Plant Design for System Flexibility – Minimizing Process Modification Requirements in a Changing Biosolids Environment

Wastewater and biosolids treatment processes are designed to support regulatory requirements for effluent quality and solids final use. However, it is common that future changes in the regulatory environment or solids management area can require subsequent modifications to the plant's processes. While the objective of the original design is to provide for anticipated future requirements, it can be difficult to predict when, or if, more stringent requirements will be imposed. Since higher levels of treatment correspond to greater capital and operating costs, treatment that exceeds anticipated needs is typically not desirable. Consequently, the goal is to design flexible systems that meet current needs but minimize future facility obsolescence or abandonment.The design for the Wakarusa WRF in Lawrence, KS incorporates features that support initial liquid stream and biosolids treatment requirements, but allows relatively easy conversions and upgrades to meet potential tightening of effluent treatment criteria as well as changes in biosolids final use within the lifespan of the plant. These design features avoid abandoning or replacing equipment or facilities. This paper discusses design approaches incorporated in the Wakarusa treatment processes that can maximize system flexibility, which, in turn, will minimize costs associated with removal or abandonment of existing treatment processes.