1. Key Points of Physical Cleaning
Physical cleaning involves adjusting the flow rate to generate a suitable water flow to wash away contaminants adhering to the membrane surface.
Typically, the flushing flow rate for a single membrane element is 2~2.5 m³ /h for 4-inch membranes and 7~12 m³ /h for 8-inch membranes. To ensure the safety of the membrane element during cleaning, the cleaning pressure should not exceed 0.3 MPa, and flushing once a day is optimal.
2. Physical Cleaning Steps
The recommended steps for physical cleaning are as follows:
(1) Stop the system as described above;
(2) Start the flushing pump;
(3) Turn on the inlet pump and check the flow meter at the same time;
(4) Adjust the inlet valve to bring the flow rate and pressure to the design values;
(5) After cleaning for about 15 minutes, slowly close the water inlet valve and stop the water inlet pump.
3. Precautions
(1) When designing the system piping, the maximum flow rate and maximum instantaneous pressure during flushing must be considered, especially the concentrate piping and valves must have sufficient operating margin.
(2) When selecting the system water pump, the maximum flow rate required for flushing must be considered, especially the inlet water pump must meet the flushing requirements.
(3) When selecting instruments such as system flow meters, the maximum peak value during flushing should be taken into account.
(4) The design of a multi-segment system can be based on the segmented cleaning method.
