FOR KEY TEST PARAMETERS
MS2 virus test | Microbiological test (TPC) | Pesticide (lindane) | Heavy metal (arsenic) |
MS2 virus test
A virus is a small infectious agent that replicates only inside the living cells of other organisms. Viruses can infect all types of life forms, from animals and plants to bacteria. Based on the recent requirement of drinking water specification (IS 10500), MS2 virus was considered for testing and spiked in input water. The output sample was then tested to check the virus removal efficiency of the purifiers. Most of the tested brands reduced the percentage of MS2 virus by more than 99 per cent. Brand Pure It removed it completely. Unitex reduced it by only 90 per cent, which is not desirable in output drinking water of a purifier.
Microbiological test (TPC)
The presence of bacteria and pathogenic (diseasecausing) organisms is a concern when considering the safety of drinking water. Total plate count (nonpathogenic) was checked to judge the efficiency of the purifiers in the output water. The main test to judge the microbiological efficacy was conducted in the endurance test at defined/regular intervals. Except for Pure It and Usha Brita, none of the brands completely removed the microbes from input water. However, the level of TPC was in the range of 4–18, which is not high and is nonpathogenic.
This test was conducted keeping in view the pesticides coming into various potable water sources, viz. groundwater, rainwater, streams, etc. We had noted that some brands claimed to be effective in removing pesticides. The pesticide lindane was added
in input water in 0.5 ppm concentration. Output water was tested for the residues of added pesticide. Most of the brands removed the pesticide. Bajaj purifier could remove by 8 per cent only.
Heavy metal (arsenic)
As per the national standard, toxic substances like mercury, cadmium, arsenic, cyanide, lead, chromium and nickel should not be present in drinking water. Some of the brands tested also claimed removal of heavy metals. To examine efficiency in removing heavy metals, we used arsenic as input and tested the brands for its presence in the output water. None of the brands of water purifier was able to completely remove the heavy metal used for the test – that is, arsenic.
The presence of chlorine residue in drinking water indicates that a sufficient amount of chlorine was added initially to the water to inactivate the bacteria and some viruses that cause diarrhoea, as well as to ensure that the water was protected from recontamination. The residues of chlorine must be absent in the output water of water purifiers. Chlorine of 2 ppm concentration was added in input water and output sample was collected from the purifier.
Chlorine was not detected in any of the brands. Chlorine is actually added in drinking water in order to disinfect it and prevent the transmission of waterborne diseases, but it can also be easily perceived in the taste and smell of the water and its own disinfection by-products are a matter of concern.