Do surfactants pollute the environment? In Europe they must be biodegradable

THE surfactantsthe molecules behind soaps are among the chemical compounds most used in industry and could contribute to water pollution depending on some characteristics. Their chemical structure with one hydrophilic headwhich binds to water, and one hydrophobic tailwhich rejects it, made them become essential in numerous applicationsfrom personal cleansing (they are responsible for the foam that we like so much) to products for cleaning the house, up to cosmetics, paints and pesticides. In short, they are molecules versatile and omnipresent in our daily life. But after using soap to wash your hands, what happened to these substances? Are they harmful to the environment, pollute it, tend to accumulate, or are they disposed of without problems? The answer is not univocal: they can have a significant environmental impact, but their danger depends on several factorssuch as chemical composition, degradation speed and environmental conditions in which they are released.

To limit the damage related to their massive use, theEuropean Union has established precise regulations: the surfactants present in the products on the market must be completely biodegradable, ensuring that, in a relatively short time, these substances break down into simpler molecules And Less pollutingavoiding accumulation in the environment. Thanks to these regulations, the surfactants that we find in the deterries on the market in Europe are certainly biodegradable and with a minor impact on the environment.

What is meant by biodegradability

There biodegradability It is the ability of a chemical to be “fragmented”, in relatively short times, in simpler compounds such as Water, carbon dioxide or mineral salts. This process, carried out by enzymes present in microorganisms such as bacteria and mushrooms, leads to the complete transformation of a compound into substances less harmful for the ecosystem, avoiding their accumulation in the environment and the consequent pollution.

If the biodegradation takes place in the presence of oxygen, we speak of biodegradation aerobics; On the contrary, in the absence of oxygen, the process is anaerobic. This distinction is crucial because some substances degrade more effectively in aerobic environments rather than anaerobic: the environment is therefore an important factor for the biodegradability of the compounds. In particular, the surfactants degrade better in a Aerobic environment.

In the specific case of these molecules, they exist Two main phases of aerobic biodegradation:

• primary biodegradation: The compound loses its surfactive properties, decomposing itself in less polluting and more easily degradable substances, but not yet completely disposed of;
• complete biodegradation: the surfactant comes completely degraded in watercarbon dioxide and mineral salts, finishing the degradation process and allowing absorption in the environment without causing polluting accumulations.

Although surfactants are generally subject to these processes, their biodegradability and their environmental impact may vary according to the type and to the molecular structure of the single compound. Consequently, each surfactant will have a level of degradability and of different environmental impact.

The environmental impact of the surfactants

THE’pollution caused by the surfactants, it depends primarily on the characteristics of each tender -accepted molecule, but the environmental impact is also influenced by other factors. Scientific studies confirm how the chemical structure of the surfactant influenced its biodegradability. In particular, the hydrophobic tail It seems to play an important role: if its form is linearlike that of a hair or a thread, biodegradability increases if the shape is branchedlike the roots of a tree, biodegradation is more difficult.

However, there is a negative implication To consider: the surfactants with linear queues are more easily biodegradable, but at the same time the hydrophobic tail is stretched more The more toxicity for marine organisms increases. This means that greater biodegradability does not always coincide with a lower environmental impact. Ideally, the structure of a surfactant should balance a sufficient biodegradability with reduced toxicity.

The pollution caused by the surfactants depends on where they are released from

In addition to the chemical structure, also the waste water treatment It affects the environmental fate of surfactants. Once you enter the sewage system, these compounds are transported to the purification plants, where they tend to accumulate in sludge. The mud treatment method is crucial: in conditions aerobicin the presence of oxygen, many surfactants yes they degrade easilywhile in conditions anaerobicwhere oxygen is absent, there degradation is limited And the surfactant accumulates in sludge.

If these are then used as fertilizers in agricultural land, the surfactive molecules can be deposit in the ground! Although they can still biodegrade over time, their introduction into the environment represents a potential risk of contamination. In conclusion, the type of surfactant and the chemical structure influence the biodegradability of these molecules, but the treatment of waste water influence environmental fate.

European regulations and potential environmental risks

If the surfactant molecules were not biodegraded in useful times, we would meet unpleasant environmental consequences. For example, in the mid -1900s, in the United States, numerous detergents contained poorly biodegradable surfactants, precisely because they had one branched tail rather than linear. These, remaining intact, ended up in the sewers in the riversoriginating a large amount of foam In the river waters! The surfactants, in fact, are responsible for the formation of bubbles when we wash with soap.

To avoid this and other unwanted consequences, the rules on the surfactants currently in force in theEuropean UnionRegulation (EC) n. 648/2004, impose tight biodegradability requirements of the surfactant molecules contained in the countless home and industrial products. The European legislation in fact authorizes the entry on the market only of surfactants that meet complete biodegradation, even when present as ingredients of the various detergents. In addition, it provides a list of methods for the evaluation of the biodegradability of surfactants and indicates that these are carried out in competent laboratories compliant with specific quality rules. When we use shampoo or detergent for the dishes, we can rest assured that the surfactants that will go to the sewage system will be completely “Eco-friendly”!

The situation for the surfactants used in the field is different industrialfor which it is possible to request derogations and can be placed on the market even if they only satisfy the limits established for primary biodegradability tests.