Abstract:
To study the effect of sludge age on settling efficiency in AS process. Three types of ballasting agent; talc, powder activated carbon (PAC), and crumb rubber were added in the 3 lab-scale AS processes which controlled the sludge age as 3, 10 and 30 days. The initial settling velocity (ISV), COD removal and floc forming were studied in this research. The sedimentation tank can be design by using the ISV results. The experiment found that the talc addition made the highest ISV of 10.6 m/h. The ISV of PAC addition and crumb rubber addition were 7.2 and 6.6 m/h, respectively. On the contrary, in control set, the ISV were lower than 5 m/h that indicated worse settling. However, all of ballasting agent in this experiment made higher ISV than the control without bassasting agent in every condition. Moreover, in the term of COD removal, the result indicated that the highest COD removal more than 97% was achieved in PAC added reactor. In the same way, talc and crumb rubber had COD removal more than 95% in every condition of sludge age. Also, the study of floc formation between ballasting agent and sludge from the microscope and Scanning Electron Microscope (SEM) revealed that 3 agents can agglomerate better floc and no interference with bacterial activities in every sludge age. Moreover, the study discovered the attach of microorganisms on the crust surface of ballasting agents. In the term of sedimentation tank design, the surface area of the tank in the enhance AS by using ballasting agent was decreased, especially in talc addition. As a result, the highest Limiting Flux (GL) of talc, 1,753 kg/cb.m -day made the smallest surface area of the tank.