by ultrafiltration was validated. The impact of air backwash on these species viability was a significant information point for the implementation of this process on shellfish production farms.

scholarly journals Comparative environmental impact evaluation using life cycle assessment approach: a case study of integrated membrane-filtration system for the treatment of aerobically-digested palm oil mill effluent

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Yeit Haan Teow ◽  
Meng Teck Chong ◽  
Kah Chun Ho ◽  
Abdul Wahab Mohammad
Keyword(s):  
Activated Carbon ◽  
Life Cycle ◽  
Palm Oil ◽  
Membrane Filtration ◽  
Electricity Consumption ◽  
Sand Filters ◽  
Unit Operations ◽  
Filtration System ◽  
Pre Treatment ◽  
Aerobically Digested

AbstractAiming to mitigate wastewater pollution arising from the palm oil industry, this university-industry research-and-development project focused on the integration of serial treatment processes, including the use of moving bed biofilm reactor (MBBR), pre-treatment with sand filters and activated carbon filters, and membrane technology for aerobically-digested palm oil mill effluent (POME) treatment. To assess the potential of this sustainable alternative practice in the industry, the developed technology was demonstrated in a pilot-scale facility: four combinations (Combinations I to IV) of unit operations were developed in an integrated membrane-filtration system. Combination I includes a MBBR, pre-treatment unit comprising sand filters and activated carbon filters, ultrafiltration (UF) membrane, and reverse osmosis (RO) membrane, while Combination II excludes MBBR, Combination III excludes UF membrane, and Combination IV excludes both MBBR and UF membrane. Life cycle assessment (LCA) was performed to evaluate potential environmental impacts arising from each combination while achieving the goal of obtaining recycled and reusable water from the aerobically-digested POME treatment. It is reported that electricity consumption is the predominant factor contributing to most of those categories (50–77%) as the emissions of carbon dioxide (CO2), sulfur dioxide (SO2), nitrogen oxides, and volatile mercury during the combustion of fossil fuels. Combination I in the integrated membrane-filtration system with all unit operations incurring high electricity consumption (52 MJ) contributed to the greatest environmental impact. Electricity consumption registers the highest impact towards all life cycle impact categories: 73% on climate change, 80% on terrestrial acidification, 51% on eutrophication, and 43% on human toxicity. Conversely, Combination IV is the most environmentally-friendly process, since it involves only two-unit operations – pre-treatment unit (comprising sand filters and activated carbon filters) and RO membrane unit – and thus incurs the least electricity consumption (41.6 MJ). The LCA offers insights into each combination of the operating process and facilitates both researchers and the industry towards sustainable production.

A Method for Correlating the Characteristics of Centrifugal Pumps in Two-Phase Flow

1978 ◽  
Vol 100 (4) ◽  
pp. 395-409 ◽  
Author(s):  
Jaroslaw Mikielewicz ◽  
David Gordon Wilson ◽  
Tak-Chee Chan ◽  
Albert L. Goldfinch
Keyword(s):  
Centrifugal Pump ◽  
Two Phase Flow ◽  
Flow Direction ◽  
Semiempirical Method ◽  
Head Loss ◽  
Phase Flow ◽  
Loss Ratio ◽  
Centrifugal Pumps ◽  
Reversed Flow ◽  
Two Phase

The semiempirical method described combines the ideal performance of a centrifugal pump with experimental data for single and two-phase flow to produce a so-called “head-loss ratio,” which is the apparent loss of head in two-phase flow divided by the loss of head in single-phase flow. This head-loss ratio is shown to be primarily a function of void fraction. It is demonstrated that the measured characteristics of a centrifugal pump operating in two-phase flow in normal rotation and normal and reversed flow directions (first and second -quadrant operation) and in reversed rotation and reversed flow direction (third-quadrant operation) can be reproduced with acceptable accuracy.

Treatment of Groundwater with Slow Sand Filtration

1988 ◽  
Vol 20 (3) ◽  
pp. 141-147 ◽  
Author(s):  
T. Hatva
Keyword(s):  
Biological Activities ◽  
Treatment Phase ◽  
Purification Process ◽  
Sand Filtration ◽  
Sand Filters ◽  
Slow Sand Filtration ◽  
Filtration Method ◽  
Pre Treatment ◽  
Full Scale Tests ◽  
Iron Manganese

The purification process and techniques of the slow sand filtration method for treatment of groundwater was studied on the basis of pilot plant and full scale tests and studies of waterworks, to obtain guidelines for construction and maintenance. The purification process consists in general of two principal phases which are pre-treatment and slow sand filtration. Both are biological filters. The main purpose of the pre-treatment is to reduce the iron content of raw water, in order to slow down the clogging of the slow sand filters. Different types of biofilters have proved very effective in the pre-treatment phase, with reduction of total iron from 50 % to over 80 %. During the treatment, the oxidation reduction conditions gradually change becoming suitable for chemical and biological precipitation of iron, manganese and for oxidation of ammonium. Suitable environmental conditions are crucial in the oxidation of manganese and ammonium which, according to these studies, mainly occurs in slow sand filters, at the end of the process. Low water temperature in winter does not seem to prevent the biological activities connected with the removal of iron, manganese and ammonium, the chief properties necessitating treatment of groundwater in Finland.

Void fraction measurements in breaking waves

2007 ◽  
Vol 463 (2088) ◽  
pp. 3151-3170 ◽  
Author(s):  
C.E Blenkinsopp ◽  
J.R Chaplin
Keyword(s):  
Void Fraction ◽  
Wave Breaking ◽  
Breaking Waves ◽  
Phase Detection ◽  
Bubble Plume ◽  
Two Phase ◽  
Void Fractions ◽  
Highly Sensitive ◽  
Energy Dissipated ◽  
Degree Of Similarity

This paper describes detailed measurements and analysis of the time-varying distribution of void fractions in three different breaking waves under laboratory conditions. The measurements were made with highly sensitive optical fibre phase detection probes and document the rapid spatial and temporal evolutions of both the bubble plume generated beneath the free surface and the splashes above. Integral properties of the measured void fraction fields reveal a remarkable degree of similarity between characteristics of the two-phase flow in different breaker types as they evolve with time. Depending on the breaker type, the energy expended in entraining air and generating splash accounts for a minimum of between 6.5 and 14% of the total energy dissipated during wave breaking.

In-Plane Vibration Damping of a U-Tube With Wet and Dry Flat-Bar Supports

2014 ◽  
Author(s):  
Paul A. Feenstra ◽  
Victor P. Janzen ◽  
Bruce A. W. Smith
Keyword(s):  
Energy Dissipation ◽  
Plane Motion ◽  
Test Facility ◽  
Vibration Energy ◽  
Test Rig ◽  
Two Phase ◽  
Support Conditions ◽  
Vibration Tests ◽  
Energy Dissipated ◽  
Steam Generator Tubes

Tests are being planned which will use AECL’s MR-3 Freon test facility and a Multi-Span U-Bend (MSUB) test rig to investigate the dynamics of tube vibration in two-phase flow, in particular those mechanisms that can cause excessive damage to steam-generator tubes. In preparation for the tests, free- and forced-vibration tests were conducted to measure the vibration energy dissipation (damping) of a single U-bend tube in air, with dry and wet anti-vibration bars, under a variety of tube-support conditions. This paper presents the relevant damping mechanisms and documents methods used to conduct the tests and to analyze the energy dissipated at the supports. Results indicate that for in-plane motion without tube-to-support contact, viscous damping related to wet AV B supports is much smaller than guidelines based on other types of supports suggest. To begin to examine the effects of the tube coming into contact with its supports, such as friction-related energy dissipation, the results of tests with light tube-to-support preloads are also presented.

scholarly journals Influence of a steam-explosion pre-treatment on the methane yield and kinetics of anaerobic digestion of two-phase olive mil solid waste or alperujo

2016 ◽  
Vol 102 ◽  
pp. 361-369 ◽  
Author(s):  
Bárbara Rincón ◽  
Guillermo Rodríguez-Gutiérrez ◽  
Lucía Bujalance ◽  
Juan Fernández-Bolaños ◽  
Rafael Borja
Keyword(s):  
Anaerobic Digestion ◽  
Solid Waste ◽  
Steam Explosion ◽  
Methane Yield ◽  
Two Phase ◽  
Pre Treatment ◽  
Kinetics Of

Comparison of four types of membrane bioreactor systems in terms of shear stress over the membrane surface using computational fluid dynamics

2013 ◽  
Vol 68 (12) ◽  
pp. 2534-2544 ◽  
Author(s):  
N. Ratkovich ◽  
T. R. Bentzen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Membrane Fouling ◽  
Two Phase Flow ◽  
Membrane Surface ◽  
Cross Flow ◽  
Membrane Bioreactors ◽  
Phase Flow ◽  
Two Phase ◽  
Computational Fluid Dynamics Cfd

Membrane bioreactors (MBRs) have been used successfully in biological wastewater treatment to solve the perennial problem of effective solids–liquid separation. A common problem with MBR systems is clogging of the modules and fouling of the membrane, resulting in frequent cleaning and replacement, which makes the system less appealing for full-scale applications. It has been widely demonstrated that the filtration performances in MBRs can be greatly improved with a two-phase flow (sludge–air) or higher liquid cross-flow velocities. However, the optimization process of these systems is complex and requires knowledge of the membrane fouling, hydrodynamics and biokinetics. Modern tools such as computational fluid dynamics (CFD) can be used to diagnose and understand the two-phase flow in an MBR. Four cases of different MBR configurations are presented in this work, using CFD as a tool to develop and optimize these systems.

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