Application of sludge from urban wastewater treatment plants in road's embankments.

While different kinds of compost have been tested for highway revegetation, sewage sludge has only been used for agricultural purposes. In this work, its application for helping vegetation establishment on roads embankments is studied. Testing areas measuring 4x5m were constructed on a new highway embankment in an arid location. Several variables are analyzed: side slope (2); sludge dosage (4); vegetative species (4). Results are presented on growth, survival rate and germination of the plants; colonization of other species; cover crop for the plots; estimation of the erosion. The species planted manually showed satisfactory results although any variable was specially significant in this case. However, in relation to the species planted using hydroseeding, 2:1 side slope presented better results than 3:2 side slope. Using hydroseeding, the performance of different species was significantly different, thyme did not grow if sludge was not applied and the cover crop was higher in plots with 3:2 side slope than in plots with 2:1 side slope, essentially due to the presence of colonizing species. Finally, the costs of the proposed treatments are figured out, being concluded that, so much from the technical as the economic point of view, it is a viable proposal for sewage sludge management.