Harn R/O Systems Blog

Pretreatment: The Last Line of Defense for Your R/O Membranes

Posted by Julie Nemeth-Harn on Apr 10, 2018 11:53:00 AM

Pretreatment Equipment - Theory of Operation

Some raw feed waters contain suspended particulate material. This material is commonly sand, iron oxides, clay or elemental sulfur.

Introduction of such materials into the membrane system can cause the development of excessive system differential pressure (dP), or even complete blockage of the brine channels with the resultant reduction of permeate flow. It can also cause physical damage to the membranes themselves. This usually results in a decrease of permeate quality and reduction of membrane life. Cartridge filtration is normally a simple and cost-effective way to reduce the amount of particulate matter reaching the membrane surface.

Interested in a Membrane Filtration Pilot Package?

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Topics: ro calculations, water quality, membrane treatment, water treatment, membrane filtration, membrane treatment system, membrane plants

How to Calculate Percent Recovery and What Affects it in a Membrane Treatment System?

Posted by Julie Nemeth-Harn on Apr 3, 2018 1:10:00 PM


Recovery is the amount of water permeated per unit time - usually in gallons per minute (gpm) and expressed as a percentage of the raw water feed flow rate. The design recovery is calculated as follows:

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Topics: membrane treatment, membrane treatment system, water treatment, ro calculations, membrane filtration, water quality, membrane plants

How to Complete a Silt Density Index (SDI) Test and Why it's Important

Posted by Julie Nemeth-Harn on Feb 27, 2018 4:56:00 PM

It is important to check on the level of semi-colloidal suspended solids in the feedwater to RO systems. The level can be estimated (not measured absolutely) by the Silt Density Index or SDI test which measures the blocking rate of a 0.45 micron filter pad under controlled pressure conditions.

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Topics: ro calculations, silt density index, water quality