Effects and modelling of ultrasonic waste‐activated sludge disintegration

Abstract

Sonication is a well-known sludge pretreatment technique with the advantages of simple operation and high efficiency. However, it is an energy-intensive process. Hence, it is very important to predetermine its sludge disintegration efficiency at varying pretreatment conditions in order to minimize the ultrasonic energy consumption. In this study, it was found that the ultrasonic sludge disintegration occurred in two stages: rapid and subsequent slow disintegration stages. For this reason, it was aimed to develop a simple and accurate mathematical model to describe the two-stage sludge disintegration as a function of pretreatment conditions. Sludge concentration and ultrasonic density along with sonication period were involved in this model as independent variables. It was determined that the mathematical model can predict accurately the degree of sludge disintegration. Thus, the proposed model was seen to be very useful for evaluating the disintegration efficiency and/or for process design using the operating parameters under different conditions.

Low intensity surplus activated sludge pretreatment before anaerobic digestion

“…Li et al (2008) confi rmed high effectiveness of alkaline conditioning by sodium hydroxide (dosage of 0.2 g/g VS), aided by ultrasonic fi eld (ultrasonic pre-treatment). Şahinkaya and Sevimli (2013) achieved sludge disintegration of 24.4% after using only NaOH as a disintegrating agent. Kim et al (2003) Similar results were obtained by Wonglertarak and Wichitsathian (2014), They concluded that the SCOD increased when pH values were increased.…”

Simulating ultrasonic activated sludge disintegration for excess sludge reduction in SBR systems

“…Only few studies focus on developing mathematical models for ultrasonic treatment (e.g., Li et al, 2010;Sahinkaya and Sevimli, 2012) and if they do, they do not consider the ultrasonic treatment in combination with the conventional activated sludge processes since their main interest is optimizing and improving the efficiency of the ultrasonic activated sludge treatment prior to sludge anaerobic digestion.…”

Ultrasonic pretreatment for Enhancing Sludge disintegration and Resource Utilization: A mini review

“…However, when the ultrasonic density increased to 1.3 -2.5 W/mL, the CST rate increased rapidly, leading to a decrease in sludge dewaterability and solids content. Serkan et al conducted experiments on sludge dewatering characteristics and found that the optimal ultrasonic density was 0.75 -1 W/mL (specific energy consumption of 60000 kJ/kg TS) [7]. When the ultrasonic density increased above 1.2 W/mL or below 0.5 W/mL, the CST level increased significantly and the sludge dewaterability decreased.…”