Updated: July 2002

1. Purpose

For reuse of water, the effluent from a sewage treatment plant is treated by the membrane filtration system. The treated filtrate is used for public such as an artificial water stream in town or a fountain in the park. The treated filtrate can also be used for the miscellaneous water demand at the factory by modifying the treatment flow.

2. Performance

When the effluent from a tertiary treatment plant of a Sewage treatment facility is treated by the membrane filtration system, the quality of the filtrate is as follows.

Most probable number of
Coliform bacteria: 0
BOD (mg/l): <1.0
Turbidity (TU): <1.0
Colour (CU): 28
Suspended solid (mg/l): <1.0

3. Characteristic

Owing to the big contribution of the gas backwashing system, the contaminants on the surface of hollow fibre membrane can be removed almost completely which result in excellent backwashing and the less clogging, less back washing water. The system can be operated not only by the crossflow but also by the deadend. The deadend operation can reduce the power consumption. Removal of contaminants such as suspended solid, colloids, algae and so on can be reached to more than 99.9%, i.e., contaminants free filtrate can be produced.

4. Principle

Gas backwashing system is to remove the contaminants lodged in the matrix and on the surface of the membrane periodically by sending compressed air from inside of the hollow fibre through to the outside.
As the gas backwashing system does not use filtrate to remove the contaminants, total volume of backwash water is relatively small.

5. Backwashing System

6. Figure (Backwashing Effect)

7. Subject

- Water Purification Plant
- Sewage Treatment Plant
- Community Plant

8. Example

The following picture shows the application to a sewage treatment plant.