Rise in Hooghly sludge threatens safe drinking water supply to Kolkata

KOLKATA: The sharp increase in sludge in the Hooghly water is threatening the operations at three major treatment plants that supply water to households in Kolkata.
The century-old plant located at Palta, 22km from Kolkata, which caters to two-third of the city’s population, is the worst-hit by the sudden rise in turbidity or suspended particles in the water from the Hooghly.
Going by records at Palta Waterworks, the turbidity level has shot up nearly four times from the usual 700 Nephelometric Turbidity Unit (NTU) during September to 2,500 NTU on Saturday night.
“We were shocked to see the turbidity level and initially, we thought it was due to some isolated incident upstream. But it has remained static since then,” said a KMC water supply department official.
The suspended particles in such high volume have threatened the functioning of water treatment units at Palta. The plant engineers are apprehensive about the damage to the machines in the sedimentation tank zone. According to a KMC engineer, if any machine develops a snag, it will be difficult for the civic body to supply safe drinking water to large parts of the city.
“Several machines work to ensure proper filtration of the water. We are being extremely cautious and are trying to protect the machines. If there is a breakdown, it will lead to a water crisis in the city,” said a civic official.
The slow sand filtration bed at Palta water treatment plant has proved to be a saviour in this hour of crisis. “It is due to this slow sand bed that we have been able to keep our plant operational. This bed is actually helping in the absorption of the high volume of sludge and is keeping our plant operational,” said the civic official. Besides, plant engineers are using huge quantities of alum as a coagulant to make the water safe for drinking.
The exercise of caution has, however, slowed down the filtration process and reduced water supply to stretches of north and central Kolkata. Similarly, the KMC engineers at Garden Reach water treatment plant and Dhapa plant are working overtime to supply safe drinking water to large parts of south Kolkata and EM Bypass.
The chairman of the KMC board of administrators Firhad Hakim on Tuesday assured citizens that the civic body engineers were working overtime to supply safe drinking water to the residents of the city.
Hakim expressed hope that the situation would become normal in another three days.