Abstract
Sewage sludge is a high-volume and low-cost waste commonly generated worldwide, so its utilization is a vital issue. The application of this waste in the manufacturing of lightweight aggregates was investigated. The process was performed using intensive mixers with volumes of 5 and 30 L, as well as the industrial 500 L mixer. Then, granulates were sintered in a tube furnace. The influence of composition and mixer size on the particle size, microstructure, mechanical performance, and stability of lightweight aggregates in different environments was analyzed. The best results were obtained for a 500 L mixer, enhancing the industrial potential of the presented process. Increasing the share of sewage sludge in the composition of aggregates enhanced their porosity and reduced the specific weight, which caused a drop in compressive strength. Nevertheless, for all analyzed materials, the mechanical performance was superior compared to many commercial products. Therefore, sewage sludge can be efficiently applied as a raw material for the manufacturing of lightweight aggregates. The presented results confirm that a proper adjustment of composition allows easy the tailoring of aggregates’ performance and cost.
Highlights
Wastewater treatment plants are one of the sources of organic waste
We investigated the manufacturing of lightweight aggregates as a potential method of sewage sludge utilization
lightweight aggregate (LWA) from sewage sludge, fly ash from power plants and waste clay in this study provides a high potential for reusing significant Sewage sludge (SS) and waste materials, resolving the disposal problem of these waste streams
Summary
Wastewater treatment plants are one of the sources of organic waste. The amount of sewage sludge produced in the European Union per year was 10 million tonnes in 2008, 11.5 million tonnes in 2015, and is expected to approach 13 million tonnes of dry matter (DM) by the end of 2020 [1].Sewage sludge (SS) produced in Poland is expected to reach 746 Gg of dry weight per year by 2022 [2].The primary method of SS disposal in Poland is through land-filling and agricultural use methods, and this practice will lead to land scarcity problems. Sewage sludge (SS) produced in Poland is expected to reach 746 Gg of dry weight per year by 2022 [2]. The biological treatment of municipal wastewaters yields large amounts (up to 2% of the influent stream volume) of sewage sludges of different types (primary, secondary, mixed, and excess sludges), which are, waste organic–mineral by-products. They must undergo further multistage processing to eliminate ecological risks and microbiological hazards [3].
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