J+A Jeta® Grit Trap

Grit removal is a prerequisite of wastewater treatment. It prevents buildup in process chambers, and erosion of equipment in the primary treatment works. The J+A Jeta® grit trap is a high performance, compact grit removal unit. With its sloping sides and specially designed impeller, it provides maximum separation of heavy mineral solids (grit) while rejecting lighter organic solids. The Jeta grit trap provides the highest possible grit removal performance in a small plan area.
  • Protection of pumps and other equipment from abrasion
  • Protection of downstream sludge handling equipment
  • Prevention of deposits in tanks, channels and vessels.
  • Reduced footprint and low head loss grit removal system
  • Integral grit washing

Grit removal is a prerequisite of any wastewater treatment plant before it enters the next phases of treatment. If not removed in the beginning of the treatment process, grit will settle and harden downstream, such as in the activated sludge tanks, resulting in a reduction of the available volume/residence time. Unremoved grit can also impact downstream equipment, such as pumps, that would face increased wear as well as potential sludge handling hurdles.

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  • The J+A Jeta® grit trap is an established technology for grit removal, with over 1,000 installations worldwide
  • The fully automatic, low headloss system consumes less energy than competitive devices
  • No submerged contact points, maintenance is reduced and easier
  • Our compact design offers a reduced footprint

Ovivo’s Jeta grit trap has been thoroughly engineered as a compact, efficient system that is economical due to lower excavation and civil works costs for new installations (by incorporating readily available, precast concrete rings in the design) or for retro-fitting the mechanisms into existing plants.

HOW IT WORKS:
Wastewater enters tangentially, flows around the system’s tank and exits parallel to the inlet. Two positive zones are set up within the grit trap chamber. The outer chamber is quiescent, and thus allows the grit to settle on the inclined floor of the chamber. The impeller’s predetermined speed produces radial forces that allow the grit to fall into the collection hopper. These forces also act on the lighter solids preventing them from entering the hopper. The lighter solids are retained in the water flow and carried out of the grit trap for processing in downstream processes. This results in much cleaner grit by preventing the organics from dropping into the grit hopper. The grit is moved to a washing, classification and dewatering plant, using a pump system.

REMOVAL EFFICIENCY:
95% removal of grit larger than 50 mesh
85% removal of grit larger than 70 mesh but less than 50 mesh
75% removal of grit larger than 100 mesh but less than 70 mesh

HEAD LOSS:
Less than 1/4 inch at peak design flow

DESIGN OPTIONS:
Original 270 design or the 360 design is available for all sizes

Why is grit removal so difficult?

Grit is often assumed to behave (settle) like clean sand in water; however, municipal grit does not behave like clean sand. Municipal grit generally has attached fats, oils and greases or other matter which changes the specific gravity from the ideal of 2.65. Also, grit includes inorganic food waste, bones, road tar, bits of metal and sticks.

How does flow through the system affect the grit load?

Grit remains in the system until it is transported to the wastewater treatment plant. The first flush significantly increases the grit load, from 10-30X on average, due to much higher flow velocities.

What happens to grit that is not removed?

Grit that is not removed at the head works will accumulate at every opportunity and harden to a concrete like material.

What quantity of grit is in municipal wastewater? How much should be expected?

Grit volume generally ranges from 0.53-5.0 FT3/MG in most wastewater treatment plants.

How is grit removed from the grit hopper?

The preferred method for grit removal is using a top mounted, self-priming grit pump. Mounting the grit pump on top of the grit trap simplifies the civil works and allows easy access for maintenance of the pump.

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