Assessment of Fine and Coarse Sewage Sludge Ashes for Their Potential Use in Civil Engineering

Abstract

New environmental challenges and research opportunities arise on the use of solid wastes as well as their basic properties. In fact, recycling of these wastes and their by-products is attracting increasing interest worldwide because of the high environmental impact in the cement, concrete and other industries. Two types (type1: Fa100 and type 2: Ba100) of sludge ashes from the sludge waste center of Camberene (Senegal) were combined with different proportions of lime to assess their potential use in civil engineering. XRF, optical microscopy and spectroscopy were used to characterize the samples. The following major elements are present in the ashes: SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO, P 2 O 5 . For the minor elements their concentration are very important in type 1 compared to those in type 2. These ashes have similar composition with cement except for CaO. The measurement of absorbance on the ashes shows a clear difference in optical absorption between samples. The lime pellet transmits more compared to Ba100 and Fa100 pellets. The materials obtained by mixing ash with lime in various proportions have a lower optical transmission with respect to lime and ash taken separately. Thus, the designed materials transmit less light which suggests an improved thermal isolation. The studied ashes suggest that they are not dangerous based on the Annex III of (criterion H14 of Directive 91 / 689 / EEC).

Analysis of aerobic and anaerobic sewage sludge disposal concepts

“…Thermal transformation of sewage sludge allows the removal of organic components of sludge and pathogenic organisms and reducing sludge weight by up to 90% (Hudziak et al, 2012;Gawdzik & Latosińska, 2014;Payá et al, 2019;Sall et al, 2020). Harmful and hazardous substances are disintegrated into environmentally inert substances or transformed into more stable forms, minimising the risk of ecological hazards.…”

“…However, studies indicate the possibilities of ash utilisation. One of the directions is to use it in the production of cement, concrete or ceramics (Payá et al, 2019;Sall et al, 2020;Chin et al, 2016). The studied ashes in terms of silicon, aluminium, iron, calcium or phosphorus oxides content show great similarities to the cement composition (Sall et al, 2020).…”

“…One of the directions is to use it in the production of cement, concrete or ceramics (Payá et al, 2019;Sall et al, 2020;Chin et al, 2016). The studied ashes in terms of silicon, aluminium, iron, calcium or phosphorus oxides content show great similarities to the cement composition (Sall et al, 2020). In another study, the authors showed that the addition of ash from sewage sludge incineration to cement mortar improves the compressive strength of the material (Chin et al, 2016).…”

Comparative Characteristics of Hydrated Lime with Fine Sewage Sludge Ash (FSSA) and Coal Fly Ash (CFA)

“…For the Al 2 O 3 the concentration in the former is instead 1.8 times higher than that in the latter. The chemical composition of FSSA and CFA is closer to that of cement produced by industries in Senegal having the following chemical composition: SiO 2 (19.53), Al 2 O 3 (7.12), Fe 2 O 3(2.22), and CaO (65.5)[29]. These oxides SiO 2 , Al 2 O 3 and Fe 2 O 3 compose the reactive part of pozzolanic materials[30] [31].…”