Design Evolution of the Solid Bowl Conveyor Centrifuge For Municipal Wastewater and Water

The evolution and application of the solid bowl conveyor centrifuge is examined for the last sixty years, decade by decade, along with future design improvements and concepts for thickening and dewatering biosolids. Considering municipal biosolids are unique, being principally soft compressible solids combined with discrete abrasive solids, design engineers had to transition from standard designs to specific designs for this application. Discussion will show these designs have evolved slowly and methodically for achieving desired process performance in combination with industrial type reliability and availability. Emphasis, especially for the US market, was directed to having a product with the lowest cost effectiveness considering capital and operating influences based on a typical EPA life evaluation period of 15 to 20 years. Details of design features are developed including those associated with bowl configurations, conveyor concepts, material of construction, electrical, automation and operating g-force.As time progressed, it may be noted that further centrifuge design changes and improvements became necessary to meet the demands of the municipal market. These included standards for a better quality discharge, more expensive disposal costs and municipal plant processing changes that produced a greater proportional amount of finer and a more compressible type biosolids.A significant topic of discussion is that the solid bowl conveyor centrifuge utilizes only a small portion of the theoretical settling capacity as defined by Sigma and other standards, This presented the opportunity to achieve significant improvements in designs lowering the overall cost per unit of flow or solid tonnage. Another significant topic of discussion is that of a mechanical item, where the first efforts are directed to mechanical issues followed by incorporation of flow dynamics and lastly electrical items and automation.