Thailand Cambodia Jungle Salt Water

[goltec]

Hi you all,


I have a water filter business in Thailand.(I am from the Netherlands)

For a customer who has a small resort in the jungle of Cambodia I have to develop a plan to change sea water into fresh water for showering etc. (not drinking).

I need someone who likes to think this over with me since this is the first time I encounter this kind of situation and I am not sure what to do.

I have done a lot of water filtration projects, but not one under these kind of conditions.

So I see it as a challenge, but I need to be pretty sure that I do the whole thing right in one time.
Not a lot of space for trying and/or mistakes because all materials etc. need to be shipped into the jungle and so there is not an easy way back and forward.

Here is the situation:

It is a small resort on a hill side.
Down the hill (200 meters with a head of 30 meters) there is a river that ends up into the sea a kilometer further or so .
Because of the tides the water level in the river rises and drops.
So we are talking about brakish water but let's go for safe and say it is sea water.
(the salt level I will know later)
Problem: corosion

I can de-salt the water with reverse osmosis but the water needs to be pre-filtered to protect the reverse osmosis membranes.

I will pre filter with sand or zeolite in a fibertank, followed by activated carbon in a second fibertank, both with a backwash valve on top.
The pre-treated salt water will be stored in a big water tank (P.E.)
from this watertank the water will be lead towards several R.O. Diaphragm pumps and from there to several R.O. Membranes.

Now we have desalted water that will be stored in a second P.E. Tank.
This water will be pumped up hill towards a large storage tank that is already situated there from which the bungalows will be fed with a regular on demand constant pressure pump.

So only the last storage tank is situated up on the hill in the resort.
The whole story before that will be situated as close as possible to the river. (25 meters from the river with a head of 4 meters).
These two locations are 200 meters away from each other and the rise of the hill side (Head) is about 30 meters.

My Idea:

Because of the tides we make a floating platform at which the pump is situated.
The pump must resist salt water so it must be a good stainless steel pump or bronze or brass.

So far I found a submersible pump that can be used with salt water.
This could be a good option because the motor is always being cooled by the surrounding water and there will never be a priming problem.

But the pump needs to be “on demand”.
This can be done by a float switch in the storage tank which is connected with the pump on the platform.

Or a pressure switch in combination with a solenoid valve which is controlled by a float switch.
(not a float valve because the pump will turn on and off very often once the valve is almost closed because of the very slow water inlet and the floatvalves I know are not corosion resistant enough).

But when a pressure switch in combination with a solenoid valve is used, I need to install a pressure tank as well I think.
And that means that the pressure tank and the solenoid valve need to be saltwater resistant as well.
(In normal situations I do not need to combine pumps with pressure switches and pressure tanks because I use "ready to go " pumps that come complete like the Hitachi pumps for home use, so I would like to avoid experimenting with combining these parts by myself.)

So for that reason it is much easier to just use a float switch in the storage tank which is connected to the pump on the platform.

But......
That situation arises an other problem.....

The pre-filters with sand and carbon I want to place in this same line , inbetween the pump and the storage tank.....
If the prefilters clog up because someone forgot to backwash them and the storage tank is asking for more water because the waterlevel drops and the float switch turns on the pump, there will be no water flow and pipes may burst or the pump might be damaged.

So to avoid that kind of situation I could install an inline pressure relief valve of 50 psi or so.
That way at least the water can escape.....

Or go for the pressure switch instead in combination with the pressure tank and solenoid valve.
That way if the filters become clogged up and there is no or not enough flow, the high pressure switch will shut off the pump.

But how to find the right combination that can also be used with salt water might not be easy.......

I have a pump with pressure switch and tank complete (ready to go) in mind but I am not sure jet if it is good enough for this job because of the salt water. : HITACHI WT-PS300GX

The submersible pump I have in mind is the : TSURUMI Submersible Corrosion Resistant Pump
(

http://www.tsurumipump.com

)

So far for the first step.




“Problem 2” :

Now the water has been filtered by the reverse osmosis and is stored in the second large PE tank.
From here I need a pump to bring the clean water up hill over a distance of 200 meters with a head of 30 meters to an other storage tank up hill at the resort.
Can this be done in 1 time? Or should it be done in smaller steps with storage tank(s) and pumps along the way?
All has to run on solar power so that is also an issue to keep in mind.......


Hope someone is willing to think a little with me in this matter.
Any ideas, suggestions or advice are greatly appreciated.

 

[itsmoked]

Thoughts:
Just because a river's height changes with a down river tide doesn't mean there is ever any saltwater involved upstream.

If you have a float the pump is attached to then you could instead use a JetPump mounted on the float. I think many Jet-Pumps are ABS plastic with just a few stainless bits like the impeller shaft. That gets rid of the corrosion issue with the pump.

I've only ever used float switches that have NO metal at all. They're mounted on water proof electrical cables and allow complete setting of the hysteresis and turn-on/off depths.

Using a pressure switch to turn off the pump during a blocked filter condition is a disaster. It will cause the pump to short-cycle for the period before it completely toasts.

You should have a controller that manages the system not "somebody" who may get ill, forget, leave, or screw-up, causing the pre-filters to clog and fail and the system to fail totally.

I'm not following why you are considering a pressure tank down the hill. I'd try to avoid one anywhere in this setting if at all possible. For final delivery I'd try to use elevation for the pressure. It is considerably simpler and can be a more understandable system for the local users/owners/repairs. It also shows lowering flow as the tank is drawing down in case there is a water making issue rather than the 2 second notice of the water just cutting off offered by pressure tanks.

Activated carbon craps-out eventually and in an unpredictable manner (until understood using the site water). How are you going to maintain it correctly?? It it loads-out the membranes can be damaged..




Keith Cress
kcress -

http://www.flaminsystems.com

 

[bimr]

It would be helpful to publish a flow diagram.

 

[goltec]

I just took samples of the water and the salt level is 1,5 % (seawater is 3,5%)
As a jet pump I could use a swimmingpool pump because I just got feedback that said these pumps come with aaisi316 stainless steel seal.

I think you are right,,, I would really like to avoid the pressuretank and switch and solenoidvalve , so I will go for the floatswitch.
The ones I have don't have any metal parts.
The idea of the pressure switch was just to avoid an over pressurized system in case the filters clog up.

The backwashing should be done automaticly but the problem is that the automatic filterheads I have can not deal with salt water recording to feedback of the manufacturer....(because of the seal)
That is why it should be done manually probably...
In that case I can install an inline pressure relief valve just in case things go wrong...
But I agree 100% that it would be so much better to have it done automaticly...

The reverse osmosis membranes should be protected by a real good pre-treatment in order to extend their lifespan as much as possible.
I might leave the carbon out....and just prefilter with sand, zeolite or / and anthracite followed by 5 micron fiber filters .

Can you explain more about what you have in mind with bringing the water up hill with "elevation" ?
you lost me there....
The pressure tank I mentioned before was only to work together with the pressure switch that I had in mind so the pump would not turn on and off so often and to avoid waterhammering etc.
That pressure tank was not meant to be any part of bringing the water up hill.


Thanks for sharing thoughts.
Really apreciate it.

 

[itsmoked]

I just took samples of the water and the salt level is 1,5 % (seawater is 3,5%)

Excellent! Now we know for sure.

As a jet pump I could use a swimmingpool pump because I just got feedback that said these pumps come with aaisi316 stainless steel seal.

Careful here, by Jet Pump I'm not referring to something like a Pool or Hotub jets pressure pump. I was refering to the more classical shallow well pump called a "jet pump".
See this wiki description scroll down to the heading "Well pumps".
[URL unfurl="true"]https://en.wikipedia.org/wiki/Injector[/url]

This is the style pump I was referring to:
ebay.com/itm/DAYTON-Shallow-Well-Jet-Pump-Plastic-1-HP

It is only a descriptive example!! You would need to find the correct one for YOUR application. It may be that a standard centrifugal pump with a foot valve will work just fine with water only a foot below... I'm certainly not the guy to spec your pump.

I think you are right,,, I would really like to avoid the pressure tank and switch and solenoid valve , so I will go for the float switch.
The ones I have don't have any metal parts.
The idea of the pressure switch was just to avoid an over pressurized system in case the filters clog up.

An over-pressure LOCK OUT switch is just fine as long is it takes a human response to reset it so you don't 'short cycle' the pump. You would typically have a beacon of some sort like a flashing red light to alert someone that water production has stopped. They'd then have a completely detailed manual to walk them thru figuring out what was specifically wrong and how to proceed.

The backwashing should be done automatically but the problem is that the automatic filterheads I have can not deal with salt water according to feedback of the manufacturer....(because of the seal)
That is why it should be done manually probably...
In that case I can install an inline pressure relief valve just in case things go wrong...
But I agree 100% that it would be so much better to have it done automatically..

I always try to solve the problem with materials or equipment that does the trick not resorting to human operation. I just see humans as the worst of all solutions because they usually don't have the required knowledge to handle any deviations. They either panic, 'try something'(always the wrong thing), or need help.

I usually dump the crummy spool valve heads on classic small filter tanks. That's the ones that look like water softener systems. Those are horrid in any service but water softening. If that's what you're doing I don't expect much success. I suggest you use the adapters offered to turn those same filter bodies into just two pipes, the input and output, and use solenoid valves that are all plastic and can take the corrosive water.

The reverse osmosis membranes should be protected by a real good pre-treatment in order to extend their lifespan as much as possible.

Absolutely!!

I might leave the carbon out....and just prefilter with sand, zeolite or / and anthracite followed by 5 micron fiber filters.

I'm not the one to guide you on this. There are things in water that really screw with membranes. Chlorine is the classic bad thing but there are probably others I don't ever have to deal with that people here know about. It certainly depends on the source water. Carbon is excellent at removing smells, organics, and chlorine and of course that all depends on your source water. You could end up with clear de-salted water that smells.

Can you explain more about what you have in mind with bringing the water up hill with "elevation" ?
you lost me there....

The pressure tank I mentioned before was only to work together with the pressure switch that I had in mind so the pump would not turn on and off so often and to avoid waterhammering etc.
That pressure tank was not meant to be any part of bringing the water up hill.

Ah, I did not follow that in your original post. Thanks for clarifying it. I thought you were somehow using it for pressurized delivery. Looking back you're using elevation above the resort for your final delivery pressure - which is great! (just what I was suggesting)

Thanks for sharing thoughts.
Really appreciate it.

You bet! May you be successful.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[ashtree]

Goltec

A couple of questions

When you say it has to run on solar , do you mean the whole system or just the the last set of pumps? Are there any limits on panel size, costs, or panel performance? Do you have storage batteries?
What sort of flows per day are you trying to do? From the type of set up you are proposing i am guessing its only a few 1000 litres per day at the most?
Thinking about the water quality other than salinity, are the media/ carbon/cartridge filters filters adequate to treat the water to a suitable standard to allow the RO to operate under all conditions? It would seem likely that during rain events and perhaps during the wet season the river might have higher levels of turbidity beyond what you can reasonably remove with filtration alone. Even if you can the SDI may be too high to get a reasonable period between membrane cleans.

As bimr suggests a process flow diagram would be good, with any known pressures, flows and volumes included. I would think at this stage two things will govern the whole system design (apart from cost):
1) How much water per day is required. This will influence membrane selection which will drive the pump selections.
2) Power supply limitations.(How many hours per day are we likely to be able to pump, and or what is the maximum amount of kwhrs that we can use).


Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[kybhosale]

If possible check for CDI option for Desalination.

Krunal Bhosale

http://waterengineer.co.in

All about Water and Wastewater Treatment

 

[ashtree]

I may be wrong but i didnt think that CDI was cost effective on seawater. It has generally been recommended(if at all) for lower salinity brackish water.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[Artisi]

Where in Thailand are you situated?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[goltec]

I am in Buriram.
Sorry for my very late reply....
I will get back on it later on....
I apreciate verry much your input...
Some things came up I really have to give priority at this moment....sorry for that...