After heavy rain, Spanish cities often awaken to refreshed air and clean streets, while the rainwater itself vanishes into storm drains along with everything it swept away. Under the ground, however, a very different story unfolds.
Once rainwater enters the sewerage network, it mixes with domestic waste water: everything that goes down shower, kitchen and bathroom drains, and toilets. This water carries fecal matter and bacteria, along with toilet paper, cleaning products, and many, other things.
