Anthracite Over Garnet: Why Dual-Media Filters Outlast Single-Layer Beds on Oily Water
Oily water is hard on filters. Across oilfield produced water, petrochemical refining and metallurgical or chemical effluent, a conventional single-layer bed tends to fail in the same handful of ways: dirt is held unevenly, the surface blinds early, filtration precision is limited, backwashing never quite restores the bed, and the effluent drifts. None of those failures are dramatic on their own, but together they make stable compliance and genuine deep treatment difficult to sustain.
SINOKLE (Shenzhen) Technology Co., Ltd. has addressed this with a dual-media filter built on a two-layer graded bed of anthracite over garnet, paired with combined air-water backwashing, fully automatic control and a compact integrated structure. The result is deep interception of suspended solids and oil with clearer effluent, steadier operation and simpler maintenance, which is why it has become a standard filtration unit in industrial oily-water deep treatment.
Two layers, one graded bed
The arrangement is deliberately simple. Anthracite sits on top: larger particle size, lower density, and responsible for coarse dirt holding and even flow distribution, which protects the layer below. Garnet sits underneath: finer and denser, doing the fine filtration and deep interception that determines the effluent number. Water moves evenly downward through a coarse-to-fine profile, and oil and suspended solids are captured stage by stage rather than all at the surface.
Backwashing uses combined air and water. The air scours, the water carries, and crucially the two layers do not mix, so regeneration is thorough and the graded structure survives cycle after cycle. That is what allows whole-filter dirt holding instead of surface-only loading, and it is what keeps the effluent precision from decaying over time.
Eight advantages over a single-layer bed
Filtration precision is the headline: the unit removes fine particles at or above 2 µm, with suspended-solids removal reaching 98% and both oil and SS in the effluent held at 5 mg/L or below. Dirt holding is stronger because the anthracite-garnet pairing uses the full depth of the bed, so filter-bed utilisation and capacity far exceed a single medium and filtration cycles run longer. Air-water backwash disturbs the bed far more effectively than water alone, so media regeneration is better and filtration performance recovers quickly.
Capacity is flexible, with series or parallel combinations and free configuration by treatment volume. Operation is fully automatic, supporting local or remote control and backwash initiation on time or on differential pressure. The structure is compact and the package complete, which suits retrofits of older plants and sites where space is tight. Maintenance is straightforward: the process is simple, backwashing is easy, the bed resists hardening and clogging, and the comprehensive operating cost stays low. Applicability is wide, covering both clear water and wastewater and spanning oilfield, refining, metallurgy, chemical and textile deep-filtration duties.
Parameters worth checking
Single-unit capacity runs from 5 to 150 m3/h. Design pressure is 0.6 to 2.0 MPa and design temperature up to 80°C. Filtration resistance stays at or below 0.12 MPa. On the water side, the unit is specified for influent oil and SS each at 50 mg/L or below, and delivers effluent oil and SS each at 5 mg/L or below. Suspended-solids removal rate is 98% and the removable particle size is 2 µm or above. Backwash is combined air-water.
Measured against a single-layer filter
The comparison is unflattering to the single-layer option. Media structure goes from one uniform medium to dual-layer gradation of anthracite and garnet. Dirt holding moves from mainly surface loading with low deep-layer utilisation to whole-filter holding with much greater capacity. Suspended-solids removal rises from the 70%-85% band to 98%. Removable particle size tightens from above 5 µm to 2 µm and above. Backwash changes from water-only, which regenerates poorly, to combined air-water. Control moves from mostly manual operation to fully automatic with remote support. Connection changes from a standalone unit to series or parallel arrangements that expand capacity. Effluent oil improves from 5-15 mg/L to 5 mg/L or below. And maintenance, which under single-layer operation means poor backwash and frequent attention, becomes simple and cheap.
Where it fits
The filter pairs naturally with front-end equipment such as the CDFU hydrocyclone dissolved-air flotation unit, the HCC hydrocyclone coalescer and the high-efficiency coalescing de-oiler, forming a pretreatment plus deep-filtration train. It is used for fine filtration ahead of reinjection or disposal of oilfield produced water and fracturing flowback fluid; for deep treatment of petrochemical and refining desalter draw-off water and tank-farm wastewater; for deep purification of metallurgical, chemical and textile effluent; and for side-stream filtration of circulating water, reclaimed-water reuse and clear-water pretreatment.
SINOKLE focuses on the oily wastewater field and holds to a product philosophy of stable reliability, economic efficiency and easy O&M. Alongside the dual-media filter, the range includes the high-efficiency fiber-ball filter, the KFM activated-media filter and the CDFU hydrocyclone flotation unit, which together support one-stop water-treatment delivery for industrial customers. With high precision, strong dirt holding, easy backwashing and wide adaptability, the dual-media filter has run stably over the long term across numerous oilfield and petrochemical projects, earning its position on cost-performance and reliability rather than on datasheet claims.