Sludge retention time effects on recovery of soluble organic matters via polyhydroxyalkanoate storage in contact stabilization process under feast/famine regime

BACKGROUND Contact stabilization (CS) can be used to capture organic matters from wastewater. However, CS is less efficient in capturing soluble organic matters (SOMs). Recovery of SOMs is required to minimize carbon emission and to maximize organic recovery from wastewater. RESULTS SOMs were recovered by applying a feast/famine (F/F) regime in a CS process. Sludge retention time (SRT) was found to regulate the recovery efficiency of SOMs. At a SRT of 4 d, 44.7% of the removed soluble chemical oxygen demand (SCOD) in wastewater was recovered and stored into intracellular polyhydroxyalkanoates (PHA), leading to 12.8% decrease of CO2 emission in comparison with the conventional activated sludge process. The storage of PHA in waste sludge harvested at a SRT of 4 d significantly increased the methane yield (187.3 +/- 5.9 mL (g VSS)(-1)). The dominant bacteria performing SOM recovery in CS belonged to the genera Tessaracoccus, norank_f__Caldilineaceacea, unclassified_f__Microbacteriaceae and Flavobacterium. CONCLUSIONS The study demonstrated that applying F/F regime in a CS process can recover SOMs via PHA storage. The regulation of SRT can enhance SCOD recovery. The study provides a solution to enhance SOM recovery from wastewater instead of being oxidized into CO2. (c) 2022 Society of Chemical Industry (SCI).