The water containing solid particles flows through the supply piping or channel inside the filtration drum, and impurities are entrapped on the interior side of the filter cloth. Subsequently, the treated water flows via the cloth outwards. In the course of this filtration process the entire filtration equipment is in idle state (it does not consume any energy). The filter cloth will become gradually clogged with influent impurities, the cloth resistance to flowing will increase, and the water level and hydrostatic pressure inside the drum will rise.
Once the set level is reached inside the filtration drum, the level sensor will automatically switch on the drum rotation drive and the backwash pump delivering the filtered water to the backwash system nozzles. The directed water stream jetted by special nozzles will remove the impurities entrapped on the interior side of the cloth into the discharge trough installed inside the drum. The sludge will be transported to the sludge pit and then delivered outside using the sludge pump that is also controlled automatically by means of level sensors installed on the sludge pit wall. If self-gravity discharge of sludge is ensured, the sludge pump will be omitted. After the backwash process is completed, the hydrostatic pressure resistance will become decreased and the drum drive and backwash pump will be switched off. The equipment will pass to idle state.
Since the raw water supply is not interrupted during the backwash process and the backwash water is supplied directly from the filtration equipment, no additional entrapment tanks for backwash water or sludge water are needed, resulting in a considerable reduction in investment costs. The sludge pit is an integral part of the equipment.
Automatic switch on/off of the filter minimizes the electric power consumption, improves the average quality of filtered water and increases the density of discharged sludge as well as the service life of the entire facility.
When the microscreen drum filter is put out of operation due to electric power failure, the filter cloth will, after some time, become completely clogged and the water will reach the emergency level. In such a case the water is discharged via an overflow; the residual filtered water will remain pure. Once the cause of failure is removed, the equipment will be able to start filtering without any intervention inside the machine. The backwash pump has sufficient water to perform high quality backwash of the filter cloth. The equipment will return to the original cycle.