The Process of Membrane Filtration In many regions, the first stage in the production of drinking or service water is to pump water directly from the sea, groundwater wells near the coast or brackish water. This untreated water must then be treated and there are different processes and combinations of processes for this purpose. One reliable method of treating water is, for example, by means of membrane filtration. With this method, very small particles are retained by a membrane and filtered out (retentate). The membrane consists of a thin, fine-porous wall which can filter practically all particles above a certain size. Smaller particles can pass through unhindered and without loss and can thereby be selected (permeate). The water is generally forced or drawn through the filter membrane. In this way, the retained particles or molecules accumulate on the membrane and are concentrated to form a filter cake. The pressure-driven membrane filtration consists of the following basic processes: Production of Drinking and Service Water from Brackish and Sea Water 10 to 100 bar 3 to 20 bar 0.1 to 5 bar 0.1 to 2 bar Required pressure differential Ions Organic compounds Multivalent ions Macro- molecules Viruses Colloids Composition Reverse osmosis < 200 Da Nanofiltration 1 kDa – 200 Da Ultrafiltration 1 – 500 kDa Microfiltration 0.1 – 0.8 μm Membrane process Zooplankton Phytoplankton Bacteria Suspended particles Microfiltration (MF): filtration of solid particles or colloid particles above a certain diameter Ultrafiltration (UF): filtration of macromolecules above a certain molecular weight Nanofiltration (NF): filtration of nano-range particles Reverse osmosis (RO): filtration of dissolved molecules or ions
Transcript
The Process of Membrane FiltrationIn many regions, the first stage in the production of drinking or service water is to pump water directly from the sea, groundwater wells near the coast or brackish water. This
untreated water must then be treated and there are different processes and combinations of processes for this purpose.
One reliable method of treating water is, for example, by means of membrane filtration.
With this method, very small particles are retained by a membrane and filtered out (retentate). The membrane consists of a thin, fine-porous wall which can filter practically all particles above a certain size. Smaller particles can pass through unhindered and without loss and can thereby be selected (permeate).
The water is generally forced or drawn through the filter membrane. In this way, the retained particles or molecules accumulate on the membrane and are concentrated to form a filter cake.
The pressure-driven membrane filtration consists of the following basic processes:
Production of Drinking and Service Water from Brackish and Sea Water
10 to 100 bar3 to 20 bar0.1 to 5 bar0.1 to 2 barRequiredpressuredifferential
IonsOrganic compounds
Multivalent ions
Macro-molecules
Viruses
Colloids
Composition
Reverse osmosis
< 200 Da
Nanofiltration
1 kDa – 200 Da
Ultrafiltration
1 – 500 kDa
Microfiltration
0.1 – 0.8 µm
Membraneprocess
Zooplankton
Phytoplankton
Bacteria
Suspended particles
� Microfiltration (MF): filtration of solid particles or colloid particles above a certain diameter
� Ultrafiltration (UF): filtration of macromolecules above a certain molecular weight
� Nanofiltration (NF): filtration of nano-range particles
� Reverse osmosis (RO): filtration of dissolved molecules or ions
The first stage in the pre-treatment generally consists of coarse particle
filtration. During this stage coarse particles which are present in the untreated water, and which could penetrate the system, are removed. Screens, strainers or coarse filters ranging in size from 1 to 5 mm are used. In the next stage the untreated water is further pre-treated to achieve the required feed water
quality for the membrane filtration downstream. After the membrane filtration, a post-treatment may be required (e.g. disinfection). Depending on the water quality required, the process stages are adapted to suit the particular requirements of the consumer as well as the actual quality of the untreated
water.
HYDAC Process Technology is engaged in the pre-treatment of saltwater prior to membrane systems. The AutoFilt RF3 or TwistFlow Strainer TFS, for
example, can be used as part of the pre-treatment process.
The following examples show that the pre-treatment process can consist of very different process stages.
Pre-Filtration Prior
to Membrane SystemsWater treatment processes generally consist of several stages which must be specially coordinated with one another.
For reliable water desalination by means of a pressure-driven membrane process, optimised pre-treatment of the untreated
water is an important prerequisite.
The pre-treatment is generally the most important step in a multi-stage water treatment process as it can strongly affect
the economic efficiency of the membrane filtration downstream. Short lifetimes of the filters and membranes installed
downstream, high maintenance costs and high energy consumption due to the high content of turbid particles, suspended solids, colloids and also to a certain
extent, organic matter, escalate the costs and have a negative effect on process reliability.
Brackish / groundwater wells
Direct sea water extraction
Pre-treatment
NF / ROPost-
treatment
Model 1Cost reductions on sea water desalination systems are predominantly made through well-engineered pre-treatment processes as these have a lasting effect on the subsequent membrane processes. With the following typical
process the pre-treatment essentially consists of the combination of coarse screens, back-flushing filters and cartridge filters.
This treatment process is explained in further detail in a case study on page 7.
Model 2In certain cases, the RF3 can also be installed before sand filters where these are used for water treatment. However, since a sand filter is a depth filter which, when operated correctly, can filter out contaminants to a few micrometers nominal, it must be decided on an individual basis to what extent
a back-flushing filter can relieve the sand filter.
coarsescreen
cartridgefilter
scaleinhibitor
chlorine-containing
flocculantpolyelectrolyte
staticmixer
staticmixer
sandfilter
carbonfilter
AutoFilt® RF3
Post-treatment
Sea water,
brackish water
Drinking water /
service water
ROROPre-
treatment
coarsescreen
cartridgefilter
5 - 15 µm
AutoFilt® RF3
scaleinhibitor
staticmixer
Post-
treatment
Sea water,Brackish water
Drinking water /Service water
ROROPre-
treatment
Model 3Membrane processes are also used increasingly in pre-treatment. Here microfiltrationor ultrafiltration membranes are used to clean the untreated water to the condition required before undergoing reverse osmosis.
With such pre-treatment processes pre-filtration is particularly necessary for
microfiltration or ultrafiltration.
The RF3 or TFS can be used here to relieve the microfiltration or ultrafiltration and increase the operating reliability of the process.
Other Possible ModelsThe pre-treatment processes for the production of drinking and service water are
varied and individual. Despite this, in many cases the RF3 and other HYDAC filters, such as the TFS, can make an important contribution towards reducing operating costs and increasing operational reliability The following table shows a selection from
the extensive HYDAC filter range from which individual pre-treatment solutions can be created. Other optional models are available on request.
1 to 90 µm25 to 3,000 µm 200 to
3,000 µm
25 to 3,000 µmFiltration
rating
up to 40 barup to 16 barup to 16 barup to 16 barPressure
up to 1,200 m³/hup to 10,000 m³/hup to 120 m³/hup to 6,000 m³/hFlow rate
G 1“ to DN 200
DN 50 to DN 900
NW 1“ to DN 100
DN 50 to DN 700
Connection
PMRFRF3 / RF4TFSPRFS
coarsescreen
ultra-filtration
AutoFilt® RF3
scaleinhibitor
micro-filtration
and/or
Post-
treatment
Seawater,brackish water
Drinking water /service water
ROROPre-
treatment
Post-treatment
ROROPre-
treatment
AutoFilt® RF3The automatic back-flushing filter Autofilt RF3 is a self-cleaning system for filtering solid particles from low-viscosity fluids.
Special features:
Advantages of the RF3
� Isokinetic filtering and back-flushing due to
conical filter elements
� Fewer back-flushing cycles
� Lower loss of back-flushing fluid
� Pulse-aided back-flushing
� Low back-flushing quantities due to cyclic control
� Compact dimensions with high filtration performance and low pressure drop
� Variable filter isometry
� User-selectable control parameters
� Static sealing
� Ready-to-operate unit
� Extends the lifetime of downstream filters
� Reduces maintenance costs
� Reduces energy consumption
� Increases process reliability by successfully removing the sand particles before the membrane filtration process
� Space-saving installation
� Flexible construction
� Self-cleaning, robust stainless steel filter elements
� No recurring additional costs
� Can be retrofitted
� Economical
AutoFilt® TFSThe Autofilt® TwistFlow Strainer TFS is a hybrid system consisting of a centrifugal separator and an inline filter.
Special features:
Advantages of the TFS
� Process reliability - not affected by fluctuations in operating pressure, flow rate or consistency of the fluid
� Specific filtration rating – consistently high filtrate quality
� Suitable for high and fluctuating levels of contamination
� No other fluids required to clean the filter element
� Pre-filtration of solid particles of a higher density – filter area can take a higher load
� Low pressure drop
� Application even at low operating pressure
� Robust construction, no moving internal parts – no spare parts required
� Space-saving installation
� Adaptation to flow rates – several TFS can be combined on one skid
� Cost-effective, economical and reliable
� Increase in process reliability during pre-
treatment prior to membrane systems
� Extension in the service life of the downstream filter
� Reduction in maintenance costs
� Reduction in energy consumption
� Space-saving installation
� Flexible design
� Self-cleaning, robust stainless steel filter
elements
� No recurring additional costs
� Can be retrofitted
� Economical
� Cost-effectiveFiltration Cleaning
Phase Phase
TFS-2 Cutaway Model
TFS-2 Filter Skid
TFS - 1G1“ (DN 25)
2 – 8 m3/h
TFS - 2DN 50
5 – 25 m3/h
TFS - 3DN 100
20 – 100 m3/h
HYDAC Inline FiltersHYDAC inline filters are suitable for continuous and discontinuous filtration of solid particles from water. To avoid
interruptions to operation during element change, change-over filters are ideal since one housing is filtering whilst the other is in
reserve.
A wide range of designs and filter materials ensures optimum adaptation to the particular
filtration task and process conditions and provides effective filtration of all types of solid particles.
Special features:
Advantages of Inline Filters� Long service life due to large filtration
areas
� Filter materials with a high contamination
retention capacity
� Low pressure drops due to flow-optimised designs
� Compact, easy-to-operate filter housing
� Very economical as most filter elements are cleanable
� Consistently high quality to ISO 9001
� Stable design
� Temperatures up to 400° C
� Pressures up to 1,000 bar
� Filtration ratings of 1 µm (absolute) up to 10 mm
� Flow rates up to 6,000 m³/h
Advantages
Furthermore, it was demonstrated that retrofitting the HYDAC Autofilt RF3 into an existing system is not difficult due to its space-saving, flexible design. In addition, the
self-cleaning, robust stainless steel filter elements mean that there are no recurring additional costs. In the meantime, this design
has now been successfully implemented in a number of other water treatment plants which had similar problems with fine sand contaminants.
Comparison showing increase in differential
pressure across the cartridge filter elements both with and without an RF3.
Case Study: Using the RF3 Prior to Cartridge FiltersIn many water treatment plants where drinking water is produced from brackish water, a treatment process consisting of pre-treatment using fine filtration and downstream reverse osmosis is often employed. The main aim of the study was, therefore, to test and evaluate an automatic backflushing filter Autofilt RF3 in the pre-treatment stage
when producing drinking water from brackish and sea water. The study revealed that the backflushing filter is ideally suited to protecting the cartridge filters. The particle contaminants which consisted of fine sand, could be continuously removed from the
untreated water which meant that the fine filter cartridges had a considerably longer service life. Retrofitting the backflushing filter in the water treatment plant demonstrated the economic and technical advantages of this concept.
� Extends the service life of the cartridge filter elements to several months
� Reduces maintenance costs and energy consumption
� Increases process reliability by successfully removing the sand particles prior to the reverse osmosis process
time [month]
∆p[bar]
0.7
0
0 1 2 3 4
Replacement of the cartridgefilter elements
without RF3 with RF3
Suppliers of Sea Water Desalination
SystemsSystem supplier total capacity (m³/d)
� IONICS US 3,368,000
� VEOLIA SIDEM FR 2,248,000
� FISIA IT 2,240,000
� DOOSAN KR 2,020,000
� WEIR TECHNA GB 1,470,000
� MHI/SASA KURA JP 1,450,000
� ONDEO FR 1,180,000
� HITACHI ZOSEN JP 885,000
� ENVIROGENICS US 810,000
� KURITA JP 780,000
� SASAKURA JP 780,000
� NOMURA JP 780,000
� ISHIKAWAJIMA JP 706,000
� VATECH WABAG AT 670,000
� VEOLIA US 660,000
� IDE IL 615,000
� SNAM PROGETTI IT 580,000
� HYDRANAUTICS US 560,000
� VEOLIA ARABIA SA 520,000
� MITSUBISHI JP 502,000
� PRIDESA ES 500,000
� CADAGUA ES 440,000
� ADVANCED EWT US 440,000
� ANSALDO IT 436,000
� USSR SU 405,000
� OTID IDE OTV IL 395,000
� MEMBRANE SYST US 380,000
� FLUID SYSTEMS US 365,000
� EMCO US 352,000
� MITSUI JP 346,000
� AQUA CHEM US 345,000
� ORGANO JP 329,000
� INIMA ES 306,000
� HYDROPRO US 287,000
Suppliers of
Membrane SystemsSystem supplier total capacity (m3/d)
� HYDRANAUTICS US 3,215,000
� DOW FILMTEC US 2,130,000
� DUPONT US 2,080,000
� IONICS US 1,430,000
� TORAY JP 1,110,000
� KOCH FLUID SYSTEMS US 1,050,000
� TOYOBO JP 425,000
� KURITA JP 425,000
� NITTO JP 333,000
� SIDMAS SA 240,000
� DESALINATION US 190,000
� DOW US 135,000
Filter InformationFurther details on the HYDAC PROCESS TECHNOLOGY products presented here can be found in the following brochures and catalogues.
![WP5 - BUSINESS PLAN & EXPLOITATION D5.5 Patents …€¦ · Microfiltration [0.1-0.5]µ m Ultrafiltration [0.005-0.05]µ m Nanofiltration [0.0005-0.005]µ m Reverse Osmosis Other(s)](https://static.documents.pub/doc/80x56/5ea1b914f25c7931fb3476b2/wp5-business-plan-exploitation-d55-patents-microfiltration-01-05.jpg)
