Investigation of the conversion of the sludge of high organic content into economically valuable products

Abstract

Sludge generated from domestic wastewater treatment is used for different purposes such as fertilizer, land reclamation, solid waste stabilization, energy production, composting etc. On the other hand, new areas for sludge utilization are favored for alternative solutions. Solidification/stabilization technique has been investigated widely for final disposal of industrial wastewater treatment plant sludge. Whereas, studies on solidification/stabilization of domestic wastewater treatment plant sludge is limited. Proposed technique in this study not only aimed for the solidification and stabilization of domestic wastewater treatment plant sludge, but also utilization of the product in various construction applications. In order to achieve this goal, solidification/stabilization technique was applied to domestic wastewater treatment plant sludge to obtain products with high unconfined compressive strength and low metal leaching. Different additives were used in the research in order to achieve the solidification of domestic wastewater treatment plant sludge. Clinoptilolite, a type of zeolite, was preferred for its high cation exchange capacity preventing metal leaching from the solidified samples, and its low price. Class C fly ash, waste of thermoelectric power plant, was used for its self-cementing property. Lime was added in order to enhance the solidification and sludge stabilization. Perlite was used in latter studies in order to benefit from its light weight and thermal insulation property. Sludge was mixed with the additives in varying ratios and cured at different media for different periods. Objective of the study is to investigate a new area for domestic wastewater treatment plant sludge utilization, such as construction applications. For this purpose, solidification/stabilization of domestic wastewater treatment plant sludge with high organic content, which is not a widely studied process, was achieved with zeolite, fly ash, lime and perlite. The products obtained have high unconfined compressive strength values and low metal leaching which indicates the applicability of the products in construction applications.