excess sludge reduction using pilot-scale lysis-cryptic growth system integrated ultrasonic/alkaline disintegration and hydrolysis/acidogenesis pretreatment

a pilot-scale lysis-cryptic growth system was built and operated continuously for excess sludge reduction. combined ultrasonic/alkaline disintegration and hydrolysis/acidogenesis were integrated into its sludge pretreatment system. continuous operation showed that the observed biomass yield and the sludge reduction efficiency of the lysis-cryptic growth system were 0.27 kg vss/kg cod consumed and 56.5%, respectively. the water quality of its effluent was satisfactory. the sludge pretreatment system performed well and its tcod removal efficiency was 7.9% which contributed a sludge reduction efficiency of 2.1%. the scod, vfa, tn, nh₄⁺–n, tp and ph in the supernatant of pretreated sludge were 1790 mg/l, 1530 mg cod/l, 261.1 mg/l, 114.0 mg/l, 93.1 mg/l and 8.69, respectively. the total operation cost of the lysis-cryptic growth system was $ 0.186/m³ wastewater, which was 11.4% less than that of conventional activated sludge (cas) system without excess sludge pretreatment.