Grit particle characterization: influence of sample pretreatment and sieving method

Abstract

Grit causes problems in water resource recovery facilities (WRRFs): clogging pipes, damaging pumps, and reducing the active volume of aeration tanks and anaerobic digesters by grit accumulation.Grit chambers are built to remove these particles. However, no standardized methodology exists to characterize grit particles for grit chamber design and operation despite the large observed variability in grit composition. Therefore, this paper proposes a combination and adaptation of existing methods to sample and characterize grit particles in view of proper grit chamber design and its modelling to ultimately optimize the efficiency of this important WRRF unit process. Characteristics evaluated included particle size distribution from sieving after different sample pretreatments, organic/inorganic fractions, and density.

Characterizing the settleability of grit particles

“…More importantly, since the organic fraction of removed grit is significant and variable (Plana et al, ), and since the density of the particles is thus variable, direct measurement of the governing characteristic, particle settling velocity, should be pursued, rather than using particle sizing that cannot easily be translated into settling characteristics. Hence, the study of the PSVD allows better estimation of the grit chamber performance and, consequently, has the potential of promoting better designs.…”

“…However, in reality, grit particles are heterogeneous particles that do not have a single representative value of specific gravity and should not be considered inorganic homogeneous spheres (Herrick, Neumayer, & Osei, ; Plana et al, ).…”

“…Thus, the Water Environment Federation's Grit Task Force has suggested a definition that considers the settling velocity of the grit particle as it exists in the raw wastewater (WEF, ). In addition, it is now recognized that the organic fraction of the grit particles is significant, and the specific gravity is variable and lies between 1.1 and 2.65 (Plana et al, ; WEF, ).…”

Geotechnical Properties of Washed Mineral Waste from Grit Chambers and Its Potential Use as Soil Backfill and Road Embankment Materials

“…Moreover, most papers concern only mineral waste characterization and grit chamber performance evaluation, with a significant proportion being site-specific [14]. Hence, the main purpose of studies is usually to optimize the design guidelines of grit chambers for mechanical wastewater treatment and their technological processes [14][15][16][17][18][19]. The papers [15,19] also present an additional purpose, which is to consider the possibility of processing and using mineral waste in construction.…”

“…The papers [15,19] also present an additional purpose, which is to consider the possibility of processing and using mineral waste in construction. The conducted research focuses on determining the physical properties of mineral waste in terms of dry matter content, the content of organic and inorganic substances, granulometric composition, specific density and the settling velocity of particles in grit chambers [14][15][16][17][18]. The sieving and sample pretreatment methods used to characterize wastewater sand particles are also included in [17].…”