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Can I recycle my Reject water back into my Feed?

Where should the UV Lamp be installed?

Will Preheating the water reduce my operating costs?

What is a Membrane Fouling Factor?

Will an Aquatec Pump work for Commercial NF Membranes?

Will UF remove heavy metals?

What is the max water temperature for flushing RO Membranes?


Is a flow restrictor needed if I am using an ASO valve with a permeate pump?

Yes you do. The flow restrictor controls the amount going to drain. The permeate pump allows you to run the system without product back pressure and ASO stops the water from flowing through the system when the tank is full.

I am considering recycling my reject water (with a TDS of 1000ppm) back into my Feed Water (which has a TDS of 400 ppm) so that it can pass through the entire system for processing -  is this advisable?  My current production rate is:  3.3GPM Product and  2.5 GPM Reject.

We do not recommend recycling the waste water. This will result in lower output, higher TDS in product and fouling of the membranes.

We are designing a 75 GPD under the counter RO unit to treat well water with bacteria problems. We would like to know where in the water stream to install the UV lamp.  We feel it should go before the membrane to prevent the contamination of the membrane. Is it the right decision? Can the treated water get contaminated in the storage tank with bacteria ?

The UV lamp should be the very first item the water flows through. You may need a second UV just before the faucet [tap].

My question is regarding RO units with respect to water temperature - and if preheating the water using waste heat makes sense in our application.

Heating the water at no cost will lower the operating pressure for your Reverse Osmosis system, and therefore lower operating costs. We will like to maintain a temperature below 80 deg F. Whether these savings are significant or not will depend on the incoming water temperature, temperature of water after heat transfer and the the capacity of the RO system.

What is a membrane fouling factor (ROSA) ?

It is a projection of how a membrane may foul over time.  For properly designed systems with a good pretreatment, this factor is 0.85 for a 3 year projection. In other words if you enter 0.85 for the fouling factor, ROSA projects the membrane performance after 3 years of operation.

Is the Aquatec Pump ok for Commercial NF Membranes?

Yes, the pump does meet the flow and pressure requirements.

Can an Ultrafiltration system be used or retrofitted with new membranes to be able to remove heavy metals as a polishing step prior to discharge to a POTW?

No. The membranes and system you will need for heavy metal removal is called a Reverse Osmosis system. It will amount to changing everything on your current system.

Can I flush a membrane with water temperature of 80 degrees C ? If not, what is the maximum possible temperature?

No. The max temperature is 45 degrees celcius.

We have a Glegg 54Te/Hr RO system that has a high inlet temperature water alarm setpoint which is set at 25C, the membranes are Hydranautics G115469-11, what is their maximum operating temperature?

40 deg C. However, the higher operating temperature cannot be used to get a higher product flow. You must reduce the operating pressure to produce no more than the designed product flow for the system.

What is the safe operating pressure for a AAA-1005 system? Would it be ok to install a booster pump and operate at 80 psi?

It is ok to operate with the pump. We recommend a maximum of 80 psi.

I have been working on properly sizing components for residential RO. In your catalog, it is recommended that for a 100GPD membrane is to use a 950ml/min flow restrictor. Does this apply to all configurations? I am putting together ROs that will be using your 100GPD membrane plus: Aquatec 8800 series booster pump (operating at 80 PSI) Aquatec permeate device 60 PSI pressure switch and an electronic shut off valve.

The flow restrictor is sized based on the capacity of the membrane, and is usually sized for 4 to 5 times the volume of the permeate (good water) that the membrane will produce.

Our residential membranes are rated at 65psi. When run at 80psi, our 100 GPD membrane will produce approximately 20% more permeate flow, but the 950ml/min flow restrictor will still be within the acceptable range.

What type of pretreatment does RO need?

Typical pretreatment consists of:

  • Coarse filtration (~80 micron) to remove large materials  - City water has typically been filtered to meet this standard.
  • Hypochlorite addition to reduce biofouling potential City water has typically been treated by chlorine or chloramines for this purpose.
  • Fine filtration using multimedia filters or clarification.
  • Carbon Filter or Bisulfite addition to reduce remove residual free chlorine.
  • Water Softener or Antiscalant to remove hardness and prevent scaling.
  • Cartridge 5 Micron Sediment filter upstream of the feed pump and membranes

    Additional pretreatment considerations: Water with higher particle contents, measured by silt density index (SDI), require a higher degree of pretreatment to achieve acceptable quality. Systems using groundwater as the feed source frequently operate without hypochlorite and bisulfte addition. Waters with high hardness may require softening and/or acid addition. Activated carbon may be needed for water with high organic content.



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All Content on this site is  intended for informational purposes for experienced water treatment professionals only.  Applied Membranes, Inc. does not assume any liability for any damages caused by the misapplication or misinterpretation of any of the information contained on this website.
Applied Membranes, Inc. 2007