The Reinhaltungverband Leoben (Styria) operates a sewage sludge composting facility since 1997, converting sewage sludge mixed with waste into compost. The sewage sludge comes from communal sources and generally meets the quality critia of compost from household refuse (BGBl. II, No. 292/2001). Occasionally, the maximum limits for chrome, nickel, and mercury are exceeded. Samples of the sewage sludge, the in- and outflowing water, the process water, as well as delivered sludges from Göss, Mautern, St. Lorenzen and Aflenz have been taken and analyzed in the time interval between May 2005 to July 2006. The heavy metals enter the sludge facility mainly in the form of particles >0,2 micrometer. A direct comparison of in- and outflow is generally not possible, since the sludge facility also absorbs and processes aggregate matter. Due to the contribution of aggregate matter, the time series analysis of the studied sewage sludge provides only limited information. It is notable that the sludge produced during spring clearly contains less chrome and nickel. During the time of the snowmelt and during a period of enhanced dust pollution in spring, the levels of chrome and nickel in the sludge raise significantly. It is supposed that snow and ice act as repositories of dust and street-gravel. Consequently, the quality of the sewage sludge in Leoben with respect to its chrome and nickel content depends on the season and on the quantity and the type of precipitation. Sporadically exceeding levels of chrome and nickel can be a result of the increased dust exposure from the heavy industry, the use of street-gravel with high chrome and nickel concentrations, or the geogenic contamination of the surroundings of Leoben. X-ray-analysis and analysis with scanning electron microscope (Herr, diploma thesis at the University of Leoben 2007) indicate that industrial dust influences the concentration of heavy metals in the sewage sludge. The study suggests that street-gravel does not contribute significantly to the heavy metal content of the sewage sludge.