Surge Analysis and Design for a Wastewater Transmission System in Hernando County

This paper presents a surge analysis and provides an engineering design to protect a wastewater transmission system in Hernando County, Florida from potential pressure surge damages. Pressure surge, also known as water hammer or hydraulic transient, is a time-varying momentary phenomenon. It happens when the equilibrium of a flow system is disturbed by a status change over a relatively short time period. Caused by either immediate start-up or shut-down of pumps, or rapid opening or closing of valves, surge events can introduce large pressure forces and rapid fluid accelerations into a water distribution system. This may result in pump and device failures, system fatigue or pipe ruptures, and even dirty water backflow/intrusion. Therefore, surge protections are extremely important for the design of hydraulic system. In this paper, surge analyses of a wastewater transmission system are performed using the HAMMER program. The simulations indicate the system with no surge protections is extremely vulnerable to surge events and might suffer serious damages from transient pressures (both downsurge and upsurge pressures). In order to mitigate potential surge damages, design engineers propose one cost-effective surge protection system including adding air valves, hydropneumatic tank, surge valves, and, more important, recommending proper operation and maintenance procedures. The final simulation results show that the proposed surge protection system can provide adequate surge protections to both the piping and deep injection well systems. Furthermore, special considerations are discussed and summarized in application of hydropneumatic tanks and air valves in wastewater systems.