Hydrothermal decomposition and oxidation of the organic component of municipal and industrial waste products

The main objective of this study was to assess and compare the hydrothermal decomposition and oxidation trends of three waste types containing various quantities of the basic ingredients of biosolids; proteins, lipids, hydrocarbons and fibres. The three waste types were wastewater treatment sludge, wood waste and dairy waste. The wastes contained approximately 1.3-2% total solids (TS) and 20 400-26 700 mg/1 chemical oxygen demand (COD). The experimental program consisted of hydrothermal treatment experiments conducted in a batch reaction vessel at temperatures in the range of 100-450 degreesC, oxidant (hydrogen peroxide) in the range of 0-150% of the COD, and reaction times of up to 60 min. The results confirmed that the waste composition, availability of oxidant, reaction temperature, and reaction time were the determining factors in terms of decomposition and oxidation effectiveness. The wood waste was the most difficult to decompose and thus required more aggressive treatment conditions to achieve results comparable to the other two waste types. The decomposition of the particulate organic matter and the maximum accumulation of dissolved organic decomposition by-products were achieved at 20% COD removal for the dairy waste, 40% COD removal for the sludge, and 60% TCOD removal for the wood waste. The data confirmed that the level of COD removal needed to achieve a desired level of accumulation of dissolved organic by-products could be achieved through balancing decomposition and oxidation using various combinations of the treatment conditions. (C) 2002 Elsevier Science Ltd. All rights reserved.