Water filter cartridges

Ken68

I have cooked (and presumably sterilized) a water filter cartridge in the microwave.
Does anyone know if this means I could re-use it safely. It's back to filtering at the same rate as a new one.
A moneysaver if so.

Volcano

Home waterfilters use both activated carbon and ion-exchange resins in them, so you'd really have to regenerate both systems. The only way to do this to the resins is with a couple of unpleasent chemicals that would be more trouble than their worth unless it was done on a large scale.

I did read something that said the carbon could be cleaned with high temperature water being flushed through it.

By microwaving the filter you are effectively heating the contents up, I can't be sure what effect this has exactly; it may be that steam has forced a pathway through the carbon and that's why the water is flowing, or the heat could have dissolved some of the impurities blocking the filter. Don't know what this has done to the resin, probably melted it.

It isn't a good idea to use filters until they block up, the last few jugs of water are likely to have what contaminants the filter can't manage leach into the water and could easily be in excess of that contained in your unfiltered tap water.

If it was that easy I reckon some mad scientist somewhere would happily share the secret though I can't find anything on the web.

Ken68

Thank you Volcano for the interest....Until about 30 years ago, in this area, porcelain charcoal filters could be bought, presumably using lump or crushed charcoal.
And I remember my parents and grandparents saying that was a standard way to filter rainwater.
Could it be, do you think, that the modern cartridges are just a way of making money.,and ordinary charcoal would be just as effective. But....how long can you use the charcoal.

Volcano

To an extent it's down to what you want to filter out of your water. Ion-exchange is a very efficient method for removing aluminium and other metals, charcoal for chlorine and many other carbon-containing compounds (chloroform etc).

Charcoal has always been used as an adsorbent, and it's quite effective, but activated carbon is far more efficient as its surface area is greater (3 grams of it has the same surface area as a football pitch!)

Could it be, do you think, that the modern cartridges are just a way of making money

Undoubtedly. They are very efficient at what they do, but in the UK where the water passes stringent tests their selling point is moot and hinges on changing the 'taste' of water (subjective) or removing the minute traces of contaminants and the 'is it/is it not dangerous for you' argument.

You could make your own filter and purchase the activated charcoal yourself. If it is just the taste you want to change then this would probably suffice. If you want the best possible drinking water then the cartridges are the way to go.

kittiwoz

If you want the best possible drinking water then the cartridges are the way to go.

Actualy this is debatable. I worked on a project sponsored by Strix (who make kettle controls and the Morphy Richards Aqua Optima filter) to try and convert the batch process of the Filter Rapide kettle into a continuous filtering and boiling process for a water dispenser for the Chinese market. (Edit: Made myself sound a bit professional here: It was a uni project, design coursework for my mechanical engineering degree. I'm not a professional engineer. Now I'm a postgrad studying industrial design.) As part of my reasearch I learned a little about the filter process and also read the WHO Guidelines on Drinking Water Quality (THICK document), looked at the info from the Drinking Water Inspectorate etc.

If you were filtering water that was not potable then filtering through one of these cartridges alone wouldn't make it so, although it would make it a a lot cleaner, removing the vast majority of bacteria but not viruses. They're actually quite good value for this purpose although you would also need to add disinfectant, or bring it to the boil or maintain it at a high temperature for an extended period of time. I can't remember what the times required at the different temperatures are. If you wanted you can find out this info for yourself from the WHO website but you'd have to shift through some really heft PDFs. I'm not going to bother trying to find the info since I asume you're interested in filtering potable tap water.

On the other hand using one to filter potable water not only removes chlorine but also other trace elements such as minerals. A lot of the trace elements removed by the cartridge are good for you. What is more their presence is often generaly prefered tastewise. This is particularly true when the water is boiled. Filtered boiled water consistently rates lowest on blind taste tests and is commonly described as "flat". Danone Activ' bottled water is marketed and sold at a premium on the basis of its added calcium. This is exactly the stuff that is present in hard water and that these filters remove.

An electromagnetic water conditioner increases the ability of the water to dissolve calcium so that although the water is still hard the calcium does not deposit out and fur up your pipes and kettle. These are easy to fit and work out much cheaper than filters. This is supposed to be particularly good value from £95 with 190 day money back guaruntee and £5 year manufacturers warranty, running costs <£3 a year. That means after two years it becomes cheaper than filters but considering it affects all the water in your house, thus improving the efficiency of your heating and prolonging the life of your appliances it's actually better value than that.

The improvement to taste produced by water filters is down to the removal of chlorine. Chlorine is an effective residual disinfectant and its presence protects against the introduction of bacteria downstream of the treatment plant. It decomposes naturally and the DWI advise that leaving a covered jug of water in the fridge overnight will remove the chlorine.

Volcano

It all boils down to (couldn't resist that!) what Ken is filtering the water for in the first place.

Danone Activ' bottled water is marketed and sold at a premium on the basis of its added calcium.

It may be, though milk has a massive calcium content of 1200 mg/l compared to that danone stuff at 30mg/l. Even Ken's tap water has around 100-180 mg/l !

An electromagnetic water conditioner increases the ability of the water to dissolve calcium

Not quite, but there is some evidence that they may affect how certain ions recrystalise, therefore the crystals don't bond so strongly to surfaces. Many of these gadgets are employed in an industrial capacity with constantly circulating water with reportedly good results.

Strange thing is, no body knows how they work. So despite the web sites claims, the physics/chemistry they describe is rubbish.

Will they work in your house? Some people swear by them, others don't. Considering the vast amount of different models and the variety of installations available what works for one may not for another. I mean, how does quality control work in manufacturing if no one knows how they work?

http://www.cranfield.ac.uk/sims/water/magnets/ [about the nearest you'll get to an attempt at a sensible explanation]

http://www.chem1.com/CQ/aquacrack.html#VIBS [retired chemistry professor says it's all rubbish]

Ken68

Havn't read all the links yet, but my object is to save money by not using metered water and without poisoning myself.
Am saving £200 a year by doing this. Am now experimenting with small lump charcoal in a net in the container of the water jug filter, and this Filter will be microwaved every so often.
PS..don't actually drink the stuff, and use the finished product for personal and dish washing after boiling, tho mixed with cold.Also am using it for cold water clothes washing in the machine.

kittiwoz

Danone Activ' bottled water is marketed and sold at a premium on the basis of its added calcium.

It may be, though milk has a massive calcium content of 1200 mg/l compared to that danone stuff at 30mg/l. Even Ken's tap water has around 100-180 mg/l !

That was rather my point. It's as much of a waste of money to pay for water with added calcium as it is to pay for a filter to remove it from your tap water.

If you are using rain water for washing then I would say, based on my memory of the various WHO publications on water quality and water treatment, that you are over treating it currently. It would be best to ensure that your water butt is covered to prevent vector contamination (e.g. flies). If the water remains undisturbed in the barrel sedimentation will occur. Water can then be drawn of via a spigot to another container and disinfected. Probably the most efficient method of disinfection is the addition of chlorine. The water butt should be cleaned and bleached on a regular basis. Filtration is not strictly necessary, sedimentation is sufficient. However if the water is turbid or there is not sufficient time to allow sedimentation to take place, filtration using a granular media, eg. through a bucket of sand, would effectively remove particulate matter allowing chemical, thermal or UV disinfection to function efficiently. This type of filtration, unlike the adsorbtion process of a charcoal filter, would not in itself reduce microbial contamination but would be a pre-treatment to allow effective disinfection but a second process.

You should beware of repeatedly re-using a charcoal filter since this can reduce the microbial quality of the water. Simply bringing the filter material to the boil does not guaruntee disinfection since the microbes are protected from the heat by the charcoal in a way they would not be if they were free in the water. You would have to maintain a rolling boil for about 10 mins to be rid of them.

The energy expense of boiling the water is unnecessary though perhaps wise for dishwashing. Other means of disinfection, apart from chlorination and bringing to a rolling boil, are UV disinfection using a commercial lamp, thermal disinfection at pasteurisation temperatures using the sun, and solar disinfection using combined UV and thermal effects.

No processing is required to soften rain water since it is soft already.

I suggest you take a look at the WHO document regarding home water treatment and safe storage (HWTSS) "Managing water in the home: accelerated health gains from improved water supply" found here. This explains and assesses the available options for HWTSS. It's focus is on developing countries but the information is comprehensive and relevant to your problem.

Ken68

.Thank you, more than enough to read, wasn't expecting such informative replies.
Will start using a sand filter, and continue to carbon filter, then boil.A money saver.

kittiwoz

Will start using a sand filter, and continue to carbon filter, then boil.A money saver.

No it isn't.

Thames Water, for example, charge approxiamtely £1.35 for 1,000 litres of water, which I am assuming is typical. Boiling 1 litre of water uses approximately 0.1kWh. So for 1,000 litres that is 100kWh. Electricity typically costs in the region of 10p per kWh so you would pay £10 to boil 1,000 litres of water. This is 740% of the cost of using the same amount of water from the mains supply.

Hence the recomendation by the WHO and International Network for the Promotion of HWTS which I have repeated above that disinfection is by chlorination using calcium hypochlorite granules. This is reliable and provides residual disinfection. I am not sure how much you should use and you would need to find out properly. However the document refers to a few mg per litre of free chlorine. Calcium hypochlorite produces 65% free chlorine. For the purposes of costing only I will assume 6mg/l calcium hypochlorite, resulting in 3.9mg/l free chlorine. I stress this may not be a suitable concentration and is suggested for costing purposes only. If you buy 1 kilo of calcum hypochlorite for about £4 and for 1,000 litres use 6g calcium hypochlorite this gives a price of 2.4 pence. At 1.8-3.6% of the price of Thames Water that's a money saver.

Another method of disinfection you could use is a UV lamp. This would not provide residual disinfection however. This has a very low energy cost which I estimate from the typical rated power and flow rates of the domestic systems I've looked at to be about 0.5p for 1,000 litres. However there is an initial cost which seems to be typicaly a few hundred pounds plus the maintainance cost of replacing the lamp every year which I think is around £20 to £50.

The carbon filter is also unnecessary and can reduce the microbial quality of the water if it is repeatedly re-used since it may develop a bio-film and harbour bacteria.

Ken68

Thank you Kiti...but I live solo and don't use the hot water cylinder here, no point in heating the whole lot to draw off only ,say, a half a gallon of hot water a day for personal and dish washing.Electric shower otherwise.
So, am boiling it anyway, not just for sterilizing.....but I do top it up with cold filtered rainwater.