The formula below can be used to calculate the total flow, in gallons per day, including recirculation
The "Recirculation" is the percent of the influent flow which is recirculated through the trickling filter. The recirculation must be expressed as a decimal. To express a percentage as a decimal, simply divide the percentage by 100. So if 2% of the influent flow was recirculated, the Recirculation would be:
Let's consider a plant with an influent flow of 72 mgd and a recirculation of 0.009. The total flow would be calculated as follows:
Be sure to convert to the correct units, if necessary. I converted 72 mgd to 72,000,000 gpd.
You may have also noticed that I added 0.009 to 1 before I multiplied the total by 72,000,000 gpd. It is very important to always perform any operation within parenthesis before simplifying the rest of the equation. Otherwise, you will get the wrong answer.