Ciarán J. Lynn

Sewage sludge ash characteristics and potential for use in bricks, tiles and glass ceramics

The characteristics of sewage sludge ash (SSA) and its use in ceramic applications pertaining to bricks, tiles and glass ceramics have been assessed using the globally published literature in the English medium. It is shown that SSA possesses similar chemical characteristics to established ceramic materials and under heat treatment achieves the targeted densification, strength increases and absorption reductions. In brick and tile applications, technical requirements relating to strength, absorption and durability are achievable, with merely manageable performance reductions with SSA as a partial clay replacement. Fluxing properties of SSA facilitate lower firing temperatures during ceramics production, although reductions in mix plasticity leads to higher forming water requirements. SSA glass ceramics attained strengths in excess of natural materials such as granite and marble and displayed strong durability properties. The thermal treatment and nature of ceramic products also effectively restricted heavy metal leaching to low levels. Case studies, predominantly in bricks applications, reinforce confidence in the material with suitable technical performances achieved in practical conditions.

Use of municipal solid waste incineration bottom ashes in alkali-activated materials, ceramics and granular applications: A review

This paper presents a literature review on the incorporation of municipal solid waste incinerated bottom ash as raw material in several markets, other than those where it is conventionally used, such as geotechnical applications and road pavement construction. The main findings of an ample selection of experimental investigations on the use of the bottom ash as precursor of alkali-activated materials, as an adsorbent material for the removal of hazardous elements from wastewater and landfill gases, as soil replacement in agricultural activities, as partial or complete substitute of raw materials for the manufacture of ceramic-based products, as landfill cover and as biogas production enhancer, were gathered, collated and analysed.

6 – Geotechnics and Road Pavements

Synopsis This chapter deals with the use of municipal incinerated bottom ash (MIBA) in unbound, hydraulically bound and bituminous-bound forms, in geotechnical and road pavement applications. As an unbound material, the geotechnical properties of MIBA are evaluated with respect to specified criteria for use as capping and subbase material, including its grading, organic content, compactability, shear strength, deformation behaviour, bearing capacity, permeability and durability. Similar analysis is undertaken on the performance of hydraulically bound mixes incorporating MIBA as an aggregate component. The use of hydraulic binder additives as a treatment to upgrade the mechanical properties of MIBA is also assessed. In bituminous-bound applications, the effect of MIBA on Marshall mix design parameters and the resultant optimal bitumen content are examined, along with testing of the deformation properties and durability of the pavement layers. Environmental impacts associated with the use of MIBA in unbound, hydraulically bound and bituminous-bound forms are covered, along with the relevant case studies that have been undertaken in this area.

3 – Municipal Solid Waste Composition, Incineration, Processing and Management of Bottom Ashes

Synopsis This chapter begins with a description of the legislation and policies affecting the practices of municipal solid waste (MSW) management, including an overview of economic and environmental aspects of waste management strategies. The composition of MSW is subsequently examined, including recent trends and the variability of its constituents across regions. A breakdown of existing types of MSW incineration systems and the main stages of these processes, including the air pollution control systems, is also provided. This chapter then describes the treatment techniques used to upgrade the performance of municipal incinerated bottom ash (MIBA), so that it can become a valuable resource for use in several markets. Finally, the chapter ends with an overview of MIBA management, covering the policies, standards and practices adopted in various countries worldwide.

9 – Case Studies and Standards

Synopsis In this chapter, information on numerous case studies is presented, providing an indication on how municipal incinerated bottom ash (MIBA) has performed in various applications in the construction industry, including aggregate manufacturing, raw feed for cement clinker production, aggregate replacement in concrete- and mortar-related materials, geotechnical applications and the construction of unbound, hydraulically bound and bitumen-bound road pavement layers. Some cases related to the management of municipal solid waste incineration plants, how some of the resulting MIBA has been processed or handled in terms of storage and some of the uses given to MIBA in ceramic-based applications and in landfills are also discussed. This chapter finishes with a section concerning the main existing standards and specifications related to the requirements for the aforementioned construction applications.

Environmental Assessment, Case Studies and Standards

This chapter provides a wide-reaching assessment of the environmental impacts of and case studies on sewage sludge ash (SSA), along with an overview of the relevant standards, for each of the construction applications dealt with in the previous chapters. The environmental assessment centres on the leaching behaviour of the material itself and subsequently when used in concrete, ceramics, geotechnical and road-pavement-related applications. Case studies deal with field tests and pilot-scale and full-scale projects with SSA, providing a valuable insight into the performance of the material under real-world conditions. These projects include the use of SSA as a fine aggregate, filler and cementitious component in concrete; as a clay replacement in ceramics; as a fill material and a soil stabilisation agent in geotechnics and as filler and fine aggregate components in road pavements.

Sewage Sludge Ash Characteristics

The characteristics of sewage sludge ash, based on 237 publications from 30 countries published since 1972, are examined, dealing with its basic physical, chemical and engineering properties. The aim is to establish a familiarity and confidence with the material and highlight its strengths, limitations and potential suitability in various construction applications. The physical characteristics deal with the visual description of the material, fineness, particle size distribution, specific gravity and bulk density, morphology and absorption behaviour. The chemical characteristics cover the oxide composition, organic content (loss on ignition), mineralogy and amorphous content, pH and element composition, including the contents of primary, platinum group and rare-earth elements. The engineering properties deal with the plasticity, crushing resistance and permeability of the material.

Sewage Sludge Ash Production

Drawing from the sourced literature of 301 publications, produced in 38 countries since 1970, this chapter examines the production of sewage sludge ash (SSA), beginning with the generation of sewage sludge during the wastewater treatment process. The basic physical and chemical properties of the sludge are assessed. The various treatments and subsequent use/disposal options for the sludge are presented, along with information on sludge management practices in Europe. The incineration process is examined, outlining the various components of the plant, the sludge behaviour during combustion and the environmental impacts arising from the process. The post-incineration processing of SSA for phosphorus recovery is also dealt with, covering the various wet chemical and thermochemical technologies that have been implemented, in both laboratories and pilot-scale projects.