The Maya could have used an amazingly modern technology of water filtering more than 2000 years ago, as studies in the Mayan city of Tikal suggest. According to this, the people there used a mixture of quartz sand and zeolite to clean the water in one of their reservoirs of toxic algae and bacteria. The zeolite for these filters was obtained from deposits around 30 kilometers away.
The Maya not only created impressive temples and cities in Central America, they also developed advanced methods to secure their water supply. Because rainwater seeped away quickly in the karst underground of the Yucatan, but it only rained there seasonally, they created extensive networks of reservoirs and canals to supply their cities and fields with drinking water. Near the city of Tikal in Guatemala, they even built a huge dam with locks – the largest hydraulic structure in the entire Maya culture.
Telltale zeolite granules in the water reservoir
But there was a problem: Especially in the water reservoirs of the Mayan cities, toxic algal blooms often developed and bacteria made the water supplies inedible, as analyzes of sediment deposits suggest. But as archaeologists working with Kenneth Tankersley from the University of Cincinnati have found out, the Maya countered at least in Tikal: Their largest water reservoir, the 58 million liter Corriental Basin in the south of the city center, apparently already had a filter system. This could have removed pathogens as well as heavy metals and organic contaminants from the water.
“The exciting thing about this system is that it would still be effective today, but the Maya discovered this principle more than 2,000 years ago,” says Tankersley. Mineral analyzes of the deposits in the Tikal reservoirs provided the first indications for the filter system. It was found that in the Corriental basin, in addition to coarse quartz sand, a noticeably high content of zeolite grains was found. Zeolite is an aluminum-containing silicate mineral that is still used today as a filter material due to its absorption capacity. “Its structure of three-dimensional microcrystalline pores creates a natural molecular sieve,” the researchers explain.
Transported to Tikal from a distance of 30 kilometers
To find out whether the zeolite granules could have accidentally entered the Maya reservoir, Tankersley and his team carried out more detailed analyzes of the mineral structure of these granules. It turned out that this special form of zeolite does not occur in the immediate vicinity of Tikal. The closest rock formation with these minerals is around 30 kilometers from Tikal in the area of Bajo de Azucar. “There is weathered volcanic tuff made of quartz and zeolite from which water leaks,” reports Tankersley’s colleague Nicholas Dunning. “This formation was locally famous for its sweet and clean water.” The Maya probably recognized that this material was linked to the cleanliness of the water and therefore transported it to Tikal.
The Maya then constructed an astonishingly modern filter system in the Corriental basin of Tikal. “They had sedimentation basins that the water flowed through before entering the reservoir,” explains Dunning. In this forecourt, an area was filled with granules, including coarse quartz sand and zeolite. The water flowed through this filter, while mats woven from plant material held back the granular filter material. But because flash floods after heavy rain kept tearing some of these mats, quartz and zeolite were also washed into the reservoir and remained there in the sediment for thousands of years.
However, chemical analyzes of the deposits suggest that this water filter must have worked well: “Corriental has only small amounts of chemical impurities and practically no traces of blue-green algae or other pollutants,” the scientists report. With this, the Maya could have constructed one of the oldest water filter systems in the world. Because the zeolite filter system in Tikal was already in operation around 2185 years ago, around 600 years earlier than comparable sand-and-gravel filters in South Asia and even 2155 years before the first zeolite filters in Europe, as Tankersley and his colleagues explain.
Source: University of Cincinati; Technical article: Scientific Reports, doi: 10.1038 / s41598-020-75023-7