title: Granulation of susceptible sludge under carbon deficient conditions: A case of denitrifying sulfur conversion-associated EBPR process.
abstract: Sludge granulation has been recognized as a promising biotechnology in wastewater treatment. Whereas the granulation of susceptible sludge in particular with a very low organic loading rate (OLR) (≤0.6 kg COD/m(3)/day or ≤ 120 mg COD/g VSS/day) is a difficult task that has not been achieved in activated sludge systems yet. This study was aimed at exploring an effective strategy for sludge granulation in the recently developed Denitrifying Sulfur conversion-associated Enhanced Biological Phosphorus Removal (DS-EBPR) process using a sequencing batch pump-lift reactor. Four strategies were studied by manipulating the factors of organic loading rate (OLR), superficial upflow velocity and sludge settling time individually or collectively. Increasing both the OLR and the superficial upflow velocity effectively promoted granule formation but at the same time led to unstable and even deteriorated reactor performance. The development of granules proceeded via several stages: formation, dispersion, reformation and stabilization. Gradually increasing the superficial upflow velocity from 5.1 to 6.8 m/h and keeping the OLR at 112.4 mg COD/g VSS/day proved to be most effective strategy for accelerating granulation while simultaneously achieving stable reactor performance. Under these conditions, the granules became stable with a diameter of 375-400 μm and displayed excellent settleability. The two major microbial groups, sulfate-reducing bacteria and sulfide-oxidizing bacteria, in the microbial community of the DS-EBPR granular sludge were enriched to 17.7% and 15.8% respectively. The newly developed DS-EBPR granular system was able to achieve an almost threefold improvement in phosphorus removal efficiency and 25% reduction in the operating cycle time compared with a flocculent DS-EBPR system.
authors: Department of Civil & Environmental Engineering, Water Technology Center, Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution (Hong Kong Branch), The Hong Kong University of Science and Technology, Hong Kong, China.
authors: Gang
authors: G
authors: Guo
authors: Department of Civil & Environmental Engineering, Water Technology Center, Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution (Hong Kong Branch), The Hong Kong University of Science and Technology, Hong Kong, China; Wastewater Treatment Laboratory, FYT Graduate School, The Hong Kong University of Science and Technology, Nansha, Guangzhou, China. Electronic address: cewudi@ust.hk.
authors: Di
authors: D
authors: Wu
authors: Department of Civil & Environmental Engineering, Water Technology Center, Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution (Hong Kong Branch), The Hong Kong University of Science and Technology, Hong Kong, China. Electronic address: thao@connect.ust.hk.
authors: Tianwei
authors: T
authors: Hao
authors: Department of Civil Engineering, Hamad bin Khalifa University, Doha, Qatar.
authors: Hamish Robert
authors: HR
authors: Mackey
authors: Department of Civil & Environmental Engineering, Water Technology Center, Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution (Hong Kong Branch), The Hong Kong University of Science and Technology, Hong Kong, China; Wastewater Treatment Laboratory, FYT Graduate School, The Hong Kong University of Science and Technology, Nansha, Guangzhou, China.
authors: Li
authors: L
authors: Wei
authors: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, China.
authors: Hui
authors: H
authors: Lu
authors: Department of Civil & Environmental Engineering, Water Technology Center, Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution (Hong Kong Branch), The Hong Kong University of Science and Technology, Hong Kong, China; Wastewater Treatment Laboratory, FYT Graduate School, The Hong Kong University of Science and Technology, Nansha, Guangzhou, China.
authors: Guanghao
authors: G
authors: Chen
mesh_terms: D019149:Bioreactors / Q000382:microbiology; D002244:Carbon; D012722:Sewage / Q000382:microbiology*; D013455:Sulfur; D014865:Waste Disposal, Fluid
chemical_list: D012722:Sewage; D013455:Sulfur; D002244:Carbon
keywords: Enhanced biological phosphorous removal; Granulation; Low organic loading rate; Sulfur conversion; Susceptible sludge