Affiliations: Department of Environmental Science and Engineering,
Hunan University, Changsha 410082, China | Institute of Water Quality and Waste Management,
Hannover University, Welfengarten D-1, 30167, Hannover, Germany
Abstract: Modeling for nitritation process was discussed and analyzed
quantlitatively for the factors that influence nitrite accumulation. The
results indicated that pH, inorganic carbon source and Hydraulic Retention Time
(HRT) as well as biomass concentration are the main factors that influenced the
conversion ratio of ammonium to nitrite. A constant high pH can lead to a high
nitritation rate and results in high conversion ratio on condition that free
ammonia inhibition do not happen. In a CSTR system, without pH control, this
conversion ratio can be monitored by pH variation in the reactor. The pH goes
down far from the inlet level means a strongly nitrite accumulation. High
concentration of alkalinity can promoted the conversion ratio by means of
accelerating the nitritation rate through providing sufficient inorganic carbon
source (carbon dioxide). When inorganic carbon source was depleted, the
nitritation process stopped. HRT adjustment could be an efficient way to make
the nitritation system run more flexible, which to some extent can meet the
requirements of the fluctuant of inlet parameters such as ammonium
concentration, pH, and temperature and so on. Biomass concentration is the key
point, especially for a CSTR system in steady state, which was normally
circumscribed by the characteristics of bacteria and may also affected by
aeration mode and can be increased by prolonging the HRT on the condition of no
nitrate accumulation when no recirculation available. The higher the biomass
concentration is, the better the nitrite accumulation can be obtained.
