Patent ID: 9688376
Date: 2017-06-27
CPC Classifications: B01D,B63J,C02F

Claim:
1. A ballast water treatment method for a ship performed on a filtration system, the filtration system having a rotary filtration apparatus including a filter with a cylindrical shape that surrounds an axis, the filter being pleated with folds in a cylinder radial direction, a cleaning nozzle for ejecting untreated water, a case that includes an outer cylindrical portion that surrounds the filter, a nozzle opening of the cleaning nozzle disposed inside the case, a filtered water channel through which filtered water is passed, a discharge channel through which discharged water that has not passed through the filter is discharged to an outside of the case, and an electric motor for rotating the filter, the method comprising the steps of: rotating the filter by the electric motor at a rotation speed during a filtering operation in a range of 20 rpm to 100 rpm; ejecting untreated water by the a cleaning nozzle towards an outer peripheral portion of the filter at a flow speed of 250 m/min or more; passing filtered water filtered by the filter by the filtered water channel from a cylindrical space inside the filter to the outside of the case at a flow rate of filtered water per unit area of the filter at 5.1 m/h or less; and discharging water that has not passed through the filter via a discharge channel to the outside of the case at a flow rate of 5% or more of the flow rate of filtered water, wherein a distance between the cleaning nozzle and a recess of the filter is 120 mm or less, and the filter has an effective filtration area of 5 m