In an RO systems that uses the ERP-1000 Permeatepump, the RO membrane always sees the full pressure across the membrane even if the tank is almost up to the same pressure. This way the system does not lose its performance.
In a normal system you would for example have 60 PSI of line pressure. If the tank sees 30 PSI, you only would have 30 PSI left for your membrane. In reality, this gives you less than 50% of your normal performance. In a permeatepump system, you would still have 60 PSI across your membrane even on 50 PSI tank pressure.
Systems Using the Aquatec Permeatepump Technology Don´t Show Negative Changes In the System Recovery Rate.
The following graphic is the result of tests on an RO Unit that allowed the disabling of the built-in Permeatepump using a ball valve. The unit was adjusted to a 4:1 concentrate to product ratio on an empty tank and an open faucet. Feed pressure was 6 bars.
The red curve shows the changes in recovery on rising tank pressure. To minimize the problem, shut off devices are used that allow to produce about 55-75% of line pressure in the storage tank. Note that in practice the whole storage tank is not used very often. Normally you work out of the top portion of the tank.
The blue curve shows the recovery using the Permeatepump. Here you can see that the recovery rate does not go down until the Permeatepump shuts the system down close to 100% of line pressure in the tank. This advantage can be used in systems that guarantee that there is always a bigger amount ( greater than 1 Liter per use) of water used. In household applications, a shut off device must be installed. This prevents the production of small amounts each time you draw a cup of water which would cause TDS-Creep.
The colored areas show the possible parameters you will see on different systems. You can easily recognize that even on the early shutdown at 60% of line pressure, the concentrate to permeate ratio is 12:1 at the end.
As RO Water quality improves, the higher your differential pressure on the membrane is, a system with a permeatepump always makes better water. Let us say that your membrane reduces 98% of the TDS in your water if you got 60 PSI across your membrane. On 30 PSI differential it will only do about 95%. In the permeatepump system, you always see full line pressure across your element, which gives you always the maximum quality water out of you system.
The following graphic is the result of tests on an RO- Unit, that allowed to disable the built in Permeatepump useing a ball valve. The unit was adjusted to a 30% recovery. Feed pressure was 6 bars. On 4.5 bars of tank pressure, the unit was shut down. With a disabled Permeatepump, the last water was produced on a differencial pressure of only 1.5 bars accross the RO- membrane. See the results of the test.
As you are saving up to 85% of the water that is going to drain, your system does not see all that water. This way, the permeatepump will also improve the life of your prefilters and booster pump.
Till now, we saw, that a normal system looses performance, recovery and rejection, the closer we get the tank to line pressure. Because of that, most systems are limited to about 60- 70% of line pressure in your tank. With the permeatepump, you don´t need that. You can even get 95% line pressure into your tank without loosing your design parameters. This of course gives you a far better Flow out of your faucet or to your equipment.
Water needs per person in the household are around 2 gallons per day. To have a fast recovery on your tank, nowadays systems have 35 GPD Membranes and up to five stages of filtration. To produce about 8 gallons of water per day, such system sends far more than 80 gallons of water down the drain. Actually on the top portion of your tank a 35 GPD membrane makes only around 15 GPD. Now with the permeate pump, you could go to a 15 GPD Membrane and still have the same amount of water that you used to get from your unit.
If you used to sell 100 GPD systems for a light commercial system, you could now use a 50 GPD system with a permeatepump.
The problem with using standard systems for commercial applications is the fact that you have high minimum pressure requirements for equipment such as coffee makers, ice makers e.t.c.
To have all stored water above this minimum pressure, you need to increase your precharge on the tank. This increases the backpressure on your membrane right from startup. As the normal unit can only put 60- 70% of line pressure into the tank, you are only able to use a small section of the performance curve of your system.
For example a system that starts at 30 PSI precharge on 80 PSI feed it would shut down at 56 PSI tank pressure. On our diagram you would see that you basicly start at 37.5% filling and only use the system to fill the tank up to 70%. The system performance would be between 30- 65% of your rated membrane performance.
With the permeate pump, you run the same unit up to 100% of line pressure and you only see a slight performance drop of 15% at the very end.
