RO system flow rates and efficency improvments

Hello Guys,

I just joined the forum at the suggestion of a RO systems supplier I have been pestering to get your opinion on an improvement to RO system efficiency and water flow rates.

I have a relatively cheap simple idea that will get the RO filters running at or above there quoted flowrates and I wanted to know if this is something that would benefit you enough to want to pay anything for it !

Firstly a bit of introduction, I'm not a window cleaner, never will be, especially hate cleaning mine. I keep fish, fussy South American varieties that need very soft water so I was looking for a reverse osmosis system to reduce the hardness for the tanks, 245 litres of 2 ppm would be nice.

While learning about setting the system up I saw that a RO system rejects about 4 litres to produce 1 litre of clean water. This didn't surprised me, I knew they were wasteful, but what I didn't know was that the efficiency and life of the membranes was linked to the inlet water conditions. Not just the water hardness, and contamination but the operating conditions, particularly water temperature.

You probably all know this but I saw that RO systems are specified at an inlet temperature of 25°C and they cannot produce the claimed gallons per day figures unless they are actually at 25°C. The amount that temperature affect the output is the surprising thing. If you check the membrane manufacture's spec a 2500 gln/day filter at 10°C inlet temperature will only deliver 1310 gln/day. Our tap water struggles to get much above that even in the summer, in winter the water temperatures can easily fall to 5°C and the 2500 gln/day filter output falls to 875 gln/day, this is only 0.58 bleeding litres per minute! Good news though, there is also an upside, if the inlet is above 25°C they exceed the rated figure and the membranes work better and cleaner. They can happily run at 35°C and a 2500 gln system will then produce 3500 gln/day so the system doesn't need to be as big, the filters last longer or you get to pump it higher. Either way 875 to 3500 is quite a big difference.

Heating the tank is the obvious answer but 200 to 1000 litres of water from cold takes a hell of a lot of heat and time to get to 35°C even a 150,000Btu central heating combi boiler would take one and a half hours to get there. Clearly this doesn't work especially when you are mobile.

Now the suggestion, I'm absolutely not selling anything! I just have an idea how this can be done and I want to know if it is worth developing it.

So for a 2500 gln system - If you have a generator on the van that could supply 3kW would you be able to use a system that came up to the full 2500 gln flowrate from a full tank of 5°C water in about 20 minutes (and would work while it was getting there)?

Smaller RO systems wouldn't need as much power so the generator could be scaled down to suit, but the tank size in fact wouldn't make much difference.

Is flow rate an issue for you, would this be enough of an advantage to interest you? Should I bu@@er off and never darken your doorstep again?

Regards,

Andy the Minion

Now this will give @sprucesomething to get his teeth into. 

The advertised GPD is American gallons which is different to UK gallon measurement hence you won't get the advertised GPD output 

Thanks Iron Giant, Yes I am aware of this but whatever units you measure water in the output reduces if the temperature is below 25C. I was quoting US gallons with all the figures, if I switch to litres the 2500US gallon it is 9463litres per day at 25C and at 5C this falls to 3444litres per day.

https://www.aquaticlife.com/blog/how-temperature-affects-ro-water-production-/

Andy the Minion said:

Hello Guys,

I just joined the forum at the suggestion of a RO systems supplier I have been pestering to get your opinion on an improvement to RO system efficiency and water flow rates.

I have a relatively cheap simple idea that will get the RO filters running at or above there quoted flowrates and I wanted to know if this is something that would benefit you enough to want to pay anything for it !

Firstly a bit of introduction, I'm not a window cleaner, never will be, especially hate cleaning mine. I keep fish, fussy South American varieties that need very soft water so I was looking for a reverse osmosis system to reduce the hardness for the tanks, 245 litres of 2 ppm would be nice.

While learning about setting the system up I saw that a RO system rejects about 4 litres to produce 1 litre of clean water. This didn't surprised me, I knew they were wasteful, but what I didn't know was that the efficiency and life of the membranes was linked to the inlet water conditions. Not just the water hardness, and contamination but the operating conditions, particularly water temperature.

You probably all know this but I saw that RO systems are specified at an inlet temperature of 25°C and they cannot produce the claimed gallons per day figures unless they are actually at 25°C. The amount that temperature affect the output is the surprising thing. If you check the membrane manufacture's spec a 2500 gln/day filter at 10°C inlet temperature will only deliver 1310 gln/day. Our tap water struggles to get much above that even in the summer, in winter the water temperatures can easily fall to 5°C and the 2500 gln/day filter output falls to 875 gln/day, this is only 0.58 bleeding litres per minute! Good news though, there is also an upside, if the inlet is above 25°C they exceed the rated figure and the membranes work better and cleaner. They can happily run at 35°C and a 2500 gln system will then produce 3500 gln/day so the system doesn't need to be as big, the filters last longer or you get to pump it higher. Either way 875 to 3500 is quite a big difference.

Heating the tank is the obvious answer but 200 to 1000 litres of water from cold takes a hell of a lot of heat and time to get to 35°C even a 150,000Btu central heating combi boiler would take one and a half hours to get there. Clearly this doesn't work especially when you are mobile.

Now the suggestion, I'm absolutely not selling anything! I just have an idea how this can be done and I want to know if it is worth developing it.

So for a 2500 gln system - If you have a generator on the van that could supply 3kW would you be able to use a system that came up to the full 2500 gln flowrate from a full tank of 5°C water in about 20 minutes (and would work while it was getting there)?

Smaller RO systems wouldn't need as much power so the generator could be scaled down to suit, but the tank size in fact wouldn't make much difference.

Is flow rate an issue for you, would this be enough of an advantage to interest you? Should I bu@@er off and never darken your doorstep again?

Regards,

Andy the Minion

Click to expand...

I would personally say that we welcome people who come up with workable ideas that will help our business, so you are always welcome to participate by asking questions. Over the years there have been those who have listened to our frustrations and come up with simple 'designer' products that have made window cleaning easier. The Univalve, Aquadapter, economic carbon fiber poles, lighter brushes, Quick Connect and the Quickloq system as a few examples.

You have to consider ours is a very basic, grassroots industry operated by a majority who aren't and never were university graduate material (myself included.)  The majority of us process water at home, transfer that water into a tank on the van and then pump that water to a brush that we use to clean a window. The loosened dirt is flushed or washed away with the water.

I for example, use a 1000 liter IBC tank stored in my garage to process water into. So we have a static r/o system that we can leave to work whilst we are out cleaning windows. So really this storage tank to us is a reservoir like a dam is to the water board.

So as window cleaners we can get away with an r/o that produces less water per hour than we would use when cleaning windows as it works in the background for longer than we do.

There are some that process their water directly into their van tank and most who do this use a big r/o system so they can do this when they come home.

In summer when the water is warmer coming to our home, our old r/o did fill the IBC tank faster. It took 28 hours in summer and 36 hours in winter. But our working hours on the glass are restricted in winter due to weather and day light hours, so we tend to use less water. I don't record house cold water temperature often, but I have never seen ours drop below 8 degrees in winter on the North East coast. It could well be different in Scotland and places in central England.

We initially started with a 275gpd r/o and processed water direct into 3 x 125 liter tanks on a trailer system. I can't say is was a guaranteed success. That r/o was upgraded to a 450gpd and a used IBC tank purchased locally put into the garage. The trailer was scrapped and a float switch with solenoid valve added to the system to switch the r/o off when the IBC tank was full. A 650 liter tank was added to a SWB Citroen Relay and that 450gpd supplied my daily requirements for a couple of years. (It took the first weekend of water processing to fill the IBC tank but once full it was a big enough buffer and I never ran out of water.

When my son joined with his 500 liter tank, supplying both our needs was a challenge but needed forward planning. So I would fill my van on Saturday, his on Sunday and that got us through the working week. When we added a third, part-time cleaner we found the r/o couldn't keep up.

So I changed the r/o to a 4040 and we haven't had an issue with water since. Yes, the part-time cleaner left and we use less water, but changing the r/o to a bigger one was the solution to having enough water to work and earn.

This brings us to the use of a generator. If you plan to warm the input water to 25 degrees for the r/o to produce faster, then you also have to consider boosting water pressure as well. Our 4040 r/o produces 2lpm of pure water and an efficiency of 97 - 98%. Our water pressure is 50psi and I don't use a booster pump. On the glass we probably use the same amount of water. My vans 650 liter tank was totally empty yesterday morning. I filled it and went to work. I was back at around 14.30 in the afternoon as its Grand father duties on Wednesday to collect the 2 grand children from school. The r/o had already switched off when I got back.

On my 450gpd I had a prefixed waste valve which was set at 3 waste to 1 pure. My current r/o has a gate valve on the waste and its peak efficiency is at a 50 - 50 ratio, hence I use less water.

For those who use hot water, the most efficient way of heating water is to heat the water on demand. It would frustrate me to spend money on heating water only to send half of it to the drain if I was warming r/o input water.

Heating water always comes at a cost, so the old business rule of economies of scale comes into play. Does the overall cost and running costs of a product justify its purchase and maintenance over a period of time? In my case, it wouldn't.

However, the American market does work slightly differently to us. Most home owners do have an outside fawcett and accept that a window cleaner will use their water supply. Using my setup as an example, my 4040 r/o is big enough to just about supply my window cleaning needs directly. I use between 1.5 and 2lpm of water whilst cleaning windows. I've also seen setups where in window cleaner has a small tank on the van and uses his r/o to replenish the water he is using from his customer's tap. But then Americans tend to have their windows cleaned twice a year and the window cleaner does inside and outside. Many homes have screens that need to be removed and cleaned so ladders are need for that anyway.

I replaced an 1800 watt heating element in my son's dish water the other day. Its a simple system of a heating coil around a metal pipe, but I have no idea how quickly it would heat a small flow of water through it in a single pass and a dish washer would heat the water with multiple passes.

https://www.ebay.co.uk/itm/1800W-Flow-Through-Water-Heating-Element-For-WHIRLPOOL-Dishwasher/253095070821?epid=911930776&hash=item3aeda44c65:g:HUAAAOSw3ntZkWUz

Then there is another system that seems very exciting but hasn't taken off. I'm not sure why. This is a water hammer.





This has been an ongoing project for over 15 years but I don't see it captured the minds of people as the future of water heating. A skeptic said of a similar unit;

When someone builds one of these, starts selling power, and retires on it, then we'll know we have something. Until then, it's fake, sadly.

43 minutes ago, spruce said:



I would personally say that we welcome people who come up with workable ideas that will help our business, so you are always welcome to participate by asking questions. Over the years there have been those who have listened to our frustrations and come up with simple 'designer' products that have made window cleaning easier. The Univalve, Aquadapter, economic carbon fiber poles, lighter brushes, Quick Connect and the Quickloq system as a few examples.

You have to consider ours is a very basic, grassroots industry operated by a majority who aren't and never were university graduate material (myself included.)  The majority of us process water at home, transfer that water into a tank on the van and then pump that water to a brush that we use to clean a window. The loosened dirt is flushed or washed away with the water.

I for example, use a 1000 liter IBC tank stored in my garage to process water into. So we have a static r/o system that we can leave to work whilst we are out cleaning windows. So really this storage tank to us is a reservoir like a dam is to the water board.

So as window cleaners we can get away with an r/o that produces less water per hour than we would use when cleaning windows as it works in the background for longer than we do.

There are some that process their water directly into their van tank and most who do this use a big r/o system so they can do this when they come home.

In summer when the water is warmer coming to our home, our old r/o did fill the IBC tank faster. It took 28 hours in summer and 36 hours in winter. But our working hours on the glass are restricted in winter due to weather and day light hours, so we tend to use less water. I don't record house cold water temperature often, but I have never seen ours drop below 8 degrees in winter on the North East coast. It could well be different in Scotland and places in central England.

We initially started with a 275gpd r/o and processed water direct into 3 x 125 liter tanks on a trailer system. I can't say is was a guaranteed success. That r/o was upgraded to a 450gpd and a used IBC tank purchased locally put into the garage. The trailer was scrapped and a float switch with solenoid valve added to the system to switch the r/o off when the IBC tank was full. A 650 liter tank was added to a SWB Citroen Relay and that 450gpd supplied my daily requirements for a couple of years. (It took the first weekend of water processing to fill the IBC tank but once full it was a big enough buffer and I never ran out of water.

When my son joined with his 500 liter tank, supplying both our needs was a challenge but needed forward planning. So I would fill my van on Saturday, his on Sunday and that got us through the working week. When we added a third, part-time cleaner we found the r/o couldn't keep up.

So I changed the r/o to a 4040 and we haven't had an issue with water since. Yes, the part-time cleaner left and we use less water, but changing the r/o to a bigger one was the solution to having enough water to work and earn.

This brings us to the use of a generator. If you plan to warm the input water to 25 degrees for the r/o to produce faster, then you also have to consider boosting water pressure as well. Our 4040 r/o produces 2lpm of pure water and an efficiency of 97 - 98%. Our water pressure is 50psi and I don't use a booster pump. On the glass we probably use the same amount of water. My vans 650 liter tank was totally empty yesterday morning. I filled it and went to work. I was back at around 14.30 in the afternoon as its Grand father duties on Wednesday to collect the 2 grand children from school. The r/o had already switched off when I got back.

On my 450gpd I had a prefixed waste valve which was set at 3 waste to 1 pure. My current r/o has a gate valve on the waste and its peak efficiency is at a 50 - 50 ratio, hence I use less water.

For those who use hot water, the most efficient way of heating water is to heat the water on demand. It would frustrate me to spend money on heating water only to send half of it to the drain if I was warming r/o input water.

Heating water always comes at a cost, so the old business rule of economies of scale comes into play. Does the overall cost and running costs of a product justify its purchase and maintenance over a period of time? In my case, it wouldn't.

However, the American market does work slightly differently to us. Most home owners do have an outside fawcett and accept that a window cleaner will use their water supply. Using my setup as an example, my 4040 r/o is big enough to just about supply my window cleaning needs directly. I use between 1.5 and 2lpm of water whilst cleaning windows. I've also seen setups where in window cleaner has a small tank on the van and uses his r/o to replenish the water he is using from his customer's tap. But then Americans tend to have their windows cleaned twice a year and the window cleaner does inside and outside. Many homes have screens that need to be removed and cleaned so ladders are need for that anyway.

I replaced an 1800 watt heating element in my son's dish water the other day. Its a simple system of a heating coil around a metal pipe, but I have no idea how quickly it would heat a small flow of water through it in a single pass and a dish washer would heat the water with multiple passes.

https://www.ebay.co.uk/itm/1800W-Flow-Through-Water-Heating-Element-For-WHIRLPOOL-Dishwasher/253095070821?epid=911930776&hash=item3aeda44c65:g:HUAAAOSw3ntZkWUz

Then there is another system that seems very exciting but hasn't taken off. I'm not sure why. This is a water hammer.

Click to expand...

Thank you for taking the time to reply Spruce, its very appreciated.

When I saw vans with tanks and the packages that go with them I had assumed that to be fully mobile the industry would be producing water on the go and recycling the the rejected water back into the tank until the TDS (or conductivity levels) reached a certain level. I had no real idea of how much water you would be using a day but I can see that if you can easily run for a day between refills then it is simpler to refil with RO produced at home.

I presume the waste water is not costing enough to be a big financial problem. I would preheat when I install my unit but it would be for eccological reason as I’m not on a meter ?

Regards,

ATM

I also should have mentioned (but forgot - its an age related thing ?) that we get no flow restrictions through our sediment and carbon prefilters when they are new. When we tested the water flow at the tap before we bought the 4040 we had 13lpm. I checked the water meter when the r/o was flushing the other day and it recorded 13 lpm. Both pressure gauges read the same pressure either side of the prefilters as well

We use a Fiberdyne 20" carbon block and a sediment filter. The Fiberdyne has a service life of 75700 liters. Thats approx 3 to 4 months water usage (waste and pure) for us these days. Unfortunately there are times when our water is full of sediment. I have been known to change the sediment filter 3 times before the carbon block is due for replacement. I can not only see the sediment filter is dark red with sediment, but the pressure gauge after the prefilter drops. When the difference is 10psi then its time to change the sediment filter. When the pressure does start to drop and can compensate the restricted flow by closing the waste gate valve fractionally, but I can only do it once.

When I change the sediment filter I have to open the waste gate valve slightly again.

This past year there has been no pressure drop and a have changed the sediment filter when I changed the carbon block.

Our r/o's work at between 97 and 98% efficiency. At one time our tap water tds was just over 250ppm. The pure after r/o was 4ppm. We use mix bead Tulsion resin to polish the remaining impurities off.

In the early days we were cleaning a house that had a big fish pond in the front. The owner was paranoid about not letting tap water into the pond. He was happy to hear how we processed water, and in those days we used a resin that was FDA approved. In time we couldn't get that any longer so went over to Tulsion. I cleaned that house for another 8 years without any problems.

The house next to my son was repossessed by the bank and the owner just left his outside pond full of fish. We didn't realise that the pond had a leak and it was only by chance that my son noticed the fish struggling in a few inches of remaining water. We pumped about 2000 liters of water into the pond over that weekend and bought some fish food to feed them. We filled the pond every Friday/Saturday with 1000 liters of r/o water until arrangements were made for a new home for the fish and the pond filled in. We did that for about 6 weeks and those fish were fine.

.

 Good man with the fish Spruce ?

Andy the Minion said:

 Good man with the fish Spruce ?

Click to expand...

The guy was a waste of space tbh.

He was adopted and had a chip on his shoulder. The adoptive parents had other children but he managed to persuade her to give him the house as all the others had families and their own places. It was mortgage free. He promptly remortagaged it up to the hilt and when the bank refused an additional loan against it he stopped paying and waited to be evicted.

He told his 'brother' who lives further down the road that he had given the fish to a good home. Now homeless, he persuaded the council to give him a council house in a nearby town.

We contacted the rspca but they couldn't do anything as they had no place to 'house' them. Basically, they weren't interested. I was told to contact the police who told me that I should contact the bank as the fish technically belonged to them. I had to wait 21 days from my letter before I could do anything about trying to find a home for them.

In that 21 day period the bank found a new owner and the new owner arranged a new home for them. The pond was filled in because they had young children. We were also told by the police that we could be charged with breaking and entering, even if we were just unlocjked the side gate to run hoses into the pond. We ignored their advise and did it anyway.

They were lovely fish - large Koi and a couple of other fish. We just couldn't let them perish as the guy with no heart could.