A pump setting is not a cationic PAM dose. Fair grade and cost comparisons require active polymer mass divided by sludge dry-solids mass over the same time period.
Calculate dry-solids loading first
Dry-solids mass flow equals wet sludge flow multiplied by solids mass fraction, with units converted consistently. For example, a feed reported at 2 percent solids uses 0.02 as the fraction. Density may be approximated only when justified; use measured mass flow when precision is important.
Calculate active polymer delivery
For a prepared dry-polymer solution, active delivery depends on stock concentration and actual solution flow. A 0.2 percent solution contains 0.002 mass fraction active polymer. Pump calibration should measure collected mass or volume over time at operating back pressure, not rely only on a dial or nameplate.
Divide active polymer by dry solids
Convert both flows to compatible units, then divide active polymer mass by dry-solids mass. Report the result as kilograms active polymer per metric ton dry solids or pounds per dry ton, and state which ton is used. Do not mix dry product dose with as-supplied emulsion dose.
Handle emulsion products correctly
Emulsion contains a specified active fraction rather than 100 percent polymer. Use supplier documentation and the agreed basis. Compare products on active polymer where possible, while also including inversion chemical, water, equipment and handling cost.
Calibrate around real operating pressure
Measure pump output at several settings and create a calibration curve. Check suction condition, pulsation, check valves and changes in solution viscosity. Recalibrate after maintenance or concentration changes. A drift in feed solids also changes the required solution flow even when the dose target remains constant.
Use the result during a trial
Hold feed and machine conditions stable, apply defined dose steps and wait for process residence time before sampling. Record filtrate or centrate, cake, capture, throughput and mechanical settings. This converts a visual trial into evidence that can support purchasing.
Check the economic denominator
Polymer price per kilogram should be combined with active dose and dry solids treated. Add the value of cake reduction, capture, throughput and less cleaning. The quality and supply page explains why specification values alone cannot establish delivered treatment cost.
The US EPA dewatering manual provides background on sludge conditioning and mechanical dewatering. Plant calculations must still use measured flows and the actual product basis: EPA dewatering design manual.
Worked calculation structure
Write the calculation as a chain of measured values so another operator can reproduce it. Start with wet feed volume per hour and measured solids fraction. Convert to dry kilograms per hour. Separately calculate solution mass flow from calibrated pump delivery and solution density, then multiply by active fraction. Divide active kilograms per hour by dry tons per hour. Keep every unit on the worksheet; most serious dose errors come from percent conversion, time-base or metric-versus-short-ton mistakes.
Manage variable feed solids
A fixed solution-flow setpoint produces a changing dose when feed solids drift. Where practical, pace polymer to dry-solids loading using reliable sludge flow and density measurement. If online solids measurement is unavailable, use frequent representative checks and define adjustment rules. Record the value used for each trial sample rather than applying a later daily average that may not represent the test period.
Separate stock concentration from secondary dilution
Secondary dilution water improves distribution but does not add active polymer. Track the concentrated stock flow and active fraction before dilution. If operators calculate dose from the final diluted flow without accounting for added water, the reported number will be wrong. Label calibration points clearly and update the worksheet when stock concentration changes.
Cross-check inventory and process totals
Compare calculated daily polymer consumption with bag or tote inventory over a meaningful period. Large disagreement can reveal feeder calibration, concentration, leakage or record problems. Also compare calculated dry solids with cake and centrate mass balance where data permit. The purpose is not perfect accounting; it is to find an error large enough to distort grade and cost decisions.
Report uncertainty honestly
Feed solids, pump flow and product active fraction all carry measurement uncertainty. Avoid presenting dose with false precision. State the sampling method and round the result sensibly. When two products appear close, repeat the trial rather than declaring a winner from a difference smaller than the likely measurement error.
Minimum operator worksheet
Keep one row for date and time, product and lot, feed flow, feed-solids sample, stock concentration, calibrated solution flow, calculated dry-solids load, active dose, machine setting and measured result. Add the person making the change and the stabilization time. A compact worksheet makes shift-to-shift comparisons possible and exposes missing inputs before a cost decision is made.