Patent ID: 7638043

Claim:
A grit chamber for a wastewater treatment plant, including a wastewater tank having a front wall which is defined with a wastewater inlet, a rear wall which faces the front wall and is defined with a wastewater outlet, a pair of side walls which connect the front wall and the rear wall and a partitioning wall which is formed adjacent to the rear wall to extend across a space defined between the pair of side walls, and sand discharge means for discharging sand sedimented in a sand sedimentation zone which is delimited by the front wall, the pair of side walls and the partitioning wall, the grit chamber comprising: a vertical floodgate installed on the partitioning wall and driven in a vertical direction to be opened downwardly from a top toward a bottom; a floodgate driving motor coupled to one end of the vertical floodgate to directly drive the vertical floodgate; an inflow amount measurement means for measuring an inflow amount of wastewater which passes through the wastewater tank; and control means connected to the floodgate driving motor and the inflow amount measurement means to control the floodgate driving motor in response to a measurement result of the inflow amount measurement means, wherein a wastewater level in the sand sedimentation zone is adjusted within a predetermined range through operation of the vertical floodgate so that a cross-sectional passage area of wastewater is changed to constantly maintain a flow velocity of wastewater which passes through the sand sedimentation zone, thereby preventing organic material which is contained in the wastewater and is other than sand, from sedimenting in the sand sedimentation zone.