Initially, 15,000 litres will be treated a day for which a cost effective technology has been developed.

The State government has on Wednesday given in-principle approval to the district administration’s proposal to treat the water accumulated in abandoned stone quarries and distribute it as drinking water using the reverse osmosis technology.

A meeting to discuss the proposal in detail will be held towards the end of this month, District Collector P.I. Sheikh Pareed told The Hindu after meeting Revenue Minister Adoor Prakash. Fund for the project has been sought from the drought relief fund.

The district administration has drawn up a proposal worth Rs. 33 lakh for launching the project on a pilot basis at a quarry at Ambalappara near Kakkanad. Initially, 15,000 litres will be treated a day for which a cost effective technology has been developed. The project will be expanded to cover more abandoned stone quarries if found successful.

Mr. Pareed said he had got the water sample from the Ambalappara quarry tested by a private agency entrusted with developing the technology, and the Water Authority. He said the idea was to construct a small retaining wall around the quarry to conserve it like a rainwater harvesting centre. The agency selected will install the machinery for the treatment process. “There is also an idea to develop a compact mobile treatment unit,” Mr. Pareed said.

However, V.N. Sivasankara Pillai, former director at the School of Environment Studies, Cochin University of Science and Technology, feels that the proposal is “not as simple as it looks.”

He said while the water collected in such quarries could be used for construction and similar purposes, its treatment for drinking water could prove expensive. “Water in abandoned quarries may have got collected over a period of time, leading to gradual growth of algae. Separating algae calls for an advanced and expensive treatment process different from the treatment methods adopted by agencies like the Water Authority to purify river water,” he said.

Mr. Pillai said water collected in quarries needs to be recharged to maintain the water balance. Recharging through rain is inadequate as a good portion of water is lost to evaporation. In such circumstances, water will have to be pumped in from surrounding areas. “Since there is thick population around these quarries, pumping in water from outside would not be safe,” he said.

Mr. Pillai recollected that a similar proposal to treat water from an abandoned quarry in Vennala by the corporation was dropped after the rehabilitation of families in the nearby areas became a problem.

District officer at the Groundwater Department V. Prasannan said there were two ways in which abandoned quarries can be utilized to meet the water needs. “The already collected water should be pumped out and the quarries should be completely cleaned after which a retaining wall should be constructed around them to prevent the inflow of polluted water from adjoining areas. In that way, quarries can be used as rainwater storage tanks,” he said.

If the inflow of water from surrounding areas is facilitated then the water should be purified before usage. Since the water is free of salinity its treatment should be cost effective,” Mr. Prasannan said. Either way he doubts whether there will be enough water for round-the-clock pumping due to three factors – indiscriminate usage of water, the usual 100-day period without rain in the State annually, and loss of water to evaporation.

K.K. Sajeevan, district officer at the Mining and Geology Department felt that proposal was feasible considering the abundance of unused quarries in the district.

“Once a quarry is fully explored and turns waterlogged, a contact is established with groundwater. Naturally, the water level rises sustaining enough water even during the summer,” he said.