EN
Dual Medium Filter
The dual medium filter utilizes a composite filter bed composed of two types of filter mediums with different densities and particle sizes. This structure enables a "coarse-to-fine" deep filtration effect, delivering outstanding retention capabilities for both suspended solids and residual oil.
- Overview
- Recommended Products
Product Introduction
The dual medium filter utilizes a composite filter bed composed of two types of filter mediums with different densities and particle sizes. This structure enables a "coarse-to-fine" deep filtration effect, delivering outstanding retention capabilities for both suspended solids and residual oil. As a result, it is commonly employed as the final polishing unit in produced water treatment systems, ensuring that the outlet consistently meets stringent discharge or reinjection water quality standards.
To meet the demanding offshore platform requirements for reliability, automation, and compactness, this equipment is typically designed as a modular skid-mounted package. It integrates an efficient air-water combined backwashing system to achieve fully automatic operation, reduce backwash water consumption, and extend the service life of the filter medium. This design satisfies the needs of offshore platforms for safe, efficient, and long-term operational performance.
The Dual Medium Filter Skid should be applicable to offshore environment, and We should at our own cost arrange inspection and obtain final certificate of the package from one of the certifying agencies authorized by COOOSO, which are ABS, DNV, BV and CCS etc.
Key Advantages & Features
• High-Efficiency Deep Filtration: The dual-layer filter medium structure (e.g., anthracite and quartz sand) forms a gradient filter bed with "coarse-to-fine" layering, achieving progressive retention of suspended solids and emulsified oil for superior and more stable outlet quality.
• High Dirt-Holding Capacity: The full depth of the filter bed is effectively utilized, significantly extending filtration cycles and reducing backwashing frequency.
• Compact Design Friendly: Allows for higher filtration velocity, resulting in a smaller equipment footprint for the same treatment capacity—especially suitable for the spatial constraints of offshore platforms.
• Economical and Efficient Operation: Combined air-water backwashing technology minimizes water and energy consumption during backwash, while maintaining strong resistance to inlet fluctuations, ensuring low lifecycle operating costs.
• Proven and Reliable Technology: As a long-validated process, it offers high automation levels, simple maintenance, and meets the stringent reliability requirements of offshore platforms.
Structure and Working Principle
The dual-media filter skid/system consists of a dual-media filter (tank body, filter media, backwash mechanism), supporting instruments, valves, pipelines, an automatic control system, platforms, ladders, railings, and a skid base.
During filtration, oily wastewater enters the filter from the top. Through the water distribution device, water is evenly distributed on the surface of the dual-media filter media. The water is filtered from top to bottom through the media layer. The oil in the wastewater fully contacts the walnut shell filter media in the layer and is adsorbed on the surface of the filter layer. At the same time, suspended solids are intercepted and removed by the filter media as they pass through the walnut shell and quartz sand filter layer. Clean water is discharged from the bottom of the filter. As time passes, the contaminant-holding capacity of the filter layer continuously increases, and the layer tends to become saturated. At this point, backwash regeneration of the filter media is required.
Backwashing is performed using a combined air-water wash to thoroughly remove attached suspended solids and oil, ensuring complete regeneration of the filter media.
To ensure uniform water distribution and high-quality effluent, the filter typically employs a radial distribution system and a fishbone collection system, or alternatively, filter caps can be used.
 |
 |
 |
Distribution System & Collection System
Workflow Introduction
The main working process of the dual medium filter is shown in the following figure:
Technical Specifications
| Parameter | Specification |
| Design Pressure | 0.6MPa，1.0MPa，1.6MPa，or specified |
| Design Temperature | 120℃ |
| Vessel Material | SA-516 Gr.70，or specified |
| Filling Height | 1200 mm |
| Filtration Velocity | ≤15 m/h |
| Setting Pressure Drop | ≤0.15 MPa |
| Backwashing Method | Air-water Combined Backwashing |
| Backwash Period | 12~24 h |
| Backwash Duration | 10～13 min, or specified |
| Air Backwashing Intensity | 13～20 L/(m2·s) |
| Water Backwashing Intensity | 10～15 L/(m2·s) |
| Backwash Water Inlet Pressure | ≥0.3 MPa |
| Outlet① | Oil Content≤15mg/L, Suspend Solid Content≤5 mg/L，Suspend Solid Particle Size≤3μm |
| Operation Mode | Switchable for Automatic, Semi-automatic, Manual |
| NOTE | ① The outlet water quality corresponds to the inlet water quality, and the specific indicators will vary according to the different inlet water qualities. |
Main Application Fields
• Treatment of oily and contaminated wastewater from onshore and offshore oilfields, petrochemical, and metallurgical industries.
• Treatment of oily and contaminated wastewater from ports, terminals, and oil depots.
• Treatment of oily wastewater from vessels and other sources.
• Filtration treatment for the reuse of oily wastewater and other oily and contaminated wastewater in recycling systems for the steel, metallurgical, and coal industries.
• Suitable for fine filtration of large volumes of reinjection water in oilfields and treatment of produced water on offshore oil platforms.
• Suitable for the filtration and advanced treatment of cooling circulating water in power plants, refineries, and petrochemical plants.
• Suitable for the pretreatment and advanced treatment of reverse osmosis and ultrafiltration in power plants, steel plants, and water plants.
