Financial Times

Extraction of sand, clay and organic fertilizer
Gold mine in Sri Lanka’s disused irrigation tanks
By Quintus Perera
A Sri Lankan firm, helped by revolutionary technology developed by a local engineer, is de-silting the country’s clogged irrigation tanks and extracting clay, sand and organic fertilizer for productive use. Industry sources said this initiative would help ease the shortage of sand for construction, replace chemical fertilizer with organic fertilizer and utilize clay for tile and brick making.

The man behind this extraordinary concept is Nihal Wanigasekera from Kurunegala, an expert in hydrology, geology and mechanical engineering. He has worked in Central Africa and was involved in mechanized mining of gold, silver and copper. He told The Sunday Times FT that he decided to return to Sri Lanka as he felt that his knowledge and expertise was most needed here.
Ceylinco Group chairman Lalith Kotalawala has given financial backing to this project with the formation of a new company, TFC Tanks Preservation (Pvt) Ltd. The directors of the company are Wanigasekera, Suranimala Diyabalanage and Commodore Ajith Boyagoda with Sudath Munasinghe as Director/General Manager.

The project aims to produce 100 tons of fertilizer and 1,000 cubes of sand per day while also churning out a substantial amount of clay. Once fully operative, the company is expected to sharply raise production, increasing sand alone by up to 5,000 cubes per day.

One of Wanigasekera’s novel creations already in operation is technology to extract gems with several machines now in operation in gem mining areas, a project that was reported earlier by this newspaper. An important feature of the desilting project planned to cover the entire country is that the required giant machines are turned out at a workshop maintained by Wanigasekera at Ibbagamuwa, Kurunegala.

The usual practice in the past is for the government to use its own funds to de-silt the country’s tanks and that has been a slow process. Under the tie-up with TFC, the government gets royalties which is beneficial to both parties and a boost to the country’s economy.

Most of Sri Lanka’s tanks are covered with silt that has been accumulated over the years and absorbs 2/3rds of its capacity. Previous methods of desilting have been to empty the water before desilting unlike the new technology where water remains while the silt is removed.

In a pilot project, 14,000 acres of the Bathalagoda tank in the Kurunegala district were selected and work has got underway. From Bathalagoda alone it is estimated that a large quantity of sand, around one million cubes could be obtained. The daily national requirement of sand is about 10,000 cubes.
Sand from the tank is washed and graded.

The ex-site price of a cube of sand is Rs 2,500 while the current market price in Colombo is Rs 4,500. Once the project encompasses the entire country, chemical fertilizer could be replaced with organic fertilizer while sand would be sold at Rs 2,000 per cube.

Bathalagoda serves 12,000 acres of paddy fields and if a 300 acre-feet of silt and soil is removed and replaced with water an additional 1.5 million bushels of paddy could be grown. Two giant processing machines have been in operation at the Bathalagoda tank in the past three months. Wanigasekera said that they soon hope to work six machines there.

“These machines are carefully designed and modified to suit precise conditions. Machines that are fitted in one location would be different from another as the silt condition and the composition of different substances would also differ,” he said.

Giant suckers are dropped into the tank bed and the silt is passed through stones and a sand, humus and clay separation machine that is installed on the banks of the tank. The silt is pumped into the machine, thoroughly mixed and passed through screw pumps that separate sand, humus and clay. The separated sand is then carried through a conveyor belt and straightaway loaded onto trucks.

The humus also passes through another machine which then gets mixed with a chemical, is turned into fertilizer and sent to the factory for packing and labelling. The fertilizer is in liquid as well as in solid form. Officials said profits from the project would be utilized to improve infrastructure facilities such as roads, electricity, water and sanitation and provide jobs for people in the area. A total of Rs 200 million has been invested with plans for 10 more projects to cover the whole country.

The project is carried out under the supervision of the Irrigation Department, Geological Survey & Mining Bureau and the Central Environmental Authority.
Wanigasekera said, “The most important factor in the case of desilting tanks is not to disturb the hard pan (bottom). We ensure the preservation of the hard pan and also unlike all other processes where the desilting is done after releasing the water, we do the desilting while the water is the tank and therefore our process will not interfere with the water use by the farmers.”

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