The great Maya city of Tikal transported zeolites for water filtration thousands of years before other cultures learned or adopted the idea, archaeologists have found. The filtration was probably much better than anything known to the Europeans who conquered the area 1,500 years later.
The Corriental reservoir was one of Tikal’s sources of drinking water. Dr Kenneth Tankersley of the University of Cincinnati found crystalline quartz and zeolite when digging at the reservoir. Neither are local to the area and would have had to be brought a long way by the standards of a people who had no beasts of burden.
No one would carry these materials so far without a good reason.
Tankersley observed the quartz/zeolite combination would have removed multiple pathogens from the water supply, including heavy metals, nitrogen-rich compounds, and bacteria. The last raises the tantalizing possibility the Maya had a germ theory of disease two millennia before Pasteur, but bacterial removal was more likely a beneficial side effect of efforts to remove other impurities. “This system would still be effective today and the Maya discovered it more than 2,000 years ago," Tankersley said in a statement.
The porous limestone on which Tikal sat, in what is now northern Guatemala, does not lend itself to wells for storing water during the dry season, so access to clean water would have been particularly essential.
In Scientific Reports, Tankersley proposes a source for the minerals and even explains how people might have come to recognize their value. A decade ago co-author Professor Nicholas Dunning reported volcanic rock known as tuff, rich in quartz and zeolite, in a scarp. “It was bleeding water at a good rate,” he said. “Workers refilled their water bottles with it. It was locally famous for how clean and sweet the water was."
The tuff deposit probably produced just as good water thousands of years ago, and some long-lost Maya scientists identified the ingredients that made it filter so effectively.
The minerals at Dunning’s site match those at Corriental, but nothing similar was found at other Tikal sites, including two other reservoirs the team excavated, indicating it was mined and transported the 30 kilometers (18 miles) to the city. That may seem a short distance today but was back then a long trek.
The minerals first appear at the reservoir around 2,200 years ago, and were replenished after flash floods until the city was abandoned more than 1,000 years later. Even older water filtration systems have been found in Egypt, South Asia and Greece, but Tikal’s version was probably superior. Zeolite is used to purify water today because its pores are well sized to filter out microbes such as cyanobacteria, and its ions bind to heavy metals.
The Aztecs and Incas transported water to their cities from clean springs, but the landscape in which many Maya lived made this unviable. Instead, the Maya built thousands of reservoirs – Tikal alone had five – only a few of which have been excavated. Consequently, we do not know how widespread zeolite use was.
The volcanoes of the region gave the Maya these minerals, but they also left high concentrations of mercury in the area. Human and natural activity washed this into water supplies, where it polluted Tikal’s other reservoirs and may have contributed to the city's collapse, the team previously showed, while the zeolites gave Corriental protection.