Not all municipal water supplies are created equal. Depending on where the reservoir is located and how far the water must travel to your tap, minerals, chemicals and pathogens can be picked up along the way. Local governments are charged with treating the water through an ongoing process of adding chemicals, filtration and removal of the treated sludge. These methods are less than perfect, however, and in some cities, it means drinking water can have a bad taste or even visible contaminants.

New York City recently announced a plan to expose 100 percent of its drinking water to ultra-violet rays, in addition to chlorination, in an attempt to neutralize all water borne pathogens in its supply. When complete, the new treatment plant will be the largest of its kind in the world, processing an amazing nine billion gallons daily.

The 160,000-sq-ft facility cost about $1.6 billion, and along with office and laboratories, is being built on city-owned property within the towns of Mount Pleasant and Greenburgh, in Westchester County. The above-ground portion of the building is constructed of structural steel with a precast façade and stainless-steel roof.

According to a report in Scientific American, the water consumed by NYC residents originates about 160 miles north of the City in the Delaware–Catskill watersheds. In the past, this water hasn't needed much in the way of added chemicals or filtration, but recently stricter EPA rules about water quality and development near the water source has prompted extra precautions.

When the plant opens, water will flow directly into 7,200-kilogram rectangular stainless steel UV disinfection reactors. As the water moves through the reactor, it will pass by one of over 200 UV lamps, zapping the pathogens into oblivion. The UV plant is said to be far more effective than filtration or chlorination alone, although no purification method is 100 percent guaranteed.