Have you ever wondered where everything we throw down the toilet ends up after flushing? Every day, millions of liters of waste water – which includes not only feces and urine, but also water from the sink, shower and household appliances – leave our homes and arrive in a place that is fundamental for the environment: the purifier. As you can see in the video, we visited the Iren plant Rapalloin the province of Genoa, to understand how this incredible purification system really works.
Pretreatment: the first barrier
It all starts with a huge pipe that carries wastewater into the plant.
Here, the first step is the pretreatmentwhere special rotating filters separate solid materials that should never be flushed down the toilet. Waste such as accumulates in the white bags next to the machinery tampons, cotton buds, razor blades, condoms, hair and plastic: anything that clogs the filters and slows down purification. The rule, therefore, is simple: only toilet paper in the toilet!
In this phase the oilssuch as fried ones or canned tuna, which should never be poured down the sink. A special machine isolates them from waste water. Finally, a separation system also eliminates the sands present in sewers.
Biological treatment: bacteria that clean
After the removal of solid materials, the most fascinating part comes into play: the biological treatment. At first glance the large tubs look like pools of boiling dirty water, but in reality an invisible army of “good” bacteria who work for us.
THE aerobic bacteria they need oxygen to live, and for this reason the tanks are continuously aerated from below. Thanks to these bubbles, the bacteria are able to oxidize organic and nitrogenous substanceseliminating most of the pollutants. Subsequently, when the air is turned off, i anaerobic bacteriawhich complete the process in the absence of oxygen. All this happens naturally, without the addition of chemicals.
Air purification
Rightly so, however, there might be a bit of a bad smell inside the system.
For this, the air inside the premises is sucked in and filtered with activated carbonwhich trap odorous molecules thanks to their extremely porous structure.
Result: outside the purifier there is no smellallowing these plants to be built even close to population centers.
Membrane filtration: clean water and separated sludge
Once the contaminants are eliminated, it’s time to separate the water from the sludge.
This happens through membrane filters: thin threads with pores as small as 0.03 microns — about 1800 times smaller than a hair! — which retain bacteria and only let water through.
On the one hand you get it clear wateron the other biological sludge rich in microorganisms.
From mud to fertilizer
The sludge is then dehydrated and treated with natural processes in which the bacteria themselves “self-digest”. After centrifugation and thickening, a dry and clean mudready to be used as ingredient for agricultural fertilizers. The water, on the other hand, is so purified that it can be released back into waterways or the sea — at a safe distance from the coast — without causing pollution.
Energy and reuse: the circular economy of purifiers
Each purifier has its own peculiarities. In Genoa, the DAC plant has all the tanks sealed to eliminate any odor and is able to produce biomethane from the sludge, covering up to 50% of energy needs. In Reggio Emilia, however, part of the purified water is reused for irrigating the fields, closing the water cycle and supporting agriculture.
Waste as resources to preserve the sea
The clean sea that we take for granted today is also thanks to these plants and the people who work there every day. Purifiers not only eliminate pollutants, but they transform waste into resourcesproducing reusable water, energy and fertilizer. I am the perfect example of circular economy serving the environment and everyone’s health.
