Reverse Osmosis Plants. What’s your experience?

The railway that I volunteer at is considering installing a Reverse Osmosis plant to treat its locomotive water. I’ve heard a variety of anecdotes about the pros and cons and I’m wondering what the experience of posters here has been of changing over to this system. What sort of water were you changing from and what were the benefits? Did the change cause any problems and how much does it cost to run?

 

Whilst I'm sure the wibble on here may be interesting it's probably worth getting into contact with railway loco departments directly. GWSR has reverse osmosis and I'm sure the relevant people would be happy to discuss it with you.

 

The SVR has RO plants at both ends of the line. They were crucial in stopping the boiler problems we had around the turn of the century.

Bridgnorth water, in particular, is very unkind to boilers. I'm sure the department would be happy to provide advice.

Regards,

jtx

 

Having spent 8 years with Thames Water Engineering in their clean water supplies division I suppose I should be able to reel off all you need to know... However well engineered plant lasts a long time (50+ years was not unusual) so we were only just beginning to install RO in my last year or so, primarily as a method of removing nitrates from the water as some river and groundwater (borehole) sites were suffering from farmers over zealous applications of fertiliser...

Things you need to bear in mind are:-

RO should not really be considered as a filter. The water is 'forced' (not technically but near enough) through a membrane under high pressure to remove the contaminates. If you feed in 'dirty' water the membrane clogs very quickly and you either have to have an auto back-wash cycle fairly frequently (on the posh & expensive kit) or manually change the (quite expensive) disposable cartridges fairly regularly on the not so posh but still expensive kit so good filtration before the RO plant is a must.

You also need to know your water. Yes this may sound silly but the water you get could vary considerably from day to day as the supplier may be using one source during the day and switch to another during the night or perhaps in summer, when groundwater levels drop, they may have to stop using certain boreholes and pipe water in from a different area. All this can make a difference on what treatment the water has had, what the residual level of chlorine is and even quite noticeable differences in the hardness of the water (From your location I'm guessing you are in quite a hard water area) This could all affect how long a membrane cartridge would last. Most water companies seem to be quite helpful here. They have to regularly sample at customers taps by law (EDIT. see note below) anyway so a 'phone call to your local suppliers help line may well get them to sample your water and give you a complete report of the make-up of your water - for free!!!! This would also be essential information for any RO plant supplier for them to match their system to your water. If they don't ask for this or don't do their own sampling be cautious, some salesmen will say their it can do anything without sampling and it may do - for a while. Then you might start to find cartridges blocking sooner than expected (plant too small or water 'cloudy' - ["Turbidity" is the technical name for 'cloudiness' in water]) ) or higher than expected running costs (capacity too big) etc. etc.

Running costs will obviously depend on how much water you need to treat and how long the membrane cartridges will last (I'm assuming you won't be going for the (significantly more) expensive auto wash kit). Remember that pre-filtration. The better that is the longer your cartridges will last. Electricity usage will depend on the size of pumps etc. If you are looking to fill a tank a day it may be worth running a smaller pump/system for a longer time that a larger (more power hungry) pump/system for a shorter time.

Finally I'd ask do you really need RO? What is it you are really trying to do? RO gives you practically 'clean' water with next to nothing else in it but if you then store it in a tank which is not just as scrupulously clean you'll be picking up contaminates all the time. If you are just looking to reduce the hardness then a good ion exchange (NOT one of the so called 'electro magnetic' ones) commercial water softener could be a much cheaper option.

Also remember that RO will remove the residual chlorine from the water so you will have no disinfectant. If it's to be stored in a tower or outside tank for a while (2 - 3 weeks), in the sunlight, where the water could get warm (anything over 20 deg. C) you could be looking at a Legionella hazard for your crews from any fine spray generated while they are filling the loco. It's best to store water for as short a time as possible and make sure there is a good turn over of water in any tank. By that I mean let the tank empty so it is only 1/3 full (or less) before you fill it up again. Might be difficult depending on the size of your tank and the needs of your loco's but you get the idea.

Hope this helps.
Alan

EDIT Added:- Just to avoid confusion water supply companies do not have to sample every customers tap so don't be disappointed if they haven't been to see you. They just take a representative sample from each of the distribution 'zones' in their supply area.

 

Makes the tea taste funny....

 

GCR has gone from dire loco availability to having a surplus and being able to hire some out since the RO plant went in. How much of that is down to the RO plant and how much is down to other factors is something you'd have to discuss with those 'in the know' but one thing I have picked up on is that it tends to run out of treated water half way through big galas, at which point we have to revert to town water with chemical treatment. Clearly this isn't ideal, but I guess the alternative would have been a humungous (hence more expensive) RO plant running at a fraction of its capacity for 48 weeks of the year.

 

And have recently replaced the kit at Kidder IIRC

I was at the Welsh Highland a couple of years back and they said they use untreated water with washouts every 200 days. As an alternative to RO, perhaps preserved lines should move areas lol

Patrick

 

Nope, it's the other way round. Water from a RO plant has no taste and no trace elements so all you are tasting is the tea!

Try brewing the same tea from hard and soft water. They taste totally different!

 

exactly, I have one at home and it's brilliant. It has dual cylinders and when so much water has passed the first it switches to the second and flushes the first. No electricity involved, works on water pressure alone. The salt is only used in the flushing process so does not enter the household system at all.

 

The F&WHR don't have any RO plants however they do have a boiler treatment regime. Water is softened at locations where this is necessary mainly Porthmadog. A daily dose of treatment is added to the locos water tank in the morning which prevents build up of scale and sludge, scavenges oxygen, and maintains the ph of the water. This is combined with a rigorous blowdown regime at the start and end of the day, as well as careful monitoring of the boiler water in each loco. Different sized engines get different doses. Locos are very rarely washed out despite being in steam practically every day for 9 months of the year. Loco availability is very good with some engines running over 15,000 miles a year and boiler problems are few and far between. In fact they are throwing away tubes that would be good for another 10 years.

The FR also benefits from the fact that it's loco fleet largely remains the same, using the same water from the same locations and receiving the same treatment. So this makes it easier to monitor, predict and adjust the treatment accordingly.

Tim

 

Porta or TIA Treatment?

 

The issue at Kidder AFAIK was the original membranes / filters had become obsolete during the life of the plant and needed replaciing with up to date equivalents. Almost a new set up

 

The Kent and East Sussex have used a reverse osmosis plant for several years

 

The Dartmouth Steam railway had an RO plant fitted in Paignton around 4 years ago. It is absolutely worth it's weight in gold. We went through a terrible stage of water problems, causing considerable damage to both 7827 & 5239's boilers. We are still catching up with the knock on effect this had on the workshop. Fortunately the problems were discovered before too much damage was done to 4277.

If you need any more details, don't hesitate to contact me.

 

Are you able to elaborate in detail about the damage caused to 7827 & 5239.