Reverse Osmosis Homebrew / Pressure required from pump to membrane?

[ianabc]

Brent Swain has a diagram in his wonderful booklet... Oragami Metal Boatbuilding (Perhaps look at origamimagic.com and view Genoa 55 !)

The diagram shows a homebrew R.O> unit using a standard (long) RO membrane, stainless steel pipe with welded flanges and he uses a standard pressure washer pump of Italian origin, most likly with ceramic piston and bunga rubber o ring seals.

My question is ... what pressure is required from the pump to the membrane?

 

[kandoma]

around 60 bar, depending on salinity of the water. (it runs very sloooowly in the red sea)

Peter

 

[kandoma]

around 60 bar, depending on salinity of the water. (it runs very sloooowly in the red sea)

Peter

 

[kandoma]

around 60 bar, depending on salinity of the water. (it runs very sloooowly in the red sea)

Peter

 

[snowleopard]

Re: Reverse Osmosis Homebrew / Pressure required from pump to membrane

how do you manage to post 3 times- whenever i press the continue button twice i get a 'post already exists' error message. incidentally you can get rid of the extra ones if you 'edit' within an hour of posting.

back to the topic, a pressure washer produces around 120 psi or 8 bar. nothing like enough to push the water through the membranes. i have a watermaker which uses a comparatively low pressure pump like that, then feeds the output into a hydraulic amplifier ( the best known example of this is the Spectra). that steps the pressure up to the required level.

 

[kandoma]

Re: Reverse Osmosis Homebrew / Pressure required from pump to membrane

sorry for the multiple entries, I tried to delete them, but was unsucessfull.

Some watermakers are using a heavy duty powerwasher with pressure reduction valve. But this systems are not very economical.

A modern watermaker recycles the unused part of the pressure back to the system. Only the delta of input to output pressure is needed. A pressurewasher usually needs around 2 Kilowatt of electrical energy compared to a well designed watermaker which is in the range of 150 plus Watts.

By the way, the energy recycling is done without any springs. Two carefully calculated openings in the pump regulate the power. Some of the waste water is guided to the back of the piston. Absolutly failproof.

Peter

 

[ianabc]

Re: Reverse Osmosis Homebrew / Pressure required from pump to membrane

Thinking outside the box.......I run the 16 hp Yanmar 2GM20 to charge the batteries so that I can then run the 4000 GBP watermaker on 12 volts....OR I run the Yanmar and use the 1/4 of the power from the crankshaft pulley to a CAT 3CP1140 positive displacement pump (2000 psi) with triple ceramic seals and Buna-n o-rings. (300 GBP) Then the 316 ss sch. 80 ipe and welded end caps and 100 GBP RO media....... Now we're talking a small percentage of a commercial unit.

 

[Anonymous]

Re: Reverse Osmosis Homebrew / Pressure required from pump to membrane

....but if you run the watermaker from the engine shaft you can only make water when the main engine is running. The dc watermaker you are comparing it with draws only 20A to make around 60 litres per hour, and can be powered by main engine alternator, or generator, or wind, or solar, or towed generator and any combination as conditions change. Much more flexible.