WET News

High frequency vibrating technology can tackle rag and grit issues 8 WET NEWS JUNE 2016 I n the wastewater treatment industry, the age old problems associated with rag and grit, and the associated detrimental effects, have troubled operators for years. Acute effects include screen blinding, reduced throughput and pipe and pump blockages. The chronic effects are excessive wear, lost production, bypass effects with solids build-up in downstream tanks, and the resulting clean-out costs. These problems have almost become tolerated in treatment works today with operators becoming comfortable with a duty/standby approach being adopted. This however is not addressing the core issue – rag and grit need to be removed from the flow process as quickly as possible. Northern Ireland company, CDEnviro is tackling this issue head-on using high frequency vibrating technology. High frequency screening addresses a number of core issues that are apparent within conventional screening solutions: Surface tension Surface tension, particularly within high viscosity and high solids loading sludge flows, has meant that screening flowrates in static or slow moving screens has hit an upper limit. With only the incoming slurry pressure working to overcome surface tension, an inherent material property, screening flow rates are reduced to what can be forced through the screen under pressure. However, high frequency screens are not bound by this glass ceiling of flowrate. While these vibrations move the screen through the sludge, the surface tension is broken and the pressure of the liquid is able to drive flow through the screen much more quickly. The results are flowrates that Maintaining the flow with good vibrations ONSITE RaggiNg & gRit are unusually large given the available screening area, or conversely, screens that can be placed in high flow applications without need for duplication. Blinding Blinding is vigorously discouraged within high frequency screening. A traditional screening system, during its best efforts to increase flowrate, must also force rag against the static screening mesh. The result is blinding of the screening apertures, reduced efficiency, and before long, manual intervention is needed. However, with a high frequency screen, rag is encouraged to be repeatedly li‡ed off the screening surface, such is the force of the vibrations on the individual particles. Therefore, rag is disinclined from blinding or pegging on the screening media. • across the world, the struggle with common foes; rag and grit, is about to get a shake-up. CDEnviro's Philip Mcglade reveals all. projEcT SpEcS • Prevent associated detrimental effects caused by rag and grit • Remove rag and grit from the flow process as quickly as possible Recovered grit can be finally dewatered on a separate section By discharging directly onto the S:MaX g screen, a buffer tank is no longer required.

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