This study describes multiple-hearth incineration investigations conducted at the Water Pollution Control Plant (WPCP) in Hamilton, Ontario. The objectives of the study were to determine, under controlled conditions, the fate of selected heavy metals present in the sludge and to determine optimal operating conditions to minimize clinker formation and residual organic content of the ash. A factorial experimental design which included four levels of temperature, three levels of throughput rate and three levels of centre shaft speed was conducted.
Within the constraints of the experiment, zinc, iron, magnesium, aluminum, nickel, copper, calcium, chromium, lead, silica and phosphorus proved to be conservative and remained in the ash. Varying proportions of cadmium, mercury and arsenic were classified to the gas stream. The destruction of total carbon was essentially complete under all test conditions, with the minimum level being 98.7%. Clinker formation was observed only under conditions of high temperature combined with a long furnace residence time.