Pre-treatment of wastewater sludge before anaerobic digestion – Hygienisation, Ultrasonic treatment and Enzyme dosing
Pre-treatment of sludge before anaerobic digestion can increase methane production and degradation of organic matter. There are various pre-treatment methods for this purpose. Anaerobic digestion tests were performed for comparison of three pre-treatment methods (hygienisation, ultrasonic treatment and enzyme dosing) used
separately or in combination on biosludge and mixed sludge. COD solubilisation and methane potentials from the differently pretreated sludges were used for comparison. Pilot-scale digestion was further used for evaluation of hygienised/untreated mixed sludge in semi-continuous operation.
The results show that pre-treatment of biosludge leads to increased methane potential, especially hygienisation and ultrasonic treatment. Combining enzyme dosing with hygienisation or ultrasonication implies additional increase in methane potential while hygienisation combined with ultrasonication does not.
Increased COD solubilisation seen after pre-tretment does not always bring about an increase in methane potential. On the other hand, pre-treatment methods like ultrasonication can lead to higher methane production although the COD solubilisation is low.