Harn R/O Systems Blog

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

Posted by Julie Nemeth-Harn on May 10, 2021 9:00:00 AM

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.

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

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

Posted by Julie Nemeth-Harn on Nov 16, 2020 9:45:00 AM

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: water quality, ro calculations, silt density index

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

Posted by Julie Nemeth-Harn on Oct 5, 2020 1:10:00 PM

Membrane systems operating at 82% recovery will convert 82% of the total raw water input into treated permeate, with the remaining 18% being sent to waste as concentrate (or reject). The recovery rate is monitored using flow meters installed in the permeate and concentrate piping.

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