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

► A 400 m3/d lysis-cryptic growth system was operated for excess sludge reduction. ► Observed biomass yield of the pilot-scale system was 0.27 kg VSS/kg COD consumed. ► A sludge reduction efficiency of 56.5% could be achieved. ► The operation cost was $ 0.186/m3 wastewater and it was reduced by 11.4%. ► Water quality of effluent was satisfactory and sludge lysis system performed well.