Technical reference covering fixed packing, honeycomb and lamella tube settler structure, performance parameters (Tables 2-1, 2-2) and main applications.
← Back to Tube Settler MediaFixed packing (Figure 2-1) was first used in the early 1970s. Materials include phenolic resin with glass-fibre cloth and curing agent, unsaturated polyester resin with glass-fibre cloth and curing agent, and plastic. Fixed packing mainly includes honeycomb and corrugated-plate hard packings.
Biological contact oxidation tanks often use fixed packing. Operating data show the following advantages of fixed packing:
However, this packing demands very uniform water and air distribution, and biofilm detachment can be difficult, causing clogging. At high organic concentration the honeycomb packing clogs easily; once clogged, treatment efficiency drops sharply and the structure can even be damaged. This packing also needs support frames, making installation and replacement inconvenient and raising investment and operating costs, so it is now rarely used and many older retrofits have been replaced.
Honeycomb packing is mostly made of FRP and plastic. Key characteristics: ①high specific surface area, from 133 m²/m³ to 360 m²/m³ (set by the inscribed-circle diameter); ②high porosity, up to 97%–98%; ③light yet strong, with stack height up to 4–5 m; ④smooth walls with no dead corners, so aged biofilm detaches easily.
Disadvantages: ①if the honeycomb pore size does not match the BOD load, biofilm growth and detachment fall out of balance and the packing clogs; ②with an unsuitable aeration method, velocity inside the tubes is hard to keep uniform. Countermeasures: ①match the honeycomb pore size to the BOD loading rate; ②use full-surface aeration; ③leave a 200–300 mm gap between layers, with each layer no more than 1.5 m high, so water redistributes between layers, forming a mix of steady and turbulent flow for even distribution and preventing the lower media from deforming under pressure.
Honeycomb packing has two main forms: hexagonal honeycomb and lamella (inclined) tube settler.
Hexagonal honeycomb packing (Figure 2-2) is a block assembled from straight hexagonal tubes, in either inclined-tube or straight-tube form. Materials: polypropylene (PP), polyvinyl chloride (PVC), co-polymer (ethylene-propylene), and glass fibre (FRP). The inclined tube is mainly used for sedimentation and desanding. It offers a large wetted perimeter, small hydraulic radius, stable laminar flow, and particle settling that is not disturbed by turbulence. Assembly advantages include high toughness, strong assembly strength, no deformation or brittle cracking, long service life, and an anti-aging period extended by 5–8 years on top of the 3–5 years of PP, so it is widely used in water supply and drainage engineering.
See Table 2-1 for main performance parameters of hexagonal honeycomb packing.
| Parameter | Size / mm | Standard size / (mm×mm×mm) | Thickness / mm | Surface area / (m²/m³) | Porosity / % | Density / (kg/m³) |
|---|---|---|---|---|---|---|
| Glass fibre (FRP) | ||||||
| D25 | 1000×500×1000 | 0.5 | 236 | 94 | 95 | |
| D30 | 1000×500×1000 | 0.5 | 169 | 95 | 75 | |
| D40 | 1000×500×1000 | 0.5 | 148 | 96 | 61 | |
| D50 | 1000×500×1000 | 0.5 | 119 | 97 | 50 | |
| D60 | 1000×500×1000 | 0.5 | 99 | 97 | 42 | |
| Polypropylene (PP) | ||||||
| D25 | 1000×500×1000 | 0.5 | 200 | 95 | 46 | |
| D35 | 1000×500×1000 | 0.6 | 140 | 96 | 32 | |
| D50 | 1000×500×1000 | 0.6 | 100 | 97 | 27 | |
| D80 | 1000×500×1000 | 0.8 | 62 | 93 | 22.8 | |
Inclined tube: ①large wetted perimeter, small hydraulic radius; ②stable laminar flow, particle settling unaffected by turbulence; ③with a 1 m tube length, design for 3–5 t/(m²·h) effective load and keep V₀ at 2.5–3.0 mm/s for best effluent; ④at an intake with honeycomb tube of 2.0–3.0 m length, safe operation at 50–100 kg/m² sediment content; ⑤a tube-settler basin handles 3–5× a horizontal-flow basin, and 2–3× an acceleration or pulse clarifier.
Straight tube: ①higher efficiency than the activated sludge method, with a hydraulic load of 100–200 m³/(m²·d) and organic load of 2000–5000 g/(m³·d), reducing footprint; ②lower aeration intensity.
Lamella tube settler (Figure 2-3) is a block formed by assembling plastic tiles; the material is polyethylene copolymerized with polypropylene, i.e. PP/PE co-polymer plastic honeycomb inclined board. Main advantages: high toughness, strong assembly strength, no deformation or brittle cracking, long life and long anti-aging period; service life extends from 3–4 years for polyethylene/polypropylene to 8–10 years in water. Water plants increasingly choose co-polymer type inclined media.
See Table 2-2.
| Pore size / mm | Inclined length × width × length / (mm×mm×mm) | Media thickness / mm |
|---|---|---|
| Φ35 | 1000×500×1000 | 0.4 |
| Φ50 | 1000×500×1000 | 0.5 |
| Φ80 | 1000×500×1000 | 0.8 |
The inclined tube is mainly used for sedimentation and desanding, and is currently one of the most widely used and mature water-treatment devices in water supply and drainage engineering. It offers a wide application range, high treatment effect and a small footprint. It suits inlet desanding, general industrial and domestic water settling, oil separation, and tailings thickening, for both new projects and retrofits of existing tanks, with good economic results. Sedimentation basins using hexagonal honeycomb packing settle faster, reducing settling time and raising output and water quality, making it an effective way to expand and upgrade water plants and wastewater plants. The straight tube is mainly used as a microbial carrier in high-rate biological filters, tower biofilters, submerged biofilters (contact oxidation), and rotating biological contactors, for biological treatment of industrial organic and municipal wastewater.