The RRK Engineering Duplex Polishing Filter assembly is designed to fit the manufacturers need for an inexpensive, but reliable, system to filter effluent containing solids before discharge or before entering an ion exchange system. Designed with a backup filter so the system is not "down" while backwashing, it is easy to operate and maintain.

The system features a large buffer tank with level controls monitoring the solution flow rate. pH is adjusted to the correct level to allow the residuals to precipitate out. A pump feeds solution from the buffer tank to one of the two media filters. The effluent passes to the media filters where the residuals are removed. A microprocessor base controller monitors the level in the holding tank and after a set time or when the holding tank hits high level, the columns switch and what was the primary column is backwashed and the secondary column now becomes the primary. Should a high-high level be reached, both columns are placed in parallel service until a low level signal is reached then the system automatically goes into a backwash cycle of the previous primary filter.

A pressure sensor is available to initiate the backwash cycle as an option. A manual override of the timer to start a backwash cycle is included. A digital flow meter, pH control, flow and pH monitoring are some options available.

Operation: Your effluent stream is fed to the buffer tank. The solution is recirculated continuously through the filters and pH is adjusted. When the first level control is reached and the pH is correct, the solution is sent to drain. Should the flow be too high or the first filter flow rate too low, the level reaches the second setpoint and a valve opens allowing solution to pass to a second media filter in parallel with the first. Upon reaching low level, the system reverts to the recirculation mode and the primary filter is backwashed.

Operating modes - The system has four operating modes:

1. Recirculation - water is pumped through one of the media filters and is returned to the main holding tank. This mode is initiated upon receiving a low level signal.

2. Pump down - water is diverted to drain after passing through a media filter. This state is initiated upon the water level in the system reaching the midlevel probe.

3. Dual pump down - upon reaching the high level probe, water is pumped through both media filters in parallel until a low level signal is recieved.

4. Backwash - at the end of a timed cycle or after a dual pump down mode, the filter that was on line is take off line and is backwashed. The other filter becomes the online filter. The backwash water is returned through a bag filter to the main tank.