Centralized iron-dosing into returned sludge brings multifaceted benefits to wastewater management

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Author(s)

  • Zhetai Hu
  • Haoran Duan
  • Zhiyao Wang
  • Jing Zhao
  • Liu Ye
  • Min Zheng
  • Shihu Hu

Detail(s)

Original languageEnglish
Article number117536
Journal / PublicationWater Research
Volume203
Online published11 Aug 2021
Publication statusPublished - 15 Sept 2021
Externally publishedYes

Abstract

Iron salts (i.e. FeCl3) are the most used chemicals in the urban wastewater system. Iron is commonly dosed into sewage or the mainstream system, which provides multiple benefits such as enhanced phosphorus removal and improved sludge settleability/dewaterability. This study reported and demonstrated a new approach that dosed FeCl3 into returned sludge in order to bring two more benefits to wastewater management: short-cut nitrogen removal via the nitrite pathway and less biomass production. This approach is achieved based on our findings that with similar amount of FeCl3, centralized iron dosing into a sidestream sludge unit generated iron concentration two orders of magnitude higher than the common mainstream dosing (e.g. 10–40 mg Fe/L-wastewater), leading to sludge acidification (pH = 2.1) with Fe (III) hydrolysis. Together with accumulated nitrite in the supernatant of the sludge, ppm-level of free nitrous acid was generated and thus enabled sludge disintegration, cell lysis, and selective elimination of nitrite-oxidizing bacteria (NOB). Long-term effects on nitrifying bacteria and overall reactor performance were evaluated using two laboratory reactor experiments for over one year. The experimental reactor showed stable nitrite accumulation with an average NO2/(NO2 + NO3) ratio above 80% and ∼30% observed biomass yield reduction compared to those in control reactors. In addition, the centralized sludge dosing strategy still provided benefits such as improved settleability and dewaterability of sludge and enhanced phosphorus removal. © 2021 Elsevier Ltd. All rights reserved.

Research Area(s)

  • Excess sludge reduction, Iron-dosing, NOB suppression, Shortcut nitrogen removal

Citation Format(s)

Centralized iron-dosing into returned sludge brings multifaceted benefits to wastewater management. / Hu, Zhetai; Duan, Haoran; Wang, Zhiyao et al.
In: Water Research, Vol. 203, 117536, 15.09.2021.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review