The aim of this study was to evaluate some advantages and potential risks of application of sewage sludge from the Municipal Wastewater Treatment Plant in Sokółka to urban soils. The sewage sludge used in the research was free of Salmonella and viable helminth ova—Ascaris sp., Trichuris sp., Toxocara sp. The study also included the determination of concentrations of Cd, Cr, Cu, Mn, Ni, Pb and Zn in soil and in the aboveground parts of lawn grasses and selected physical and chemical properties of soils fertilized with different doses of sludge. The narrow ratio of carbon to nitrogen on test areas provides conditions for rapid decomposition of the organic matter and may cause a gradual release of metals into the soil solution, thus making them more available to the plants. The bioconcentration factor of heavy metals in the plants along the main streets of Białystok is characterized by considerable local variation. Based on these results, it was found that plants absorbed small amounts of Mn, Ni and Pb, while Zn, Cr, Cu and Cd were easily consumed, which may indicate their high mobility.