Effect of short time low temperature thermal pretreatment on sludge anaerobic digestion and correlation analysis

Abstract:

The effect of thermal pretreatment with temperature between 70 and 120℃ and last for 20min on sludge organic matter solubilization, heavy metal release and anaerobic digestion was investigated. Flocs as well as cells were broken down and organic matter was released to liquid phase. Solubilisation of properties such as COD, carbohydrate, protein, DNA and ammonia all increased with temperature below 110 ◦C and experienced a significant jump at 100◦C .However, solubilisation of major organic compounds decreased at 120◦C. Cells of microorganism were broken down at 100◦C. The concentrations of heavy metals in the soluble phase increase with temperature. But no remarkable increase was observed for heavy metal release. VS removal and biogas production were investigated to evaluate the effect of thermal pretreatment on efficiency of anaerobic digestion. Both the two characteristics reached peak at 110◦C. Correlation matrices of biogas production per VS eliminated and VS removal rate with SCOD, soluble protein and soluble carbohydrates were explored to determine the influence of these selected variables on anaerobic digestion. Then the influence of soluble protein and soluble carbohydrates on biogas production per VS is illustrated by the stepwise linear regression equations.

Key words:Low temperature thermal pretreatment; Solubilisation; Waste activated sludge; Anaerobic digestion