Evaluation of ultimate biochemical carbon separation technology based on ultra-short sludge retention time activated sludge system

Abstract

The ultra-short sludge retention time (SRT) activated sludge (USSAS) process (SRT≤4 d) can achieve efficient carbon separation and has great potential for achieving energy savings and resource recovery. Following the principles of system stabilization, organics separation, organics recovery and organics resourcing, in the present study, the effects of different SRTs (0.5, 1, 2, 3 and 4 d) and hydraulic retention times (HRTs, 1, 1.5, 2, 3 and 4 h) on the stability, adsorption capacity and resource recovery potential of the USSAS system were investigated, and biochemical carbon separation mechanisms were summarized. The results showed that the organic component content of the USSAS system was greater than that of conventional activated sludge (CAS) system, but the sludge settling performance of the sludge was poor, and the boundary conditions for stable operation were SRT= 2 d and HRT= 2 h. Once the boundary conditions were breached, the system showed potential risks of bulking. The USSAS system exhibited high organic matter separation capacity and good adsorption performance, while the carbon recovery potential showed that the carbon was bio-captured more than it was mineralized and that microbial degradation of organic matter was limited. The results of resource potential studies showed that the polyhydroxyalkanoate (PHA) content and sludge calorific value in the USSAS system were greater than those in the CAS, indicating that the USSAS system offers high resource utilization potential.