Engineering aspects and practical application of autotrophic nitrogen removal from nitrogen rich streams

The efficiency of wastewater treatment practices can be significantly improved through the introduction of new microbial treatment technologies. In order to meet increasing stringent discharge standards, new applications and control strategies for the sustainable removal of ammonium from wastewater have to be implemented. Partial nitrification to nitrite was reported to be technically feasible and economically favorable, especially when the wastewater with high ammonium concentrations or low C/N ratios was treated. For successful implementation of the technology, the critical point is how to maintain the partial nitrification of ammonium to nitrite. Nitritation can be obtained by selectively inhibiting the nitrite oxidizing bacteria through appropriate regulation of the system's DO concentration, microbial SRT, pH, temperature, substrate load, operational and aeration pattern, inhibitor and so on. This review addresses the microbiology, its consequences for application, the current status regarding application, and its future developments.

Biological nitrogen removal with nitrification and denitrification via nitrite pathway

Presently, the wastewater treatment practices can be significantly improved through the introduction of new microbial treatment technologies. To meet increasingly stringent discharge standards, new applications and control strategies for the sustainable removal of ammonium from wastewater have to be implemented. Partial nitrification to nitrite was reported to be technically feasible and economically favorable, especially when wastewater with high ammonium concentrations or low C/N ratios is treated. For successful implementation of the technology, the critical point is how to maintain partial nitrification of ammonium to nitrite. Partial nitrification can be obtained by selectively inhibiting nitrite oxidizing bacteria through appropriate regulation of the system's DO concentration, microbial SRT, pH, temperature, substrate concentration and load, operational and aeration pattern, and inhibitor. The review addressed the microbiology, its consequences for their application, the current status regarding application, and the future developments.

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Control of aeration, aerobic SRT and COD input for mainstream nitritation/denitritation.

Partial nitrification to nitrite (nitritation) can be achieved in a continuous process without sludge retention by wash out of nitrite oxidising bacteria (NOB) while retaining ammonia oxidising bacteria (AOB), at elevated temperatures (the SHARON process) and, as demonstrated in this paper, also at low dissolved oxygen (DO) concentrations. Enriched AOB was attained at a low DO concentration (0.4 mg l(-1)) and a dilution rate of 0.42 day(-1) in a continuous process. A higher oxygen affinity of AOB compared to NOB seemed critical to achieving this. This was verified by determining the oxygen half saturation constant, Ko, with similar oxygen mass transfer resistances for enriched AOB and NOB as 0.033+/-0.003 mg l(-1) and 0.43+/-0.08 mg l(-1), respectively. However, the extent of nitritation attained was found to be highly sensitive to process upsets.

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Papers

Nitrite accumulation by aeration controlled in sequencing batch reactors treating domestic wastewater