Characterization of activated sludge settling properties with a sludge collapse-acceleration stage

[EN] The sedimentability of the activated sludge can be affected by the presence of a large variety of coagulants and polymers from a previous physical-chemical process. In this paper, the activated sludge settling process in industrial wastewater treatment plants where the sludge does not settle in a conventional way is studied. The two observed constant hindered settling velocity stages and the instant the intermediate sludge acceleration period occurs are described. A variation of the Richardson and Zaki model is used to characterize the two stages of constant settling velocity. The concentration of suspended solids, where a sudden decrease of hindered settling velocity was observed, is calculated. Finally, a new hypothesis to explain the processes triggering the collapse of the initial homogeneous sludge structure and the existence of an acceleration period is formulated. Asensi Dasí, EJ.; Alemany Martínez, E.; Seco Torrecillas, A.; Ferrer, J. (2019). Characterization of activated sludge settling properties with a sludge collapse-acceleration stage. Separation and Purification Technology. 209:32-41. https://doi.org/10.1016/j.seppur.2018.07.006