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Drinking water purification.

One of the alternatives to offer and obtain drinking water outside the big bottling brands are water purifiers. Like bottling companies, water purifiers must comply with standards and regulations to ensure that the water offered meets the appropriate characteristics for human use and consumption. In the case of Mexico, the Mexican Official Standards (NOM) are those that establish the regulations necessary to market or provide water quality. These regulations establish the limits of contaminants allowed in water intended for human consumption, which guarantees that purified water is safe and complies with the appropriate physical, chemical and microbiological parameters. The NOMs that must be considered for drinking water are:

  • NOM-127-SSA1-2021, "Water for human use and consumption. Permissible limits of water quality".
  • NOM-201-SSA1-2015, "Products and services. Water and ice for human consumption, packaged and in bulk. Sanitary specifications."

NOM-127-SSA1-2021

  • Indicates maximum allowable levels of chemical, microbiological and physical contaminants.
  • Establishes the sampling methods to evaluate the physicochemical parameters of water.
  • It specifies the methods of analysis to evaluate the physicochemical parameters of water.
  • Suggests corrective actions in case of non-compliance for the limits.

NOM-201-SSA1-2015

  • Indicates the permissible quality limits that water and ice must meet.
  • Stipulates the sanitary specifications to be met by containers and labels.
  • Establishes requirements for sampling and analysis of water and ice.
  • Establishes as a rule the requirements for the sanitary authorization of establishments that produce, pack or distribute water and ice for human consumption.
  • It sets out the requirements for the training of personnel working in these establishments.

Which drinking water is best?

Raw water treatment is a crucial process to ensure that water is safe for human consumption. This involves the removal of chemical and biological contaminants that could pose a health risk. Chemical contaminants can include substances such as heavy metals, industrial chemicals, pesticides and organic compounds, while sanitary contaminants can include bacteria, viruses and other pathogenic microorganisms. The availability of adequate equipment is necessary to carry out effective water purification. This includes filtration systems, disinfection, ozonation and other purification methods. This equipment not only ensures the removal of contaminants, but also improves the taste and clarity of the water, making it more pleasant to drink for the end consumer.

How to offer quality drinking water?

Feed water disinfection

First, the raw water used by the purification plants to sell it as drinking water must go through disinfection processes, which is commonly based on chemical disinfection with chlorine. Chlorine is an oxidizing agent that reacts with the cellular structure of microorganisms that may be present in water from wells, pipes or the municipal water network that feeds the purifier. The administration of chlorine to raw water is normally given in its liquid form (sodium hypochlorite) because it is an economical, easy to administer and store. When chlorine in its sodium hypochlorite form comes into contact with water, it generates hypochlorous acid, which is the compound that performs the disinfection with effects such as protein denaturation, oxidation of cellular components, etc. The process of dosing chlorine to drinking water can be simplified through a dosing pump that periodically administers the chemical in a precise way.

Feed pump and pressurization

The entire drinking water purifier system requires the installation of a feed pump with sufficient capacity to ensure a constant flow of raw water through the treatment systems. An efficient feed pump can help minimize operating costs by optimizing the use of energy and resources. By maintaining proper control over raw water flow and pressure, wasted energy can be avoided. The feed pump can adjust its speed and flow rate to accommodate these variations, ensuring that the plant can deliver the required amount of purified drinking water at all times. In addition, it is also important to mention that this type of pump is relevant at the end of the drinking water treatment process, as its pressure is used to pressurize and carry out the filling process of either demijohns or smaller bottles.

Granular media filtration

Raw water, in its natural state, has a composition that often includes suspended solids, such as soil particles, sand, decaying organic matter, microorganisms, and other contaminants specific to the water source. These suspended solids in water can not only influence the turbidity of the water, but also affect the quality of the water in terms of its suitability for human consumption. To remove these types of undissolved contaminants, physical filtration is performed through granular media which can be: silica gravel, silica sand, zeolite, anthracite, garnet, zeolite. In cases where the source water has a large amount of iron and manganese, catalytic granular media such as Katalox can be used. If pH values are not adequate, pH regulating media can be used to reduce acidity, such as calcite or calcite and corosex. These granular media are arranged in a tank according to the size of the particle they retain, with the finest media being placed at the bottom.

Purification with activated carbon

Activated carbon is produced from carbonaceous materials, such as wood, coconut shell or mineral charcoal, which are heated at high temperatures in the absence of oxygen to create a porous structure. This process removes impurities and creates an extremely porous surface with a large surface area, resulting in its high adsorption capacity. Adsorption is a process in which atoms, ions or molecules of a substance adhere to the surface of the activated carbon, including by-products generated during the initial chlorine disinfection. As the water flows through the activated carbon tank, impurities and contaminants dissolved in the water come into contact with the porous surfaces of the activated carbon, which acts as a purifier. The contaminants adhere to these surfaces due to chemical forces, resulting in better tasting and smelling water. Adsorption is a process in which atoms, ions or molecules of a substance adhere to the surface of the activated carbon due to chemical forces, such as Van der Waals forces, rather than a chemical reaction that transforms them.

Hard water softening

Depending on the water source, there may be a high concentration of minerals that modify the taste of the water. If the consumer expects the taste of the drinking water offered by the purification plants to be similar to the taste of water from large bottling companies, it is necessary to subject the liquid to softening with cationic resins. This is due to the fact that to obtain the taste desired by the consumer, the water must be treated with a reverse osmosis system, which is susceptible to incrustations caused by the minerals in the water, which over time will affect its components and the product offered. Water hardness is due to the presence of calcium (Ca2+) and magnesium (Mg2+) ions, which can cause problems such as scale formation in pipes and purification plant equipment. Ion exchange resins or cationic resins have the ability to retain calcium and magnesium while releasing sodium into the water. However, over time, the cation resin becomes saturated with calcium and magnesium ions and needs to be regenerated. This is accomplished by flushing the resin with a concentrated sodium chloride solution (brine). The brine contains a high concentration of sodium ions, which displace the calcium and magnesium ions retained in the resin.

Reverse Osmosis RO

The reverse osmosis system is a water treatment and purification technology that removes a large amount of contaminants including mineral salts, heavy metals and dissolved contaminants from the water, as well as any sediment and even microorganisms left over from previous treatment processes. The reverse osmosis membrane is the essential component of this process. It is designed to allow water to pass through its microscopic pores while effectively retaining contaminants, salts and other unwanted solutes. Reverse osmosis membranes are generally made of semi-permeable polymers that filter at the molecular level. Reverse osmosis systems are widely used in industries where high quality water is required, such as the food and beverage industry, pharmaceutical production and thus in the purification of drinking water.

Conservation of stored water

Once the water has passed through the aforementioned equipment, it is common for it to be stored in tanks before being marketed as drinking water, so keeping microbial growth under control is important so that the stored water retains its quality until it is provided to the consumer. The storage tank must be equipped with an ozone generator which, like chlorine, has oxidizing capabilities that prevent the generation of microorganisms, but in this case without leaving any residue. Through an electric current it breaks down oxygen molecules (O2), releasing individual oxygen atoms (O). These individual oxygen atoms recombine with oxygen molecules (O2) to form ozone molecules (O3).

Benefits of drinking water treatment

  • Odor and taste expected by the consumer: Chemical and organic compounds that can give rise to unpleasant tastes and odors in the water are eliminated, thus meeting consumer expectations.
  • Compliance with quality standards and regulations: Using complete treatment methods ensures compliance with official Mexican standards for marketing drinking water.
  • Consistency in water quality: Allows the adjustment of the physical and chemical characteristics of the water such as pH, hardness and mineral concentration, which ensures consistency in the drinking water offered.

Other sources.

Diario Oficial de la Federación: NOM-127-SSA1-2021

Diario Oficial de la Federación: NOM-201-SSA1-2015

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