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Biological municipal wastewater nutrients removal in
anaerobic-aerobic (low dissolved oxygen) sequencing batch
reactor: effect of organic carbon source addition
Zheng Xiong, Li Hongjing, Tong Juan, Chen Yinguang
State Key Lab of Pollution Control and Resources Reuse, School of Environmental Science and
Engineering, Tongji University, Shanghai (200092)
Email: yg2chen@yahoo.com
Abstract
The effect of addition of organic carbon sources (acetic acid and waste activated sludge alkaline
fermentation liquid) on anaerobic-aerobic (low dissolved oxygen, 0.15-0.45 mg/L) biological
municipal wastewater treatment was investigated. The results showed that carbon source addition
affected not only the transformations of polyhydroxyalkanoates (PHA), glycogen, nitrogen and
phosphorus, but the net removal of nitrogen and phosphorus. The removal efficiencies of TN and TP
were respectively 61% and 61% without organic carbon source addition, 81% and 95% with acetic acid
addition, and 83% and 97% with waste activated sludge alkaline fermentation liquid addition. It
seems that the alkaline fermentation liquid of waste biosolids generated in biological wastewater
treatment plant can be used to replace acetic acid as an additional carbon source to improve the
anaerobic-aerobic (low dissolved oxygen) municipal wastewater nutrients removal although its use was
observed to cause a slight increase of effluent BOD and COD concentrations.
Keywords: Anaerobic-aerobic (low dissolved oxygen); nitrogen and phosphorus removal; municipal
wastewater; alkaline fermentation liquid; waste activated sludge
1. Introduction
As the key nutrients of causing eutrophication, nitrogen and phosphorus in effluents are enforced
to remove from wastewater in many countries. The treatment of wastewater by biological technology
has been widely adopted because of its easily operation and low pollution generation. It is well
known that the efficiencies of nitrogen and phosphorus removal are affected by the available
biodegradable organic carbon, such as short-chain fatty acids (SCFAs). The concentration of SCFAs
in municipal wastewater, however, is usually not very high, which might affect biological nitrogen and
phosphorus removal (BNPR) process. Thus, extra organic carbon addition is required for satisfied
nutrients removal and low effluent nutrients levels (Chae et al., 2004; Dytczak et al., 2007; Elefsiniotis
et al., 2004; Kampas et al., 2009; Lim et al., 2008a,b; Thomas et al., 2003).
During BNPR, the anaerobic and aerobic stages are usually included. In a conventional BNPR
process, the dissolved oxygen (DO) concentration, which is not controlled in the aerobic phase, is
usually around 2 mg/L. Recently, several studies reported that both nitrogen and phosphorus can be
removed in an anaerobic-aerobic (low DO, less than 1 mg/L) sequencing batch reactor (de Kreuk et al.,
2005; Zeng et al., 2003). In this new BNPR, the DO level is controlled below 1 mg/L, and
simultaneous nitrification, denitrification, and phosphorus uptake are observed, which results in less air
supply and lower organic carbon demand for nitrogen and phosphorus removal compared with the
conventional BNPR process.
In a previous study we observed that the ratio of propionic to acetic acid in wastewater gave
impact on the anaerobic-aerobic (low DO, 0.15 ~ 0.45 mg/L) phosphorus and nitrogen biological
removal (Li et al., 2008). Using the synthetic wastewater as the influent, it has been observed that the
change of propionic/acetic acid ratio did not significantly affect the ammonium nitrogen (NH
4
+
-N)
removal, but both phosphorus and total nitrogen (TN) removal were improved with the increase of
propionic/acetic acid ratio.
Nevertheless, as seen from the literature all the studies regarding the anaerobic-aerobic (low DO)
process have focused on the synthetic wastewater with sufficient SCFAs (acetic acid or its mixture with
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