Abstract: Compared to conventional oxidation ditches, an integrated oxidation
ditch with vertical circle (IODVC) has the characters of concise configuration,
simple operation and maintenance, land saving and automatical sludge returning.
By the utilization of vertical circulation, an aerobic zone and an anoxic zone
can be unaffectedly formed in the IODVC. Therefore, COD and nitrogen can be
efficiently removed. However, the removal efficiency of phosphorus was Iow in
the IODVC. In the experiment described, a laboratory scale system to add an
anaerobic column to the IODVC has been tested to investigate the removal of
phosphorus from wastewater. The experimental results showed that the removal
efficiency of TP with the anaerobic column was increased to 54.0% from 22.3%
without the anaerobic column. After the acetic sodium was added into the
influent as carbon sources, the mean TP removal efficency of 77.5% was
obtained. At the same time, the mean removal efficiencies of COD, TN and
NH_3-N were 92.2%, 81.6% and 98.1%, respectively, at 12 h of
HRT and 21–25 d of SRT. The optimal operational conditions in this study
were as follows: recycle rate=1.5–2.0, COD/TN > 6, COD/TP > 40, COD
loading rate=0.26–0.32 kgCOD/(kgSS·d), TN loading rate
=0.028–0.034 kgTN/(kgSS·d) and TP loading
rate=0.003–0.005kgTP/(kgSS·d), respectively.
