Storage Tank

A storage tank has been set on the recycle line from the dewatering unit to the inlet of the primary clarifier, after the ADM to ASM interface. Its behaviour depends upon the flow rate from the dewatering unit, the available storage volume and the fate of the stored reject water.

The reject water cannot be stored in the tank when the tank is full. In such a case, the reject water has to be recycled directly to the inlet of the primary clarifier until the storage tank has been emptied and can receive water again. Furthermore, a limit has been set for the reject water outflow from the tank.

There are two component of Storage Tank block:

1. storage bypass
2. storage tank

Storage bypass unit

Four scenarios

1. when the current liquid volume in the storage tank is between the minimal and maximal values. All reject water flow rate from the dewatering is admitted to the storage tank. Next outflow of storage tank is set to Qsetpoint_s

2. when the current liquid volume in the storage tank is larger than or equal to the maximal value and the reject water flow rate from the dewatering is smaller than or equal to the Qsetpoint_s. All reject water flow rate will go to the storage tank and next outflow of storage tank is set to Qsetpoint_s.

3. when the current liquid volume in the storage tank is larger than or equal to the maximal value and the reject water flow rate from the dewatering is larger than the Qsetpoint_s. All reject water flow rate will be bypassed to the primary clarifier and next outflow of storage tank is zero

4. when the current liquid volume in the storage tank is smaller than or equal to the minimal value. All reject water flow rate from the dewatering will go to the storage tank.However, the next outflow of storage tank will set to zero.

Inputs

1. Output from Dewatering (Reject Flow)
   1. Q
   2. T
   3. Soluble
   4. Particulate
2. Qsetpoint_s = 0 Liquid flow rate set point at the outlet of the storage tank
3. The last output from storage tank
   1. The current liquid volume in storage tank (needed for control)
   2. Will have to go through storage delay block to avoid algebraic loop problem

Parameters

1. Volume of storage tank: Vol_S = 160 m3

Ouputs

1. bypass flow
   1. Q
   2. T
   3. Soluble
   4. Particulate
2. flow into storage tank
   1. Q
   2. T
   3. Soluble
   4. Particulate
   5. Extra output: The next output flow rate for storage tank

Storage Tank unit

ODE is based on mass balance just like the one in primary clarifier