Guidelines For Grit Pumping And Piping

By Isaiah LaRue, Municipal Wastewater Systems Manager, Smith & Loveless Inc.

Efficient grit removal in wastewater resource and recovery facilities (WRRFs) is more crucial than ever. The rising application of membrane bioreactors (MBRs), specialized pumping equipment, and fine bubble diffusers in plant infrastructure require protective equipment up front to maximize service life and operation. Complete vortex grit removal systems, designed to optimize downstream operations, comprise grit chambers, grit handling equipment and grit washing/dewatering. But what if the grit removal system itself is not performing optimally?

Many times, the assumption is that the physical grit removal device (i.e."grit chamber") is not performing correctly. Closer diagnostics may actually reveal that grit is being removed from the wastewater stream but getting plugged in the second-stage grit handling scheme, which typically entails the grit pump (to transfer the removed grit from the chamber), grit concentrator or cyclone (for separation of residual organics), and a grit washing/dewatering device (to clean and dry the removed grit). There is an old saying that a chain is "only as strong as the weakest link." For many complete grit removal systems, the weak link occurs when grit is pumped