Hi Bob,
Just out of curiosity, what kind of output and efficiencies are the current reverse osmosis (standard residential scale if there is such a thing?...and, if you know commercial outputs please share as well) systems capable of?
Back in the early 90's I was into reef aquarium keeping and sourcing RO water for changes/top-off was one of the keys to keeping a healthy reef. However, the RO units of that time period created a very small percentage of usable water compared to the waste water.
Maybe I understood it wrong at the time (re: waste water) but just wondering if you can shed some light on the RO process? E.g., for X number of gallons passed thru a given system X gallons are purified.....and does this number change when processing sea water?
Thanks.
With RO, the tap water is pressed against a semi-permeable membrane, and only water molecules (in theory) cross the membrane. There are a number of molecules and ions that can pass at lessor rates than, say, sodium, calcium, and other mineral salts which are typically rejected about 95% in a new membrane. The trouble is, as the raw water is forced against the membrane, the contaminants build up and must be flushed away or the membrane will build up plaque and foul. The pressure of most municipal water supplies is typically enough, but at low pressures comes low performance and low efficiency. Many basic RO systems use 7-10+ gallons of raw water to produce a gallon of pure. Our design uses about 2.5 - 3 gallons for each gallon of pure. (Water used to purify drinking/cooking water for typical family of four is normally less than water used in a 5 minute shower.) Our design adds deionization as a tertiary phase of purification, removing what RO does not, resulting in exceptionally pure water, free of all dangerous contaminants, and tastes amazing. We normally market to health care professionals who resell to their client/patients. We export globally.
Most residential systems now use about a 50 gallon/day membrane so there is fast recovery when the tank is emptied. (A valve stops production when the tank is full.) A number of products have been made with a goal of reducing the brine water produced, but they all have problems yielding a decrease in contaminant rejection.
Commercial systems can produce about any amount you might desire, all depending on $$. Our lab systems typically produce at 125 GPD rates, and often have large storage tanks (the size tank of say a typical private water well. It is all about peak demand and time available to replenish. We use pumps on those systems, and have a little better recovery as a result, but our residential systems have about the best ratio for home units. Commercial systems can have up to about 50% recovery rate, but require high pressure and a lot of maintenance to keep membranes from fouling. And of course, residentail water seldom is higher than about 2000 parts per million (ppm), sea water is 30,000-40,000 ppm.
Someone asked about selling sea salt - yuk! All the toxins of the world end up in the oceans, so not a high quality source for salt. There are salt deposits with almost 100% purity, and there are some products available that are "sea salts" but typically mined from ancient sources.
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