A novel approach for phosphorus recovery and no wasted sludge in enhanced biological phosphorus removal process with external COD addition.

In enhanced biological phosphorus removal (EBPR) process, phosphorus (P) in wastewater is removed via wasted sludge without actual recovery. A novel approach to realize phosphorus recovery with special external chemical oxygen demand (COD) addition in EBPR process was proposed. During the new operating approach period, it was found that (1) no phosphorus was detected in the effluent; (2) with an external addition of 10 % of influent COD amount, 79 % phosphorus in the wastewater influent was recovered; (3) without wasted sludge, the MLVSS concentration in the system increased from 2,010 to 3,400 mg/L and kept stable after day 11 during 24-day operating period. This demonstrates that the novel approach is feasible to realize phosphorus recovery with no wasted sludge discharge in EBPR process. Furthermore, this approach decouples P removal and sludge age, which may enhance the application of membrane bioreactor for P removal.

A rheological approach to analyze aerobic granular sludge.

Aerobic granular sludge is one promising biotechnology in wastewater treatment. Despite intensive researches on granular architecture and strategies to improve treatment efficiency, there are still some elusive material parameters needed to stimulate the granulation process. The main aim of this study was to evaluate aerobic granular sludge innovatively using the universal rheology methodology, in terms of processability or quality and texture. Steady shear and oscillatory measurements were performed. Basic rheological characterization showed that aerobic granular sludge was a shear-thinning Herschel-Bulkley fluid with yield pseudoplasticity. Meanwhile, granular sludge presented characterized viscoelastic behaviors in dynamic sweeps highlighting its superiority to flocculent sludge. Furthermore, a Wagner-type constitutive model incorporating a relaxation and damping function was introduced and able to describe the time-dependent and non-linear viscoelastic behaviors. This study could make a further step on predicting rheological properties, helping improve the actual sludge treatment process and the operation of sludge dewatering.

Species of phosphorus in the extracellular polymeric substances of EBPR sludge.

In this study, the species of extracellular phosphorus and their transformation during extracellular polymeric substances (EPS) extraction were explored by using (31)P nuclear magnetic resonance spectroscopy. Results show that the extraction methods had a substantial influence on the phosphorus species in the extracted EPS. Cation exchange resin method was more appropriate for extracting EPS from the enhanced biological phosphorus removal (EBPR) sludge. Orthophosphate, pyrophosphate and polyphosphate were the main species of phosphorus found to be present in the EPS, which together accounted for about 6.6-10.5% of the total phosphorus in the EBPR sludge. The high percentage of extracellular phosphorus and their diverse species might reveal a new insight into the characteristics of the phosphorus in EPS in EBPR system.