Author(s): Abdullah Shanableh
Article publication date: 1996-12-01
Vol. 14 No. 3 (yearly), pp. 543-556.
134
Keywords
waste, sludge, water
Abstract
Water is a supercritical fluid at temperatures and pressures above the critical point, 374.2°C and 22.1 MPa. The unique properties of supercritical water (SCW) include complete solubility of oxygen and organic compounds, poor solubility of inorganic salts, improved mixing, enhanced mass transfer rates, and strong ability to dissolve organic solids. The recently developed supercritical water oxidation (SCWO) technology relies on the properties of SCW to create a useful and effective oxidation reaction medium. The oxidation of hazardous organic wastes and sludges can proceed to complete in SCW, and this can be achieved in a totally enclosed treatment facility. This paper described an investigation of SCWO for destruction of a highly contaminated biological sludge. The destruction of the organic contaminants was virtually complete in relatively short residence times. Above 99 percent chemical oxygen demand (COD) reduction was achieved within 5 minutes at 450°C, 15 minutes at 425°C and 25 minutes at 400°C. The process produced a clear and odorless effluent and a disposable ash with good settling characteristics. The process is applicable to a wide range of hazardous wastes and sludges and can become thermally self sustaining at low concentrations of organic wastes