Kusters Water offers a complete line of packaged biological wastewater treatment systems. Standard Plants are designed to operate in the extended aeration mode of activated sludge, providing 24-36 hours of aeration retention time allowing the plant to operate effetively over widely varying flow rates and waste loadings while providing lower overall solids production. When required, the system design can be modified to provide advanced forms of treatment, such as phosphorus (P) and nitrogen (N) removal.