I'm running a chlorine experiment for our community patient setup so thought I would post the whole thing here for comment and scrutiny.
We're using a single patient RO. The DWA one is what we have in around 50% of our homes, the other 50% use the Aqua Uno which is mechanically identical.
We'll be taking the measurments with our Chlorosense meter. Our Chlorosense test strips are stored in the fridge and the calibration of the meter is to be verified before every test using the calibration standards supplied by Palintest.
The tap water is straight from the main and after a quick measurement this morning we recorded an incoming chlorine level of 0.8ppm.
This water is going to feed through a 10 micron particulate filter which is connected in series to another filter bowl which will house our current carbon filter - the Pentek C1.
To ensure a realistic contact time between carbon and water we are going to feed the RO permeate through a regulator set to give a flow of approximately 500mls/min. This should simulate an average draw from a machine. The drain from the RO will obviously be acting as normal with a flow of approx 2000mls/min.
We will measure daily to see how the carbon begins to exhaust making note of how many running hours/litres have occurred.
Measurements will all be taken at least 1 hour after starting the RO every day to ensure accurate contact time.
We will plot 3 axis on our chlorine graph; incoming water, post carbon and just out of curiosity, post RO.
If you have any comments as the experiment unfolds then please feel free to post within the thread.
If you've anything that is an image you can certainly insert it into posts otherwise I think you can only copy and paste.
If you want to send it to me anyway I can always take a few screen shots and we can compare experiments
So if you passed about 3500 litres, this would be about 7 sessions of 5 hours, including the disinfect at the start and end of each session. Were you expecting more from the filter.
I suppose the next thing is to try testing a few carbon block filter, that will hopefully give longer running time. This also goes to show how having redundancy is imprtant as the chlorine went high very quickly.
The filter hasn't performed as well as required tbh. Our filter changing regime is once a month and this experiment has shown that the filter alone has only lasted around two and a half weeks of a thrice weekly dialysis program.
From a safety point of view the patient is still being exposed to chlorine levels well below the allowed limits - phew!
Should the RO be considered part of the chlorine removing setup? I think not but it can provide the redundancy that you mention I suppose!?
I think I am going to continue the experiment with the current filter to see how the exhaustion pans out and see just how far we can push it before a patient risks exposure with the protection of the RO. I think it would be interesting to connect the RO straight to tap water and see what results it brings.
I have a carbon block filter standing by for stage 2 so we'll hopefully see a dramatic improvement.
If anyone out there knows how to calculate the approximate contact time using a cartridge filter and the flows I've been tabulating I think it would be interesting to see what it is.
The manufacturer specifies capacity of the 10" C1 is 11250 litres at 3.8 l/min flow. Capacity tested at given flow
rate using 2 ppm free available chlorine to 0.5 ppm breakthrough. So this is a bit disappointing.
I think it would be worth testing the latest CFB-plus filters. Each 20" CRB filter is specified at 20 times the capacity you measured.
It would save me putting any effort in to testing it myself too !
Cheers for the info Chris, I guess manufacturer's specs and reality can be two different things!
Our current filter setup is all in 10" bowls so my next test is with a 10" carbon block to see if we can get away without having to mod our installs.
Depending on our next test it could influence whether we upgrade to 20" bowls for future installs at least.
Either way I know our patients are safe on the monthly changing regime but my goal is to change just every 6 months when the techs visit to take samples etc... I know the patients would love to lose the hassle of changing them.
For me to put it forward though at our next MDT I'm going to have to have the evidence to back it up.
Hi Ian, email me your spread sheet and I can input the test data from one of our units if you like. It's a satellite unit with 10 stations where we have a small central plant using chlorplus block cartridges for chloramine removal. Might be interesting to compare?
The data is from a plant supplying 10 stations @ 3 shifts per day from 19/9/14 to 26/2/15. The filters used are x2 chlorplus 20" and x2 chlorplus 20"BB. Filters were changed after sample eight.
The data shows that over three months and approximately 1500 cubic meters of water passed, the filters are able to reduce the chlorine level down below the limit for feeding into the RO, even when our water is at it's coldest and the chloramine level is highest.It also shows that we have a decent amount of spare capacity if the level were to unexpectedly increase at the end of their life, even without relying on the RO to reject.
It's possible that we could make some efficiency savings here so I'm going to experiment with a different filter configuration over the next year.