APPLICATION FIT
Confirm the biological process before selecting cross-flow MBR
Cross-flow MBR does not replace the complete wastewater process with a tubular membrane. It combines biological degradation with high-MLSS solids separation where the project must retain active biomass, tolerate load variation, and produce stable membrane permeate.
Suitable for initial assessment
Further confirmation required
- COD/BOD biodegradability, toxicity inhibition, salinity, ammonia nitrogen, and nutrient balance
- Temperature, pH, sludge properties, foaming, oil content, and long-term load variation
- Existing biological tank volume, HRT, SRT, aeration capacity, and sludge-discharge conditions
- Downstream discharge or reuse objective and whether NF, RO, or other polishing is required
- Influent load
- Flow, COD/BOD, ammonia nitrogen, total nitrogen, SS, oil, and variability
- Biological conditions
- MLSS, HRT, SRT, DO, temperature, pH, salinity, and nutrients
- Existing system
- Tank volume, aeration, sludge return, sludge wasting, site space, and utilities
- Treatment objective
- Discharge, reuse, NF/RO feed, or other polishing interface
PROCESS ROUTE
Biological degradation and external cross-flow separation form a continuous loop
The flowsheet explains the basic boundaries. Reactor zoning, pump sets, membrane-train count, recycle location, CIP method, and downstream interfaces depend on water quality, capacity, and site conditions.
- 01Biological reactor
Convert organics and target contaminants under approved HRT, SRT, temperature, dissolved-oxygen, and nutrient conditions.
- 02Membrane-section feed
A feed pump sends mixed liquor to the external membrane loop. Pump-inlet conditions and protection depend on sludge properties.
- 03Cross-flow membrane loop
Maintain cross-flow circulation in the tubular membrane to retain sludge, suspended solids, and particles while permeate passes through the membrane.
- 04Permeate and downstream interface
Route membrane permeate to collection, discharge, reuse, or polishing such as NF/RO according to the target water quality.
- 05Concentrated-sludge return
Return membrane concentrate to the biological system and waste excess sludge according to sludge age and system mass balance.
Core engineering principle:The biological section determines whether contaminants can be converted; the tubular membrane section determines whether activated sludge and permeate can be separated reliably. Their design boundaries cannot be combined into one performance claim.
PROCESS RESPONSIBILITY
The biological system degrades; the tubular membrane separates solids
Clear responsibilities are required to interpret COD, ammonia nitrogen, MLSS, permeate suspended solids, and downstream treatment correctly and to avoid presenting membrane-module performance as complete biological-system performance.
- Biological section
- Convert organics and target contaminants according to biodegradability, load, temperature, and aerobic or anoxic conditions.
- Membrane separation section
- Retain active sludge, suspended solids, and particles to maintain biomass and produce solids-separated membrane permeate.
- Downstream section
- Add NF, RO, activated carbon, oxidation, or other polishing according to discharge or reuse targets. Membrane permeate is not assumed to meet every final specification directly.
The tubular membrane alone does not guarantee total COD, ammonia nitrogen, or total nitrogen removal. Final performance depends on influent biodegradability, biological design, operating conditions, and downstream treatment.
ENGINEERING BOUNDARY
Use only the confirmed MLSS range as a public screening reference
Brochure references, existing project operating data, and new-project guarantee values are different evidence levels. This page does not extrapolate one project flux, energy use, or cleaning cycle to other duties.
| Engineering item | Current public reference | Project-specific confirmation |
|---|---|---|
| Mixed-liquor MLSS | Cross-flow MBR public reference: 12–40 g/L | Set the actual window from sludge viscosity, temperature, salinity, filterability, and circulation conditions |
| Membrane operating flux | No universal design value | Reference flux applies only to the corresponding project; establish new-project values from feed, sludge properties, temperature, and cleaning strategy |
| Cross-flow circulation conditions | No universal public value | Determine from channel, membrane trains, hydraulic loss, sludge properties, pump configuration, and energy objective |
| Membrane-permeate parameters | No universal COD, ammonia, or SS guarantee | Distinguish biological-treatment performance, membrane solids-separation performance, sampling point, and downstream requirements |
| Energy use and membrane life | No universal commitment | Affected by system scale, circulation method, fouling load, cleaning, and O&M conditions |
| CIP and maintenance cycle | Defined by project | Confirm against contaminants, temperature, chemical compatibility, performance recovery, and site drain conditions |
Formal technical documents must list design conditions, design values, guarantee values, analytical methods, sampling locations, assessment period, and exclusions separately.
MBR ROUTE SELECTION
Cross-flow, air-lift, and anaerobic MBR serve different duties
The three routes are not simple tiers. Selection must consider biological process type, MLSS, circulation method, wastewater biodegradability, energy conditions, and resource-recovery objectives together.
External cross-flow tubular MBR
- Biological process
- Primarily aerobic or project-defined biological treatment with external pump-driven cross-flow circulation.
- Screening profile
- High MLSS, high load, high suspended solids, or significant feed variability.
- Public reference
- MLSS 12–40 g/L; other parameters are project-specific.
Air-Lift Tubular MBR
- Biological process
- Aerobic biological treatment combined with air-lift tubular membrane separation.
- Screening profile
- For moderate-MLSS duties where air-lift circulation matches project hydraulics.
- Public reference
- MLSS 8–12 g/L; aeration, circulation, and sludge properties require review.
Anaerobic Tubular MBR (AnMBR)
- Biological process
- Anaerobic reaction combined with external tubular membrane separation.
- Screening profile
- High-strength biodegradable organic wastewater and resource-recovery objectives.
- Key confirmation
- Organic loading, toxicity, temperature, biogas use, and downstream nitrogen removal.
Final route selection may require sample testing, sludge-filterability testing, or pilot validation and cannot rely only on the industry name or one COD value.
SOLUTION SCOPE
Define the membrane loop, biological system, and site interfaces separately
The following supports preliminary assessment and detailed design. It does not mean every project automatically includes all equipment, civil works, installation, or performance responsibility.
Core membrane section
- Tubular membrane modules, racks, and cross-flow circulation pump sets
- Feed, permeate, recycle, discharge, and CIP circuits
- Pressure, flow, level, and other instrumentation and control interfaces
Optional engineering scope
- Biological-tank process review, aeration, and sludge-return system
- Equalization, pretreatment, CIP, dosing, and automation
- Downstream NF, RO, reuse, or polishing interfaces
Owner / EPC interfaces
- Civil tanks, buildings, site piping, and utilities
- Sludge disposal, chemical storage, and CIP-waste routing
- Local standards, safety requirements, installation, and plant-wide interlocks
Final scope, biological-performance responsibility, membrane-separation guarantee, design responsibilities, and interface conditions follow the mutually approved technical and commercial documents.
APPLICATION ROUTES
Define application routes by biodegradability and system load
The industries below can enter preliminary assessment, but cannot share one MLSS, flux, energy use, cleaning cycle, or treatment performance.
Landfill leachate
Configure biological treatment, cross-flow MBR, and downstream NF/RO around high organic load, ammonia nitrogen, salinity, and variability.
Chemical and pharmaceutical wastewater
Review biodegradability, toxicity inhibition, and salinity before defining biological load, sludge concentration, and membrane-separation boundaries.
Food and beverage wastewater
Configure biological treatment and membrane circulation for organic load and batch variation, with attention to fats, temperature, and cleaning conditions.
Oily and high-SS wastewater
Determine oil form and its effects on biology and membrane fouling; add upstream oil removal or pretreatment where required.
Industrial-park mixed wastewater
Define equalization, biological treatment, and membrane redundancy around mixed sources, shock loads, and feed variation.
High-load biological-system upgrade
For upgrades where conventional settling is limiting and high biomass must be retained ahead of polishing.
PROJECT EVIDENCE
Support preliminary screening with real capacity, route, and operating records
Customer names remain anonymous. Recorded flux and permeate MLSS apply only to the corresponding project and operating conditions and are not new-project design or guarantee values.
LANDFILL LEACHATE · COMMISSIONED 2017
425 m³/d external cross-flow tubular MBR at an anonymous Foshan landfill
- Route
- External cross-flow tubular MBR + two-stage NF + concentrate treatment
- MLSS
- Membrane feed 15,000 mg/L; membrane permeate below 1 mg/L
- Reference flux
- 60–100 LMH; this project record only
Site image for this project is not public
LANDFILL LEACHATE · COMMISSIONED 2018
4,000 m³/d external cross-flow tubular MBR at an anonymous Guangzhou landfill
- Route
- External cross-flow tubular MBR
- MLSS
- Membrane feed 15,000 mg/L; membrane permeate below 1 mg/L
- Reference flux
- 60–80 LMH; this project record only
Project data comes from existing public material. Customer naming, image rights, and quantitative values still require final approval before formal publication.
RESOURCES
Selection resources and next steps
ProductPEK tubular membrane details
Public resourceTubular membrane brochure
Project preparationProject evaluation worksheet
TECHNICAL FAQ
External cross-flow tubular MBR frequently asked questions
What do the biological reactor and tubular membrane each do in cross-flow MBR?
The biological reactor converts biodegradable contaminants under suitable conditions. The tubular membrane retains active sludge, suspended solids, and particles and produces membrane permeate. Membrane separation does not replace biological reaction or guarantee all COD, ammonia-nitrogen, or total-nitrogen parameters by itself.
Can MLSS 12–40 g/L be used directly as the design range for every project?
No. It is a public screening reference for cross-flow MBR. The actual operating window must also consider sludge viscosity, temperature, salinity, filterability, circulation hydraulics, biological load, and maintenance conditions.
Can the 60–100 LMH and 60–80 LMH records be used for a new project?
No. They are operating records from two existing landfill-leachate projects and serve only as project evidence. New-project flux and membrane area require actual water quality, sludge properties, and validation data.
When should cross-flow MBR be selected instead of air-lift or anaerobic MBR?
Cross-flow MBR is generally assessed first for high-MLSS, pump-driven external circulation and high-load aerobic duties. Air-lift MBR serves moderate-MLSS aerobic duties where gas-liquid lift circulation is suitable. AnMBR serves high-strength biodegradable wastewater and resource-recovery objectives. Final selection is project-specific.
What does a cross-flow MBR process solution typically include?
The solution scope normally defines tubular membrane modules, racks, circulation pumps, feed, permeate, recycle, CIP, instrumentation, and control interfaces. Inclusion of biological tanks, aeration, equalization, pretreatment, downstream polishing, civil works, and installation depends on the formal technical boundary.
What data is required for preliminary assessment?
Provide at least design flow and variation, COD/BOD, ammonia nitrogen, total nitrogen, SS, oil, salinity, temperature, pH, existing biological process, tank volume, MLSS, HRT, SRT, aeration conditions, discharge or reuse objective, and a water-analysis report.
CROSS-FLOW MBR EVALUATION
Submit water quality and the existing biological process for preliminary cross-flow MBR assessment
Upload a water-analysis report, existing flowsheet, and operating records where possible. The engineering team will first assess biological suitability, membrane-separation boundaries, missing data, and whether sludge testing or pilot validation is recommended.
Submitted information is used only for preliminary project assessment. Final biological route, membrane area, flux, energy use, treatment performance, scope, and guarantee conditions are defined in the formal technical documents.