Abstract: To make it possible to raise a door body even if it is damaged by an impact of vehicle traffic or falling objects when it is in a lowered state, and to keep the door body in a raised state even if it is damaged by a water pressure of a tsunami or a high tide when it is in a raised state. A door body 2 of a floating flap gate 1 is disposed at an opening or at an access way. When water flows in, a forward end 2b of which swings upwards, in a direction in which the water flows in and within a plane in a height direction, around a base end 2a thereof which serves as a center of rotation, to block the opening or the access way. The door body 2 is formed from a hard polyurethane foam 4 in the form of a sheet.

Abstract: A seawater desalination system includes an intake part buried in a sand layer of the seafloor to take in seawater passed through the sand layer, an anterior filtration part filtering seawater conveyed from the intake part, and a posterior filtration part filtering seawater conveyed from the anterior filtration part, using a reverse osmosis membrane. The anterior filtration part includes a first anterior filtration line including a first ultrafiltration membrane, a second anterior filtration line including a second ultrafiltration membrane having a molecular weight cut-off less than that of the first ultrafiltration membrane, and a switching part switching a path through which seawater flows between the first and second anterior filtration lines provided in parallel with each other. The system controls the switching part in accordance with dissolved oxygen content in the seawater taken in by the intake part, thereby improving the efficiency of seawater filtration with the ultrafiltration membranes.

Abstract: A seawater desalination system includes an intake part buried in a sand layer of the seafloor to take in seawater passed through the sand layer, an anterior filtration part filtering seawater conveyed from the intake part, and a posterior filtration part filtering seawater conveyed from the anterior filtration part, using a reverse osmosis membrane. The anterior filtration part includes a first anterior filtration line including a first ultrafiltration membrane, a second anterior filtration line including a second ultrafiltration membrane having a molecular weight cut-off less than that of the first ultrafiltration membrane, and a switching part switching a path through which seawater flows between the first and second anterior filtration lines provided in parallel with each other. The system controls the switching part in accordance with dissolved oxygen content in the seawater taken in by the intake part, thereby improving the efficiency of seawater filtration with the ultrafiltration membranes.

Abstract: To provide a cleaning apparatus suitable for removing clogging substances trapped in a surface layer of a sand filtration layer. A cleaning apparatus equipped with drive wheels serving as a driving device configured to move across a surface of a sand filtration layer. A pump and a jet nozzle are provided as an agitation device configured to agitate a surface layer portion of the sand filtration layer only at a desired depth, and which blows the clogging substances upward into the seawater in a turbid water intake pit together with a filtration sand. A perforated pipe for suctioning turbid water, a pump, an ejector, and a discharge pipe for dilute turbid water are provided as a suction and discharge device configured to suction turbid water blown upward into seawater in the water intake pit by the agitation device, and discharge it to outside of the turbid water intake pit.

Abstract: To reduce the size, scale of construction, and running cost of an apparatus for cleaning a sand filtration layer. A cleaning system which removes clogging sediments from a sand filtration layer 2, used with an apparatus for an infiltration intake of seawater which performs a seawater intake, by means of a water intake pipe 4 buried in the supporting gravel layer 3, after the seawater has been infiltrated through the sand filtration layer 2 and a supporting gravel layer 3 on an ocean floor. This cleaning system is provided with a diffuser pipe 7 having blow holes 6, and which is buried in the supporting gravel layer 3, as well as a compressed air delivery device 8 for feeding an air into the diffuser pipe 7. The system operates by blowing the air from the blow holes 6 to agitate the filtration sand of the sand filtration layer 2, to remove the sediments which have become trapped in or accumulated on the sand filtration layer 2.

Abstract: To prevent a door body from shaking significantly when it rises. A floating body flap gate is provided which is disposed on a roadway surface in an opening; and causes a door body to rise to block the opening when water is trying to flow in from the opening by using a water pressure of the water which is trying to flow in and a buoyancy of the door body. The door body is formed with three door body blocks, which are separated in the vertical direction. These door body blocks which are separated in the vertical direction, are connected by rotation mechanisms for rotation at a specified angle within a vertical plane in a direction in which the water is trying to flow in from the opening. The door body is not subject to significant shaking, regardless of the water level at which the water tries to flow in from the opening.

Abstract: To provide a cleaning apparatus suitable for removing clogging substances trapped in a surface layer of a sand filtration layer. A cleaning apparatus equipped with drive wheels serving as a driving device configured to move across a surface of a sand filtration layer. A pump and a jet nozzle are provided as an agitation device configured to agitate a surface layer portion of the sand filtration layer only at a desired depth, and which blows the clogging substances upward into the seawater in a turbid water intake pit together with a filtration sand. A perforated pipe for suctioning turbid water, a pump, an ejector, and a discharge pipe for dilute turbid water are provided as a suction and discharge device configured to suction turbid water blown upward into seawater in the water intake pit by the agitation device, and discharge it to outside of the turbid water intake pit.

Abstract: To clean sediments and the like trapped not only in a top layer of a sand filtration layer, but also in intermediate layers. A seawater infiltration method which uses a water infiltration intake unit which is formed in advance and provided with a water intake pipe embedded in a gravel layer which forms a deep layer of the sand filtration layer, and a backwashing pipe embedded in a sand layer which forms an intermediate layer and a surface layer of the sand filtration layer, and a water suction pipe which is disposed above the sand layer. A desired number of water infiltration intake units are combined to form a sand filtration layer at an installation site on an ocean floor, and they intake seawater from the sea which has undergone natural infiltration in the sand filtration layer and this is introduced into the water intake pipe. The seawater infiltration rate is set at less than 400 m/day.

Abstract: To make it possible to raise a door body even if it is damaged by an impact of vehicle traffic or falling objects when it is in a lowered state, and to keep the door body in a raised state even if it is damaged by a water pressure of a tsunami or a high tide when it is in a raised state. A door body 2 of a floating flap gate 1 is disposed at an opening or at an access way. When water flows in, a forward end 2b of which swings upwards, in a direction in which the water flows in and within a plane in a height direction, around a base end 2a thereof which serves as a center of rotation, to block the opening or the access way. The door body 2 is formed from a hard polyurethane foam 4 in the form of a sheet.

Abstract: To prevent a door body from shaking significantly when it rises. A floating body flap gate is provided which is disposed on a roadway surface in an opening; and causes a door body to rise to block the opening when water is trying to flow in from the opening by using a water pressure of the water which is trying to flow in and a buoyancy of the door body. The door body is formed with three door body blocks, which are separated in the vertical direction. These door body blocks which are separated in the vertical direction, are connected by rotation mechanisms for rotation at a specified angle within a vertical plane in a direction in which the water is trying to flow in from the opening. The door body is not subject to significant shaking, regardless of the water level at which the water tries to flow in from the opening.