Investigation of the Effect of Different Amounts of Sawdust on Physical and Chemical Parameters of Municipal Solid Waste compost

Composting is one of the best methods for solid wastes disposal, therefore, some efforts seem to be essential for improving its process and its products quality. The aim of this study was to investigate the effect of sawdust admixture on composting process of municipal waste and some physicochemical parameters of compost such as temperature, pH, EC, heavy metals concentration and nutrient content.

4 piles were prepared and different amounts of sawdust were added (0, 16, 3 and 70%). Every day the temperature was measured within each pile; pH and EC were measured weekly; and heavy metals andnutrient content were measured in final products.

The pile without sawdust showed fluctuation in thermophilic temperature, and the gradual decrease in temperature was started on day 33, whereas this decrease was started on day 18 for 16 and 32% treatments. The pH value was shown to increase on day 21 and then slightly decreased to end of process. The pH value in final product was maximum in 0% treatment (8.1) and it was minimum in 70% treatment 7.73). The EC value showed a slight increase in all treatments during the composting process. Treatments with sawdust showed a low EC value in final products. 0% treatment gave a maximum amount (4.884) of EC and 32% treatment gave a minimum amount (4.235) of EC. The concentration of heavy metals and nutrients, except for Na and K, decreased with sawdust admixture. This was due to dilution effect of sawdust because of low metal content. Na concentration increased with sawdust admixture due to high content of Na in sawdust and used water.

Temperature fluctuation was controlled in composting piles and thermophilic temperature was preserved in active composting phase with sawdust admixture. Also compost quality was improved and heavy metals content decreased; therefore, the negative effects of compost on human health decreased with addition of sawdust