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 m3, 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 °C. VS removal was up to 38.5% at 288 h and 41.2% at 360 h. The soluble chemical oxidation demand (SCOD) and ammonia nitrogen (NH4+–N) increased rapidly before 144 h, 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.

► A cylindrical one-stage ATAD digester of effective volume 10 m3 was designed.
► The digester achieved good stabilization effects as two-stage ATAD systems.
► The temperatures in one-stage ATAD system was up to 61.5 °C.
► The system achieved good pathogen inactivation and 41.2% of VS removal at 360 h.
► The results are useful for practical operation of the one-stage ATAD system.