Evaluation of sludge from water and sewage treatment plants as a landfill cover layer

Abstract The management of sludge from water and sewage treatment plants (WTP and STP, respectively) is still a challenge due to its high complexity and high costs. In that regard, this research proposes to evaluate the potential of using sewage sludge and water sludge as cover material for landfills. The methodology involved three steps: (i) characterization of WTP sludge, STP sludge, and clay soil used in landfill cover; (ii) alkaline stabilization (CaO or Ca(OH) 2 ) to sanitize the sludge before making it a landfill cover product; and (iii) geotechnical evaluation the mixtures of WTP and/or STP sludges with CaO or Ca(OH) 2 before and after blending with natural soil. The selected material was tested in a pilot landfill cell to verify its influence in leachate quality. The results showed that it is environmentally feasible to sanitize the sludge with low lime levels. Geotechnically, the WTP and STP sludge stabilized with 5%, 10%, and 15% CaO are not suitable, but when natural soil was blended, the geotechnical behavior was similar to a natural soil used as landfill cover. The study showed that using the sludge treated as landfill cover provides environmental benefits.