Innovative anaerobic upflow sludge blanket filtration combined bioreactor for nitrogen removal from municipal wastewater

In this research, a novel laboratory scale anaerobic/upflow sludge blanket filtration combined bioreactor
was designed and operated to improve the efficiency of the upflow sludge blanket filtration process for the simultaneous
removal of phosphorus and nitrogen from wastewater. The anaerobic/upflow sludge blanket filtration technique was
developed by adding an anaerobic reactor to its influent and operated by varying the main process parameters in order
to gain the optimum conditions. The results showed that biological removal efficiency of nitrogen and preservation of
sludge blanket strongly depend on wastewater characteristics, hydraulic retention time, sludge age and process controlling
parameters. The combined bioreactor performed a total nitrogen removal efficiency of 96.6 % with the sludge age of 25
days, total hydraulic retention time of 24 h and optimum “chemical oxygen demand/nitrogen/phosphorus” ratio of 100/
5/1. This ratio also improved the compaction quality of sludge blanket in the upflow sludge blanket filtration clarifier.
The average specific nitrification and denitrification rates occurred during the process can be expressed as 4.43 mg NOx-
N produced/g VSS.d and 5.50 mg NOx-N removed/g VSS.d at the optimum ratio, respectively. To avoid sludge rising due
to denitrification process, the optimum total hydraulic retention time of 16 to 24 h was achieved based on the effluent
quality. This study suggested that the anaerobic/upflow sludge blanket filtration bioreactor at the optimum operational
conditions can be an effective process for removal of nutrients from municipal wastewater.