Producing drier grit

Producing drier grit

Hydro GritCleanse from Hydro International

Hauling and disposal of effluent and grit is often one of the largest budget items wastewater treatment plant operators need to consider. Those costs are only going to increase, too, as landfill space fills up across North America. Taking a proactive approach to reduce the total amount going to the landfill may be a partial answer. Hydro International recently introduced the Hydro GritCleanse fluidized-bed grit washing system — a unit that significantly reduces volatile solids content to produce cleaner and drier grit. Cutting volatile solids grit reduces weight, volume and water content, which can significantly reduce odors and save money on landfill costs.  

The system retains 95 percent of grit 106 microns and larger and discharges washed grit with less than 5 percent volatile solids, according to the company. Flow is introduced tangentially into a conical clarifier, forcing the grit to contact the vessel walls, creating drag forces and establishing a rotary flow pattern. Incoming grit settles into the low-velocity boundary layer at the inside wall of the vessel. The structured, laminar flow pattern allows retention of fine and slowly settling grit particles, while the interior baffle prevents short-circuiting.

Once in this boundary layer, grit is further decelerated and settles to the bottom of the unit into the gently agitated fluidized bed, where physical forces separate fixed and volatile solids by density. This causes grit to fall to the bottom of the bed while the lighter organic materials remain in suspension at the top of the bed.

Washing occurs in the fluidized bed as organic material attached to the grit particles is scrubbed away due to friction between particles. The higher-density cleaned sand descends to the bottom. Once the grit is captured, organic particles flow out of the unit for additional treatment downstream. Cleaned grit is intermittently discharged to a dewatering screw.

According to the manufacturer, the GritCleanse unit works best when paired with its grit separation systems such the HeadCell and Grit King to provide a complete advanced grit washing and dewatering system. The system can be deployed for grit washing where very low volatile solids levels are required. It is suited for new wastewater treatment plants, plant retrofits and as a replacement for worn out or ineffective grit washing and dewatering systems. 



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