Integrated control strategy for dual sludge ages in the high-concentration powder carrier bio-fluidized bed (HPB) technology: Enhancing municipal wastewater treatment efficiency.

The high-concentration powder carrier bio-fluidized bed (HPB) technology is an emerging approach that enables on-site upgrading of wastewater treatment plants (WWTPs). HPB technology promotes the formation of biofilm sludge with micron-scale composite powder carriers as the core and suspended sludge mainly composed of flocs surrounding the biofilm sludge. This study proposed a novel integrated strategy for assessing and controlling the sludge ages in suspended/bio-film activated sludge supported by micron-scale composite powder carrier. Utilizing the cyclone unit and the corresponding theoretical model, the proposed strategy effectively addresses the sludge ages contradiction between denitrifying bacteria and polyphosphate-accumulating organisms (PAOs), thereby enhancing the efficiency of municipal wastewater treatment. The sludge age of the suspended (25 d) and bio-film (99 d) sludge, calculated using the model, contribute to the simultaneous removal of nitrogen and phosphorus. Meanwhile, the model further estimates distinct contributions of suspended and bio-film sludge to chemical oxygen demand (COD) and total nitrogen (TN), which are 55% and 42% for COD, 20% and 57% for TN of suspended sludge and bio-film sludge, respectively. This suggests that the contribution of suspended sludge and bio-film sludge to COD and TN removal efficiency can be determined and controlled by the operational conditions of the cyclone unit. Additionally, the simulation values for COD, ammonia nitrogen (NH4+-N), TN and total phosphorus (TP) closely align with the actual values of WWTPs over 70 days (p < 0.001) with the correlation coefficients (R2) of 0.9809, 0.9932, 0.9825, and 0.837, respectively. These results support the theoretical foundation of HPB technology for simultaneous nitrogen and phosphorus removal in sewage treatment plants. Therefore, this model serves as a valuable tool to guide the operation, design, and carrier addition in HPB technology implementation.

Targeted clean extraction of phosphorus from waste activated sludge: From a new perspective of phosphorus occurrence states to an innovative approach through acidic cation exchange resin.

Waste activated sludge (WAS) is an important source of non-renewable phosphorus (P) recovery. Given the factor that the occurrence states of phosphorus in WAS determines its recovery efficiency, the spatial distribution and chemical speciation of phosphorus were comprehensively and simultaneously analyzed by in-situ and step-by-step extraction methods for the first time. It was confirmed that the phosphorus in solid phase of WAS could be mainly divided into three parts: polyphosphate in cells, extracellular polymeric substances (EPS)-bound P, and phosphate precipitated with metals (P-precipitates) in extracellular inorganic minerals. Among these forms, EPS-bound P (mainly orthophosphate, Ortho-P) and P-precipitates (mainly Ca-P, Fe-P, Al-P, and Mg-P) were the major forms of phosphorus in WAS, accounting for 65%-82% of total phosphorus (TP). Owing to the acid solubility of P-precipitates, acid extraction could be a potentially effective means for phosphorus recovery. However, the co-solution of metals may hinder the phosphorus recovery and the EPS-bound P cannot be recovered by acid extraction. To enhance phosphorus release from EPS and reduce metal interference, a targeted clean extraction technology using acidic cation exchange resin (ACER) was also developed. The results showed that a low dosage ACER could effectively extract EPS-bound P and P-precipitates, and the content of phosphorus in the extract exceeded 50% of TP. Compared with acid extraction, the release efficiency of TP increased by 13%-23%, and the dissolved metal content decreased by more than 90% in the extract by ACER. This was attributed to the acidification and metal capture by ACER. Finally, more than 90% of Ortho-P in the extract was recovered as calcium phosphate, which alleviated the depletion of phosphorus resources.

Occurrence State and Molecular Structure Analysis of Extracellular Proteins with Implications on the Dewaterability of Waste-Activated Sludge.

The occurrence state and molecular structure of extracellular proteins were analyzed to reveal the influencing factors on the water-holding capacities of protein-like substances in waste-activated sludge (WAS). The gelation process of extracellular proteins verified that advanced oxidation processes (AOPs) for WAS dewaterability improvement eliminated the water affinity of extracellular proteins and prevented these macromolecules from forming stable colloidal aggregates. Isobaric tags for relative and absolute quantitation proteomics identified that most of the extracellular proteins were originally derived from the intracellular part and the proteins originally located in the extracellular part were mainly membrane-associated. The main mechanism of extracellular protein transformation during AOPs could be represented by the damage of the membrane or related external encapsulating structure and the release of intracellular substances. For the selected representative extracellular proteins, the strong correlation (R2 > 0.97, p < 0.03) between the surface hydrophilicity index and α-helix percentages in the secondary structure indicated that the water affinity relied more on the spatial distribution of hydrophilic functional groups rather than the content. Destructing the secondary structure represented by the α-helix and stretching the polypeptide aggregation in the water phase through disulfide bond removal might be the key to eliminating the inhibitory effects of extracellular proteins on the interstitial water removal from WAS.