Removal of Cr³⁺ and Hg²⁺ using compost derived from municipal solid waste

Recycling biodegradable fraction of municipal solid waste as compost is increasingly important nowadays. Therefore, this investigation was conducted to find an alternative use of compost as more waste is being recycled. Humic substance content of compost is a potential sorption medium for heavy metals. Batch experiments were used to determine compost capability to uptake Cr³⁺ and Hg²⁺ from synthetic wastewater under different conditions. It was found that the particle size of compost is not related to its humic substance nor its removal capacity. The finer compost particle sizes do not necessarily have a higher humic content and higher removal capacity. Decrease of pH was observed during experiments due to hydrogen ion displacements by the heavy metal. Compost also exhibited the potential to be reused after acid leaching of previous heavy metal uptake to 3 times. Pelleting the compost increased the permeability up to 7 times of its original but the cationic exchange capacity value decreased although not significant. It makes compost media applicable for continuous column operation.