System and method for treating wastewater and resulting primary and biological sludge

摘要

A method of treating primary sludge and biological sludge produced by a wastewater system is disclosed. A portion of the biological sludge is thermally hydrolysed 32. The method entails cooling the thermally hydrolysed biological sludge by mixing primary sludge with the thermally hydrolysed biological sludge. By mixing the primary sludge and the thermally hydrolysed biological sludge, sensible heat is transferred from the thermally hydrolysed biological sludge to the primary sludge which raises the temperature of the primary sludge and lowers the temperature of the thermally hydrolysed biological sludge. Thereafter, the mixed sludge is directed through a pasteurisation process 34 and then to an anaerobic digester 36. In one aspect, the primary sludge and the thermally hydrolysed biological sludge are mixed in a pressurised structure 38 at a pressure greater than atmospheric pressure. In a further aspect, the thermally hydrolysed biological sludge in the pressurised structure is not cooled by heat exchangers.