A River of Remains
At Varanasi, the Ganges River becomes a site of spiritual devotion and complex biochemistry. The primary cremation ground, Manikarnika Ghat, operates 24 hours a day, processing between 100 and 200 bodies daily. This continuous ritual, along with inputs from other ghats like Harishchandra, introduces a unique and concentrated load of chemical constituents directly into the river system. The main component of human cremated remains is tri-calcium phosphate (Ca3(PO4)2), the mineral matrix of bone. An adult cremation yields roughly 3-4 kilograms of this "ash".
The sheer volume of these deposits fundamentally alters the river's chemistry. The ash is highly alkaline, with a pH similar to bleach (11-12.5), and contains significant amounts of phosphate (47.5%), calcium (25.3%), and sulfate (11%). Studies on the Ganga at Varanasi show elevated levels of these ions, contributing to increased water hardness and alkalinity, particularly around the cremation ghats. This constant influx creates a measurable chemical plume. While municipal sewage and industrial effluent are major polluters, the cremation ghats provide a consistent, localized source of phosphates, potassium, and various trace metals. This nutrient loading can influence aquatic ecosystems downstream.
The Biochemical Aftermath
The introduction of ash and other ritual materials affects important indicators of river health. One is Dissolved Oxygen (DO), the amount of free oxygen available for aquatic life. Healthy rivers typically have DO levels of 8 mg/L or higher; levels below 5.0 mg/L put aquatic life under stress. Studies in Varanasi have recorded DO levels dropping to 4 mg/L in polluted stretches. The decomposition of organic matter from partially cremated remains and other offerings increases the Biochemical Oxygen Demand (BOD), where microbes consume oxygen to break down waste.
The ash contains trace elements and heavy metals. Depending on an individual's life, remains can contain small amounts of iron oxide, magnesium, zinc, and even mercury from dental fillings. While individual contributions are small, the cumulative effect of thousands of cremations adds to the river's load of persistent pollutants. The river water at Varanasi also shows high concentrations of coliform bacteria, largely from untreated sewage, making it unfit for drinking or bathing according to WHO standards. The combination of chemical loading from ash, high BOD, and bacterial contamination creates a challenging environment for the river's natural purification processes, which rely on adequate oxygen to support aerobic bacteria.