Thermal hydrolysate as a carbon source for denitrification

Thermal hydrolysate is the liquid fraction (supernatant) of thermally treated wastewater sludge. The objective of the present study was to investigate the quality of thermal hydrolysate as a carbon source for denitrification. Steady state denitrification experiments in moving bed biofilm reactors were carried out. It was demonstrated that 2/3 of the COD in the thermal hydrolysate was utilised as a carbon source in the post denitrification step, with a retention time of 52 minutes. This degree of utilisation is about the same as reported for biological hydrolysate, which generally has been considered to be of better quality as a carbon source than thermal hydrolysate. The yield of soluble COD in the thermal hydrolysis process (180°C in 30 minutes) was found to be 28%. Typical COD-yields for biological hydrolysis are around 11%.