It depends on the application ...

It depends on the application and the medium particle size to be filtered, Drum screens are often used to remove course particles, then some plants use a flocculation and DAFF plant before cartridge filters to reduce the load onto the cartride filters or some plants have sand filters after flocculation and before the cartridge filters to reduce the load onto the cartridge filters. I guess to determine the most cost effective solution one would need to understand the medium and application to better advise or provide a answer.