Anaerobic single-tank nitrification/denitrification process
Outline
Through the effective use of existing civil construction frameworks, we have developed a new treatment system that realizes improved quality of water and energy saving, as well as reduced LCC when compared with the A2O process. This treatment process was developed through a joint research effort undertaken by Tokyo Metropolitan Gov., Bureau of Sewerage, Tokyo Metropolitan Sewerage Service Corporation and METAWATER Co., Ltd.
- Outline of treatment flow
- Conceptional, cross-sectional view of treatment for the tank
- Change of nitrogen in the direction of flow from the tank
Features
Improved water quality
By generating an aerobic zone and anoxic zone in the aerobic tank serving to repeat the nitrification and denitrification through the use of the swirl flow mechanism, it achieves the same level of water quality as obtained by advanced treatment processes.
Optimal control of air flow that realizes energy saving
By means of the nitrogen oxide meter and ammonia meter installed in the aerobic tank, it monitors the nitrification/denitrification status to control the aeration air flow and keep it at an optimal level.
Reduced costs for modification and maintenance
It reduces the degree of modification of the existing civil construction frameworks required for introducing advanced treatment processes. It requires neither anoxic tanks, mixers nor nitrification liquid circulation pumps.
Principle of the treatment
Same level of performance as seen with A2O process
With the AO process used as the base, it causes nitrification and denitrification inside the aerobic tank (indicated as the single-tank nitrification/denitrification tank on the figure below) through the use of the nitrogen oxide meter and the ammonia meter to achieve the treatment performance equivalent to that seen in the A2O process.
Air flow control
With the deep-tank type aerobic tank divided into two (2) sections, the air flow is individually controlled for each of the sections, using the nitrogen oxide concentration as the metric for the front section and the ammonia concentration for the rear section.
Comparison with conventional technology
Using the nitrification/denitrification reaction that is the same as the one used in the A2O process, the N2O emission factor is approximately one tenth of that seen with the standard active sludge process
The removal of nitrogen during sewage treatment consists of two (2) stages: nitrification and denitrification using the actions of microorganisms. During nitrification, ammonia contained within the sewage turns into nitric acid. During denitrification, nitric acid turns into nitrogen gas. Through the release of the nitrogen gas into the atmosphere, the removal of nitrogen is completed.
* Source: “Earth Plan 2017”, Tokyo Metropolitan Gov., Bureau of Sewerage
Features of this process and comparison with conventional technology
