New Delhi, Dec 8: Padma Shri awardee and renowned scientist Dr. Ajai Kumar Sonkar has warned that Reverse Osmosis (RO) systems, commonly used for drinking-water purification, are significantly increasing uranium concentrations in groundwater across several regions of India, including Delhi, Bihar, and the Andaman Islands.
Recent reports have highlighted rising uranium levels in groundwater, but Dr. Sonkar states that a critical scientific factor remains overlooked: the continuous discharge of RO reject water, which is many times more concentrated with uranium, is quietly contaminating both soil and groundwater.
RO Systems Concentrate Uranium Instead of Eliminating It
Dr. Sonkar explains that groundwater naturally contains trace amounts of uranium due to geological factors.
RO systems do not eliminate uranium; they concentrate it in the reject water. If groundwater contains 30 µg/L uranium, RO reject water may contain 100–300 µg/L or higher.
India currently has no guidelines for safe RO waste disposal. Reject water is routinely discharged into drains, open soil, or soak pits, allowing uranium-rich water to percolate back into shallow aquifers, increasing contamination over time.
A Dangerous Cycle of Recontamination
According to Dr. Sonkar, RO usage creates a harmful cycle:
1. Uranium-bearing groundwater is extracted.
2. RO systems concentrate uranium 5–10 times in the reject water.
3. Reject water seeps into soil and aquifers.
4. Groundwater uranium levels increase.
5. The same contaminated water is extracted again.
“With each cycle, the concentration of uranium in groundwater rises further,” he warned. The problem is especially severe in cities with heavy RO usage and limited groundwater recharge.
Contamination Extending to Soil and Food
Dr. Sonkar added that the impact is no longer limited to water. “When uranium-rich reject water enters soil, it contaminates not only groundwater but also agricultural land. Vegetables and crops absorb uranium through their roots,” he said.
This means: leafy vegetables, grains, fruits, tuber crops, and other produce can accumulate uranium when grown in contaminated soil. This extends the risk from water to soil and now to food, posing a widespread health hazard.
Two Forms of Uranium Toxicity
Dr. Sonkar highlighted that uranium presents two types of health risks:
1. Radiological Toxicity: Long-term ingestion can expose the body to alpha radiation, increasing the risk of DNA damage and potentially cancer.
2. Chemical (Heavy Metal) Toxicity: This is more immediate. Uranium behaves similarly to lead and cadmium, primarily impacting the kidneys, causing: nephrotoxicity, tubular damage, reduced filtration capacity, chronic kidney dysfunction.
Repeated small exposures can cause accumulation and long-term harm.
Why Developed Nations Don’t Face This Problem
Dr. Sonkar explained that countries such as the US, Europe, Australia, and the UAE use Zero Liquid Discharge (ZLD) systems for community-scale RO plants.
In ZLD systems: RO reject water is evaporated, solids are collected, and the residue is sent to hazardous-waste facilities. “No liquid waste is allowed to percolate into soil or groundwater,” Dr. Sonkar noted.
India lacks such mandatory systems, allowing RO waste to become a silent but potent contributor to rising uranium levels.
About Dr. Ajai Kumar Sonkar
Dr. Ajai Kumar Sonkar is a Padma Shri awardee, internationally recognized scientist, and pioneer in marine biotechnology and water research. His work spans environmental microbiology, groundwater chemistry, and sustainable water purification systems.