What are the advantages and disadvantages of AAO and AO processes? (Part 4)
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
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
The experimental data show that the COD removal rate of the AO process has a weak regularity with the change of the C/P ratio, and there is no obvious correlation. It can be seen that the C/P ratio is not the main factor affecting the organic matter removal effect of the AO process.
For the AAO process, no matter how the influent C/P ratio changes, the COD removal rate is higher than 85%.
Relevant studies have pointed out that more than 79% of the COD is consumed in the anaerobic zone for the synthesis of PHA, the internal storage of cells, while in the anoxic zone, 6%-11% of the COD is used for cell growth and denitrification consumption, and in the aerobic zone. There is almost no COD consumption in the area, because after cell death, refractory substances such as cell walls enter the mixture again, which increases COD.
Written by: Jasmine
Contact email: Kate@aquasust.com
4.2 Influence of influent C/P ratio on denitrification of two processes
The effect of C/P ratio on the denitrification effect of AO process has no obvious regularity, and the fluctuation range of TN removal rate is relatively large. This may be due to the fact that other factors besides C/P ratio have a stronger effect on the denitrification of AO process than C/P ratio.
The C/P ratio has little effect on the denitrification effect of the AAO process. Although the C/P ratio varies greatly, the TN removal rate is relatively stable.
This is mainly because the C/P ratio of general sewage is relatively high. Excessive COD entering the anoxic zone will inhibit the absorption of phosphorus. In the anoxic zone, the C/N ratio is always higher than the minimum actual demand, and denitrifying bacteria will use it. Excessive external carbon sources rapidly denitrify without affecting the removal of TN.
Written by: Jasmine
Contact email: Kate@aquasust.com
4.3 Influence of influent C/P ratio on phosphorus removal by two processes
In the AAO process, when the C/P ratio is lower than 80, the phosphorus removal rate fluctuates significantly. When the C/P ratio is higher than 80, the phosphorus removal rate is stable above 85%, and the phosphorus concentration in the effluent is less than 0.5 mg/L. The phosphorus removal rate of the system is basically no longer affected by other factors, indicating that the influent water in the AAO system When the C/P ratio is higher than 80, stable and efficient effluent quality can be achieved.
This is because when the C/P ratio is high, the carbon source provided by the influent is higher than the carbon source required for the release of phosphorus in the anaerobic zone, so the phosphorus removal rate is higher. When the C/P ratio is low, due to the limitation of COD, the phosphorus absorption capacity of phosphorus accumulating bacteria decreases, resulting in low phosphorus removal efficiency.
For AO process, the effect of C/P ratio on its phosphorus removal effect has no obvious regularity, which indicates that C/P ratio has little effect on microbial assimilation.
Written by: Jasmine
Contact email: Kate@aquasust.com
Aquasust hope you have understood the characteristics of AO and AAO through this article, and thoroughly understood their respective removal rates of COD, NH3-N, TN, and TP in sewage, as well as temperature, influent C/N ratio, influent C Influence of /P ratio on nitrogen and phosphorus removal by two processes.
Written by: Jasmine
Contact email: Kate@aquasust.com