Nitrification process: dissolved oxygen: aerobic nitrifying bacteria need sufficient dissolved oxygen to carry out the nitrification reaction, which is usually maintained at about 2-4 mg L. pH: The suitable pH range for nitrifying bacteria is 70-8.0, the optimal pH is 75-8.0。Temperature: The suitable temperature range for nitrifying bacteria is 20-30°C, and the optimal temperature is 25-30°C. C-n ratio: Nitrifying bacteria need to consume a certain amount of organic matter as an electron donor, and the C-n ratio is usually controlled at about 4-6.
Denitrification process:
Dissolved oxygen: Denitrifying bacteria need to carry out denitrification reaction in an anoxic environment, and the dissolved oxygen is usually controlled at 05 mg l or less. pH: The pH range suitable for denitrifying bacteria is 65-8.0, the optimal pH is 70-7.5。Temperature: The suitable temperature range for denitrifying bacteria is 20-35°C, and the optimal temperature is 30-35°C. C-n ratio: denitrifying bacteria need to consume a certain amount of organic matter as an electron donor, and the C-n ratio is usually controlled at about 2-5.
In wastewater treatment, the following factors will affect the number and proportion of nitrifying bacteria and denitrifying bacteria, except for temperature
1.pH: Nitrifying and denitrifying bacteria have different ranges for pH. The suitable pH range for nitrifying bacteria is 70-8.0, the optimal pH is 75-8.0；The pH range for denitrifying bacteria is 65-8.0, the optimal pH is 70-7.5。If the pH is too high or too low, it will affect the growth and metabolism of nitrifying and denitrifying bacteria, thus affecting the treatment effect.
2.Dissolved oxygen: Nitrifying bacteria are aerobic bacteria and require sufficient dissolved oxygen for the nitrification reaction. Usually, nitrifying bacteria need to keep dissolved oxygen at around 2-4mg L. Denitrifying bacteria are anaerobic bacteria and need to control dissolved oxygen at 05 mg l or less. If the dissolved oxygen is too high, it will inhibit the growth and metabolism of denitrifying bacteria.
3.Nutrients: Nitrifying and denitrifying bacteria require certain nutrients for growth and metabolism. Generally, nitrifying bacteria need ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen as nutrients, while denitrifying bacteria need organic matter as an electron donor. If the nutrients in the wastewater are insufficient, it will affect the growth and metabolism of nitrifying bacteria and denitrifying bacteria, thus affecting the treatment effect.
4.Hydraulic retention time: Hydraulic retention time refers to the amount of time wastewater stays in the treatment system. If the hydraulic retention time is too short, the nitrifying bacteria and denitrifying bacteria will not have enough time to grow and metabolize, which will affect the treatment effect.
5.Load: Load is the amount of organic matter or ammonia nitrogen entering the treatment system per unit of time. If the load is too high, the number of microorganisms in the treatment system will not be enough to treat the wastewater, which will affect the treatment effect.
Therefore, in wastewater treatment, it is necessary to comprehensively consider the above factors and control the appropriate temperature, pH value, dissolved oxygen, nutrients, hydraulic retention time and load, etc., to ensure the growth and metabolism of nitrifying bacteria and denitrifying bacteria, and improve the treatment effect.
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