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Reverse Osmosis Membrance Pollution

RO membranes pollution includes bio pollution, particles pollution, chemical pollution and colloid pollution. Membranes pollution is caused by : 1, inorganic depositing, 2,organic adsorption. 3particles and 4, Microbiology adsorption and creation(bio pollution).On commonly, Anti-infiltration membranes is polluted because of long operation time. For avoiding membranes damage or function lost, the input water must be pre-treated correctly and removed pollution to control pollution situation.

Keeping completed operation record is the best method of finding and pollution immediately. System operation record must be detail and clear. Temperature, pressure, TDS, SDI and restored rate of water-filling shall be recorded clearly for operators to grasp the changing of system.

一、 Common pollution foreseen

1、 particles pollution

Pre-treatment has defects in design and equipments, safe filter not sealed well, coagulation or condensation volume not applicable, pre-treatment flow rate too fast. Appearance: Fist stage pressure difference raises.

  2Bio pollution (gradually shown)

Main composition of organic precipitation are live and dead microbiology, hydrocarbons derivatives, natural organic polymer and all matter including carbon. Appearance: Fist and second stage pressure difference raises.

  3 Colloid pollution (gradually shown)

During membranes separated, metallic ion concentrating and solution PH value changing may cause depositing of metallic hydroxide. Primary appearing light reducing of salt-escape, then raising, at last, the end stage pressure drop and water-out reduces.

4 Chemical construction (fast shown)

When water-input has Ca2+, HCO-3, CO32-, CaCO3 may deposit on membranes. During membranes separating, deposition of CaCO3 may be forecasted through LSI value. Appearance: second stage pressure difference raising, water-out and salt- escape reduces.

二、 Pollution situation on membranes

    Pollution characters does not depend fully on chemical natural of raw water.

Relative location of pollution on membranes surface includes three layers. The upper layer is common loose adsorption zone including sediment, particles, loose CaCO3 and bio matter. Second layer is fixed adsorption zone including CaCO4, BaSO4, SrSO4, Fe oxide and hydroxide. Third layer is near membranes surface and difficultly to be removed with common chemical method. At this zone, it mainly deposits dehydration compound Portland, close construction deposition compound, organic hydrocarbon, oil and organic with ion.

First zone is in flow tube formed byconcentrated water separated net on membranes surface. Here collects main large volume pollution which includes CaCO3,crystallization, bio membranes, net organic membranes, particles, colloid pollution and coagulation, they cause system pressure-drop increasing, pressure raising and water-out reducing.

Second zone is on membranes surface. Here commonly collects Portland, hydroxide, polymer, organic and metal oxide, etc. This pollution may cause water-out and salt-escape reducing.

In solution or high water-content, much pollution gradually reduces hydration. This chemical result causes caking, deposition or adsorption on surface. At the second zone, portland forms a low viscosity colloid pollution and a undissolved pollution and close deposition of CaCO3, CaSO4, CsCO4. Many organic and metal hydrocarbons have same procedures and deposits on membranes surface.

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