By Ritambhara
The Sushruta Samhita water purification rules, set out in the Sanskrit medical text’s chapter on liquids, told physicians to boil foul water, heat it in the sun or plunge red-hot iron into it, then clear it with kataka seeds. A laboratory study published in 2020 found those seeds removed about 93 per cent of turbidity.
The Sushruta Samhita is the founding Sanskrit treatise of Indian surgery, attributed to the physician Sushruta, whom tradition links to Kashi, now Varanasi. Encyclopaedia Britannica dates him to about the 6th century BCE, while scholarly estimates for the surviving text run to about 500 CE. The quotations below come from Kaviraj Kunja Lal Bhishagratna’s English translation of 1907.
How the Sushruta Samhita judged water
The Sushruta Samhita treated water as a substance to inspect before anyone drank it. Bhishagratna’s translation lists the marks of spoiled water as “roughness, sliminess, warmth”, “a varied colour, and the presence of mire, sand, and shreds of moss”, a distinct taste and an unpleasant smell. The text recommends lake or tank water in Hemanta, the early winter. For the rains, it advises collecting water from a house’s waterspouts “in a clean receptacle”, an early instruction for rooftop harvesting.
The purification methods Sushruta listed
The Sushruta Samhita methods in Bhishagratna’s translation are these.
- Boiling the water, or heating it in the sun.
- Immersing “a red-hot iron, or hot sands or stones” in it.
- Seven clarifying agents: kataka fruits, the gem gomedha (hessonite), lotus roots, the roots of aquatic mosses, a linen cloth, a pearl and a crystal.
Kataka is the clearing nut tree, Strychnos potatorum, which grows in the deciduous forests of central and southern India, according to the C.P.R. Environmental Education Centre in Chennai. Down To Earth described in 1995 how kataka seeds are crushed into a paste and stirred into muddy water to clear it.
What modern tests found
Majed Alenazi and colleagues reported in 2020, in IOP Conference Series: Materials Science and Engineering, that a Strychnos potatorum seed coagulant removed about 93 per cent of turbidity from test water. A coagulant is a substance that makes fine suspended particles clump together and sink. A 2023 study in the journal Heliyon found the same seeds removed 81.5 per cent of turbidity from washing-machine waste water.
Nitrate and fluoride in India’s groundwater
The Sushruta Samhita methods deal with mud and germs. India’s groundwater now carries dissolved chemicals that settling and boiling leave in place. The Central Ground Water Board’s Annual Groundwater Quality Report 2024, released in January 2025, found nitrate above the safe limit of 45 mg per litre in 20 per cent of samples from 15,259 monitoring locations. The same report found excess fluoride in 9.04 per cent of samples. It linked the nitrate to fertiliser pushed down by heavy irrigation, to livestock waste and to sewage, pressures traced in our guide to the fertiliser subsidy in India.
The Sushruta Samhita asked physicians to examine water by sight, touch, taste and smell before use. Nitrate and fluoride escape all four senses, so the same discipline now depends on chemical testing of wells. Earlier in this series, Varahamihira’s rules for finding groundwater and Charaka’s chapter on epidemics showed other early writers reading water with the same care.
Sources
- Kaviraj Kunja Lal Bhishagratna (tr.), Sushruta Samhita vol. 1, Sutrasthana, 1907, via Wisdom Library
- Maurya, Singh and Pal, Journal of Ayurveda and Integrated Medical Sciences, 2025
- Encyclopaedia Britannica, Sushruta
- C.P.R. Environmental Education Centre, Strychnos potatorum
- Down To Earth, Seeds of purity, 30 October 1995
- Alenazi et al., IOP Conf. Series: Materials Science and Engineering 888, 2020
- Heliyon, September 2023
- PTI via ThePrint, 2 January 2025
- Down To Earth, 15 January 2025
- Millennium Post, 3 January 2025
