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Effects of Al3+ on the microstructure and bioflocculation of anoxic sludge

2020; Elsevier BV; Volume: 91; Linguagem: Inglês

10.1016/j.jes.2020.02.010

1878-7320

Lanhe Zhang, Jing Zheng, Shulei Tian, Haifeng Zhang, Xiaohui Guan, Suiyi Zhu, Xiaoyu Zhang, Yuxuan Bai, Ping Xu, Jian Zhang, Zheng Li,

Coagulation and Flocculation Studies

The aluminum ions generated from mining aluminum, electrolytic aluminum and the industrial production of aluminum-based coagulants (such as AlCl3 and Al2(SO4)3) enter sewage treatment plants and interact with activated sludges. An anaerobic/anoxic/oxic (A2O) process was used to reveal the effects of Al3+ on the pollutant removal efficiencies, bioflocculation and the microstructure of sludge. The results showed that a low concentration of Al3+ improved the pollutant removal efficiencies and increased the sludge particle size. However, a high concentration of Al3+ hindered microbial flocculation and reduced the pollutant removal efficiencies. With a 10 mg/L Al3+ addition, the chemical oxygen demand (COD), total nitrogen (TN) and NH4+-N increased by 3%, 16% and 27%, and reached as high as 68%, 60% and 87%, respectively. At the same time, the dehydrogenase activity, flocculation ability (FA) and contact angle of the sludge reached their maximum levels at 41.3 mg/L/hr, 45% and 79.63°, respectively. The specific surface area of the sludge decreased to 7.084 m2/g and the sludge pore size distribution shifted to concentrate in the mesoporous range. Most of Al3+ was adsorbed on the surface of sludge, changing the physicochemical properties and physical structure of the sludge.