Flushing a Reclaimed System for Better Performance — Theory, Practice and Results

The City of Tampa conducted a project to eliminate residual debris from a reclaimed water system and provided modifications to prevent excessive bio-growth. Bio-growth reduction was evaluated using a GIS-based hydraulic model. Model runs were made to determine the water age and chlorine residual based on a bulk chlorine decay coefficient determined though testing. The model was calibrated after field testing of chlorine residuals. The calibrated model was utilized to determine options for maintaining water quality.The unidirectional flushing program was designed and conducted. The construction contract included installation of permanent blow-offs and metered bleed-offs to reduce water age. Debris left from the original construction of the system and significant bio-growth were encountered and flushed from the system.The project demonstrated that water age can have a significant adverse effect on the operation of a reclaimed water system, especially a system that is not yet at design capacity.