MF/UF Membrane System¶
Source: NJ Stormwater BMP Manual, Chapter 11, Section 11.8 (2026)
Microfiltration/Ultrafiltration (MF/UF) membrane systems are advanced engineered stormwater treatment units that pass stormwater through hollow-fiber or flat-sheet membrane modules with pore sizes in the 0.01–0.1 micrometer range, physically excluding suspended solids, fine particles, bacteria, and some viruses at the membrane surface. They represent one of the highest-performance stormwater treatment technologies available in the NJ BMP Manual and achieve near-complete suspended solids removal for the treated volume.
MF/UF membrane systems are classified as Non-GI in the 2026 NJ BMP Manual. They do not provide groundwater recharge and do not generate VRC. They are capital-intensive, require significant electrical infrastructure and ongoing maintenance, and are typically reserved for applications where extremely high treatment standards are required: industrial sites with stormwater NJPDES permit limits, water reuse stormwater recycling projects, and situations where receiving water sensitivity demands > 90% particle removal.
Performance (2026): - TSS removal: > 95% for particles within filtration range - Does not remove dissolved nutrients (TN, TP) without additional treatment stages - Requires backwash cycle that generates waste stream requiring management
Primary stormwater functions:
- Very high TSS removal — > 95% for filterable particulate fraction
- Bacteria/pathogen reduction — hollow-fiber UF excludes particles including bacteria
- Used for stormwater reuse — membrane effluent may be suitable for reuse after disinfection
- Non-GI: enclosed system; no native soil infiltration; no VRC generated
Source: NJ Stormwater BMP Manual, Ch. 11, Section 11.8 (2026)
| Parameter | 2026 Requirement | 2023 Requirement | Notes |
|---|---|---|---|
| Membrane specification | NJDEP-certified MF or UF hollow-fiber or flat-sheet membrane module | Same | Certification data required for water quality credit |
| NJDEP certification | Must be certified per NJDEP MTD program | Same | Verify current certification at time of design |
| Design flow rate | Sized for WQV design storm peak flow through membrane system | Same | Transmembrane pressure (TMP) governed by flow rate and fouling |
| Pre-treatment | Coarse screening and pre-sedimentation stage required before membrane | Same | Protect membrane from rapid fouling by coarse particles |
| Chemical cleaning | Periodic chemical clean-in-place (CIP) protocol required | Same | Citric acid or sodium hypochlorite per manufacturer recommendation |
| Backwash waste | Backwash and CIP waste volumes must be managed; may require collection sump | Same | Design waste management path before finalizing system |
| Electrical infrastructure | Pump station and control system required; design for reliability including backup power | Same | Power outages disable system unless backup provided |
| Bypass | High-flow bypass required for flows above system capacity | Same | Size bypass to handle 10-year design storm without membrane passage |
Source: NJ Stormwater BMP Manual, Ch. 11, Section 11.8 (2026)
Infrastructure Requirements
- Requires permanent electrical connection, pump station, programmable logic controller (PLC), and typically a building or enclosure for membrane module protection
- Not suitable for remote or unmaintained stormwater facilities
Operational Complexity
- Membrane systems require trained operators for backwash programming, CIP scheduling, and performance monitoring; not appropriate for facilities without dedicated maintenance staff
Backwash Waste Management
- Backwash water and CIP chemical waste must be discharged to sanitary sewer, contained, or otherwise managed per NJDEP/muncipal sewer authority requirements
When Appropriate
- Best suited for: industrial stormwater permits with strict discharge limits; stormwater reuse systems; sites near Class I waterways with very low particle loading limits; or when NJPDES permit limits cannot be met by conventional BMPs
Source: NJ Stormwater BMP Manual, Ch. 11, Section 11.8 (2026)
Routine — Per Manufacturer’s Protocol
- Automated backwash cycles programmed into PLC; verify backwash cycle frequency and duration are operating per design protocol at each quarterly inspection
- Monitor transmembrane pressure (TMP) trends: rising TMP indicates membrane fouling; initiate chemical CIP before TMP reaches the threshold that triggers automatic shutdown
Quarterly Inspection
- Inspect pre-treatment screening stage for blockage; clean debris capture screen
- Inspect membrane modules for visible damage (broken fibers, cracked modules)
- Review automated monitoring logs for alarm history between quarterly visits
Annual Chemical Clean-in-Place (CIP)
- Perform full CIP per manufacturer’s protocol annually or as triggered by TMP data
- Document CIP chemicals used, volumes, and disposal path
Source: NJ Stormwater BMP Manual, Ch. 8; Ch. 11, Section 11.8 (2026)
Design Errors
- Pre-treatment stage inadequate — coarse particles reach membrane surface directly; membrane fouling accelerates within first season; replacement well ahead of design life
- Electrical infrastructure not designed — power supply inadequate for pump station; system cannot operate at design flow; stormwater bypasses membrane untreated
- Backwash waste path not planned — design completed without backwash management; construction-phase conflict with sewer authority or regulatory agency
Construction Issues
- Membrane module installed prior to end of construction activity — construction sediment during fine grading plugs membrane within first events; full replacement required
Long-Term Performance Risks
- Progressive irreversible fouling — without regular CIP, biofilm and mineral scale permanently reduce membrane permeability; replacement required far ahead of design life
- Power interruption — stormwater system receives flows but pump station is off; all volume bypasses membrane; 100% bypass during power outage without backup power
Source: NJ Stormwater BMP Manual, Ch. 11, Section 11.8 (2026)
Governing Regulations
| Rule Section | Topic | Engineering Relevance |
|---|---|---|
| N.J.A.C. 7:8-5.3(d) | Water Quality Treatment | > 95% TSS removal; satisfies 80% TSS standard (and exceeds it) |
| N.J.A.C. 7:8-5.3 | Green Infrastructure Requirement | Non-GI — no VRC generated |
| N.J.A.C. 7:9A | NJPDES Stormwater Discharge Permits | Membrane systems often required for NPDES industrial permit compliance |
| NJDEP MTD Certification | Manufactured Treatment Device Program | Certification required for regulatory water quality credit |
BMP Manual Sources
- NJ Stormwater BMP Manual, Chapter 11, Section 11.8 (2026) — MF/UF Membrane Systems
- NJ Stormwater BMP Manual, Chapter 8 (2026) — Operation and Maintenance
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