The effect of free nitrous acid pretreatment on the anaerobic digestibility of thickened waste activated sludge

Sludge pretreatment technologies as an avenue to improve solids handling in a WWTP has gained attention and significant research efforts are being directed towards studying several available techniques. The use of FNA as a chemical pretreatment for the AD has shown the potential to enhance the hydrolysis stage by releasing the internal organic matter of TWAS via its biocidal action. The effect of FNA on improving the biodegradability of TWAS was investigated in this thesis. The effect of the FNA on the TWAS characteristics and the methane production in batch tests was first studied. The optimum FNA dose was determined from the batch tests based on both solubilization and methane yields and then tested in a semi-continuous flow system. As the semi-continuous flow system failed when the optimum FNA dose obtained from the batch study was used, another set of semi-continuous flow experiments were conducted using different FNA doses