Abstract:
One of the most serious problems encountered in biological wastewater treatment processes is the
production of waste activated sludge (WAS). Sonication, which is an energy-intensive process, is the
most powerful sludge pre-treatment method. Due to lack of information about the combined pretreatment
methods of sonication, the combined pre-treatment methods were investigated and it was
aimed to improve the disintegration efficiency of sonication by combining sonication with alkalization
and thermal pre-treatment methods in this study. The process performances were evaluated based
on the quantities of increases in soluble chemical oxygen demand (COD), protein and carbohydrate.
The releases of soluble COD, carbohydrate and protein by the combined methods were higher than
those by sonication, alkalization and thermal pre-treatment alone. Degrees of sludge disintegration in
various options of sonication were in the following descending order: sono-alkalization >sonothermal
pre-treatment >sonication. Therefore, it was determined that combining sonication with
alkalization significantly improved the sludge disintegration and decreased the required energy to
reach the same yield by sonication. In addition, effects on sludge settleability and dewaterability and
kinetic mathematical modelling of pre-treatment performances of these methods were investigated.
It was proven that the proposed model accurately predicted the efficiencies of ultrasonic pretreatment
methods.