If the required polymer dose for a gravity thickener is 8 mg/L and the flow to the thickener is 0.91 mgd, what should the chemical feeder setting be in mL/min, given a 70% active polymer agent?

To determine the correct chemical feeder setting in mL/min, it is essential to first calculate the total required polymer dose based on the flow rate and then adjust for the concentration of the active polymer.

1. Flow Rate Conversion: The flow to the thickener is given as 0.91 mgd (million gallons per day). To convert this to liters per minute (L/min), use the conversion factor where 1 mgd equals approximately 3785 liters per day (L/day) and then convert days to minutes:

[

0.91 \text{ mgd} = 0.91 \times 3785 \text{ L/day}

]

[

= 3447.35 \text{ L/day}

]

[

= \frac{3447.35}{1440} \text{ L/min} \approx 2.40 \text{ L/min}

]

2. Calculating the Polymer Requirement: The required polymer dose is 8 mg/L. Therefore, the total amount of polymer required per minute is calculated by multiplying the flow rate in L/min by the dose in mg/L:

[

\