Reuse and recycling options for solid prescribed industrial wastes and brown coal fly ash

Abstract

This dissertation presents the results of detailed investigation of the possible use of stabilised sludge and brown coal fly ash as raw material ingredients for road construction and manufacture of building bricks. The thesis is organised into seven chapters including a general introduction chapter. A literature review of solid waste management practices employed in Australia and some selected countries are discussed (chapter 1) together with waste generation from power stations. Particular attention is given to industrial waste disposal into Victorian landfills and the current waste management system in the state is compared with international best practices. The sampling program and sample collection methods used in this study are described in chapter 2. The results of the preliminary waste characterisation of treated solid industrial wastes from waste treatment plant, mainly slurry (liquid sludge), filter cake and stabilised sludge are presented in this chapter to provide a snapshot of the organic and inorganic composition of the waste materials. It also enabled the identification of key target analytes of concern for further study. The methodologies and analytical instruments employed in the sampling plan and analyses used are also discussed in this chapter. Chapter 3 focuses on elemental, organic and ionic chemical analysis of filter cake and stabilised sludge from industrial waste treatment plant using different analytical techniques. This chapter also contains elemental characterisation of brown coal fly ash from power stations in the Latrobe Valley, Victoria, Australia. The leachability of heavy metals from filter cake and stabilised sludge samples are also presented in this chapter and the identified components that can impact on the potential reuse/recycle of the solids were examined by using different analytical techniques to improve the treatment performance in terms of transfer of contaminants from liquid to solid phases. The principles and applications of XRD, TGA and SEM techniques to the analysis of environmental samples are discussed in chapter 4. XRD and TGA analyses were conducted on filter cake and stabilised sludge from industrial waste treatment plant,whereas SEM analysis were performed on fly ash, mixture of fly ash and stabilised sludge, bricks produced from sludge/fly ash and clay fired at 1000 °C. Characterisation of the waste materials with these techniques revealed that phase, thermal and morphological properties are useful to understand the complex mineral composition and the performance of waste materials for certain end use applications. The suitability of stabilised sludge and brown coal fly ash mixtures as road base and sub-base material (chapter 5) was investigated by measuring index properties, pH and electrical conductivity, compaction, unconfined compression strength, California bearing ratio, triaxial shear stress and permeability tests. This chapter also discussed the physical and mechanical properties of the individual waste streams (sludge and fly ash) as a first step in identifying its potential application for reuse/recycle as raw material ingredient in road construction. The results obtained in this chapter indicate that the addition of fly ash to the stabilised sludge and curing time were the most important factors to improve the physical/mechanical properties of the waste materials. The combination of stabilised sludge and fly ash as raw material ingredients for making building bricks was considered in chapter 6. The characteristics of bricks made from these waste materials in different mixtures were investigated. The successful development of a new process for making bricks is detailed in this chapter and the product is referred to as Enviro-brick. This process provides an opportunity for reducing the environmental impact of solid industrial wastes from waste treatment plants and power stations. The conclusions and implication for further research are presented in chapter 7.