MBR Design Tool

MBR Design Tool - User Guide

This tool assists engineers in designing Membrane Bioreactor (MBR) systems for wastewater treatment. MBR technology combines conventional activated sludge treatment with membrane filtration, providing high-quality effluent suitable for reuse applications.

How to Use This Tool

Project Information: Enter project details (name, client, designer, date)
Influent Characteristics: Define flow rates, COD, BOD, TSS, and nutrients
Biological Design: Set MLSS, SRT, HRT, and F/M ratio parameters
Membrane Design: Select membrane type, flux, and calculate required area
Aeration & Energy: Review oxygen requirements and energy consumption
Sludge Management: Calculate sludge production and wasting rates
Design Summary: Review and export the complete design report

Key MBR Design Parameters

Parameter	Typical Range	Unit	Description
MLSS	8,000 - 12,000	mg/L	Mixed Liquor Suspended Solids concentration
SRT	15 - 30	days	Solids Retention Time
HRT	4 - 8	hours	Hydraulic Retention Time
F/M Ratio	0.05 - 0.15	kg BOD/kg MLSS/d	Food to Microorganism ratio
Membrane Flux	15 - 30	LMH	Liters per m² per hour (net flux)
TMP	10 - 40	kPa	Trans-Membrane Pressure

MBR Configuration

Submerged MBR (iMBR)
Membranes immersed in bioreactor tank. Lower energy, simpler operation. Common for municipal and small industrial applications. This tool designs submerged MBR systems.

Project Details

Project Name

Project Number

Client Name

Project Date

Designer

Reviewer

Site Location

Design Horizon years

Application Type

Application

Treatment Goal

Wastewater Source

Select Wastewater Type

Design Flow Rates

Average Daily Flow (ADF) m³/day

Maximum Daily Flow (MDF) m³/day

Maximum Weekly Flow (MWF) m³/day

Maximum Monthly Flow (MMF) m³/day

Peak Hourly Flow (PHF) m³/hour

Peaking Factor (MDF/ADF)

Influent Characteristics

Total COD mg/L

Soluble COD mg/L

BOD₅ mg/L

TSS mg/L

VSS mg/L

TKN mg/L

NH₃-N mg/L

Total Phosphorus mg/L

Alkalinity mg/L as CaCO₃

Temperature (Design) °C

Temperature (Min) °C

Effluent Requirements

Target COD mg/L

Target BOD₅ mg/L

Target TSS mg/L

Target NH₃-N mg/L

Target TN mg/L

Target TP mg/L

Calculated Loads

COD Load

500

kg/day

BOD Load

250

kg/day

TSS Load

250

kg/day

TKN Load

kg/day

TP Load

kg/day

BOD:N:P Ratio

100:18:3

Biological Process Flow Diagram

Biological System Configuration

Based on your effluent targets, the following biological processes are recommended:

BOD/COD Removal

Required

Aerobic Zone

Nitrification

Required

NH₃ → NO₃

Denitrification

Required

Anoxic Zone

P Removal

Required

Bio-P/Chemical

Recommended Configuration

Current Configuration: MLE Process - Modified Ludzack-Ettinger for nitrogen removal

Biological Design Parameters

Target MLSS mg/L Typical: 8,000-12,000 mg/L

MLVSS/MLSS Ratio Typical: 0.75-0.85

Aerobic SRT days Typical: 10-20 days

Minimum HRT hours Typical: 4-8 hours

Target F/M Ratio kg BOD/kg MLSS/d Typical: 0.05-0.15

Yield Coefficient (Y) kg VSS/kg BOD

Endogenous Decay (kd) 1/day

Design Temperature °C Typical: 15-25°C

Number of Trains

Nitrification Design

Nitrification Required?

Max Nitrification Rate (μm) 1/day @ 20°C Typical: 0.6-0.8

Autotrophic Yield (Yn) kg VSS/kg NH₃-N

Autotrophic Decay (bn) 1/day

Half-Saturation (Kn) mg NH₃-N/L

Safety Factor (SF) Typical: 2.0-3.0

Temperature Coefficient (θ)

DO in Aerobic Zone mg/L Typical: 1.5-3.0

SRT Selection Method

Calculated Min SRT

5.0

days

Selected SRT for Nitrification
12.5
days

NH₃-N Oxidized

kg/day

Alkalinity Consumed

236

kg CaCO₃/day

Denitrification Design

Denitrification Required?

Denitrification Configuration

SDNR (Pre-Anoxic) kg NO₃-N/kg MLVSS/d Typical: 0.04-0.12

SDNR (Post-Anoxic) kg NO₃-N/kg MLVSS/d Typical: 0.01-0.03

Anoxic Zone Fraction Typical: 0.25-0.40

Internal Recycle Ratio (IR) × Q Typical: 2-4 × Q

Return Sludge Ratio (RAS) × Q

External Carbon Required?

NO₃-N to Denitrify

kg/day

TN Removal Efficiency

Effluent TN

mg/L

Alkalinity Recovered

kg CaCO₃/day

Phosphorus Removal

Bio-P Removal?

Chemical P Removal?

Target Effluent TP mg/L

Anaerobic Zone Fraction Typical: 0.10-0.15

Bioreactor Sizing Results

Total Bioreactor Volume
250
m³

Volume per Train
125
m³

Actual HRT

6.0

hours

Actual F/M

0.10

kg BOD/kg MLSS/d

Volumetric Loading

1.0

kg BOD/m³/d

MLVSS

8000

mg/L

Aerobic Volume

175

m³

Anoxic Volume

m³

Total SRT
21.4
days

Aerobic SRT
15
days

Membrane Tank Flow Diagram

Membrane Selection

Membrane Type

Membrane Material

Nominal Pore Size

Module Configuration

Membrane Design Parameters

Design Net Flux LMH (L/m²/h) HF: 15-25, FS: 20-30 LMH

Peak Flux LMH

Membrane Area per Module m²/module

Modules per Cassette

Standby/Redundancy %

Filtration Cycle minutes

Backwash Duration seconds

Backwash Flux LMH

Membrane System Sizing

Required Membrane Area
2083
m²

Total Installed Area
2396
m²

Number of Modules

modules

Number of Cassettes

cassettes

Actual Net Flux

17.4

LMH

Membrane Tank Volume

m³

Permeate Flow

41.7

m³/h

Backwash Volume

2.0

m³/cycle

Chemical Cleaning

Maintenance Clean Frequency days

MC Chemical (NaOCl) mg/L

Recovery Clean Frequency days

RC Chemical (Citric Acid) mg/L

Oxygen Requirements

O₂ for BOD Removal kg O₂/kg BOD removed

O₂ for Nitrification kg O₂/kg NH₃-N

O₂ Credit for Denitrification kg O₂/kg NO₃-N

Safety Factor

Aeration System

Diffuser Type

Process Air SOTE %

Alpha Factor MBR typical: 0.4-0.6

Beta Factor

Membrane Scour Air Rate Nm³/m²/h

Blower Efficiency %

Blower Discharge Pressure kPa

Aeration Results

Actual O₂ Required (AOR)

350

kg O₂/day

Standard O₂ Required (SOR)

700

kg O₂/day

Process Air Flow

2500

Nm³/h

Membrane Scour Air

720

Nm³/h

Total Air Flow
3220
Nm³/h

Blower Power
95
kW

Energy Summary

Aeration Energy

2280

kWh/day

Permeate Pumping

120

kWh/day

Recirculation Pumping

180

kWh/day

Miscellaneous

100

kWh/day

Total Daily Energy
2680
kWh/day

Specific Energy
2.68
kWh/m³

Sludge Treatment Flow Diagram

Sludge Production

Observed Yield

0.35

kg VSS/kg BOD

VSS Production

kg/day

TSS Production

110

kg/day

Sludge Volume (at MLSS)

m³/day

Sludge Wasting

Wasting Source

Wasting MLSS mg/L

Waste Sludge Flow
11.0
m³/day

Calculated SRT

20.0

days

Sludge Mass in System

2500

Sludge Handling

Thickening Method

Thickened Sludge Solids %

Dewatering Method

Dewatered Cake Solids %

Thickened Sludge Volume

2.2

m³/day

Dewatered Cake Volume

0.55

m³/day

Cake Mass

550

kg/day

Design Summary Report

Complete MBR Process Flow Diagram

Project Information

Project Name	-
Client	-
Location	-
Design Date	-

Design Criteria Summary

Parameter	Value	Unit
Design Flow (ADF)	1000	m³/day
Influent BOD	250	mg/L
Influent COD	500	mg/L
Influent TSS	250	mg/L
Effluent BOD Target	10	mg/L
Effluent TSS Target	5	mg/L

Bioreactor Summary

Parameter	Value	Unit
Total Bioreactor Volume	250	m³
Number of Trains	2	-
MLSS	10000	mg/L
Total SRT	21.4	days
Aerobic SRT	15	days
HRT	6.0	hours
F/M Ratio	0.10	kg BOD/kg MLSS/d

Membrane System Summary

Parameter	Value	Unit
Membrane Type	Hollow Fiber	-
Total Membrane Area	2396	m²
Number of Modules	69	-
Design Flux	20	LMH

Energy & Utilities Summary

Parameter	Value	Unit
Total Energy Consumption	2680	kWh/day
Specific Energy	2.68	kWh/m³
Total Air Flow	3220	Nm³/h
Blower Power	95	kW

Sludge Production Summary

Parameter	Value	Unit
Sludge Production (TSS)	110	kg/day
Waste Sludge Flow	11.0	m³/day
Dewatered Cake	550	kg/day