Reverse Osmosis
Six stages, one membrane with pores about a ten-thousandth of a micron across, and a lab report on every batch. Here is exactly what happens to the water before it reaches the bottle.
What reverse osmosis actually is
Osmosis is water moving on its own from a weak solution to a strong one through a membrane, trying to even the two sides out. Reverse osmosis does the opposite on purpose: put the dirty side under enough pressure and you force pure water backwards through the membrane, leaving the dissolved contaminants behind.
The membrane is the whole trick. Its pores are roughly 0.0001 microns — small enough that a water molecule fits and almost nothing else does. A bacterium is about 5,000 times bigger. A dissolved salt ion, a nitrate, a trace of lead: all of them are turned away and flushed to drain.
A sediment filter cannot do this. A carbon jug cannot do this. Boiling certainly cannot — it kills microbes but concentrates the salts and metals that are left behind.
Six stages, in order
Each stage exists to protect the next one. Skip the pre-filters and the membrane fouls in weeks; skip the post-treatment and the water tastes flat.
Sediment filtration
A graded 5-micron cartridge takes out sand, silt, rust and suspended particles. This is housekeeping — it stops the finer stages from clogging.
Activated carbon
Carbon adsorbs chlorine, chloramines and the organic compounds behind bad taste and odour. Critical, because free chlorine destroys an RO membrane.
Carbon block polish
A denser second carbon pass catches whatever slipped through and drops residual chlorine as close to zero as the instruments can read.
The RO membrane
High-pressure pumps push water through a semi-permeable membrane. Dissolved solids, nitrates, heavy metals, bacteria and viruses stay on the reject side and go to drain.
Mineral rebalancing
RO water is close to blank, so calcium and magnesium are metered back in — for taste, for a stable pH, and because your body has a use for them.
UV & ozone finish
Ultraviolet light deactivates anything that survived, and a controlled ozone dose keeps the storage tank and the sealed bottle sterile.
Things that don’t make it through
Groundwater in and around the twin cities picks up a predictable set of problems on its way to a tap. Reverse osmosis addresses all of them in one pass rather than one filter per contaminant.
- Dissolved salts — sodium, chloride and sulphates that make water taste brackish and are hard on the kidneys at volume
- Nitrates — from agricultural runoff and leaking sewerage; a genuine risk to infants
- Heavy metals — lead and cadmium leached from old pipework and fittings, plus arsenic where it occurs naturally
- Bacteria, cysts and viruses — including the coliform group that turns up after any pressure loss in a distribution main
- Chlorine and its by-products — removed by the carbon stages before the membrane ever sees them
- Turbidity and sediment — the visible half of the problem, and the easiest part to fix
“Doesn’t RO strip the good minerals too?”
Yes — it does. A membrane cannot tell a calcium ion from a lead one. That is why the process does not end at stage four.
Raw feed
High and unpredictable TDS. Whatever the ground gave it that week — salts, nitrates, metals, plus the minerals you actually want, all mixed together.
Near-blank water
Almost everything is gone, wanted and unwanted alike. Very low TDS, flat on the tongue, and not what we would ask anyone to drink by the litre.
Rebalanced
Calcium and magnesium metered back to a controlled dose. Stable pH, a clean round taste, and a mineral profile we can put a number against on every batch.
The point of remineralising is control. Instead of taking whatever the aquifer happened to contain, we set the profile deliberately and verify it before the batch ships.
How we know it worked
A purification line is only as good as the testing behind it. Membranes degrade, seals fail, pre-filters saturate — none of it announces itself. So the assumption we work from is that something is always about to go wrong, and the job of the lab is to catch it first.
- TDS and conductivity read continuously across the membrane, alarmed on drift
- pH, turbidity and residual ozone checked at fill on every batch
- Microbiological plating on a fixed schedule, with holds until results clear
- Independent third-party verification on a rolling cycle
- Filters and membranes replaced on hours run, not on how they look
- Batch codes on every bottle, traceable back to the shift that filled it
Common questions
Is RO water safe to drink every day?
How is this different from a home RO unit?
What TDS does Aqua Green bottle at?
Doesn’t RO waste a lot of water?
Does boiling do the same thing?
Six stages, three bottle sizes
500 ml, 1.5 litre and the 19 litre home and office bottle — all filled off the same line, all tested the same way.