The one-stage autothermal thermophilic aerobic digestion for sewage sludge treatment

One-stage autothermal thermophilic aerobic digestion (ATAD) is promising for sewage sludge stabilization in small- and medium-sized wastewater treatment plants (WWTPs). A one-stage ATAD large-scale digester was designed with effective volume 10 m(3), and batch-mode operation was conducted on sewage sludge to evaluate the effectiveness of the one-stage ATAD process and analyze the sludge stabilization under thermophilic aerobic condition. Autothermal thermophilic digestion could be achieved in the one-stage ATAD system at temperatures up to 61.5 degrees C. VS removal was up to 38.5% at 288h and 41.2% at 360 h. The soluble chemical oxidation demand (SCOD) and ammonia nitrogen (NH4+-N) increased rapidly before 144h, and then decreased. The supernatant total nitrogen (STN) reached the highest concentration of 2565 mg L-1 at 72 h and then decreased moderately. At the end of digestion, the concentrations of SCOD, STN, and NH4+-N were still up to 10,616, 1944, and 1170 mg L-1, respectively. The ATAD sludge had poor dewatering characteristics, but it could achieve efficient pathogen inactivation, making the digested sludge more valuable for land application. (C) 2011 Elsevier B.V. All rights reserved.