Research on Drying Effect of Different Additives on Sewage Sludge

AbstractWith the increasing amount of sewage sludge produced in China, it has been a serious environmental problem because of its containing heavy metal, virus and some organic pollutant. However, high water content is a critical problem to treat sewage further. Deep dehydration of sludge (moisture content≤60%) has significant relationship with subsequent treatment and disposal. We should optimize process technology, aiming at improving drying effect and reducing economic cost. To add some chemicals to dewater sewage sludge is one of the cost-saving technologies. This study examined the influence of additives on dewatering characteristics of sewage sludge, and the additives includes lime, coal ash, diatomite, sodium dodecyl sulfate (SDS) and fly ash from municipal solid waste incinerator. As to each additive we tried different additional ratio from 5% to 30% based on mass. It is found that lime (analytically pure) is the most efficient to dewater sewage sludge, then the next is coal ash, diatomite, sodiumdodecylsulfate (SDS) and fly ash. The result demonstrates that as to lime the addition dose of 25% is cost- effective. What's more, we performed experiments of adding two kinds of additives to find out if there is any interaction between additives so that the dewatering function can be strengthened or reduced. As lime has the best result in solely addition and because it can disinfect the sewage sludge, it is added in every combination experiments with different addition ratio, for example, combination of lime (5%) and coal ash (20%), or combination of lime (10%) and diatomite (10%). We found that the dewatering function is seldom strengthened or reduced, and it is just like adding the two additives respectively