How long should wastewater be retained in a grease interceptor for effective separation?

For effective separation in a grease interceptor, the wastewater should be retained for a minimum of 30 minutes. The process of grease separation relies on the physical properties of fats, oils, and grease (FOG) which tend to float on water due to their lower density. During this retention time, the FOG has the opportunity to rise to the surface, allowing the clearer water to exit from the bottom.

If wastewater is retained for a shorter period, such as 15 minutes, it may not provide sufficient time for the FOG to effectively separate and rise, leading to inefficiencies in the interceptor's design and potentially resulting in FOG being discharged into the sewage system. On the other hand, retaining wastewater for an hour may exceed the necessary separation time, which could result in diminishing returns and may lead to operational inefficiencies without additional benefits. Therefore, the optimal retention time for effective separation is set at 30 minutes to balance efficiency and effectiveness in grease removal.