Modelling and Control of Water and
Wastewater Treatment Processes
Disturbances and manipulated variables
The main goal of this exercise is to implement the systems for carbon and nitrogen removal in
SUMO and get acquired with the influence of disturbances and manipulated variables on the
process dynamics.
Task 1: Carbon Removal System
Consider the plant designed for carbon removal described in Figure 1.
BIOREACTOR
SETTLER
INFLUENT
EFFLUENT
AIR
SLUDGE RECIRCULATION
EXCESS SLUDGE
Figure 1: Simplified activated sludge process.
It is required to:
1. Implement the system in Sumo considering the activated system as one completely mixed
reactor (with a volume is 10000 m3 ) plus an ideal settler (use Sumo’s default parameters).
2. Identify the possible manipulated and controlled variables.
3. Simulate the system in Sumo for different disturbances:
• Influent flowrate change ± 10%;
• Influent COD change ± 10%.
Examine some changes in the following variables:
• Return flowrate change ± 10%;
• Wastage flowrate change ± 10%;
• Airflow rate change ± 10%;
4. Plot the concentrations that are mainly affected by these changes.
5. Discuss your findings.
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Task 2: Nitrogen Removal System
Consider the plant designed for carbon and nitrogen removal described in Figure 2.
BIOREACTOR
SETTLER
INFLUENT
EFFLUENT
AIR
INTERNAL RECIRCULATION
SLUDGE RECIRCULATION
EXCESS SLUDGE
Figure 2: Simplified activated sludge process.
It is required to:
1. Replace the complete mix reactor in Task 1 with two complete mix reactors in series
(anoxic and aerated), keeping the same total volume and including an internal recirculation flowrate.
2. Identify the possible manipulated and controlled variables.
3. Implement the model in Sumo until it reaches the steady-state.
4. Analyze the system for different disturbances:
• Influent flowrate changes ± 10;
• Influent COD change ± 10%;
• Influent ammonia changes ± 10.
5. Examine some changes in the following variables:
• Internal recirculation flowrate change ± 10%;
• Return flowrate change ± 10%;
• Wastage flowrate change ± 10%;
• Airflow rate change in the aerobic zone ± 10%;
6. Plot the concentrations that are mainly affected by these changes.
7. Discuss your findings and make comparisons with Task 1.
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