Cocoamidopropyl Betaine Dosage Dependence of Short-Time Aerobic Digestion for Waste-Activated Sludge Reduction

Cocoamidopropyl betaine (CAPB) has newly been found to improve the reduction of waste-activated sludge (WAS) by a short-time aerobic digestion (STAD) process. This work systematically discloses the influences of CAPB dosage on the reduction of WAS by the STAD process. Results showed that CAPB lower than 0.10 g/g of TSS (total suspended solids) mainly increase the organic substances release and low-molecular weight (MW) fractions proportion via its surfactant action, leading to the increased concentration of soluble biopolymers. The concentration of soluble PO43--P and NH4+-N increased during the biopolymers release, but gradually decreased in the later stage. Moreover, the specific oxygen uptake rate (SOUR) of digested sludge (denoted as aerobic microorganisms activity) was increased, resulting in the increased biodegradation rate of WAS chemical oxygen demand (k(COD,WAS)). A higher amount of CAPB (>0.10 g/g of TSS) led to cell lysis and intracellular polymeric substances (IPS) release, which led to an additional increase of PO43--P, NH4+-N, soluble organic matters, and its low MW fractions; all these fractions gradually decreased later. Nevertheless, cell lysis reduces both pH value and SOUR, which caused the decrease of CAPB biodegradation rate and k(COD,WAS). This study lays the foundation for improving the reduction efficiency of WAS in the STAD system by optimizing surfactant dose.