Sludge return ratio is an important operating parameter in the sewage treatment system, which affects the treatment effect, energy consumption and cost of activated sludge treatment. The correct sludge return ratio can ensure the right sludge concentration in the biological treatment unit and improve the efficiency of contaminant removal. Here are some common ways to adjust the sludge return ratio:
1.Monitoring sludge concentration:
Sludge concentration (MLSS or MLVSS) in activated sludge mixtures is measured periodically to assess the microbial biomass in the biological treatment unit.
The sludge return ratio is adjusted based on the sludge concentration and the desired sludge age (SRT).
2.Analyze the quality of the inlet and outlet water:
Detect the concentration of pollutants such as COD, ammonia nitrogen, total nitrogen, and total phosphorus in the inlet and outlet water to evaluate the treatment effect.
If the contaminant removal efficiency decreases, it may be necessary to increase the sludge return ratio to increase the sludge concentration in the biological treatment unit.
3.Consider the inlet load:
Changes in the influent load have a direct impact on the operating status of the biological treatment unit. When the influent load increases, the sludge reflux ratio should be increased appropriately to maintain a higher sludge concentration and better treatment effect.
On the contrary, when the influent load is reduced, the sludge return ratio can be appropriately reduced to avoid the waste of energy consumption caused by excessive backflow.
4.Sludge age control:
Sludge age is the average residence time of activated sludge in the system. By adjusting the sludge return ratio, the sludge age can be controlled within the appropriate range.
In general, nitrifying bacteria require a longer sludge age, while denitrifying bacteria and organic degrading bacteria require a shorter sludge age. Therefore, the sludge return ratio needs to be balanced according to the treatment objectives and microbial needs.
5.Evaluate sludge settling performance:
The sludge sedimentation performance is good, which can ensure that the sludge in the clarifier can be effectively separated. If the sedimentation performance is poor, it may be necessary to reduce the sludge return ratio to reduce the sludge concentration in the biological treatment unit.
6.Consider sludge digestion and disposal capacity:
The adjustment of the sludge return ratio also needs to consider the subsequent sludge digestion and disposal capacity. If sludge digestion or disposal capacity is limited, excessively high sludge return ratios should be avoided.
7.Gradual adjustment:
When adjusting the sludge return ratio, it should be done gradually to avoid the impact of sudden changes on the system.
After each adjustment, the system should be given sufficient time to acclimatize to the new operating conditions and to monitor the system's response.
8.Use models and empirical formulas:
Mathematical models or empirical formulas can be used to determine the performance of the system under different sludge return ratios as a reference basis for adjustment.
The correct sludge return ratio adjustment requires a combination of factors and needs to be flexibly adjusted according to the actual situation. Through continuous monitoring, analysis and adjustment, the optimal sludge return ratio can be found for optimal operation of the wastewater treatment system.