Membrane Bioreactor (MBR) Companies
MBR system suppliers for high-quality effluent, reuse-ready water, and compact wastewater plants in tight footprints.
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Buyer's guide
The buyer's guide to membrane bioreactor (mbr)
MBR Design Parameters: Flux, Mixed Liquor Concentration, and Fouling Control
Membrane Bioreactor (MBR) systems combine activated sludge biological treatment with ultrafiltration (UF) membrane separation, replacing the secondary clarifier in conventional activated sludge. The UF membrane (pore size 0.02 to 0.4 microns, typically hollow fibre or flat sheet submerged in the bioreactor) retains all suspended solids and most bacteria, producing a clear effluent with turbidity below 0.2 NTU and BOD below 5 mg per L without a final polishing filter.
MBR enables operation at mixed liquor suspended solids (MLSS) of 8,000 to 15,000 mg per L (vs 2,000 to 4,000 mg per L for conventional AS), reducing bioreactor volume by 30 to 50 percent and enabling compact footprint for upgrading constrained sites.
Membrane flux (the volumetric flow of permeate per unit membrane area, expressed in L per m2 per hr, LMH) is the primary design parameter. Net flux (accounting for backwash and relaxation cycles): 10 to 25 LMH for submerged hollow fibre MBR, 15 to 30 LMH for pressurised sidestream MBR. Transmembrane pressure (TMP) increases with fouling; operation targets TMP below 0.3 bar; TMP above 0.5 bar triggers chemical cleaning.
Coarse bubble aeration (air-scouring) at 10 to 20 Nm3 per hr per m2 of membrane area is used to scour biofilm from hollow fibre surfaces; this is the dominant energy consumer (0.3 to 0.8 kWh per m3 of treated water). Relaxation (no permeation, aeration continues) every 10 to 12 minutes for 30 to 60 seconds, and backpulsing with permeate, maintain flux.
MBR effluent quality enables direct reuse applications: BOD below 5 mg per L, SS below 1 mg per L, turbidity below 0.2 NTU, and 99.99 percent removal of bacteria and parasitic cysts (Cryptosporidium, Giardia). For potable reuse, MBR is followed by RO and UV or advanced oxidation (ozone plus H2O2) in an indirect potable reuse (IPR) train.
Capital cost of MBR systems: $200 to $800 per m3 per day of design flow for municipal applications (larger than conventional AS due to membrane procurement but savings on clarifier and filter). Operating cost premium over conventional AS: $0.05 to $0.20 per m3 for membrane replacement and cleaning chemicals (membranes replaced every 5 to 10 years, cost $20 to $50 per m2). Net lifecycle cost is often competitive with conventional AS plus tertiary filtration plus UV.
Frequently asked questions
What is a membrane bioreactor (MBR) and how does it work?
An MBR (Membrane Bioreactor) combines biological treatment (aerobic activated sludge) with ultrafiltration membrane separation in a single process. Wastewater enters the bioreactor where bacteria oxidise organic matter and ammonium. Instead of settling in a clarifier, the mixed liquor is filtered through a UF membrane (pore size 0.02 to 0.4 microns) that retains all biological solids (bacteria, floc) and allows only clean permeate to pass. The biological solids remain in the reactor and continue treatment - sludge is wasted periodically to maintain target MLSS (8,000 to 15,000 mg per L). Result: effluent with BOD below 5 mg per L, SS below 1 mg per L, and no Giardia or Cryptosporidium cysts in the permeate (absolute removal by membrane size exclusion). Footprint is 30 to 50 percent smaller than conventional activated sludge for the same flow.
What are the advantages and disadvantages of MBR over conventional activated sludge?
Advantages: (1) Superior effluent quality - BOD below 5 mg per L, SS below 1 mg per L, pathogen removal by physical exclusion; (2) Compact footprint - no secondary clarifier needed, 30 to 50 percent smaller bioreactor at higher MLSS; (3) Reuse-ready effluent requiring only UV or RO for direct reuse; (4) Greater process stability - MLSS not limited by settleability; (5) Lower sludge production per unit BOD (longer SRT reduces net sludge yield). Disadvantages: (1) Higher capital cost (membranes add $50 to $200 per m3 per day of capacity); (2) Membrane fouling requires regular cleaning (maintenance cleaning with hypochlorite weekly, recovery cleaning quarterly) and eventual membrane replacement (5 to 10 years); (3) Higher aeration energy for membrane scouring (0.3 to 0.8 kWh per m3 additional vs conventional); (4) Sensitivity to high-concentration oils and grease which rapidly foul membranes.
How are MBR membranes cleaned?
MBR membrane cleaning follows a hierarchy: (1) Maintenance cleaning (weekly): backpulse with 200 to 500 mg per L sodium hypochlorite (NaOCl) solution for 30 to 60 minutes to remove biofilm from membrane surfaces; (2) Recovery cleaning (every 3 to 6 months or when TMP exceeds 0.5 bar): remove membrane modules, soak in 1,000 to 2,000 mg per L NaOCl for 6 to 12 hours to remove organic fouling, followed by 0.5 to 1 percent citric acid soak for inorganic (calcium/iron) scaling; (3) Ex-situ cleaning: where in-place cleaning is insufficient, membranes are removed from the reactor and cleaned in dedicated vessels. Cleaning effectiveness is assessed by recovery of clean water flux (Jcw) and clean water TMP versus new membrane baseline. If flux does not recover to above 80 percent of new membrane values after recovery cleaning, membrane replacement is scheduled. Membrane lifetime: 7 to 15 years for well-operated systems.
What is the minimum footprint achievable with an MBR?
MBR minimum footprint depends on design flow, treatment objective, and membrane type. For a 1,000 m3 per day municipal MBR: bioreactor volume (HRT 4 to 8 hours) approximately 170 to 340 m3; membrane tank area at net flux 20 LMH requires approximately 50 to 80 m2 of submerged membrane area, housed in a tank footprint of 20 to 40 m2. Total process footprint (bioreactor, membrane tanks, blowers, control building) approximately 200 to 500 m2, versus 1,000 to 2,000 m2 for equivalent conventional AS including clarifiers and tertiary filters. Compact containerised MBR units are available for flows below 200 m3 per day in a single 20-ft or 40-ft shipping container. These are used for industrial sites, remote communities, and temporary installations. Container MBR flow range: 20 to 200 m3 per day; footprint 15 to 30 m2 including all process equipment.
Illustrative scenario · Textile manufacturing
A composite drawn from typical projects in this category, not a single client engagement. Figures are indicative.
- Challenge
- A technical textile manufacturer in Yorkshire discharged 800 m3 per day of dye-house effluent (COD 1,800 mg per L, BOD 650 mg per L, colour 3,200 Hazen units, SS 240 mg per L) to a combined sewer under a trade effluent consent with colour 200 Hazen units, BOD 300 mg per L, and SS 200 mg per L limits. The site footprint was constrained to 250 m2 for new treatment infrastructure.
- Approach
- Designed a submerged MBR (bioreactor 300 m3 volume, hollow fibre UF membrane, net flux 18 LMH) with a pre-aerated equalisation tank (200 m3, 6-hour HRT) to dampen colour and COD load variations from batch dye processes. Coagulation pretreatment (ferric sulphate 40 mg per L) before the equalisation tank improved colour removal from 40 percent to 78 percent. Total footprint: 220 m2 including blowers, membrane tanks, and control building.
- Outcome
- Effluent BOD consistently below 15 mg per L, SS below 5 mg per L, and colour below 150 Hazen units over 18 months of operation. Trade effluent consent compliance rate 100 percent. The MBR effluent quality was sufficient to allow 35 percent recycle to the dye house rinse process, reducing freshwater consumption from 800 to 520 m3 per day and saving 45,000 GBP per year in water and trade effluent charges.
Questions to ask shortlisted providers
5
- 01
What design membrane flux (net LMH) have you used and what is the peak flux at peak flow, and can you provide TMP and fouling data from similar installations on comparable feed water?
Membrane flux is the most important design parameter for MBR capital cost (higher flux means less membrane area and lower cost) and for operational reliability (higher flux increases fouling rate and TMP, requiring more frequent cleaning and earlier membrane replacement). A design at 25 LMH net flux using peak-flux data from clean water is not the same as 25 LMH achieved consistently on high-SS biological mixed liquor. Ask for actual operating data from reference installations, not test bench data.
- 02
How does the system handle feed flow surges and load spikes without membrane fouling or process upset, and what is the equalization tank sizing basis?
MBR biological treatment is more stable than conventional activated sludge but the membrane is sensitive to sudden changes in MLSS (caused by sludge washout in overload events) and to high oil and grease concentrations that rapidly blind hollow fibre membranes. A design without adequate equalization (minimum 4 to 6 hours of average flow) or without a surge flow bypass to a holding tank is vulnerable to membrane fouling events that can take 24 to 72 hours of recovery cleaning to resolve.
- 03
What is the membrane module replacement schedule and cost over a 20-year operating period, and are the proposed membranes from a manufacturer with a proven track record above 10 years in service?
Membrane replacement is the largest lifecycle cost variable for MBR systems. Hollow fibre modules cost 20 to 50 GBP per m2 of membrane area and are typically replaced at 7 to 15 years. A system requiring replacement at year 7 rather than year 12 increases 20-year lifecycle cost by 30 to 50 percent. Ask for the manufacturer's global installed base at the proposed operating flux and MLSS, and for data on achieved membrane service life in comparable applications.
- 04
What is the aeration energy for membrane scouring, and how does this compare with the conventional activated sludge baseline for our wastewater composition?
MBR membrane scouring aeration (coarse bubble diffusers below the membrane modules) is the dominant energy cost in most MBR systems: 0.3 to 0.8 kWh per m3 additional versus conventional AS. For a 1,000 m3 per day MBR, this adds 100 to 290 MWh per year in energy cost (15,000 to 45,000 GBP per year at 0.15 GBP per kWh). Energy-efficient aeration strategies (intermittent aeration, variable-frequency drive blowers, high-efficiency diffusers) can reduce this by 20 to 40 percent and should be included in the design.
- 05
What chemical cleaning protocol is included in the maintenance schedule, and what are the annual costs for maintenance cleaning chemicals and the frequency and duration of recovery CIP events?
MBR cleaning costs are often underestimated in capital proposals. Weekly maintenance cleaning (hypochlorite backpulse at 200 to 500 mg per L) costs 2,000 to 8,000 GBP per year in chemicals. Quarterly recovery CIP (NaOH plus EDTA at pH 11, followed by citric acid at pH 3) costs 5,000 to 20,000 GBP per year in chemicals and labour. System downtime during CIP (typically 6 to 12 hours per vessel) must be planned into the operational schedule without interrupting effluent discharge compliance.
What drives cost in this category
4
- Design flow and membrane area required
- MBR capital cost for industrial applications: 500 to 2,000 GBP per m3 per day of design flow (highly variable by wastewater strength and required product quality). A 500 m3 per day MBR treating 1,000 mg per L BOD industrial effluent costs 400,000 to 1,200,000 GBP in equipment and installation. Membrane area is the primary capital cost driver: at net flux 18 LMH, 500 m3 per day requires approximately 1,200 m2 of membrane at 25 to 50 GBP per m2 = 30,000 to 60,000 GBP in membranes alone.
- Bioreactor civil works and footprint
- For greenfield sites, MBR bioreactor tanks (typically concrete, GRP, or stainless steel) cost 150 to 400 GBP per m3 of tank volume. A 300 m3 bioreactor costs 45,000 to 120,000 GBP in civil works. For brownfield retrofit of an existing activated sludge plant (converting secondary clarifiers to MBR membrane tanks), civil cost is 30 to 50 percent lower than greenfield. The compact footprint benefit of MBR (30 to 50 percent smaller than conventional AS) is most valuable where land is constrained or expensive.
- Energy cost for aeration and membrane maintenance
- MBR energy consumption: biological aeration 0.3 to 0.8 kWh per m3, membrane scouring aeration 0.2 to 0.5 kWh per m3, permeate pump 0.05 to 0.15 kWh per m3. Total: 0.55 to 1.45 kWh per m3. For a 1,000 m3 per day MBR at 0.18 GBP per kWh, annual energy cost is 36,000 to 95,000 GBP. Versus conventional AS plus tertiary filtration: 0.3 to 0.7 kWh per m3 total energy. The MBR energy premium is 0.25 to 0.75 kWh per m3, or 17,000 to 49,000 GBP per year at this scale.
- Effluent quality and trade effluent charge reduction
- MBR effluent quality (BOD below 5 mg per L, SS below 1 mg per L) reduces Mogden formula trade effluent charges significantly versus untreated or partially treated effluent. For an 800 m3 per day industrial discharge at 1,500 mg per L BOD and 300 mg per L SS (full strength industrial effluent), the Mogden surcharge reduction from MBR treatment to discharge-quality effluent typically saves 150,000 to 400,000 GBP per year in trade effluent charges, providing payback of 3 to 8 years on the MBR capital investment.
Key regulations and standards
4
- Water Industry Act 1991: Trade Effluent Consent and MBR as Treatment Standard
- Water companies issuing trade effluent consents under WIA 1991 Section 118 set limits based on what is treatably achievable. For industrial effluents above 1,000 mg per L BOD or with specific micropollutants (dyes, solvents, APIs), water companies may specify MBR or equivalent biological membrane treatment as the required pre-treatment standard in the consent. DWI and the receiving water company will specify the minimum treatment standard; a proposal that achieves compliance by dilution rather than treatment is not acceptable under the consent terms.
- EU Industrial Emissions Directive 2010/75/EU (retained in UK): BAT for Textile Discharges
- The IED BAT Conclusions for textile manufacturing (EU 2016/902) specify Best Available Techniques for wastewater treatment including biological treatment (activated sludge or MBR) as BAT for high-BOD dye-house effluent. UK sites subject to IED must apply BAT in their environmental permits. MBR achieving BOD below 10 mg per L and SS below 10 mg per L is consistent with BAT; conventional biological treatment achieving BOD 30 to 50 mg per L without tertiary filtration may not satisfy BAT requirements for new consent applications.
- BS EN 12255: Wastewater Treatment Plants (Membrane Bioreactor Systems)
- BS EN 12255 (parts covering membrane bioreactors) provides European standards for the design, construction, and commissioning of MBR wastewater treatment plants. Key provisions: membrane element specifications (pore size, bubble point pressure test), integrity testing protocols, membrane cleaning procedures, and effluent quality monitoring requirements. Compliance with BS EN 12255 demonstrates design conformance for planning applications, building control, and environmental permit applications.
- WRAS Approval: Membranes Used in Water Reuse Applications
- Where MBR permeate is to be reused for cooling tower make-up, toilet flushing, or other non-potable reuse applications, the membrane modules must not impart substances above recognised health-based limits into the permeate. WRAS approval or DWI List of Approved Products listing is required for membranes used in any application where the permeate may contact human skin or be inhaled (cooling tower make-up). Membranes used for effluent treatment only (not in contact with drinking water) do not require WRAS approval.