EWT Water Technology – Water Treatment

EWT Water Technology

Multi-media Filter

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Within the scope of water treatment, filtration ist a mainly physical process for removal of suspended solids from liquids. The liquid to be filtrated flows through a filter medium, which results in the suspended solids being retained by this filter medium. A multi-media filter ist a vessel for filtration, with a layered filter bed consisting of different filter material, for example silica sand and anthracite coal, serving as filter medium.

With increasing service life, the differential pressure between the filter inlet and out increases for a given volume flow, as more solids are being retained within the filter medium. Eventually, the filter medium needs to be either backwashed or replaced.

A multi-media filter requires periodic backwash, either with water only, or with both air and water.

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Design Example:

multi-media filter

Multi-media filter plant, two lines, fully automated backwash with air and water.

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Technical Data:

filtrate volume flow available from approx. 1.5 up to 120 m³/h for each line
amount of lines usually 2x50%
smaller plants also 1x100% or 2x100%
larger plants also 3x33% or 4x25%
filtration grade approx. 5 ... 25 μm, without flocculation
approx. 0.5 ... 5 μm, with flocculation
filtrate quality turbidity ≤ 0.1 ... 1 NTU
total suspended solids (TSS) ≤ 0.5 ... 1 mg/L
differential pressure at nominal flow rate usually ≤ 0.5 bar
operating temperature usuually 5 ... 40 °C
backwash intervals usually 12 ... 72 h
backwash duration approx. 15 minutes, for water backwash
approx. 10 minutes, for air and water backwash
backwash water volume flow usually operating volume flow × 2 ... 4
waste water approx. 2 ... 80 L for each 1 m³ filtrate
recommended raw water quality total suspended solids (TSS) ≤ 40 mg/L
filter medium • anthracite coal
• dolomite
• garnet sand
• granular activated carbon
• pumice
• silica sand
• ...
total service life of the filter medium usually ≥ 10 years for removal of suspended solids only
in some cases ≤ 6 ... 12 months for special applications
material options pressure vessel • glass-reinforced plastic (GRP)
• carbon steel (e.g. S235JR, P265GH)
• stainless steel (e.g. 1.4301, 1.4404)
pipelines • polyvinyl chloride (PVC)
• polypropylene (PP)
• stainless steel (e.g. 1.4541)
valves • polyvinyl chloride (PVC)
• polypropylene (PP)
• stainless steel (e.g. 1.4408)
gaskets • etyhlene propylene diene monomer rubber (EPDM)
• polytetrafluorethylene (PTFE)
• NBR composite
control options differential pressure monitoring • local display
• remote measurement
filtrate quality monitoring • manual sampling and analysis
• continuous turbidity measurement
line change-over • manually
• fully automated
backwash • manually
• fully automated

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further downloads

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2018-05-05 • water treatment made in GermanyCompany InformationPrivacy