Ultrasonic treatment enhances sludge disintegration and degradation in a photosynthetic bacteria‐bioelectrochemical system

Abstract Excess sludge contains a large amount of organic matter, most of which is present in the form of bacteria and extracellular polymeric substances. In this study, a photosynthetic bioelectrochemical system ( BES ) combined with ultrasonic treatment ( UT ) was investigated to mineralize sludge. The sludge was disintegrated by the UT , and the supernatant separated from the treated sludge was further degraded through a bioelectrochemical system containing photosynthetic bacteria ( PSB ‐ BES ). The UT efficiency was enhanced by supernatant separation. The PSB ‐ BES method effectively improved the degradation of the soluble chemical oxygen demand ( SCOD ) from the supernatant. The SCOD and protein removal were increased 1.4 and 1.5 times, respectively, compared to BES without PSB . In addition, the effects of several key operating factors including illumination, voltage, and temperature were systematically investigated. This study provides a basis for further development of sludge mineralization processes. Practitioner points The sludge was disintegrated by the ultrasound treatment. The supernatant separated from treated sludge was further degraded by a bioelectrochemical system combined with photosynthetic bacteria. The ultrasonic treatment efficiency was enhanced by supernatant separation. The PSB‐BES method effectively improved the soluble chemical oxygen demand (SCOD) degradation from the supernatant. The effects of several key operating factors including light (dark–photo), voltage, and temperature were systematically investigated.