Come si rende potabile l'acqua di fiumi e laghi? I passaggi prima di arrivare ai rubinetti di casa

Summary

This video explains the complex process of making water from rivers and lakes drinkable, starting with the removal of large particles through coagulation and flocculation, followed by disinfection using ozone to eliminate harmful microorganisms. The process continues with filtration using activated carbon and fine sand to remove remaining impurities. Finally, UV disinfection ensures that all pathogens are destroyed, making the water safe for consumption. The video highlights the importance of water treatment plants and their role in providing clean water, specifically focusing on plants in regions like Basilicata and Sardinia, where surface water is primarily used.

Takeaways

• 😀 To make water drinkable, it needs to be both microbiologically pure (without harmful microorganisms like bacteria and viruses) and chemically safe (with safe levels of potentially harmful substances).
• 😀 Potable water can come from underground sources (aquifers), surface waters (rivers and lakes), or be desalinated from seawater.
• 😀 The process of purifying surface water involves several stages, starting with the extraction of water from rivers or lakes to avoid debris like mud and leaves.
• 😀 The first major step in water treatment is coagulation, where a coagulant is added to help particles of dirt stick together and fall to the bottom of the water.
• 😀 Flocculation is the next step, where these coagulated particles form clumps called 'flocs' that are heavier and sink to the bottom.
• 😀 Some water requires additional substances (flocculants) like sand or polymers to help form denser flocs and make them easier to separate.
• 😀 After coagulation and flocculation, the water moves to a sedimentation phase, where the flocs settle at the bottom, and the clearer water is collected from above.
• 😀 Disinfection is a crucial step where ozone is introduced into the water to kill microorganisms by oxidizing them. This process is enhanced by passing the water through a compartmentalized tank.
• 😀 Filtration follows disinfection, where water passes through fine layers of activated carbon and fine sand to trap any remaining particles or metals.
• 😀 A final disinfection step involves exposing the water to ultraviolet (UV) light, which destroys any remaining pathogens, ensuring the water is completely safe to drink.
• 😀 In Italy, regions like Basilicata and Sardinia rely heavily on surface water for drinking water supply, while other regions mainly use groundwater, which requires different treatment processes.

Q & A

What makes water safe for drinking?

Water must be microbiologically pure (free from living microorganisms like bacteria, viruses, algae) and chemically safe (with substances below harmful levels) to be considered safe for drinking.

What are the two main sources of potable water?

Potable water can come from either underground sources, such as aquifers, or from surface waters, such as rivers or lakes.

What is desalination, and where is it used?

Desalination is the process of removing salt from seawater to make it potable. It is commonly used in coastal areas where freshwater is scarce.

How does the water treatment process for surface water begin?

The process starts with water being drawn into the treatment plant using suction systems positioned to avoid debris like mud, leaves, or branches.

What are coagulants, and what role do they play in water purification?

Coagulants are substances added to water that neutralize the electrical charges on suspended particles, causing them to clump together and settle out of the water, helping to clarify it.

What happens during the flocculation process in water treatment?

In flocculation, the coagulated particles form larger clumps, known as flocs, which then settle at the bottom of the tank for easier removal.

What additional substances may be used when coagulants alone are not sufficient?

In cases where coagulants aren't enough, coadjuvants such as micro-sand or natural polymers like alginate are added to help form heavier flocs and improve their separation.

How does ozone help disinfect water during treatment?

Ozone is an oxidizing agent that destroys pathogens like bacteria and viruses by breaking down their cell walls. It also oxidizes harmful metals, turning them into less harmful forms.

What is the purpose of filtration in water treatment?

Filtration removes the remaining particles, including disintegrated microorganisms and metals, by passing the water through layers of fine sand and activated charcoal, which trap these impurities.

How does ultraviolet (UV) light further purify water?

UV light is used in the final disinfection stage to break down the DNA of any remaining pathogens, preventing them from reproducing and ensuring the water is safe for consumption.

Why is the treatment process different for water from underground sources?

Water from underground sources typically requires different treatments due to its different chemical composition and contamination levels, such as needing more focus on removing dissolved substances rather than suspended particles.