Promoting waste activated sludge reduction by linear alkylbenzene sulfonates: Surfactant dose control extracellular polymeric substances solubilization and microbial community succession.

Short-time aerobic digestion (STAD) was proved to promote the reduction of waste activated sludge (WAS). This study systematically disclosed the influential characteristics and mechanisms of linear alkylbenzene sulfonates (LAS) dosage on the reduction of WAS in STAD system. Flow cytometer (FC) combined with SYTOX Green (SG) dye was used to differentiate extracellular polymeric substances (EPS) release and cell lysis of WAS during STAD process. LAS lower than 0.10 g/g total suspended solids (TSS) brought about EPS solubilization and the decrease of sludge floc size, and the accumulated soluble microbial products (SMP) could be biodegraded by heterotrophs. Moreover, the activity of microorganisms (denoted as specific oxygen uptake rate (SOUR)) and proportion of bacteria functional for LAS and SMP biodegradation dramatically increased, leading to a high LAS biodegradation rate (kLAS) and increased WAS biodegradation rate (kCOD, WAS). Even more LAS (> 0.10 g/g TSS) caused cell lysis, leading to the decreased kTCOD and kLAS, and therefore inhibit the reduction of WAS. High WAS reduction and LAS biodegradation rate were achieved at the LAS dosage of 0.10 g/g TSS in STAD system. This study lays the foundation for improving WAS reduction by optimizing surfactant dose in STAD system.

Simultaneously enhanced biopolymers production and sludge dewaterability of waste activated sludge by synergetic integration process of short-time aerobic digestion with cocoamidopropyl betaine and calcium oxide.

Waste activated sludge (WAS) has seriously threatened the environment safety and the public health due to its rapid growth and complex components. Simultaneously enhanced the biopolymers production and the sludge dewaterability of WAS were investigated by synergetic integration process of the short-time aerobic digestion (STAD) with cocoamidopropyl betaine (CAPB) and calcium oxide (CaO). STAD could improve the biopolymers production by biosynthesis. CAPB could further significantly enhance the biopolymers production and optimized the constituents. CaO (0.1-0.2 g/g TSS) could dramatically enhance the sludge dewaterability by forming a multi-grid skeleton in WAS, while the biopolymers production could almost remain stable. Especially, the synergetic integration process of STAD with 0.1 g CAPB/g TSS for 8 h and 0.1 g CaO/g TSS could cost-effectively enhance both the biopolymers production and the sludge dewaterability. The produced biopolymers showed strong adsorbability for heavy metals (eg, 375 mg Cu2+/g biopolymers). Accordingly, the developed novel process is of big significance for resource utilization and volume reduction of WAS.