Most of the dehydrated sludge processed from a wastewater treatment plant is only about 25% dry. This means that for every ton of dry sludge there are three tons of water with the corresponding repercussion on hauling and dumping expenses.

At the wastewater treatment plant in Valladolid, a thermal drying system was installed using direct convection that results in 90% dryness. This is a great improvement for environmental reasons and resulted in savings in hauling and dumping costs. To cover the additional power costs and make this investment economically feasible, a cogeneration plant run on biogas powered motors was installed to produce electricity using the heat from the combustion gasses for the drying process.

DRACE medioambiente pioneered this process for which it received the IBERDROLA 1999 National Award for Technological Innovation in Water Management and Use.