Collect measured inputs
Record sludge volumetric flow, feed total-solids fraction, representative density, neat emulsion flow and declared active fraction. Use synchronized averages over a stable operating interval.
Pump dial settings and nominal sludge solids are not sufficient. Verify the polymer pump and use recent feed-solids analysis.
Calculate dry-solids loading
Dry-solids mass flow equals sludge volumetric flow multiplied by density and total-solids fraction. Keep units explicit and convert both flows to the same time basis.
When density is approximated, state the assumption. For concentrated or unusual sludge, measure it because a small error propagates into the reported dose.
Convert neat product to active mass
Active-polymer flow equals neat-emulsion mass flow multiplied by active fraction. If the pump is measured volumetrically, use product density from the current technical data.
Active dose is active-polymer mass divided by dry-solids mass. Report it consistently as kilograms active per tonne dry solids or an equivalent unit.
Use the result in a dose curve
Plot capture, cake solids, throughput and operating symptoms against active dose. Identify the lowest stable window that meets the combined endpoint instead of choosing the maximum cake solids point alone.
Repeat measurements when feed total solids move. A constant neat flow produces a changing dry-solids dose if sludge loading changes.
Compare commercial offers
Convert each supplier's neat price and active fraction into cost per active kilogram, then apply the verified active dose. Add effects on disposal, solids loss, wash water and throughput.
Carry the calculation into the delivered treatment cost comparison rather than comparing drum price alone.
Keep unit conversions explicit
Write each conversion factor beside the calculation and keep mass, volume and time units visible. For example, distinguish percent total solids expressed as a fraction from a percentage number, and distinguish kilograms per hour from litres per hour.
Use a spreadsheet or control-system calculation only after checking it against one manual example. A correct formula fed by the wrong density, active fraction or time basis can create a plausible but misleading dose.
Control measurement uncertainty
Feed solids sampling, pump pulsation and short process runs can introduce more uncertainty than the apparent difference between two products. Use composite or repeated samples and long enough steady periods to represent the separator residence time.
Report a practical dose range when the data do not support a single precise value. The purpose is a stable control window that operators can maintain, not an artificially exact laboratory number.
Audit automated dose calculations
When a control system paces polymer to sludge flow, verify the configured pump curve, active fraction, density, total-solids signal and engineering units. Check minimum and maximum outputs and confirm what happens when a signal fails or freezes.
Compare the displayed active dose with a manual calculation from measured flows during routine checks. Alarm limits should identify implausible dose changes early enough for an operator to protect capture and cake quality.