Watermaker question

[Allan]

Does anyone know the approximate "yield" of a watermaker. That is, if you pump in, say 100ltr of seawater, how much freshwater would you expect to get out?
I assume the brine waste would be more salty than the input water.
Allan

 

[pyrojames]

Roughly 12-15% is converted to fresh water. Just starting the process of building my own.

 

[Allan]

Many thanks.
Allan

 

[PaulJS]

We are currently getting a 3 gallon per minute product rate at 285 ppm for an 18 gpm sea water flow rate at 800 psi.
Although this is obviously from a commercial set up, this ratio and product quality is fairly typical for reverse osmosis membranes (permeators).

Just remember, DO NOT use grease or any other oil based lubricant on the seals for the permeators, or indeed any of the seals in the water system, and ensure that no bleach (chlorine) gets to the permeators either.

Hope this helps.

Paul

 

[Allan]

Do you know how many ppm normal seawater is? I assume it changes around the world.
Allan

 

[PaulJS]

Can't tell you how many ppm normal sea water is, it's off the scale on our test gear, but my employers criteria for potable water are "less than 500 ppm salt, and more than 5 ppm chlorine, I do know that here in the Persian Gulf we have especially salty sea water though!
As I said earlier RO permeators don't like chlorine so we dose the product water after a non-return valve as it goes into our tanks. For a small boat this could be done by dosing the tanks with something like Milton fluid or chlorination tablets, and in my experience you can't even taste the chlorine at such low concentrations.
In a properly functioning RO plant there shouldn't be any need for product chlorination as the permeators shouldn't let any pathogens pass, but the 5 ppm standard is a hangover from when we used vacuum evaporators where the temperature was far too low to sterilise the product. However in real life there is always is a chance of pathogens passing a permeator seal, so I think it's safer to add a touch of chlorine.

Paul

 

[PaulJS]

Seawater is around 35000 PPM saline, sorry but PaulJS is using the wrong membrane as I assume he is cleaning brackish water the product flow he reports is way above what should be achieved with sea water. RO systems that remove salinity should produce water at less than 5 ppm turbidity, my echotek system has always achieved this.

The output from a sea water membrane is stated on the membrane at X litres per hour or day with a pressure of 800 or 1000 PSI and temp of 77 deg F and input water at 35,000 PPM saline.

more info here :
http://msdssearch.dow.com/Published...seps/pdfs/noreg/609-00055.pdf&fromPage=GetDoc

Errm, no, you assume wrong, I never mentioned turbidity, I was talking about salinity. By the way, I'm sitting 60 miles out in the Persian Gulf and had just checked these figures in the Engine Room.
Our plant is a Village Marine Tec PW4000 Reverse Osmosis Desalinator, and to quote from the manual, section 1.0, page 1 :-
"The VMT Seawater Desalinator is a single pass, fully transportable purification system that uses reverse osmosis as its method of seawater desalination. This unit produces potable (drinking) quality water with salt concentrations of <500 ppm from seawater with concentrations as high as 35,000 ppm."
However I have just noticed a typo in my first post where I should have typed "15 gpm" rather than "18 gpm", so we are actually getting nearly 20% product, which is marginally above the manufacturers figures which claim a minimum of 2.1 gpm and a maximum of 2.8 gpm product at a 15 gpm seawater flow rate.

Maybe worth mentioning that our plant does have a sand filter, and a 5 micron filter in series on the SW inlet side of the HP pump.

Paul

 

[PaulJS]

No worries!
Gallons (US or Imperial), or litres, it's all the same so long as we can drink what comes out...
The only time I use the word "turbidity" is with regard to the solids carried - but not dissolved - in water, maybe a slightly different interpretation to wherever you are.

Paul

 

[vas]

Roughly 12-15% is converted to fresh water. Just starting the process of building my own.

sorry for bringing up an oldish thread...

I've also looked around for diy or cheap RO systems, care to explain what you're building?
Assuming its RO are you going for the karcher (sp?) hi-press pump plus standard RO membranes in a manual setup with a lifting pump and prefilters?

If the price is right, I'd be very much interested in having a go myself as well but no concrete solution found as yet, more like heresay and speculation

cheers

V.

 

[ianabc]

diy watermaker

using pressure washer pump see

yahoo groups

origami metal boats


Some discussions on self made units using capped stainless steel pipe the length of the standard membrane with pressure washer pump run off main engine pulley with heavy duty belt.

 

[Sybaris]

sorry for bringing up an oldish thread...

I've also looked around for diy or cheap RO systems, care to explain what you're building?
Assuming its RO are you going for the karcher (sp?) hi-press pump plus standard RO membranes in a manual setup with a lifting pump and prefilters?

If the price is right, I'd be very much interested in having a go myself as well but no concrete solution found as yet, more like heresay and speculation

cheers

V.

I was tricked into buying a kit made with a Karcher pump a few years ago and I can categorically tell you not to even try it for 3 reasons.

1) The yield rate for Dow chemical Filmtec membranes which are by far the most common is from 2 to 8% (it depend on the size) according to their own documentation. What this means is that you not only need to pump water through the membrane at pressure (800psi) but also at quantity. A high pressure washer does give the pressure but not the quantity as there is no need for them to waste more water than needed for their intended purpose - cleaning.

2) The materials used in Karcher type pumps are not made for salt water and will deteriorate quite quickly.

3) They are extreeeemely noisy to run on board a yacht.

I changed my pump to a General Pump piston pump (that is the make) which has a throughput of about 816 lit/hour. I have two SW30-2540 membranes with a stated recovery (yield) rate of 8% each, giving me a theoretical yield of 65 lit/hour each. My effective production is around 130 lit/hour which is pretty spot on what it should be.

The SW30-2540 has a maximum feed flow rate of 1360 lit/hour so I could have bought an even beefier pump and produced up to 216 lit/hour.

There is no magic to this regardless of what others might say, and the most important part of the system is the pump.

Cheers,
Per

 

[vas]

Per,

thanks a lot for your post and notes!

Now, yes I would definitely go for a DOW RO so the SW30-2540 you're suggesting is the smallest (ahem, within reason...) with a good yield rate of 8%. Surprisingly it's only 200odd usd on offer, but will be back on that.

Pump wise and talking about a mobo with plenty of space in the engineroom, I'd probably go for the largest pump I'd get coupled to an el.motor running 24V if I find a decent motor or 220V via the genny. Not keen on the pulley off engine setup as my engines rev up to 2600rpm and max for the pumps is 1700. Further, I'd rather use the watermaking facility without having to rev one engine that much for hours, better use the gen which is going to be used for other things at the same time.
Looks like you have the WM3615C and also looks like if I want to use only one RO membrane, I could do with the larger WM4215 pump able to produce 75lt/h of fresh water on ideal conditions. Not bad!

Qs
where do you get the DOW RO from europe, not planning to go through customs for a 1m long tube! I see you are around the area so to speak, did you buy in GR or TR or brought it from the UK?
Regarding the pump, I'll have to find the powerneeds to get a suitable motor and calculate loads. Also, seems that pump can do -50psi, installing it just above waterline with the seacock 1m away and .5m below waterline, means I don't really need a liftup pump, right? or due to a 10micron or so prefilter I should really use one?
Any draft layout of your setup, if you don't mind, or pointers to reasonable solutions much appreciated!

Being quite handy with automations coming from a few complex BMS installations background, I guess hooking up this setup with a few sensors (in and out water pres, oil pump temp, output volume) and a bit a programming I could have a reasonably failsafe setup.

cheers

V.

 

[pyrojames]

I got a CAT277 pump for direct engine drive,new from an Ebay MoD or similar disposals site. Planning on using Dow 2540 membrain and housing. Other bits and pieces as required. Probably use a Jabsco pump as low pressure supply, as this will double as a back up freshwater pump if need be.

Redesigning engine mounts to double for CAT mounting and magnetic clutch assembly.

 

[Sybaris]

Looks like you have the WM3615C
Qs
where do you get the DOW RO from europe, not planning to go through customs for a 1m long tube! I see you are around the area so to speak, did you buy in GR or TR or brought it from the UK?
Regarding the pump, I'll have to find the powerneeds to get a suitable motor and calculate loads. Also, seems that pump can do -50psi, installing it just above waterline with the seacock 1m away and .5m below waterline, means I don't really need a liftup pump, right? or due to a 10micron or so prefilter I should really use one?
Any draft layout of your setup, if you don't mind, or pointers to reasonable solutions much appreciated!

Hi V,

Spot on, I have the WM3615C. I bought it from SK Watermaker in the US for $1'175.-. It runs off a Marathon 2hp electric motor (110V, 60Hz we have an American boat with a 110V Onan) also from SK Watermaker for $350.- In hindsight I would now have gone for the WM4215C instead simply because the membranes can handle the larger throughput and would then yield even more production water as I wrote in my previous message.

I don't know where to get the DOW RO's in Europe and I am about to get two replacement units from the US at around $200 each. My existing ones got messed up last summer but that is another story.

My water intake is around 60cm below the water lever, and the pump is around 30cm below the water level. I use one pre-filter and with my setup I do not need a booster pump.

My complete setup is very simple and totally manual (the way I prefer to keep it). Sea-cox - strainer - T-valve for input water - pre-filter (I have been using between 5 and 20 micron, but will from now on stick to 5 micron) - hp pump - membane vessel #1 - in series with - membrane vessel #2 - hp pressure gauge - hp valve - brine drainage - T-valve for production water

My operational procedure is as follows:

pre-procedure

* install the pre-filter, open the sea-cox, bleed the pre-filter vessel to fill it with water.
* set the production T-valve to direct the water to a 15 lit container.
* make sure the hp valve is fully open (i.e. no pressure).

startup

* switch on the hp pump.
* let the pump run a minute or so and check the pre-filter to make sure there are no more air bubbles, check all the lp hoses which in my case are transparent so you can see a clean water flow without air bubbles, check for any possible leaks.
* slowly turn the hp valve to increase the pressure up to 800psi - Dow is quite clear in all documentation that it is very important to do this slowly (below 10psi/sec) to avoid damage to the membranes. That means it should take about 1.5 min to build up the pressure to 800psi.
* I now wait until I have around 10 lit of production (fresh) water in my container and check my TDS meter which for me is typically 250-290 ppm (in the Med and the red Sea), I then turn the production T-valve to direct the water to our fresh water tank.
* (optional) Log start time of production, and the current ppm reading

during operation

* Check about every half hour to make sure the pressure is stable and everything looks and sounds normal.

shut down

* (optional) Log the current ppm reading
* (optional) Turn the production T-valve to direct the water to manually fill up a few empty 1.5 lit water bottles to use as our drinking water (handy to store in the fridge for cold drinking water) and in the process measure the production flow by the time it takes to fill a 1.5 lit bottle.
* Slowly (see above) again reduce the pressure to 40psi.
* (optional) Log the end time of production.
* Let the pump run at 40 psi in order to flush out the high salt concentration in the membranes a bit (a minute or so) before changing the input T-valve so that the input water is taken from my 15 lit container instead of from the sea-cox and let the container empty completely before shutting off the hp pump. This way the membranes are left with clean production water inside.
* Remove the pre-filter, rinse it off, and then hang it up outside to dry in the sun.

Cheers,
Per

 

[vas]

Hi V,

Spot on, I have the WM3615C. I bought it from SK Watermaker in the US for $1'175.-. It runs off a Marathon 2hp electric motor (110V, 60Hz we have an American boat with a 110V Onan) also from SK Watermaker for $350.- In hindsight I would now have gone for the WM4215C instead simply because the membranes can handle the larger throughput and would then yield even more production water as I wrote in my previous message.

I don't know where to get the DOW RO's in Europe and I am about to get two replacement units from the US at around $200 each. My existing ones got messed up last summer but that is another story.

My water intake is around 60cm below the water lever, and the pump is around 30cm below the water level. I use one pre-filter and with my setup I do not need a booster pump.

My complete setup is very simple and totally manual (the way I prefer to keep it). Sea-cox - strainer - T-valve for input water - pre-filter (I have been using between 5 and 20 micron, but will from now on stick to 5 micron) - hp pump - membane vessel #1 - in series with - membrane vessel #2 - hp pressure gauge - hp valve - brine drainage - T-valve for production water

My operational procedure is as follows:

pre-procedure

* install the pre-filter, open the sea-cox, bleed the pre-filter vessel to fill it with water.
* set the production T-valve to direct the water to a 15 lit container.
* make sure the hp valve is fully open (i.e. no pressure).

startup

* switch on the hp pump.
* let the pump run a minute or so and check the pre-filter to make sure there are no more air bubbles, check all the lp hoses which in my case are transparent so you can see a clean water flow without air bubbles, check for any possible leaks.
* slowly turn the hp valve to increase the pressure up to 800psi - Dow is quite clear in all documentation that it is very important to do this slowly (below 10psi/sec) to avoid damage to the membranes. That means it should take about 1.5 min to build up the pressure to 800psi.
* I now wait until I have around 10 lit of production (fresh) water in my container and check my TDS meter which for me is typically 250-290 ppm (in the Med and the red Sea), I then turn the production T-valve to direct the water to our fresh water tank.
* (optional) Log start time of production, and the current ppm reading

during operation

* Check about every half hour to make sure the pressure is stable and everything looks and sounds normal.

shut down

* (optional) Log the current ppm reading
* (optional) Turn the production T-valve to direct the water to manually fill up a few empty 1.5 lit water bottles to use as our drinking water (handy to store in the fridge for cold drinking water) and in the process measure the production flow by the time it takes to fill a 1.5 lit bottle.
* Slowly (see above) again reduce the pressure to 40psi.
* (optional) Log the end time of production.
* Let the pump run at 40 psi in order to flush out the high salt concentration in the membranes a bit (a minute or so) before changing the input T-valve so that the input water is taken from my 15 lit container instead of from the sea-cox and let the container empty completely before shutting off the hp pump. This way the membranes are left with clean production water inside.
* Remove the pre-filter, rinse it off, and then hang it up outside to dry in the sun.

Cheers,
Per

Per,

really appreciate the detailed operation procedure you described. Have to admit that on reading it first, had the urge to forget about the whole project

Anyway, over the last couple of days had a go at the only shop in town dealing with high pressure staff (mainly for tractors, diggers, etc) and they did come up with some reasonable solutions for the hp bits.

HOWEVER, I do have some Qs if you could help and don't mind:

1. does the wet part of the pump HAVE TO be ss? Would chrome or nickel do? (much much cheaper and readily available on 3 pot layouts for the production I want) FYI, I can get a 3piston nickel one made in Italy (sorry don't remember brand name) for less tha 500 euros iirc [check this interesting paper on corrosion of various materials, does imply that ss is not the only solution]
2. anything wrong with direct coupling to a 2.5hp engine that should be enough to drive 1X2540 membrane? Allegedly smoother and quieter and I guess with the rubber coupling, not much can go wrong, correct? I'm asking as I see most ppl couple them via pulleys.
3. any smart way of automating the 10psi/sec increase?
using industrial plcs or the building management system I'll be using along the craft, in combo with 2 pressure sensors on the circuit I should be able to slowly lift pressure but I need a ss or chrome (?) pressure release valve that can accept a stepmotor for such operation. Anything to suggest? I could program it conservatively and make sure it ups the pressure at a 5psi/sec rate and wouldn't mind taking 3-4mins to reach the right pressure tbh.
4. Was thinking of using a 20-30lt exptank for storing clean potable water for sink side use as per the system I use at home (RO membrane into a storage tank pressurised via a membrane system) Would that make sense? If I'm using the RO membrane daily I could have my drinking water without resorting to storing it in 1.5lt plastic bottles and the extra cost would be less than 50euro for the tank!


cheers

Vassilis

PS. there's a 12V 8A 30lph system for 1200ukp on ebay for the last few days and yesterday advertised on here as well, but I'm not so keen on the low energy option idea as this pulsing can only do harm to the membranes I guess...

 

[x-ray]

Karcher an membranes

I was tricked into buying a kit made with a Karcher pump a few years ago and I can categorically tell you not to even try it for 3 reasons.

1) The yield rate for Dow chemical Filmtec membranes which are by far the most common is from 2 to 8% (it depend on the size) according to their own documentation. What this means is that you not only need to pump water through the membrane at pressure (800psi) but also at quantity. A high pressure washer does give the pressure but not the quantity as there is no need for them to waste more water than needed for their intended purpose - cleaning.

2) The materials used in Karcher type pumps are not made for salt water and will deteriorate quite quickly.

3) They are extreeeemely noisy to run on board a yacht.

Cheers,
Per

Running a Karcher system myself, i would like to respond on that.
1) The smallest Karcher (2.10 or similar at 60 Euros) runs easily at
250 to 300 L/hr at 800 psi, what is above the minimum specification from
Dow/Filmtec for the SW30 2540, producing 45 L/hr drinking water on that.
I even regulate the Karcher down by using an electronic power controler.
2) The materials in Karcher are not made for salt water, that is true.
By flushing the system with freshwater after use, it will have a life expectation of 2 yrs. Remember it costs 60 Euros, how many Karchers
could you have bought for the money spent on your pump ?
3) Yes, they are noisy, so built it in the engine compartment, or under in the
bilge somewhere, that-s one reason why I tune it down on lower revs,
but still....
4) The real problem with Karcher-Systems is their power-consumption.
My one is plugged in a sine-inverter, which draws 100 A/12V while running the Karcher. You need to find a way to supply the Amps, before considering the Karcher-System.
You still may upgrade to a more expensive pump anytime you wish,
the rest of the system will stay the same. Also, it-s easy to upgrade to a
second membrane staged in.

By the way, if you need a supplier for the Filmtec membrane in europe
pm me.
Cheers
X-ray

 

[x-ray]

Karcher and membranes

I was tricked into buying a kit made with a Karcher pump a few years ago and I can categorically tell you not to even try it for 3 reasons.

1) The yield rate for Dow chemical Filmtec membranes which are by far the most common is from 2 to 8% (it depend on the size) according to their own documentation. What this means is that you not only need to pump water through the membrane at pressure (800psi) but also at quantity. A high pressure washer does give the pressure but not the quantity as there is no need for them to waste more water than needed for their intended purpose - cleaning.

2) The materials used in Karcher type pumps are not made for salt water and will deteriorate quite quickly.

3) They are extreeeemely noisy to run on board a yacht.

Cheers,
Per

Running a Karcher system myself, i like to respond on that.
1)I have the smallest Karcher (2.14 or similar for Euro 60,-) in my system,
giving easily 300 L/hrs at 800 psi., giving me 45 L/hrs product water. I do regulate it down to that figure, by using an electronic power control unit.

2)The Karcher is not made for salt water. That is true, but by flushing the
system with potable water after use, it has a life expectation of 2 yrs.
Remember, 60 Euros. How many Karchers could you buy for the cost of
your pump ?

3) They are noisy, that is true, that is one reason why i rev it down,
built it in the bilge, but still.....
4) The real problem is the power consumption.
I run mine by using a sine-inverter, which will draw 100 A/12V from the
batteries, the genny, or whatever will supply the energy.
Before considering the Karcher system, this is the problem, wich has to be
solved before.
Anyway, you can upgrade to a better quality pump anytime you wish.
The rest of the system stays the same, I think of staging in a second membrane.
By the way, if you need a supplier for Filmtec-membranes in Europe,
PM me.
Cheers
X-ray

 

[vas]

Running a Karcher system myself, i would like to respond on that.
1) The smallest Karcher (2.10 or similar at 60 Euros) runs easily at
250 to 300 L/hr at 800 psi, what is above the minimum specification from
Dow/Filmtec for the SW30 2540, producing 45 L/hr drinking water on that.
I even regulate the Karcher down by using an electronic power controler.
2) The materials in Karcher are not made for salt water, that is true.
By flushing the system with freshwater after use, it will have a life expectation of 2 yrs. Remember it costs 60 Euros, how many Karchers
could you have bought for the money spent on your pump ?
3) Yes, they are noisy, so built it in the engine compartment, or under in the
bilge somewhere, that-s one reason why I tune it down on lower revs,
but still....
4) The real problem with Karcher-Systems is their power-consumption.
My one is plugged in a sine-inverter, which draws 100 A/12V while running the Karcher. You need to find a way to supply the Amps, before considering the Karcher-System.
You still may upgrade to a more expensive pump anytime you wish,
the rest of the system will stay the same. Also, it-s easy to upgrade to a
second membrane staged in.

By the way, if you need a supplier for the Filmtec membrane in europe
pm me.
Cheers
X-ray

X-ray,

I'll probably not go for a karcher pump, but I may go for a decent nickel aluminium bodied pump for 400euro or so (compared to almost a grand for a proper ss one!). Coupled to a half decent 220V motor with the bits and bobs leaves me way under 1000euro.
All then comes down to getting a good price for the RO membrane here in EU land, hence PM on its way to you

cheers

V.

 

[Sybaris]

Running a Karcher system myself, i would like to respond on that.

I did several weeks worth of testing with the Karcher before giving up and my production was not more than 50lit/h using 2 (two) SW30 2540 membranes. This is almost exactly what the Filmtec specification states (see attachment to my earlier post), i.e. 8% yield with a pump through-put of 300 lit/h of salt water gives 24lit/h of production water for each membrane.

If you are getting 45lit/h from one membrane your yield is 15% (at 300lit/h) and 18% (at 250lit/h) which would make Dow Chemicals very happy indeed.

I do however agree that it is a good way to start and build the system because as you say you can replace the pump anytime you want in the future because the rest of the installation can stay the same.

One of my concerns was that given the corrosion I was getting after only a few weeks I was worried about possible damages made to the membranes. As it happened they did however work just fine when I upgraded the pump.

Cheers,
Per

 

[Sybaris]

Hi Vassilis,

Have to admit that on reading it first, had the urge to forget about the whole project

Yes looking at my message now it does actually sound very complicated, but it really isn't. I like to keep it manual because that way I know what is going on and I can fix things if they go wrong.

1. does the wet part of the pump HAVE TO be ss? Would chrome or nickel do? (much much cheaper and readily available on 3 pot layouts for the production I want) FYI, I can get a 3piston nickel one made in Italy (sorry don't remember brand name) for less tha 500 euros iirc [check this interesting paper on corrosion of various materials, does imply that ss is not the only solution]

I don't know the answer to that.

2. anything wrong with direct coupling to a 2.5hp engine that should be enough to drive 1X2540 membrane? Allegedly smoother and quieter and I guess with the rubber coupling, not much can go wrong, correct? I'm asking as I see most ppl couple them via pulleys.

No, that is how mine is connected. My pump and motor are so smooth there is no way you can hear them above the normal generator sound level.

3. any smart way of automating the 10psi/sec increase?
using industrial plcs or the building management system I'll be using along the craft, in combo with 2 pressure sensors on the circuit I should be able to slowly lift pressure but I need a ss or chrome (?) pressure release valve that can accept a stepmotor for such operation. Anything to suggest? I could program it conservatively and make sure it ups the pressure at a 5psi/sec rate and wouldn't mind taking 3-4mins to reach the right pressure tbh.

I can't answer that. The startup and shutdown using my manual method is much simpler than my previous detailed explanation would have it sound. Since I get a large yield each time I run it I don't need to run it as often.

4. Was thinking of using a 20-30lt exptank for storing clean potable water for sink side use as per the system I use at home (RO membrane into a storage tank pressurised via a membrane system) Would that make sense? If I'm using the RO membrane daily I could have my drinking water without resorting to storing it in 1.5lt plastic bottles and the extra cost would be less than 50euro for the tank!

Yes that is a great idea. My method of filling up a few 1.5lit plastic bottles is not required at all. I only do it to measure my production rate (number of seconds to fill one bottle gives you a pretty precise calculation), and as I said we like storing them in the fridge, but it is only the way I prefer to do it.

Cheers,
Per