Water quality determines such important factors as the health of ecosystems, the safety of human contact (in the bathroom, for example), and its suitability for consumption. The required standards depend on the use that is going to be made of it: the same quality parameters are not required for its consumption, for its industrial use or to guarantee the biological balance of an ecosystem.
In this post, Aqua Drink will talk about the quality parameters of water for human consumption, the regulations that govern them and how they are measured.
What do we understand by water quality?
The term “quality” refers to the property or properties inherent to something that allow us to judge its value, so to judge the value of water (and also sediments) we will refer to physical, chemical and biological properties, also called parameters.
Knowing these parameters is of great importance to manage their effects (for example, on people’s health, on the balance of ecosystems, etc.). If we know the colour of the water, we can know if there are dissolved substances that can be harmful to the environment. health smell and taste give us information about the products used for disinfection, such as chlorine.
Water quality parameters, therefore, are those that measure the absence (or rather a certain controlled range) of contaminants, and are governed by these parameters:
Colour
Pure water has no colour, it is completely transparent. In this way, any type of colouration in the water indicates contamination, generally by materials foreign to the system, and is usually due to a suspended material and/or a dissolved one.
The colour produced by a suspended material is called apparent colour, while that produced by a dissolved material, even after the suspended material has been removed, is known as true or real colour.
The colour of the water is measured in the laboratory by visual comparison or by the spectrophotometric method.
The WHO does not give a guideline value in relation to health, it only recommends a value below 15 mg/L Pt/Co (platinum-cobalt). Depending on the circumstances local, and when it reaches 30 mg Pt-Co/L the WHO recommends classifying it as not suitable for consumption.
Turbidity
Clear and light-transparent pure water is a sign of purity. Thus, if there is turbidity in the water, it means that there is contamination. Turbidity in water occurs when there are solid materials in suspension or dissolved or microbial loads, although there are differences between them in their ability to absorb light.
Cloudy water is generally considered unfit for consumption, since various materials responsible for turbidity can be toxic or create optimal conditions for toxic chemicals, so in turn, the more harmless the water is, the less turbidity it usually is. introduce. On the other hand, turbid waters have an impact on the photosynthetic capacity of the bottom, since they prevent the propagation of light in the deeper layers.
There are various ways to measure water turbidity, depending on the standard applied: infrared light or white or visible light that passes through a water sample, using nephelometers or optical turbidimeters, which determine the intensity of the scattered light.
The WHO does not give a health-related guideline value, it recommends that turbidity be as minimal as possible and points out that the values should be below 5 UNF (Nephelometric Turbidity Units), depending on local circumstances, ideally they should be below 1 UNF, and when the turbidity reaches 6 UNF it is recommended to classify the water as unfit for consumption.
Smell and taste
When water is pure, it is tasteless and odourless (it has no taste or smell). Therefore, if any type of taste or smell can be perceived, there is contamination in the water. The taste and smell of water can be explained by natural or artificial causes.
Artificial ones are usually related to the disinfection process (chlorination), which is why we perceive that the water in one area of a city has a different taste than that of another. However, there are natural causes for the taste and smell, such as the action of some natural impurities dissolved in the water.
Some compounds that give water taste and odour can be toxic, so it is essential that drinking water has as little taste and odour as possible.
Conductivity
Pure water has a very low level of conductivity (ability to conduct electrical current) (for example, distilled water has a conductivity level of 1 µmho).
Conductivity in water can be caused by the presence of metals such as iron and aluminium (positively charged ions) or inorganic compounds such as nitrate, sulfate and phosphate. Hence, seawater has a conductivity one million times greater than freshwater, since the salts present in it dissociate into ions. It is measured in micromhos.
The conductivity of water is determined by measuring the AC resistance of a solution between two electrodes.
pH
pH is the measure that determines the concentration of hydrogen ions in water. Pure water usually has a pH between 6.5 and 8.
Below 7 it is considered acidic, but it is still drinkable, unless it reaches levels below 5.5, generally due to the presence of metals in solution from industrial discharges or pesticides or slurry, or even due to causes. natural, such as acid rain, microbes in the soil, tree roots or rock formations such as pyrite.
Alkaline water is water that has a pH above 7, and can be produced naturally by passing over rocks and collecting minerals, as occurs in some springs, or artificially by electrolysis. Some claim that alkaline water is beneficial for health because it neutralizes acidity in the blood, but there are no conclusive studies to support this conclusion.
To determine the pH in water, pH meters are used.
Ammonium
Ammonium is naturally present in water, coming from the decomposition of organic matter (proteins, amino acids…), as well as from water disinfection processes with chloramine.
By oxidizing first into nitrite and then into nitrate (which we will talk about below), measuring ammonium and these two elements allows us to predict how long it takes for water to become contaminated with organic matter: when the concentration of ammonium is higher than that of nitrite and nitrate, contamination with organic matter has been recent.
Coliform bacteria and Escherichia coli (E. coli)
Water for human consumption should not contain bacteria, since they are the great enemy of public health.
If the water has the presence of coliform bacteria or Escherichia coli (E. coli), it means it has been contaminated. This can happen, as we explain in this post, if rainwater containing livestock excrement leaks into tap water pipes, for example.
