The agronomic value of the sewage sludge of Tenerife. Physico-chemical characteristics of the refuse-sludge compost and related products

This paper evaluates the most important agronomic characteristics of the sewage sludge from the Tenerife wastewater treatment plant and the compost obtained by composting of this sludge with the organic fraction of municipal refuse. A comparative study is also carried out on several commercial products used as organic dressings on the island's agricultural soils.

From the results obtained, the direct use (after sterilization) of sewage sludge could be very interesting from the agricultural point of view. The compost obtained, because of its high total (43·6%) and oxidisable (37·3%) organic matter content, its high fertilizer elements concentration (N, 2·8%; P, 1·3%; K, 1·6%; Ca, 5·2% and Mg, 1·1%), its balanced essential elements content and moderate toxic heavy metals levels, can be considered a good organic fertilizer whose use could represent a great saving in chemical fertilizers and replace the manures formerly used, which are now almost non-existent. In addition, it could compete advantageously with the products at present on sale in the island because of its lower cost and better agronomic quality.