After last week’s conversation on water, I wanted to address a few more topics…
Is Reverse Osmosis 100% Pure?
“Does reverse osmosis remove all of the mineral ions? I heard it was more like 90% pure, and distilled water would be closer to 99% pure. In that case, would reverse osmosis water be different than distilled?”
Distilled water is heated and the steam is cooled. So if there are volatiles in there, it will not get rid of them. In fact, it can concentrate those chemicals. There is also the danger that some of the contaminants can be carried in the steam and get re- dissolved into the water. But assuming that does not happen, distilled water will be very pure or have little contaminants.
I believe that RO can achieve the purity levels that is found in distilled water but it depends on what is there to begin with.
The RO process uses a membrane, and this works, partially on the size of the pores so it restricts those big molecules. It also works through ionic exclusion. So the greater the charge, the better it is at keeping the ions out. So it is better at removing ions like Calcium which has a charge of 2+ than Sodium which has a charge of 1+. RO is also better at removing volatiles than distillation.
So is there a difference? Yes. The process is different. As to purity, it will depend on the source you’re starting with.
What Is the Best Water to Drink?
“If a person wanted to have a good source of water available instead of tap water, what would be the best method:
- reverse osmosis
- carbon filter
- bottled water
Again, it will depend on what you’re working with. I think it is best to get the water analyzed and choose the best one from what you find. You also have to take into account the technical requirements.
Distilled water requires a lot of energy to produce. RO requires the water to pass trough the membrane at high pressure. It is also slow, so you may need some sort of storage mechanism.
Carbon filtration will remove volatile chemicals but won’t remove heavy metals.
“Can you give some pros and cons of each method ?”
Distilled Water Pros
- Can remove viruses and bacteria
- Can remove salts, like sodium, magnesium, heavy metals like lead, arsenic and mercury
Won’t remove volatiles.
Is energy intensive.
A lot of water is wasted to produce the distilled water.
Strips away trace minerals. Will also affect taste.
Reverse Osmosis Pros
The membrane will remove organic compounds, including volatiles, salts and minerals. Will remove bacteria and viruses
- Some chemicals can pass through as the sizes of their molecules are smaller than the pores of the membrane. As they lack a charge, they won’t be excluded as the ionic salts. This includes some pesticides and herbicides.
- Strips away trace minerals. Will also affect taste.
- RO needs high pressure water. So if this is a large system, some infrastructure needs to be in place to be used, though there are some table top devices.
Carbon Filter Pros
- Can remove most chemical compounds like pesticides and herbicides and volatiles.
- Retains trace minerals
- Not energy intensive and is low cost.
- Effectiveness of filter reduces over time
- Effectiveness also depends on the type of filter used and how long it passes through the filter. So this depends on whether the filter has large or small pores or if the water passes through quickly or slowly.
Bottled Water Pros
- Convenient if you’re on the go
- Uses or is sold in a plastic bottles.
Besides the use of being wasteful, some plastics can leach VOCs into the water. Check the type of plastic your bottle contains to see if it’s safe.
How to Choose Plastic Bottles
Finally, let’s address the toxicity in plastic bottles. There’s a real concern about toxic elements leaching out of our water bottles.
To avoid this problem, it’s best to use a reusable stainless steel water bottle for traveling and/or drinking water in your car or at work.
But you might be traveling some place where you have to get a bottle of water. If that’s the case, check the bottom of the bottle. The type of plastic used may be one of seven types:
- The ThPET/PETE: Polyethylene Terephthalate (water & soda bottles, cooking oil bottles)
- HDPE: High-Density Polyethylene (detergent bottles, milk jugs, vitamin bottles)
- PVC: Polyvinyl Chloride (shower curtains, shrink wrap, building materials, toys)
- LDPE: Low-Density Polyethylene (shopping bags, six-pack rings, cd/dvd cases)
- PP: Polypropylene (bottle caps, dishes, candy containers, yogurt containers)
- PS: Polystyrene (Styrofoam cups, take-out food containers, peanuts, egg cartons)
- Other: Polycarbonates + many others (Reusable water bottles, baby bottles, Tupperware)
The numbers to avoid are 3, 6 & 7. These are the plastics that contain hazardous chemicals that may leech in the water.
The safer ones (but not necessarily environmentally-friendly) are:
1, 2 — for these plastics, make sure they are not exposed to heat or UV light, as they may breakdown and release chemicals in the process. #2 is considered safer.
5 — this plastic is considered very robust and safe. So is #4.