A team of researchers at the National Institute CSIR-National Institute for Interdisciplinary Science and Technology (NIIST) here has developed a process (patent filed) to address the issue of perchlorate contamination of water sources in the country.
Led by Krishnakumar B, Senior Principal Scientist in the Environmental Technology Division at the CSIR-NIIST, Thiruvananthapuram, the team is implementing the technology at a contaminated site in Keezhmad panchayat in Aluva in Ernakulam district.
Jal Jeevan Mission funds
Fully funded by the Jal Jeevan Mission, Ministry of Jal Shakti, Government of India, the project oversees purging of the perchlorate contaminated water from one of the abandoned (closed) wells to be treated to a potable quality level, an official spokesman said.
The demonstration plant can generate around 2,000 litres of potable water and will be operated at the site initially for a period of three months. The capital cost is ₹3 lakh, and the cost of production of pure water at 20 paise per litre (including operator charge).
Being a strong oxidising agent, perchlorate salts are widely used in the strategic sector, space research and development units and many industries including crackers and matchbox making.
First reported event
Severe contamination of groundwater, as well as surface water sources, has been observed around places where perchlorate salts are handled in bulk. The public health concern arises from perchlorate’s penchant to interfere with the normal functioning of the thyroid gland.
Studies conducted by CSIR-NIIST from 2009 to 2015 had revealed high levels of perchlorate in well water samples around the Ammonium Perchlorate Experimental plant in Aluva. It was the first report of high levels of perchlorate in drinking water samples in the country.
Keezhmad and Edathala were the affected panchayats. Perchlorate level of up to 45,000 micrograms per litre was observed in the community wells in the Kulakkad region of Keezhmad panchayat, the spokesman said.
Wells decommissioned
Subsequent studies by the State Health Department revealed elevated TSH levels (indicating hypothyroidism) among those who took perchlorate contaminated well water in Keezhmad. Three of the highly contaminated community wells there had to be decommissioned.
Recent studies by CSIR-NIIST (July, 2021) found that even after 10 years, the level of perchlorate in the closed community wells was assessed at 9,090- to 1,490 micrograms per litre, several magnitudes higher than the existing WHO guidelines.
The perchlorate anion is highly stable in water and is difficult to remove using conventional water treatment technologies. CSIR-NIIST’s hybrid process (bio-physical) for treating perchlorate contaminated water is now emerging as a sustainable solution to the issue.
UF, RO processes
In this process, toxic perchlorate contaminated water will be initially treated in a bio-reactor with a specially developed bacterial system that detoxifies (degrade) the toxic perchlorate into non-toxic chloride and oxygen, the spokesman explained.
The bioreactor-treated water will be passed through a combination of custom-designed ultrafiltration (UF) and reverse osmosis (RO) units for removing any residual contaminants. The rejects from UF and RO are also treated in the bioreactor leaving hardly any discharge.
The installation and operation of the treatment plant will ensure support and co-operation of the Keezhmad grama panchayat and residents of Kulakkad colony, the spokesman pointed out.
Decontaminating soil
Research at CSIR-NIIST on perchlorate assessment and remediation for the last 12 years has also developed a process for decontaminating soil and other matrices. Contaminated soil at perchlorate bulk handling sites also is a major contributor to groundwater contamination.
NIIST has developed an ex-situ remediation approach that has many advantages compared to existing methods practised abroad. Perchlorate handling sites can adopt these remedial approaches to avoid environmental contamination and a public health hazard.