Filter Bag Solids Loading: Convert Concentration into Mass

A liquid filter bag enquiry often lists flow and micron rating but omits how much solid material reaches the filter. Concentration alone does not describe that workload: the same concentration at twice the flow carries twice the incoming mass per hour. Calculating the mass rate gives buyers a clearer starting point for a trial.

Use the calculation below when discussing INCEFILTER liquid filter bags. It describes incoming solids, not a guaranteed dirt-holding capacity, removal percentage or operating life.

Keep concentration, flow and time in compatible units

For concentration C in milligrams per litre and liquid flow Q in cubic metres per hour:

Incoming mass rate (kg/h) = C (mg/L) × Q (m³/h) ÷ 1,000.

The conversion follows from 1,000 litres in one cubic metre and 1,000,000 milligrams in one kilogram. EPA’s loading-calculation guidance likewise combines concentration and flow with the appropriate unit conversions. The hourly metric expression here is a purchasing calculation, not an environmental reporting instruction.

For a hypothetical feed containing 50 mg/L of measured suspended solids at 20 m³/h, the incoming mass is 1 kg/h. Over eight hours at those unchanged conditions, 8 kg reaches the filtration stage. These are illustrative process values, not INCEFILTER product specifications.

Calculate changing conditions by period

If concentration or flow changes, calculate each representative operating period separately and add the masses. Do not assume that multiplying an average concentration by an average flow gives the correct total when both vary together.

The total is 6.4 kg. Multiplying the simple averages, 60 mg/L and 20 m³/h, by four hours gives only 4.8 kg. This example shows why batch records and representative concentration measurements matter.

Do not equate incoming mass with captured mass

Some particles may pass through the selected media. A total suspended-solids result also does not describe the distribution of particle sizes or how the solids behave. Ask what the laboratory measured and how representative the sample is of the liquid reaching the filter.

A mass balance using inlet and outlet concentrations needs comparable samples, flow information and a defined system boundary. For sampling discipline, see the trial sampling plan guide; its recordkeeping principles can also support a bag-filter trial when the method is appropriate to the process.

Why this is not a filter-life calculator

Dividing an assumed bag capacity by incoming kg/h can create false precision. Actual changeout depends on the approved operating limits and outlet-quality requirements as well as what is retained. A capacity result from another liquid or test contaminant is not automatically transferable.

Use the calculation to explain the duty, then run a documented evaluation with the proposed bag and housing. Keep an operating and differential-pressure log and compare trials using cost per accepted volume. Record a measured result separately from a supplier estimate.

Send a useful solids-loading enquiry

Send INCEFILTER your flow, concentration report and operating schedule. Include the liquid, temperature, particle information, bag dimensions, housing and required filtrate quality. Mark unknown values rather than filling them with assumptions. Ask what further measurements are needed before selecting a bag or estimating changeout frequency.

Reference: US EPA: Hierarchy of Loading Calculations, for the concentration-and-flow basis of mass loading.