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Overview
The Type II filter block (high-density polyethylene filter block) is a single-pass water and air distribution brick, suitable for deep-bed filters in advanced wastewater treatment and water reuse projects. The product has an HDPE shell with a concrete-filled cavity. The bricks are laid on support feet and adjacent bricks are clipped together in rows to form continuous water and air distribution channels at the bottom of the filter. They also serve as the media support layer, replacing the conventional gravel support layer.
During backwashing, the air-water mixture enters the reflective internal cavity from the bottom of the brick, mixes thoroughly and is then sprayed out evenly through the gaps between adjacent bricks, giving water and air distribution across the whole filter floor with no dead zones. During normal filtration, water is distributed evenly through the lower channels, avoiding local high velocities that would disturb the media and cause short-circuiting.
Construction and Features
Construction
HDPE shell: integrally injection moulded with a smooth, complete surface free of bubbles and weld lines; corrosion and ageing resistant, suited to wastewater and reclaimed water environments.
Concrete infill: the cavity of the brick is filled with concrete of not less than C35, providing counterweight and overall compression capacity.
Support feet: each brick has 8 support feet with a centre-to-centre spacing of 107.5 mm, ensuring stable laying and even load distribution.
Clipping arrangement: adjacent bricks clip together with a 7-8 mm gap and a 203 mm centre-to-centre spacing; the gap forms the water and air distribution channel.
Key Features
Uniform water and air distribution: continuous gaps over the whole floor discharge water and air with no dead zones or preferential flow, giving effective backwashing.
High strength: compressive strength of not less than 20 kN with lateral deformation of no more than 1 mm after load release, able to carry deep media beds and operating loads.
Chemical resistance: resistant to oxidation by 10% sodium hypochlorite solution, with mass change and swell rate after drying both within ±0.5% and no significant change in shell colour or appearance.
Easy to install: clip-together connections and standardised dimensions give high construction efficiency and reduce civil works and installation costs.
Maintenance-free: simple structure with no wearing or consumable parts and a long service life.
Technical Parameters
| Parameter | Type II filter block |
| Overall dimensions B x H x L (mm) | 203 x 187 x 543 |
| Shell thickness (mm) | ≥2.0 |
| Number of support feet | 8 |
| Support foot spacing L₁ (mm) | 107.5 |
| Gap between clipped bricks δ (mm) | 7-8 |
| Centre-to-centre spacing of clipped bricks L₂ (mm) | 203 |
| Mass per brick (kg) | 22-23 |
| Equivalent filter open area ratio (%) | 3.5-4.5 |
Note: the parameters above follow Table 2 of CJ/T 47-2016 Filter Blocks for Water Treatment; permissible dimensional deviations comply with GB/T 14486. Bricks can also be made to the specifications required by the project design.
Physical Properties and Chemical Stability
| Parameter | Requirement |
| Compressive strength | ≥20 kN (lateral deformation no more than 1 mm after load release, no cracking or damage) |
| Cold resistance | -20 ± 2 °C |
| Heat resistance | 80 ± 2 °C |
| Oxidising agent resistance | Resistant to oxidation by 10% sodium hypochlorite solution; mass change after drying no more than ±0.5%, swell rate no more than ±0.5%, no significant change in colour or appearance (shell) |
| Sanitary performance | When used for domestic drinking water treatment, the filter block and its rubber rings shall comply with GB/T 17219 |
Materials and Standards
The shell is made of high-density polyethylene (HDPE) complying with GB/T 11115-2009, with no more than 5% recycled material.
The concrete infill complies with GB 50164 and is of not less than C35 strength.
Rubber sealing rings: complying with GB/T 28604 for drinking water and GB/T 21873 for non-drinking water.
Standard: CJ/T 47-2016 Filter Blocks for Water Treatment.
Our company is a drafting unit of the industry standard for Filter Blocks for Water Treatment. Our products are widely used in the water and air distribution systems of deep-bed filters in municipal wastewater treatment plant upgrades, reclaimed water reuse and advanced industrial wastewater treatment projects.
