Membrane process calculator

Membrane Flux, Area & Train Sizing Calculator

Screen membrane area, modules, train arrangement, N+1 availability, and a configurable flux regulator that dispatches only the required number of trains while holding the selected flux ceiling.

Preliminary membrane design screen: Enter a net flux supported by membrane supplier data, pilot testing, or proven comparable operation. This calculator does not select a membrane product or certify a sustainable flux. It makes the assumed flux, cleaning availability, module area, and train-resilience checks explicit.

Input parameters

Define flow, net-flux basis, modules, redundancy, and optional flux regulation.

Design flow envelope

Average Permeate Flow

m³/day

Peak-Flow Factor

peak flow = average flow × peak-flow factor

Flow Used for Installed-Area Sizing

Net flux and cleaning basis

Flux Calculation Mode

Use direct net flux when downtime and backwash have already been included in the supplier or pilot basis.

Selected Net Design Flux

LMH; site- and membrane-specific design assumption

Long-Cleaning Availability

percent; keep at 100% where your net flux already includes long-cleaning downtime

Module, train, and redundancy arrangement

Effective Membrane Area per Module/Cassette

m²/module; supplier-certified effective area

Maximum Modules per Train

physical train constraint

Duty Trains Normally Online

trains filtering in normal operation

Standby / Maintenance Trains Installed

installed but not normally filtering

Trains Out of Service for Contingency Check

trains unavailable for the selected N+1 review

Installed-Area Design Margin

percent; explicit capacity allowance before module rounding

Flux regulation and membrane air-scour hand-off

Enable Flux RegulatorAutomatically reports the minimum number of available trains required to keep each operating case at or below the selected flux ceiling. This is an operating dispatch screen, not an automatic plant controller.

Regulated Flux Ceiling

LMH; normally equal to or below the selected effective net design flux

Membrane Specific Aeration Demand, SAD_m

Nm³/(m²·h); optional supplier or pilot input

Scour-Air Duty Factor

percent of time the membrane scour air is active

Trains Online for Scour-Air Hand-off

trains used for the stated scour-air case

Calculated results

Area, physical train arrangement, duty flux, and regulation response.

Enter values and select Calculate to view the membrane area and train-sizing screen.

Governing equations

The primary input is a transparent, effective net design flux. The calculator converts the selected flow into area, applies the explicit margin, rounds the arrangement to equal modules per train, and then checks actual fluxes against the selected design criterion.

Q_peak = Q_avg × peak-flow factor

J_net,protocol = (J_f × t_f − J_b × t_b) ÷ (t_f + t_r + t_b)

J_{net,effective} = J_net × cleaning availability

A_base = Q_size × 1,000 ÷ (24 × J_{net,effective})

A_target = A_base × (1 + area margin)

Modules/train = ceil[A_target ÷ (duty trains × area/module)]

J_case = Q_case × 1,000 ÷ (24 × available membrane area)

Required regulated trains = ceil[Q_case × 1,000 ÷ (24 × J_ceiling × area/train)]

Interpretation

Flux is permeate flow per unit membrane area. The sustainable value depends on membrane configuration, wastewater characteristics, mixed-liquor conditions, temperature, cleaning strategy, and proven supplier or pilot performance. This page is intended for preliminary screening and not final OEM selection. MBR flux, TMP, permeability, and shear reference [1]

Membrane flux, area, and train-sizing basis

Documentation revision: 2026-10-02. This page documents the calculation basis so an engineer can trace the inputs, units, assumptions, and review needs. Results are preliminary screening estimates; they are not a permit determination, OEM guarantee, or construction/procurement approval.

Method and source basis

The calculator converts the selected average or peak flow and effective net flux into membrane area, then rounds the area to equal modules per duty train. Protocol mode calculates net flux from filtration, relaxation, and backwash time; direct mode uses the entered net flux. Normal, peak, and user-selected train-out cases are reported separately.

The sources below provide technical context or analytical/design methodology. They do not endorse this calculator's defaults, and any jurisdiction-specific requirement applies only where that authority has jurisdiction.

U.S. EPA, Membrane Bioreactors Wastewater Management Fact Sheet (2007)
Oklahoma DEQ, Guidance WQD-002: Membrane Bioreactor (2017)
CEN/TR 15897:2018, Submerged Membrane Bioreactor Technology
WEF Manual of Practice No. 36, Membrane Bioreactors

Assumptions, limitations, and review actions

Flux must be justified by membrane-specific pilot, OEM, or comparable long-term operating evidence at the design temperature, MLSS/solids, SRT, wastewater quality, cleaning strategy, TMP/permeability, and air-scour condition.
Cleaning availability, backwash time, downtime, and area margin must not be double-counted. The train-out field is a user-defined contingency check, not automatic proof of N+1 compliance.
This arithmetic does not model fouling, biological performance, hydraulics, manifold losses, membrane integrity, controls, or energy. Peak/full-duty blower and train arrangements require separate supplier and hydraulic review.

Professional review checkpoint

Before using the result for specification or operation, reconcile it with representative site data, the applicable permit and design standard, the selected equipment or membrane supplier's current data, and a qualified wastewater/process engineer. Record the input basis, date, units, and any pilot, bench-test, or comparable full-scale evidence used to select the assumptions.