Abstract: A filter module for a filter battery includes an outer wall that surrounds a chamber having inflow and outflow ends. An inner wall divides the chamber into a plurality of compartments including an inflow compartment, outflow compartment, bi-directional compartment and drain compartment. Each compartment extends from the inflow end to the outflow end of the chamber. First and second holes are formed in the outer wall providing access to the bi-directional and outflow compartments, respectively. For each module, a filter is positioned outside the chamber and along a flow path between the bi-directional compartment and the outflow compartment. A valve directs flow within the module and switches the module between modes. In fluid filtering mode, fluid passes sequentially through the inflow compartment, bi-directional compartment, filter and then the outflow compartment.