ABSTRACT
Sludge processing accounts for approximately 30 to 40% of the capital costs and 50% of the operating costs in a typical municipal wastewater treatment plant. 1 Both primary and waste activated sludges must be concentrated and stabilized before ultimate disposal. Anaerobic digestion is the most common stabilization method. Since waste activated sludge (WAS) represents about two-thirds of the total sludge volume, any process for improving WAS digestion will significantly reduce overall wastewater treatment plant costs.
