How Gravity (And a Little Coagulant) Could Transform How Communities Clean Water

Tuesday, December 23, 2014

Purifying water is a problem as old as civilization. When people started living together in anything bigger than traveling bands of shepherds and hunters, potable water became a shrinking resource. The rotating belt of local oases or springs could satisfy you while you were constantly on the move but once you started needing the communal watering hole to keep your animals upright or your crops alive, cooperation became more tenuous and waterborne diseases became sundry. Getting sick from your drinking water was the tradeoff for settling down, and we’ve been repaying the debt ever since.

Making a dent in that bill has been the mission of thousands of nonprofits, institutes, NGOs, technology evangelists, well-intentioned individuals, and crusading celebrities. AguaClara, a decade old engineering project started by professors at Cornell University that is currently expanding its reach, is adding their name to the list by combining techniques that would have been familiar to the Romans and ones that would impress Elon Musk. It’s called “floccing”, and it might change how communities clean their water.

The process, in practice, is pretty simple, which makes it especially attractive for communities where specialized engineering skills are in short supply. (AguaClara currently operates in Honduras and India.) The engineering behind the process was years in the making, however,and involves water being injected with a coagulant that charges dissolved solids in the water and attracts them to each other. After undergoing a series of sharp 180 degree turns in the “flocculator” the clumps of sediment start to get heavier and eventually form a blanket on the bottom of the pipeline while the purified water flows overhead. Any microbes are taken out with a controlled dose of chlorine and ultra-fine particles are caught by a sand-based filter. (The process’ waste is funnelled out through a dedicated pipeline and staff engineers are currently trying to repurpose it as fertilizer.)

Source: This Big City (link opens in a new window)

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