Reduction of excess sludge production in sequencing batch reactor (SBR) by lysis–cryptic growth using homogenization disruption

A lysis–cryptic growth system, which combined high-pressure-homogenization (HPH) for sludge disruption, was proposed to reduce excess sludge production in SBR. Experimental data was analyzed with the aid of response surface models to determine the optimal HPH disruption pressure, which was 70 MPa. By combining a 5.4 m3/d pilot SBR with HPH disruption, the new system achieved a 42.4% sludge reduction rate over a 75 days operation. Based on measurement of oxygen uptake rate and activity of the dehydrogenase, the lysis–cryptic growth system resulted in negligible change of the sludge activity. However, an increase of 0.04 mg/L of total-phosphorus (TP) and 2.40 mg/L suspended-solids (SS) was observed in the effluent due to the process of lysis–cryptic growth. Except for above listed points, the new system demonstrated improved sludge reduction performance while the direct cost of pilot SBR lysis–cryptic growth was only 0.177 US dollar per kilogram (dry sludge) according to estimation.