Design and optimization of a semi‐industrial cavitation device for a pretreatment of an anaerobic digestion treatment of excess sludge and pig slurry

Abstract

The use of hydrodynamic cavitation (HC) as a wastewater treatment and anaerobic digestion pretreatment is a well-known process. However, most of the experiments have been done at laboratory scale and using a low concentration of total solids in the sludge treated. In this study, the waste-activated sludge has been mixed with pig slurry with the aim of treating two wastes rich in nutrients and organic matter. The HC has been studied not only at laboratory scale but also at industrial scale (up to 500L), using a novel rotating device consisting of a rotor with multiple teeth that rotate inside a grooved stator. The effectiveness of the process has been calculated using the disintegration degree (DD) and analyzing the volatile fatty acids, while the energy efficiency has been determined with specific energy of the sludge solubilization (SESCOD ) and the specific energy. Results show that both the SESCOD and the specific energy decrease when the cavitation process is scaled from laboratory scale to industrial scale. Specifically, SESCOD decreases from 2.71×102 to 0.16×102 kJ/gSCOD and specific energy decreases from 3.58×104 to 2.85×103 kJ/kgTS while DD values show reasonable values up to 17%. PRACTITIONER POINTS: A new industrial hydrodynamic cavitation device has been developed to treat industrial wastewater without chemical additives A volume up to 500L has been treated at industrial scale experiments. Sludge with 7% of total solids content was satisfactorily disintegrated. The process scale-up lead to an energy efficiency enhancement.