Extreme Duty sludge mixers from WesTech Engineering provide vigorous mixing of digester contents to prevent stratification and improve the anaerobic process. They reliably speed gas production while reducing foaming and scum accumulation. They were originally developed to reduce the high service costs of egg-shaped digester mixers, but are now used for maximum efficiency and durability in all digester-mixing applications. 801/265-1000; www.westech-inc.com.