What are the advantages and disadvantages of AAO and AO processes? (Part 2)
Written by: Jasmine
Contact email: Kate@aquasust.com
1. Comparative analysis of AAO and AO removal performance
1.1 AAO, AO process: COD removal performance comparison
1.2 AAO, AO process: comparison of denitrification performance
1.3 AAO, AO process: comparison of phosphorus removal performance
1.4 AAO and AO process: comparison and summary of removal performance
2. Influence of temperature on nitrogen and phosphorus removal by AAO and AO
2.1 Influence of temperature on COD removal by two processes
2.2 The effect of temperature on the denitrification of the two processes
2.3 The effect of temperature on phosphorus removal by two processes
3. Effects of Influent C/N Ratio on Nitrogen and Phosphorus Removal by AAO and AO
3.1 Influence of influent C/N ratio on COD removal in two processes
3.2 Influence of influent C/N ratio on denitrification of two processes
3.3 Influence of influent C/N ratio on phosphorus removal by two processes
4. Effects of Influent C/P Ratio on Nitrogen and Phosphorus Removal by AAO and AO
4.1 Influence of influent C/P ratio on COD removal in two processes
4.2 Influence of influent C/P ratio on denitrification of two processes
4.3 Influence of influent C/P ratio on phosphorus removal by two processes
Written by: Jasmine
Contact email: Kate@aquasust.com
At present, most of the nitrogen and phosphorus removal technologies used in sewage treatment plants all over the world are biological methods, such as AO process, AAO process, oxidation ditch process, AB process, SBR process, etc...
These processes do not sound advanced, and they look quite simple, but it takes a lot of work to really understand their respective advantages and disadvantages and compare which ones are good and which are bad.
To this end, I read a lot of literature, but after a study, I found that most of the comparative analysis of peers focused on AAO, SBR, and oxidation ditch processes, and few people compared AO and AAO processes.
Therefore, in order to explore the characteristics of AO and AAO, thoroughly understand their respective removal rates of COD, NH3-N, TN, and TP in sewage, as well as temperature, influent C/N ratio, and influent C/P ratio. Regarding the impact of nitrogen and phosphorus removal by process, I visited Director Wang of Xinling Sewage Treatment Plant. Director Wang directly took out the monthly averages of the influent and effluent indicators of Xinling Sewage Treatment Plant in 2019 (AO process) and 2021 (AAO process), and gave me the following comparative analysis.
Written by: Jasmine
Contact email: Kate@aquasust.com
2. Influence of temperature on nitrogen and phosphorus removal by AAO and AO
2.1 Influence of temperature on COD removal by two processes
Temperature has little effect on the removal of COD in AAO process. Even if the temperature is lower than 5 degrees Celsius, the removal rate of COD can reach more than 85%, which shows that temperature has little effect on the conversion of organic matter by phosphorus accumulating bacteria.
The removal of COD by the AO process tends to decrease between 5-15 degrees Celsius as the temperature increases, and then increases again. This may be because the number and structure of bacteria in the system will change when the climate is alternating between cold and warm. processing capacity of organic matter.
Written by: Jasmine
Contact email: Kate@aquasust.com
2.2 The effect of temperature on the denitrification of the two processes
Undoubtedly, the effect of temperature on the denitrification of the two processes is relatively obvious - both processes have a significant increase in the TN removal rate as the temperature increases. Especially for the AO process, when the temperature is higher than 15 degrees Celsius, the TN removal rate increases almost linearly.
So why, elevated temperature can enhance the denitrification performance of both processes? On the one hand, the increase in temperature is conducive to the growth and reproduction of activated sludge microorganisms and improves the efficiency of nitrogen assimilation; on the other hand, the increase in temperature also enhances the metabolic activity of nitrifying bacteria and denitrifying bacteria in the system, making the system The ability of denitrification and denitrification is enhanced.
It is generally believed that the most suitable growth temperature for nitrifying bacteria is 25-30 degrees Celsius. When the temperature is less than 15 degrees Celsius, the nitrification rate is significantly reduced, and the activity of nitrifying bacteria is also greatly reduced. When the temperature is lower than 5 degrees Celsius, the life activities of nitrifying bacteria almost stop.
It is worth mentioning that sometimes even at low temperature (less than 5 degrees), the TN removal rate of the two systems will not be lower than 40%, which means that the two systems mainly rely on the assimilation of microorganisms in the activated sludge at low temperature. Denitrogenation.
Written by: Jasmine
Contact email: Kate@aquasust.com
2.3 The effect of temperature on phosphorus removal by two processes
From the actual situation, the phosphorus removal rate of the AAO process increases correspondingly with the increase of temperature, especially when the temperature is higher than 20 degrees Celsius, the TP removal rate tends to be stable.
This is because the key to biological phosphorus removal is to rely on the phosphorus removal activity of phosphorus accumulating bacteria, and increasing the temperature is beneficial to increase the activity of phosphorus accumulating bacteria and improve the phosphorus removal rate.
However, the regularity of phosphorus removal by AO process with temperature changes is not strong, and there is no obvious correlation. This is because the AO process has no anaerobic section, and there is no condition for the survival of phosphorus accumulating bacteria. The removal of phosphorus only depends on the assimilation of microorganisms, so the temperature has little effect on the assimilation of microorganisms in this process.
Written by: Jasmine
Contact email: Kate@aquasust.com