PARIS (May 31, 2013) – The smelly sewage of Paris once festered within the cracks of the streets' cobblestones, dumped out of windows from chamber pots. Today, Paris has a practically invisible sewer network that is an underground city. Victor Hugo made it famous in his novel, Les Miserables.

"Paris has another Paris under herself; a Paris of sewers; which has its crossings, its squares, its blind alleys, its arteries, and its circulation, which is slime minus the human form," Hugo wrote.

In 1200, Paris had no waste disposal system at all. The city's citizens breathed the wastewater fumes in the open air. The lack of proper sanitation affected thousands of Parisians who were plagued with the "Black Death." Today, a sophisticated system of four principal tunnels exists underneath the City of Light. The network is 2,093 kilometers (1,300 miles) long. If stretched out, it would cover the path from Paris to Istanbul.

Within this advanced, underground system, blue and yellow signs indicate the names of the Paris streets above. The network is operated by "Section de l'Assainissement de Paris," the municipal department of Paris for Sewage. Xylem France has the maintenance contract for all the pumps that are used. More than 70 pumps are in operation and about 90 percent of them are Flygt pumps, including five dry-pit Flygt CT3500 140kW pumps that were installed in 1990 in one of the larger pumping stations, "poste Mazas." The pumping stations collect the urban wastewater and transport it to the wastewater treatment plant.

This sophistication took time to develop and evolved through the years. In the early Middle Ages, Parisians’ drinking water was obtained directly from the Seine. Wastewater was poured onto fields. It was disposed onto the unpaved streets of the urban landscape and then filtered back into the Seine. In 1370, a vaulted sewer was built on Rue Montmatre. During Napoleon’s reign, a 19-mile-long sewer was constructed beneath Paris.

The Industrial Revolution produced iron pipe and steam-digging equipment, and by 1850, Baron Georges Haussmann and engineer Eugene Belgrand had developed a system of separate channels for drinking water and sewage. Belgrand reshaped the system, increasing the size of the drains and roads. He started a treatment plant and built aqueducts so the city could pump in drinking water from surrounding areas.

It was not until 1894 that laws were enforced requiring that the discharge of all wastewater and storm-water runoff be funneled into the sewers.

Today, 1.2 million cubic meters of wastewater is collected and disposed of daily.