Affiliations: School of Municipal & Environmental Engineering,
Harbin Institute of Technology, Harbin 150090, China | Ocean University of China, Qingdao 266003, China | School of Environmental Science and Engineering,
Shanghai Jiaotong University, Shanghai 200240, China
Abstract: Simultaneous biological phosphorus and nitrogen removal with
enhanced anoxic phosphate uptake via nitrite was investigated in an
anaerobic-aerobic-anoxic-aerobic sequencing batch reactor
((AO)^2 SBR). The system showed stable phosphorus and
nitrogen removal performance, and average removals for COD, TN and TP were 90%,
91% and 96%, respectively. The conditions of pH 7.5–8.0 and temperature
32°C were found detrimental to nitrite oxidation bacteria but favorable to
ammonia oxidizers, and the corresponding specific oxygen uptake rates (SOUR)
for phase 1 and 2 of nitrification process were 0.7 and 15
mgO_2/(gVSS·h) in respect, which led to the nitrite
accumulation in aerobic phase of (AO)^2 SBR. Respiratory
tests showed that 40 mgNO_2-N/L did not deteriorate the
sludge activity drastically, and it implied that exposure of sludge to nitrite
periodically enabled the biomass to have more tolerance capacity to resist the
restraining effects from nitrite. In addition, batch tests were carried out and
verified that denitrifying phosphorus accumulation organisms (DPAOs) could be
enriched in a single sludge system coexisting with nitrifiers by introducing an
anoxic phase in an anaerobic-aerobic SBR, and the ratio of the anoxic phosphate
uptake capacity to aerobic phosphate uptake capacity was 45%. It was also found
that nitrite (up to 20 mgNO_2-N/L) was not inhibitory to
anoxic phosphate uptake and could serve as an electron acceptor like nitrate,
but presented poorer efficiency compared with nitrate.
Keywords: denitrifying phosphorus accumulation organisms (DPAOs), shortcut nitrification and denitrification, anoxic phosphate uptake, sequencing batch reactor (SBR), nitrite, electron acceptor
