Marine Discharge Compliance Using PolyCera®Titan Ultrafiltration Membranes
Application Overview
Offshore oil and gas platforms generate produced water that must be treated reliably before discharge to the marine environment. The challenge in offshore water treatment is intensified by limited platform space, variable influent quality, safety requirements, and the need for stable operation under offshore conditions.
CNOOC (China National Offshore Oil Corporation) and PolyCera® carried out a 26-month produced water treatment pilot on an operating offshore platform in the East China Sea from 2021 to 2023. The objective was to validate a compact, reliable, and easy-to-operate treatment process capable of handling fluctuating oil concentrations while meeting offshore discharge requirements.
Following successful pilot validation, PolyCera® was selected to supply 10 offshore produced water treatment units for CNOOC-operated platforms. The systems range in capacity from 100 t/d to 1,000 t/d and are designed for compact offshore installation with footprints of approximately 30 to 90 m², depending on unit size.
Project Background
The Huangyan 2-2 offshore platform project was initiated in September 2025. The system was manufactured, certified, transported offshore, installed, commissioned, and accepted within an 8-month project cycle.
The project achieved:
- 100% milestone completion
- First-time CCS certification approval
- 0 safety incidents
- Full commissioning and acceptance after offshore installation
The system was designed to upgrade the existing produced water treatment process by adding a deep treatment stage for more stable removal of dispersed oil, emulsified oil, dissolved oil, suspended solids, and colloidal contaminants
Process Design for Offshore Water Treatment
The treatment train combines PolyCera® Titan ultrafiltration with resin adsorption polishing. The process was designed for stable offshore operation, high recovery, and reliable discharge compliance.
The process includes:
1. Produced Water Feed
Produced water from the offshore platform enters the advanced treatment system after the existing coalescing separation step. During the monitoring period, feed oil concentration varied from 69 to 197 mg/L, with an average of 111.29 mg/L.
2. Self-Cleaning Prefiltration
A self-cleaning filter removes larger hard particles before the membrane system, protecting the ultrafiltration membranes from mechanical damage and supporting stable long-term operation.
3. PolyCera® Titan UF Membrane Filtration
PolyCera® Titan ultrafiltration membranes remove suspended solids, colloids, heavy oil, free oil, and emulsified oil. The crossflow filtration configuration and concentrate recirculation help reduce surface accumulation and delay membrane fouling.
The membrane stage provides:
- Physical separation of oil and suspended solids
- Stable operation under variable feed conditions
- High fouling resistance in oily produced water
- Compatibility with offshore footprint constraints
4. Resin Adsorption Polishing
A regenerable resin adsorption system removes dissolved oil and remaining organic contaminants that are not fully retained by ultrafiltration. The adsorption system uses a 3-vessel configuration with two vessels in operation and one standby vessel. Steam regeneration enables repeated resin reuse and supports continuous operation.
5. Discharge-Compliant Treated Water
The combined membrane and resin process produced treated water with measured oil concentrations below 12
mg/L, significantly below the national discharge limit of 30 mg/L.
Commissioning Optimization
The key challenge was intermittent and uneven influent flow. A fixed-time operating sequence created unnecessary production, backwashing, and wastewater generation when feedwater availability was low. This initially limited water recovery to approximately 50%.
PolyCera implemented an adaptive control strategy based on real-time feed pressure and flow monitoring. The system automatically enters standby mode when operating conditions are not met and resumes production when feed pressure and flow recover.
This optimization increased product water recovery from 50% to 90%.
Additional commissioning work addressed membrane fouling behavior and discharge-line backpressure during resin regeneration. Automated CIP logic was implemented based on operating pressure differential and runtime, while the regeneration sequence and pressure relief configuration were adjusted in coordination with the platform team.
Results of Offshore Water Treatment Project
The system performance was validated through 40 days of continuous monitoring from March 31 to May 5, 2026, across 40 sampling cycles.
The PolyCera® system delivered the following results:
- Discharge Compliance
- Measured outlet oil concentration was below 12 mg/L, compared with a national discharge limit of 30 mg/L
- Stable Treatment Under Variable Feed Conditions
- Feed oil concentration ranged from 69 to 197 mg/L, with an average of 111.29 mg/L
- Low Product Water Oil Concentration
- Product water oil concentration ranged from 2.4 to 22 mg/L, with an average of 11.30 mg/L
- High Oil Removal Performance
- The system achieved an overall oil removal rate of 89.8%
- Improved Water Recovery
- Adaptive control increased water recovery from 50% to 90%
- Offshore-Ready System Design
- The system was delivered as a modular skid package with automated controls, local and central operation modes, and CCScertified equipment suitable for offshore platform conditions
- Safe Project Execution
- The project was completed with 0 safety incidents and passed CCS certification on the first submission
Conclusion
The CNOOC Huangyan 2-2 offshore produced water project demonstrates the suitability of PolyCera® Titan UF membranes for demanding offshore oil and gas applications.
By combining ultrafiltration with regenerable resin adsorption, the system provided stable removal of free oil, emulsified oil, suspended solids, colloids, and dissolved oil under variable offshore conditions.
The project achieved measured outlet oil concentrations below 12 mg/L, an average product water oil concentration of 11.30 mg/L, 89.8% oil removal, and 90% water recovery after control optimization.
The successful offshore commissioning, CCS certification, and follow-on award of 10 treatment units confirm that the solution has moved from pilot validation to repeatable platform deployment.