[Partial nitrification in SBR under normal temperature and limited oxygen condition].

Partial nitrification was researched in a SBR reactor under the limited oxygen condition (DO 0.3-0.4 mg/L) and the normal temperature of 14.1-24.2 degrees C to produce the correct influent for ANAMMOX process from secondary wastewater (NH4+ -N 30-100 mg/L). The influent for the ANAMMOX process must be composed of NH4+ and NO2- in a ratio of 1/1.31 and therefore only a partial nitrification of ammonium into nitrite was required. The control of alkalinity and the indication of monitoring profile of DO allowed to achieve this partial nitrification with a final effluent only composed of NH4+ -N and NO2(-) -N at the right stoichiometric ratio. The equal consumption of HCO3- /NH4+ in secondary wastewater resulted in a natural pH decrease when approximately 57% of NH4+ -N was oxidized. When the pH dropped to a certain level, the lowering of the metabolic rate of the ammonium oxidizer would lead to rapid decline of the oxygen uptake rate (OUR) in reactor, and the jump characteristic point (it was distinguished by the jump over 1.0 mg/L of DO value) in the DO profile would emerge, which signalled the end-point of the partial nitrifying. The optimum alkalinity of partial nitrification was studied under 4 concentrations in the range of NH4+ -N 30-100 mg/L of secondary wastewater. The result indicated that the bicarbonate/ammonium ratio was the key factor influencing the nitrification ratio (NO2-/NH4+), and it was absolutely possible to successfully achieve partial nitrification that provided right substrate for ANAMMOX reactor through the control of the alkalinity.

[Effects of nitrite on phosphorus uptake in anaerobic/oxic process].

Abstract:Intermediate products of biological nitrogen removal process, nitrate and nitrite, could be used as electron acceptors for phosphorus removal. This study investigated the effects of nitrite on phosphorus uptake in anaerobic/oxic (A/O) biological phosphorus removal process. The results indicated that in addition to oxygen and nitrate (DPB(Na), Denitrifying Phosphorus removal Bacteria with nitrate as electron acceptor), to some extent, nitrite can also serve as electron acceptor to achieve the nitrite denitrifying phosphorus removal (DPB(Ni)). The quantity and rate of phosphorus uptake of DPBNi, however, were evidently lower than that of DPBN,. The nitrite existed in anoxic reactor made no difference to the quantity and rate of denitrifying phosphorus removal. But it would reduce the consumption of nitrate. Moreover, the data showed that the aerobic phosphate uptake of DPBNi was lower than that of anaerobic phosphorus-released sludge in traditional A/O process. However, there was no much difference between these two kinds of sludge in terms of the total phosphorus uptake quantity and the effluent quality.

Anaerobic ammonium oxidation for advanced municipal wastewater treatment: is it feasible?

Anaerobic ammonium oxidation (ANAMMOX) is a recently developed process to treat ammonia-rich wastewater. There were numerous articles about the new technology with focus on the ammonium-rich wastewater treatment, but few on advanced municipal wastewater treatment. The paper studied the anaerobic ammonium oxidation (ANAMMOX) process with a down flow anoxic biofilter for nitrogen removal from secondary clarifier effluent of municipal wastewater with low COD/N ratio. The results showed that ANAMMOX process is applicable to advanced wastewater treatment with normal temperature as well as ammonia-rich high temperature wastewater treatment. The results indicated that ammonia removal rate was improved by raising the nitrite concentration, and the reaction rate reached a climax at 118.4 mgN/L of the nitrite nitrogen concentration. If the concentration exceeds 118.4 mgN/L, the ANAMMOX process was significantly inhibited although the ANAMMOX bacteria still showed a relatively high reactivity. The data also indicated that the ratio of NO(2-)-N: NH4(+)-N = 1.3:1 in the influent was appropriate for excellent nitrogen removal. The pH increased gradually along the ANAMMOX biofilter reactor. When the ANAMMOX reaction was ended, the pH was tend to calm. The data suggested that the pH could be used as an indicator to describe the course of ANAMMOX reaction.