Characterisation of Grit to Develop an Integrated Plant Solution

Grit entering a plant is varied in its nature however traditional design practice revolves around a single particle size and density.Therefore a greater understanding the characterisation of the influent grit is key to developing an overall solution for a site. Sampling programs should be set up to establish the characterisation of grit being captured in each tank and that within the primary sludge stream.This paper talks about issues faced in the design of grit systems and at one such site where the results of grit characterisation showed the system was complex, with a number of different factors affecting particle movement. In particular:• Heavier particles followed the path of least resistance;• Lighter particles will distribute more evenly throughout the tanks• Movement of grit particles was influenced by influent pump operation, channel mixing and the geometry of the tanks;• A significant proportion of the grit in wet weather were small, light, particles which passed through to the sludge stream.