Water better than WHO would want it

RO for the right reason

Contamination is quite another issue

NEW DELHI: Keerat Singh of Paschim Vihar has installed an advanced water purification system in his home, the local wisdom being that tap water requires reverse osmosis ( RO ) filtration for it to be pure enough for drinking. Like his neighbours, Singh doesn’t know that the water supplied by Delhi Jal Board to the area has a total dissolved solids ( TDS ) count of around 85mg/l, an excellent range for raw water supply even by global standards.The RO water purifiers Singh’s family uses reduces TDS to 29mg/litre, removing not only essential minerals, but also wasting a large volume of water in doing so.DJB has long claimed that the water it supplies to residences in Delhi has TDS levels well below the Bureau of Indian Standards ceiling of 500 mg/l. The water utility has gone so far as to claim that no RO filters are required in any home to rid the water of unwanted solids.The negative perceptions about piped water have, however, left residents reluctant to accept DJB’s claims about the quality of its supply. TOI, equipped with TDS meters, visited 60 residential colonies with varying geographies and income levels to assess DJB’s claims. The findings showed an over whelming majority of the colonies getting water with dissolved solids in the 100-200 mg/l range — a level even better than the 300 mg/l prescribed by World Health Organization, irrespective of the character of the colony. For example, RK Puram Sector-3, a government colony, gets water with 80-90mg/l TDS, but Ravidas Camp, a JJ cluster nearby, too has water of similar quality at 90-98mg/L.Moderate to high TDS in water not only changes the taste of water, but also poses health hazards. Tuhin Banerji, water expert at NEERI, confirmed that RO filtration was necessary to remove these solids, especially if underground water was used for drinking purposes. However, studies by the Massachusetts Institute of Technology have established that most RO purification systems discard 70-75% of the raw water fed to them. This rejected water can be used for some household purposes other than drinking or gardening, but is thrown away.Given the wastage of precious water, the National Green Tribunal asked the central government on May 28 to formulate a policy to ban the use of RO filters in areas where TDS levels in water was below 500mg/l.In TOI’s tests, locations like Rohini’s Sectors 8 and 14, Mayur Vihar Phases I and III, Chittaranjan Park, Trilokpuri, Khureji Khas, Rajouri Garden and Tagore Garden showed TDS values of 80-90 mg/l, meaning an RO filter would be ill-advised in homes there. In some cases, there were inconsistencies in readings within the same colony. While TU block in Pitampura received water with 75-80 mg/l TDS, the SU block a few streets away had water with TDS in the 310-330mg/l range. A DJB official explained that the entire colony did not receive water from the same source. “There are several colonies that are supplied by different plants based on proximity and the pipeline network. One colony could well be getting water from two different water treatment plants,” he said. Also, how old or well-maintained the water pipelines are can well cause two houses or apartment buildings in the same DJB area to have varying TDS counts.While tap water was generally ‘pure’ as far as dissolved solids were concerned, water extracted by borewells, as at Sarvodaya Enclave, returned results showing TDS at as high a level as 1100 mg/l. Many households, especially in south Delhi, use both piped water and borewell water with 480-1100mg/l TDS, meaning they certainly require RO systems to improve the quality of the water they use.There, however, is rising awareness about the TDS levels, especially among households planning to install a water filtration system. Renu Kaur, for instance, installed a ultra-violet purification system rather than an RO device in her J Block Rajouri Garden home after finding that tap water there had low TDS readings. “We only found out about the TDS level in our water when we wanted to put in an RO filter. We were told the TDS here were between 80 and 90 mg/l and a UV filter was, therefore, better suited for our needs,” said Kaur. Her new UV filter, she claimed, eliminated the strange smell in the DJB supply while maintaining TDS at a healthy level of 65-70 mg/l. In some locations, like Laxmi Nagar, RO purifiers brought down TDS levels from still-safe 485mg/l to as low as 28.In west Delhi’s Sham Nagar locality in Vishnu Garden, the DJB water TOI tested was dark in colour. “We cannot use the supplied water due to the smell and colour, though RO improves the quality,” said resident Geeta Bansal, adding that the people there had to recently start using submersible pumps for water that was clearer, but with higher TDS levels of around 470 mg/l.DJB officials said the colour of water mostly changes due to contamination or corroded pipes. “We advise users to get their pipelines checked periodically to receive clean water,” said an official. DJB vice-chairman Dinesh Mohaniya asserted that the utility supplied water of “global standards” up to the ferrule points and most contamination took place beyond that. “Almost 99% of reports on contamination involve galvanised service pipelines beyond the ferrule point. These need to be replaced every 15 years,” said Mohaniya.Water at all water treatment plants were within the acceptable limits of TDS. DJB officials explained the higher TDS counts at the consumer point as being the result of blending underground water at the tail end or due to ill-maintained pipes from the ferrule point onward. “Even then, the end point TDS levels are still within the permissible range,” an official added.