Abstract
In recent years, an enormous amount of sludge is generated every day from zero liquid discharge treatment plant due to rapid expansion of industrial parks in Ethiopia. About 30,000 tons of partially dried sludge discharged to the environmental without proper waste management from all industrial parks. Thus, posing serious environmental problems. One of the most plausible means to recycle the excess sludge resource is converting it into energy-efficient brick by combining with clay. Bricks were prepared by incorporating textile sludge at different proportions (10–40%) and temperature (600, 900 and 1200 °C). Clay and sludge samples were collected from the Addis Ababa brick factory PLC and Hawassa Industrial Park. Results revealed that 10 and 20% sludge bricks satisfied criteria of class “A” bricks as per Ethiopia standards, with the compressive strength of 30.43 and 29.10 Mpa, respectively, at 1200 °C. About 26 and 50% of energy were saved during firing of 10 and 20% sludge-containing bricks, respectively, compared with pristine clay bricks. Moreover, too low concentrations of selected heavy metals found in the brick leachate, showing the sludge, were effectively stabilized in the burnt clay bricks. Thus, based on the results, we suggest the rapid utilization of huge amount of partially dried sludge resources for low-cost and efficient large-scale brick production. This will mutually benefit both the industrial parks and brick production industries. In addition, this will create thousands of jobs to the local people. Above all, the solid waste will be managed properly at textile industrial parks.
Highlights
Textile industry sludge is one of the main pollution problems worldwide due to its dye-containing wastewater
Energy-efficient bricks were prepared by incorporating textile sludge at different proportions and temperatures
The compressive strength of textile sludge bricks reduced considerably from 30.43 to 2 MPa when the textile sludge content increased from 10 to 40%, and it increases with firing temperature
Summary
Textile industry sludge is one of the main pollution problems worldwide due to its dye-containing wastewater. The thermal treatment of sludge involves incineration, gasification, and pyrolysis as a means of disposal, which are costly and may contribute to air pollution, and the residue with high content of toxic metals still has to be disposed off to the environment (Đurđevic et al 2019; Juel et al 2017; Oladejo et al 2019). An alternative technique to treat or stabilize hazardous waste is solidification method and using the solid as construction materials such as ground leveling, brick, or concrete. These can be applied in several instances for the cases of sewage, textile sludge, and arsenicrich filter materials (Arsenovic et al 2012; Barnat-hunek and Wdowin 2016; Patel and Pandey 2012; UNDP et al 1998). Sewage sludge ash can provide as resource for phosphorous and material for clay brick manufacturing (Ottosen et al 2020)
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