While probing the reasons for water contamination at the city's reservoirs, an audit team from the National Environmental Engineering Research Institute (NEERI) has found that the chlorination system used at the reservoirs has been giving erroneously high chlorine level readings. This anomaly could lead to serious consequences, if not corrected in time.
The reservoirs are the last place where the water can be purified water before it reaches your taps.
The Brihanmumbai Municipal Corporation (BMC) uses chlorine comparators to check chlorine levels. In this method, an Ortho-toluidine solution (OT) is mixed with the water sample. The level of chlorine in the water is then determined through a colour code test. Many officials admit privately that this method is rudimentary.
NEERI's audit team has found that the method has been throwing up erroneously high readings of chlorine. For instance, two samples were collected by NEERI at the Bandra outlet of the Pali Hill reservoir on September 21. The sample tested with the OT solution displayed a chlorine level between 1.75 and 2 mg/l. In comparison, the level in the sample tested with a DPD solution was found to be between 0.7 and 1 mg/l.
A senior civic official told HT, "This high estimation of chlorine is a cause for concern. At many places, the level through our tests was shown to be as low as 1 mg/l. This new revelation could mean that such samples had hardly any chlorine, making the water very vulnerable to contamination."
Dhaval Desai from the Observer Research Foundation said the findings need to be taken seriously. "The issue of high estimation needs to be verified thoroughly, since it concerns the health of the citizens."
Additional municipal commissioner Rajiv Jalota, in-charge of water supply, agreed. "The NEERI report has pointed this out to us. Although the OT solution we employ is a standard solution in such tests, we will get to the bottom of this and check what can be done to better this."