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From: Roy P (no email)
Date: Fri Aug 18 2006 - 02:41:56 EDT
On Thursday 17 August 2006 12:32 pm, Norm of Bandersnatch wrote:
> gallons per hour varies with size and power consumption. my big watermaker
>requires the genset, and i'm not sure how many watts it needs total. the
>specs list 15 amps at 110 volts for the high pressure pump, but nothing for
>the feed water pump or electroincs and solenoid valve. rated at 25 gph
>output, it has settled to 17 gph for years. this is in seawater. in the st
>johns river, which is not very salty, at this moment it is pinning the
>product flow gauge at way over 30 gph.
Hello All
Great posts Norm !
While I have no experience with seawater specific RO systems, I own a water
treatment company. NO MARKETING PLUG HERE.. I'M NOT IN THE MARINE MARKET.
We sell and build commercial and residential RO systems for land based
freshwater use. While the design is somewhat different, the main factors that
influence a given size NEW membrane's production rate are basically the same.
This may a bit technical for the topic, but it should help explain in more
detail, why the output of a given RO system can vary,
1) Water Temperature
Thin Film Composite (TFC) membranes will produce 1.7% less/more product water
for every degree Fahrenheit lower/higher, respectively, that the Raw water
inlet temperature is.
For example... If an RO membrane is rated to produce 17 gallons/hour at 77
degrees F inlet water temp, it would produce (77-60)*1.7=28.9% less product
water at 60 degrees F. (12.087 Gallons/hour)
Sailing in Norway in winter ? Then you'll be making less water.
2) Raw Water inlet pressure (into the membrane)
The lower the raw water inlet pressure, the lower the production rate.
This is affected by your High pressure pump's capacity
3) Product Water outlet Pressure (from the membrane)
The lower the product water outlet pressure, the higher the production rate.
4) Total Dissolved Solids (TDS) level
Salt in seawater is a dissolved solid.
The higher the level of dissolved solids in the water, the lower the
production rate of a membrane.
A combination of all these factors decides what the production rate of a RO
membrane will be.
In addition, as the membrane ages, the production rate, and how much solids
are prevented from being in the product water (rejection rate), changes.
Hope this helps a bit.
Best Regards
Roy
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