Automatic backwash filter for ballast water management system

The utility model provides an automatic backwash filter for a ballast water management system. The automatic backwash filter mainly comprises a washing motor, a transmission assembly, a filtering assembly, a lower barrel body assembly, an upper barrel body assembly and a differential manometer; the filter assembly is composed of four filtering barrels; filter ports are uniformly distributed on a sewage drainage shaft, wherein the upper end of the sewage drainage shaft is closed while the lower end of the sewage drainage shaft has a hole; the transmission shaft is composed of a driving wheel system, a limiting mechanism, a fixing plate and four driven wheel systems; threads are formed in a through hole of a bearing bushing, so that the bearing bushing is connected with a screw shaft in a threaded connection way; a key groove is formed in a hollow shaft, so that the hollow shaft is connected with the screw shaft through keys; the threads and another key groove with a through end are formed in the circumferentia