Background: Sewage sludge (Biosolids) is a byproduct of wastewater treatment that accumulates in large quantities. Effective STABILIZATION and disinfection of sewage sludge prior to land application are necessary to not only protect human health, but also to induce the public its benefits and safety. Currently, many wastewater treatment plants in Iran dispose great amounts of untreated sewage sludge to the environment. Objectives: The purpose of this work was to upgrade wastewater treatment plants by lime STABILIZATION of waste sludge. Materials and Methods: Lime STABILIZATION of waste sludge from Shoosh wastewater treatment plant was performed in a 10-L reactor.Microbial quality of lime-stabilized sludge was checked for 6 weeks in the reactor. During this stage, pH, FC (fecal coliforms) and viable helminthes ova density were determined and compared with sludge stabilized criteria suggested by USEPA.Results: Average number of fecal coliforms and viable helminthes ova in waste sludge were 1.65 × 1012 MPN/g of dry solids (DS) and 353 ova/4 g of dry solids, respectively. Conclusions: The results of this study showed that sewage sludge STABILIZATION with hydrated lime reduced fecal coliforms more than 99.99% and also stabilized sludge covered standards of class B of USEPA criteria.