Relative Performance of Grit Removal Systems

Grit is a nuisance material that causes abrasive wear to mechanical equipment increasing maintenance and operational costs while reducing equipment performance and useful life. Grit that is not captured in the headworks accumulates in processes throughout the plant, reducing capacity and detention time, and adversely influencing flow and circulation patterns2. Deposited grit must be manually removed, handled, hauled and disposed. Abrasive wear, process inefficiencies and basin cleaning operations increase treatment plant operating expenses.Choosing a grit removal technology has often been based on equipment price with little regard for device efficacy and consequent grit removal efficiency. The industry has lacked an unbiased side-by-side comparison of the currently available technologies. As a result, owners and engineers are forced to navigate a field of, what can be conflicting, performance claims made by various equipment manufacturers. This situation is perpetuated by the fact that there is no accepted, peer reviewed test standard for grit sampling and analysis.The purpose of this paper is to encapsulate various grit removal system performance data generated by a consistent and repeatable sampling and analysis methodology for the purpose of comparing virtually all grit removal technologies in terms of their effectiveness. Results determined with this sampling method corroborates with the operating history and performance at the tested plants with respect to grit removal, suggesting the accuracy of the test method6. The data provides an unbiased side-by-side comparison of the actual performance of grit technologies based on a repeatable sampling and analysis methodology that owners and engineers can utilize to protect plants from deposition, abrasive wear and associated costs from this nuisance material.