Flocculation of activated sludge flocs by stimulation of the aerobic biological activity

Water Research
Britt-Marie WilénPer Halkjær Nielsen

Abstract

Activated sludge flocs are known to deflocculate under short-term anaerobic conditions, but little is known about possible reflocculation under subsequent aerobic conditions. When activated sludge flocs from two wastewater treatment plants deflocculated under anaerobic conditions with well-defined shear conditions, they could be almost, but not completely, reflocculated by aeration for 1-2 h under the same shear conditions. If the biological activity was reduced by adding azide, chloramphenicol or by decreasing the temperature, no or only very little reflocculation took place. This indicated that the reflocculation was under direct or indirect microbial control. Only a small part of the reflocculation was due to improved flocculation properties obtained by oxidation of Fe(II) to Fe(III), which is a better flocculant. Fe(II) was produced under the anaerobic conditions by microbial iron reduction, and it was oxidized to Fe(III) within less than one hour after the aeration was started. However, by comparing two different sludges with different capabilities for iron reduction, iron oxidation and responses to substrate addition, it was found that the aerobic biological activity most likely was of greatest significance for the observ...Continue Reading

References

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Citations

Nov 12, 2014·Environmental Science. Processes & Impacts·Shengnan XuZhiqiang Hu
Jul 10, 2012·Water Research·Jixiang YangJules B van Lier
May 23, 2012·Water Research·Artur Tomasz MielczarekPer Halkjær Nielsen
May 26, 2009·Biotechnology Advances·Xian-Wei LiuHan-Qing Yu
Apr 4, 2006·Journal of Environmental Management·M F ColmenarejoR Borja
Dec 14, 2017·Water Science and Technology : a Journal of the International Association on Water Pollution Research·Zhenchao Zhang

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