Water Quality

Local authorities make significant efforts to provide clean and safe drinking water—free from suspended particles and unwanted substances, and chlorinated to eliminate bacteria and viruses.

However, once the water is treated and inspected by the local governing body, it travels through distribution networks that cannot be continuously monitored for contaminants such as dirt, rust, or hazardous metals like lead, which may come from aging pipelines. Additionally, testing for pesticides and herbicides at the water sources is not always continuous due to the complexity of these analyses.

As a result, there is a need to purify water at the point of use for reasons related to:

• Aesthetics, by removing rust, dirt, and other suspended particles, as well as eliminating the unpleasant odor and taste of chlorine.
• Health, by removing volatile organic compounds (pesticides, herbicides), dangerous metals (lead), by-products of chlorine reactions with organic compounds (halogenated hydrocarbons), microbes, viruses, and potentially even radioactive particles.

There are products on the market with considerable differences in quality and various places of origin, resulting in a wide range of prices.

A thorough market analysis will demonstrate that low-cost products without proper support and warranties often become costly in the long term. When dealing with products that safeguard our health, the priority must always be on quality.

As we have become increasingly mindful of “what we eat,” it is equally important to focus on “what we drink.” Therefore, the installation of a water filtration system is essential.

The effectiveness of any filter, particularly an activated carbon filter, depends primarily on two factors:

• The flow rate of water through the filter, meaning how quickly the water passes through.
• The size of the filter, which determines the available surface area for retention.

Small filters that attach to faucets have a limited retention surface. Consequently, for these filters to function effectively, the water flow rate must be kept low to allow sufficient time for thorough filtration.

Water filters are categorized into:

• Main water supply filters
• Drinking water filters (Point-of-Use Treatment)

Specifically, main water supply filters are divided into:

• Dirt/Rust and suspended particles filters
• Dirt/Rust, suspended particles, and chlorine filters

Meanwhile, drinking water filters are divided into:

• Dirt/Rust and chlorine filters (installed under or on top of the kitchen counter)
• Dirt/Rust, chlorine, bacteria, lead, and chemical filters (installed under or on top of the kitchen counter)
• Ultrafiltration filters (0.1 – 0.02 microns)
• Reverse osmosis filters (0.0001 microns), retaining over 97% of all harmful substances (installed under or on top of the kitchen counter)

Drinking water from the supply network is regularly chlorinated by local authorities to eliminate all pathogenic microorganisms.

The presence of chlorine is therefore essential until the moment we use the water. Unfortunately, chlorine and its by-products give the water an unpleasant odor and taste.

Activated carbon removes chlorine and its by-products, significantly improving the taste of the water. However, removing chlorine also reintroduces the risk of pathogenic microorganisms developing.

For this reason, it is recommended that activated carbon filters be installed close to the drinking water faucet, rather than on the main water supply, especially if the main water connection is far from the drinking water faucet.

In any case, it’s advisable to let some water run from the faucet before using it.

When a filter allows dirt or rust to pass through, one of the following may be occurring:

• The filter replacement has a pore size that is too large, while the dirt and rust particles are smaller.
• The filter replacement has not been installed correctly, allowing a portion of the water to bypass the filter without passing through the replacement.
• The filter replacement is of poor quality, either allowing water to pass through without proper filtration or deforming due to pressure fluctuations in the network, releasing particles that had already been captured.

The filter traps dirt and rust, which may carry various microorganisms.

Some microorganisms (e.g., algae) produce plant matter, or “green residue,” as they grow. These microorganisms require food and sunlight to develop. The food comes from the materials that have been captured by the filter.

As the filter replacement accumulates the dirt it removes from the water, its pores become clogged, making it harder for the water to pass through. This difficulty causes a gradual decrease in water pressure and flow when the faucet is turned on.

Activated carbon filters can become a breeding ground for contamination. For this reason, it is recommended that water not remain stagnant in the filter for more than a few hours. If this happens, it is advisable to let the faucet run for 1-2 liters before using the water for drinking or other purposes.

Carbon is the fundamental element of organic matter. The carbon used in water filters can come from inorganic sources (mineral rocks) or organic sources (e.g., coconut shells). Carbon undergoes a specialized purification process to increase its surface area relative to its volume, resulting in activated carbon.

Remarkably, 1 gram of activated carbon has a surface area of 1,000 square meters. Activated carbon has the property, through a natural process called adsorption, to attract and retain various chemical compounds on its surface, such as chlorine, its by-products, and organic compounds like pesticides and herbicides. As a result, water passing through a layer of activated carbon is purified from its undesirable components.

Activated carbon is used in two forms:

• Granular form, similar to ‘powder’
• Solid form, in the shape of a block with a fixed structure

This second form of activated carbon also achieves the filtration of suspended particles (dirt, rust).

A filter with a transparent housing allows for easy inspection at a glance. In contrast, a filter with an opaque housing needs to be opened to assess its condition.

On the other hand, a transparent housing allows light to pass through, which can promote the growth of certain microorganisms (e.g., algae).

In comparison, a filter with an opaque housing prevents their development. Therefore, it is recommended to use a filter with an opaque housing in locations exposed to sunlight or other light sources.

It is possible to use a shared filter for two or more apartments or an entire building. Naturally, a larger filter and an appropriate replacement cartridge should be selected, depending on the desired outcome.

Reverse osmosis is the most effective and comprehensive water filtration technology. It is a process where water, along with dissolved salts and any other unwanted substances, is forced under pressure to pass through a synthetic semi-permeable membrane with a pore size of 0.0001 microns. This pressure reverses the natural osmotic pressure, forcing the water to pass through the membrane while the unwanted substances are blocked and flushed away to the drainage system.

Reverse osmosis technology achieves the removal of 95-97% of dissolved salts and other undesirable substances, delivering water of a high level of purity.

Reverse osmosis is a desalination process based on the principle of osmosis, where the solvent (less concentrated solution) moves toward the dissolved substance (more concentrated solution) through a semi-permeable membrane until the concentrations are equalized. Without the semi-permeable membrane, the natural process of diffusion would occur, where the two solutions mix. The pressure required to initiate osmosis is known as osmotic pressure.

If pressure greater than the osmotic pressure is applied to the more concentrated solution, the flow is reversed, and pure water is extracted from the concentrated (saline) solution to the less concentrated solution (solvent). This phenomenon is called reverse osmosis.

In practice, a high-pressure pump continuously forces seawater into membranes housed in a high-pressure vessel. The feedwater is divided into purified water that passes through the membranes and a high-salinity concentrate, or brine. Over time, the brine becomes more concentrated.

To reduce the concentration of salts remaining, a portion of the high-salinity concentrate (brine) is removed from the vessel. If this is not done, the concentration of dissolved salts will continue to rise, requiring greater energy inputs to overcome the increasing osmotic pressure.

The amount of desalinated water that can be obtained ranges between 30% and 85% of the feedwater volume, depending on the initial water quality, the desired product quality, and the technology and membranes used.

A reverse osmosis system consists of four stages/processes:

1. Pre-treatment stage
2. Compression stage
3. Separation stage
4. Stabilization stage (final treatment)

Pre-treatment stage:
The feedwater entering the reverse osmosis system undergoes pre-treatment to protect the membranes. The purpose of this stage is to eliminate microorganisms, adjust pH, remove solid particles, and eliminate chlorine to prevent scale buildup on the membranes and extend their lifespan.

Compression stage:
Next, a pump increases the pressure of the treated feedwater to a level suitable for the membrane and the salinity of the feedwater.

Separation stage:
The semi-permeable membranes then block the passage of dissolved salts while allowing the desalinated water to pass through. As the feedwater passes through the membranes, it separates into a stream of drinking water and a stream of concentrated brine, which is discarded. Since no membrane completely rejects all dissolved salts, a small percentage of salt passes through the membrane and remains in the water.

Stabilization stage:
Finally, the produced water has low hardness and relatively low pH, so further treatment is necessary before it can be consumed. The pH is raised from around 5 to 7 by adding sodium hydroxide, and hardness is increased by passing the water through special columns containing calcium and magnesium salts.

Membrane types:
A reverse osmosis membrane selectively allows the passage of a specific species (usually water) while partially or completely retaining other species (dissolved substances). This process requires high pressure on the concentrated side of the membrane, typically 2-17 bar for freshwater and brackish water, and 40-82 bar for seawater.

To be suitable for reverse osmosis, a separation membrane must possess certain properties. It must be resistant to chemical and microbial attack, mechanically and structurally stable for long-term operation, and have the desired separation characteristics for each specific system.