Blue Spot Water

Water Purification Explained

There are various opinions about water purifiers. Some common questions are: Is it good to remove all bacteria? Is it healthy to drink water with no nutritional value? Will a mineral filter truly replace lost minerals? Can purifiers increase bad bacteria in the water? These are all valid questions that deserve to be answered.

Debunking Common Water Purification Myths

A simple and effective way to understand the need for purification is to observe the filters themselves. If tap water were truly "clean," a filter would not turn brown or become clogged. The visible discolouration on a polypropylene filter proves that our water contains contaminants. For example, if you were to filter Valpré bottled water through a sediment filter, it would not turn brown, even with its added minerals.

In fact, some South African product standards require companies to purify their water before using it to make their end-products. This demonstrates that for certain applications, municipal water is not considered clean enough to meet quality control standards.

It is crucial to understand that all purifiers have a downside if not properly maintained. It is extremely important not to drink water from your purifier if the filters have not been replaced at the right time, as they can become a breeding ground for bacteria.

Water Purification Methods

Water purification is the process of removing undesirable materials, chemicals, and biological contaminants to make water fit for a specific purpose. This can range from making it safe for human consumption to meeting the strict requirements for medical, industrial, and pharmaceutical applications.

The process follows a filtration spectrum, from removing large particles to the smallest dissolved solids. The five major methods are:

1. Particle Filtration: Removes sediment and larger contaminants.

2. Microfiltration: Removes particles up to 0.1 microns.

3. Ultrafiltration: Removes particles up to 0.01 microns.

4. Nanofiltration: Removes particles up to 0.001 microns.

5. Reverse Osmosis (Hyperfiltration): Removes particles down to 0.0001 microns.

Reverse Osmosis (RO) Purification

Reverse osmosis was first observed in 1748 but was only used for water filtration on a larger scale centuries later, famously for desalinating seawater.

The process works by forcing water through a semipermeable membrane with pores as small as 0.0001 microns. This pressure forces pure water molecules through the membrane while leaving behind larger impurity particles, which are then flushed away as wastewater. This "reverse" motion of water against its natural flow is what gives the process its name.

A crucial application of this high-purity water is for cleaning high-voltage power lines. Since the water has no dissolved minerals, it has no conductivity, making it safe for technicians to use without the risk of electrocution.

Home RO Purification Systems

In a home RO system, water goes through a series of stages, typically four to seven, to ensure the highest quality. The first stage is always a particle filter to remove sediment and other large contaminants. Subsequent pre-filters remove smaller particles, protecting the delicate RO membrane from clogging and ensuring its longevity. The specific type and number of filters in a system depend on the quality of the water source.

Some advanced RO systems include a final mineral filter after the membrane. This filter reintroduces some of the essential minerals that were removed during the RO process, ensuring the water has nutritional value and a balanced taste. This gives consumers the benefit of both purified and mineralized water from a single tap.

The Scientific Explanation of Osmosis

To understand reverse osmosis, it's helpful to first understand osmosis. Osmosis is a natural process where a solvent (like water) moves from a region of low solute concentration to a region of high solute concentration across a semipermeable membrane. This movement occurs to balance the concentration of solutes on both sides of the membrane. The force that drives this movement is called osmotic pressure.

Reverse osmosis takes this process and inverts it. By applying an external pressure that is greater than the natural osmotic pressure, water is forced from the high-concentration side (where impurities are) through the semipermeable membrane to the low-concentration side. This process allows the system to separate pure water from its contaminants, making it the most effective method for creating highly pure water for domestic, medical, and industrial use.