Samples taken from different parts of the city testify to deteriorating quality of groundwater
Residents of the city start their day by splashing brackish water on their faces.
“The water we get in our taps from the borewells sunk in our house is brackish and is often turbid,” says S Thanalakshmi, a resident of KK Nagar. Laboratory tests conducted by Enviro Care, an organisation here, on groundwater samples taken from different parts of the city testify to the deteriorating quality of the groundwater in the city.
While the permissible limits for Total Dissolved Solids (TDS) is 2000 mg/l, according to the IS 10500:2012 standards, many areas such as Kappalur, KK Nagar, Villapuram and Avaniapuram have high levels of dissolved salts and minerals. “Most mineral water companies maintain the TDS level in the water they manufacture at 50. Any figure beyond 500 means the water is not potable” says S. Rajmohan, Managing Director of Enviro Care.
Experts attribute the deterioration in groundwater quality to scant rainfall and unsound water management practices, including excessive tapping of groundwater. Geologically, the top layer of the soil has soft rocks and there are hard rocks deeper down. Groundwater near the top layer is described as the most pure and clean.
“Owing to overexploitation of our groundwater resources, the water table has dropped. As the borewells go deeper for groundwater extraction, the quality of water deteriorates owing to the presence of dissolved minerals near the hard rocks,” says T. Velrajan from the Department of Civil Engineering of Thiagarajar College of Engineering here.
Untreated water and the letting of sewage into riverbeds have been major contributors to groundwater pollution. The daily requirement for Madurai with a population of over 15 lakh is around 202 million litres. “The city has water treating plants at Avaniapuram and Sakkimangalam. Though the plants are not fully functional, the quantity of waste water from the city which is being taken there for treatment is very low,” explains J. Kanagavalli, a project coordinator with the Dhan Foundation.
The waste water which requires treatment includes water from educational institutions, hospitals, commercial and apartment complexes. “Waste water from most of these sources is directly discharged into either the Vaigai or the numerous tanks. This polluted water percolates into the ground and affects the groundwater table,” adds Ms Kanagavalli.
Tanks near Avaniapuram are dumping sites for hazardous products which mingle with the water and slowly percolate to the groundwater table.
Partially treated waste water used for irrigating fields near the sewage treatment plants also contribute to pollution, says Professor Velrajan, adding the constant use of this water to irrigate fields subsequently affects the quality of groundwater.
Studies, however, indicate that the soil is capable of filtering the impurities before the water percolates, which is chiefly why the situation has not gone out of hand.
“But coliform levels will still be high in the water,” says a researcher referring to the bacteria commonly found in faecal matter. “That is why water in the city is not potable and shouldn’t be drunk without purification,” he cautions.
Such abysmal water quality has forced people to look for alternatives. While some buy water in cans or fill tanks at houses and offices with water bought from tankers, others install the Reverse Osmosis (RO) water purification system.
Hotels have additional water needs that can’t be met by RO plants alone. “The water we get is extremely hard. As a result, we buy a load of 12,000 litres of water,” says Suresh, a hotel employee.
Despite the presence of an underground drainage system, not all apartment complexes or institutions have properly linked their discharge lines with it. “Multi-storeyed buildings such as hospitals, schools and colleges should be compulsorily linked to the underground drainage system,” says Ms. Kanagavalli.
“More than blaming authorities for inaction, people themselves should keep a check on waste water disposal in their buildings and institutions. The pollution of tanks in the city which is ultimately affecting the groundwater quality has to be stopped,” she says.
Echoing her views, Professor Velrajan explains how irrigation channels which were used for carrying water to the fields have become sewage carriers instead. “Proper linking with the underground drainage system is necessary since the sewage routed through these channels eventually lands up in water tanks. The area around water sources where the maximum recharge has to happen should be declared a pollution-free zone,” he says.
Dilution of groundwater through effective recharge methods such as roof-water harvesting is seen as the best option to improve the water quality. “Scanty rainfall aside, effective implementation of water management techniques will not only augment the water table but also improve water quality,” explains Mr. Rajmohan.