In the long history of Paris' urban development, OsmanUnderneath the construction under the leadershipThe drainage system has always been a monument of engineering wisdom.1832，The cholera epidemic swept like a black hurricaneParisThe whole city is approaching in just six months18000 lives, with a death rate of 6.4% along the Seine River.equalAt that time, Paris still retained its medieval urban texture, with narrow streets and alleys crowded with people20000 houses with poor sanitary conditions, street sewage crossflow, and sewage overflowing from cesspools poured into 25000 wells during rainstorm. The drainage system is limited to scattered open ditches andOne142 kilometers long, built in the 13th centuryofStone masonry sewer.Horse manure, kitchen waste, and industrial wastewater are all directly discharged into the Seine River without treatment——This river, which serves as both a drinking water source and a drainage channel, has become a "contradiction between death and life" in Hugo's writing.

equalottomanAfter taking charge of the transformation of Paris,Breakthrough with engineer Bergeron to introduce the concept of human circulatory system into urban planning，They believe thatClean spring water, light, and heat should be able to flow throughout the body like blood, while secretion and excretion should be carried out in secret. Osman decided to direct the turbid currents of Paris towards the Asher Purification Plant on the outskirts of the city, where the dust was purified through gravel filtration and microbial decomposition, and then the clear water source was drawn from the clear waves of the Seine River, creating a self-renewal circulation system for Paris.

Osman's Underworld in Parisnewly builtfinishUsed for draining rainwater and sewageCast iron drainage pipe networkThe layout of the pipeline network underground followsThe three-level circulation system of "capillary vein artery": tiny capillary like pipes are arranged in a dense grid throughout the urban surface to prevent local water accumulation, just like the peripheral blood vessels of the human body. These pipelines are connected to building drainage outlets and utilize gravity to naturally divert water. After initial filtering of impurities, they flow into medium-sized pipelines, known as the "vein" level. The venous pipeline has a gentle slope and is equipped with a sedimentation tank to prevent backflow, gradually directing the water flow towards a thicker main road, similar to the mechanism of venous reflux. The "arterial" hierarchical pipeline network of the main road is made of cast iron material, designed with a 4-meter-diameter arch tunnel shape to accelerate water flow velocity, and adopts a linear layout to shorten the drainage path, directing water flow to the Asher Purification Plant outside Paris.All drinking water supply and wastewater dischargeThe pipeline networkAll adopt a closed form, becoming a completeThe three-level circulation of capillaries veins arteriesWater Supply and Drainage SystemThis biomimetic design not only solved the cholera and water pollution crisis in Paris' history, but also became a model for modern urban infrastructure.

After World War I, Paris began againiterationThe industrial wastewater purification and renovation project mainly involves the construction of4 drainage channels with a diameter of 4 meters and a total length of 34 kilometers, for the purpose of passing through the purification plantindustryWastewater is treated, with a portion of the treated water being discharged to the outskirts and another portion being recycled through non potable water pipelines, such as washing city streets，Realize the reuse of industrial wastewater.

After World War II, the Paris city government further expanded and improvedundergroundCast iron drainage pipes for the water supply and drainage system, enabling each household's toilet to function properlyAnd the kitchenAll directly connected to it，Establish a complete metabolic cycle from peripheral nerves to arteriesAt present, the total length of underground cast iron drainage pipe treatment system pipelines in Paris is2400 kilometers, equivalent to the distance from Beijing to Shenzhen, discharges over 15000 cubic meters of urban sewage per day. In addition, the cast iron drainage pipes in Paris also use the same street name and house number as the road surface. If any items fall in, cast iron drainage pipe workers can retrieve them free of charge.

What's even more amazing is that asArteriesCast iron pipelineThe casting process，itsThe pipe wall, from the outside to the inside, is as follows:10mm thick iron oxide protective layer, 30mm dense cast iron layer, and 15mm ductile iron lining, this designThe intensity was not only ahead at that timeSame period stone pipeline,Even deeply inspired by current materials science.In 2021, Parisian engineers accidentally exposed deeply buried cast iron components of the 19th century Ottoman era drainage network while demolishing concrete structures built in the 1950s in the La D é fense district. Through scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis, theseThe drainage pipeThe lattice of cast iron presents a hexagonal pore network at the microscale, with a porosity of approximately37%. The principle of optimizing porosity of cast iron lattice is applied to the research and development of permeable concrete，Improve the infiltration efficiency of rainstorm to that of traditional materials3.2 times，With this material,arriveIn 1999, Paris has completed 100% complete treatment of urban wastewater and rainwater, and the accumulated water can be discharged from the road area in time no matter how much heavy rainstorm it encounters.

The modern transformation of this historical heritagestillinduce childbirthfinishmoreMultiple breakthrough achievements. In the field of materials engineering,The electrostatic adsorption technology of iron oxide thin film on cast iron pipe network has been reborn as nano photocatalytic coating in the roof renovation plan,Convert solar energy into thermal energy,send32 million square meters of zinc roof transformed into a carbon neutral technology testing site. These practices confirm that the resilience code of Paris is deeply rooted in the engineering gene pool of historical layers, and every crisis becomes a trigger to awaken dormant wisdom, making the 19th centuryCast iron drainage pipeThe cast ironLattice blooms with new forms of life in the quantum age.