Trickling Filters and RBCs · Recirculation and Loading
What Is a Trickling Filter Recirculation Ratio?
The recirculation ratio compares the flow returned to the filter with the plant's incoming flow.
Both flows must use the same units and the same time period. A ratio of 0.50 means the recirculation flow is half of the influent flow. This is a math example, not a recommended setting.
The math box shows the formula and a worked example. The total flow applied to the filter is the influent flow plus the recirculation flow.
Check where each meter is before you do the math. A meter may already show the combined flow, and adding the recirculation flow again gives a wrong answer. A higher ratio means more wetting and more dilution of strong waste, but more pumping and more water to the clarifier. A lower ratio saves power but can leave the media dry at low flow.
Key point: A recirculation ratio is useful only when you understand the flow readings and where each meter sits.
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Trickling Filters and Rotating Biological Contactors
This page comes from the course. It covers biofilm, trickling filter equipment, recirculation and loading, lab tests, sloughing, RBCs and common operating problems, one step at a time, with short knowledge checks and a certificate of completion.
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