Composting of Sewage Sludge with Sawdust on a Pilot Scale

The aims of the research were to study the characteristics of sludge composting with sawdust and investigate the changes of physical and chemical parameters on a pilot scale. The distribution of the air was equal relatively, and the oxygen was enough for the growth and respiration of microorganism in the pile. The temperatures could meet the demand of sanitation during the composting. The changes of the oxygen consumption rate and oxygen content were corresponding to the change of the temperature, and the activity of microorganism was high in the thermophilic phase. The pH value increased rapidly at first and then decreased gradually. The electric conductivity indicated that microorganism could degrade the macromolecule matter into small molecule matter, and the water soluble ion increased, especially in the thermophilic phase. The moisture content decreased remarkably during the composting, but the organic matter decreased slightly because the sawdust containing abundance of lignin was in the compost materials. The bacteria, fungi and actinomycosis were the predominant microorganism for degrading the organic matter during the composting. In total, the quality of compost could meet the demand of the sludge quality for afforestation in gardens or forests.