What percentage of the liquid depth should an outlet baffle extend in a sewage tank?

In a sewage tank, the outlet baffle is designed to control the flow of effluent while preventing surface scum from entering the outlet. The recommended extension of the outlet baffle is important for proper sewage tank operation and ensuring the separation of solids and liquids.

Extending the baffle to 40% of the liquid depth is suitable because it balances the need to keep the outlet submerged below floating solids and scum while still allowing adequate flow rate and system function. This dimension is established based on the principles of gravity separation; keeping the baffle at this height helps in maintaining effective treatment and reducing the likelihood of solids being discharged.

If the baffle were to extend further than 40%, it could lead to unnecessary restrictions on flow, while a shorter extension could risk allowing solids to leave the tank. Therefore, the 40% extension strikes a necessary balance to promote efficient effluent discharge and maintain water quality standards.