17 September 2010
By Umesh Isalkar
Despite loud promises that these gadgets suck out disease–causing bugs from drinking water, most purifiers sold across India do not completely eliminate water–borne viruses like Hepatitis E, says the Pune–based National Institute of Virology (NIV).
A study by the government–funded body that conducts research on communicable diseases and viruses evaluated eight domestic water purifiers. It found only two–one equipped with a hollow fibre membrane and the other with a gravity–fed filter–could completely remove the viruses.
The study also found no standards existed for virological evaluation of water purification devices in India and called for well–defined parameters. The NIV relied on the US Environment Protection Agency’s guide, standard and protocol benchmark for testing microbial purifiers. It was conducted by head of the NIV’s hepatitis division, Vidya Arankalle, and scientist Vikram Verma.
- The purifiers tested included those using carbon filters, ceramic candle filters, sediment filters, iodine resin gravity filters, polyester filters, ultraviolet irradiation, reverse osmosis and hollow fibre membrane filters
- Central Bureau of Health Intelligence figures show that the incidence of diarrhoea, enteric fever, viral hepatitis and cholera has been the same over the past decade
Pune: The Indian Council of Medical Research (ICMR) and the ministry of health and family welfare, government of India, extended financial support to the study of water purifiers conducted by the NIV scientists.
The purifiers that were tested included those using activated carbon filters, ceramic candle filters, sediment filters, iodine resin gravity filters, polyster filters, ultraviolet irradiation, reverse osmosis and hollow fibre membrane filters. These features were either employed singly or in a combination. The purifiers were evaluated using Hepatitis E virus (HEV) as a model. The viral log reduction value (LRV)–the capacity to eliminate viruses–was calculated for each purifier.
"The log reduction value (LRV) is the difference in the amount of virus particles between raw water (spiked with HEV) and purified water," said Verma. The USEPA criterion for reduction of viruses is 4 log. This means that if there are 10,000 particles in the water that is going to be processed, there should be no viral particles in the water after purification.
"We evaluated one purifier of each brand. The batch–tobatch or unit–to–unit variation was not evaluated. However, even with this limitation, the results indicated that six of the eight purifiers tested did not conform to USEPA standards. The purifiers did not remove the viruses completely," said Arankalle. "We need a national policy for the evaluation of such purifiers by the regulatory authorities and at the factory level. This will ensure availability of quality domestic water purifiers,"she said.
According to Arankalle, viruses remain longer than bacteria in water. "In India, the standard to evaluate the microbial performance of a purifier is for the device to provide bacteriafree water from water in which a fixed amount of Escherichia coli bacteria has been added. However, it is unsafe to rely only on bacteriological standards to assess the virological quality of water. Virological standards should be established immediately," she said.
The Bureau of Indian Standards (BIS), which looks into the standardization, certification and quality of purifiers, has already appointed a commitee to look into the NIV report.
"The first sectional meeting on water purification equipment was held at the BIS on April 28 this year. The committee discussed the nitty–gritty of formulating a regulation regarding the quality of water purifiers," said Pawan Labhshetwar, who is heading the committee formed by the BIS on water purification equipment.