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Types of Biological Fillers and Their Characteristics
| Material Type | Typical Materials | Performance Characteristics | Application Scenarios |
|---|---|---|---|
| Polymer Materials | Polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) | Strong chemical stability, acid-base corrosion resistance, density close to water (easy to suspend), hydrophobic surface requiring modification (e.g., hydrophilic coating), service life 5-8 years. | Municipal wastewater and industrial wastewater (e.g., food, chemical) treatment in aerobic/anaerobic conditions. |
| Inorganic Materials | Ceramsite, volcanic rock, zeolite, activated carbon | Large specific surface area (100-500 m²/m³), rich pore structure, strong adsorption (e.g., activated carbon), resistant to biodegradation, but heavy (bulk density 1.2-2.5 g/cm³), prone to clogging. | Advanced treatment (nitrogen and phosphorus removal), wastewater containing heavy metals or refractory organics. |
| Natural Materials | Wood, straw, shells, coral bone | Wide source, low cost, rough surface easy for biofilm formation, but easy to degrade (service life 1-2 years), may release organic carbon affecting water quality. | Decentralized rural wastewater treatment, low-cost ecological projects. |
| Composite Materials | Polymer + metal oxides (e.g., Fe₃O₄), polymer + activated carbon | Combining advantages of multiple materials, such as magnetic fillers (easy for recovery), adsorption-biological degradation synergy (activated carbon + PE), higher cost. | High-difficulty industrial wastewater (e.g., pharmaceutical, electroplating), scenarios requiring enhanced adsorption and biodegradation. |
Characteristics: Freely suspended under water flow or aeration, fully contacting wastewater without frame (support) fixation.
Typical Types:
Structure: Plastic skeleton core wrapped with fibers or activated carbon particles (e.g., MBBR + activated carbon composite fillers).
Advantage: Combining biological attachment and adsorption functions, suitable for simultaneous removal of COD and heavy metals (e.g., electroplating wastewater).
Structure: Polyethylene fiber filaments tie to a central rope, in bundle form (e.g., soft fiber fillers, elastic three-dimensional fillers), specific surface area 800-1200 m²/m³.
Advantage: Flexible fiber filaments swing easily, high mass transfer efficiency, but prone to agglomeration after long-term operation (requires regular agitation).
Structure: PE/PP material, internal porous or mesh (e.g., Kaldnes K1, K3 fillers), specific surface area 500-800 m²/m³.
Advantage: Good fluidity, avoiding dead zones, suitable for high-load wastewater (e.g., chemical, food wastewater).
Hollow Spherical/Cylindrical Fillers
Braided/Fibrous Fillers
Composite Suspended Fillers
Characteristics: Stacked or fixed in the reactor to form a fixed bed layer, requiring control of water flow velocity to prevent clogging.
Typical Types:
Structure: Irregular particles such as ceramsite, Raschig rings, Pall rings, specific surface area 50-200 m²/m³.
Advantage: Low cost, suitable for scenarios with small load fluctuations (e.g., rural domestic wastewater), but high bulk density and water flow resistance.
Structure: Ceramic or metal corrugated plate laminations (e.g., metal hole plate corrugated packings), porosity 90%-95%, specific surface area 200-500 m²/m³.
Advantage: Extremely high mass transfer efficiency, suitable for nitrogen removal (e.g., biological aerated filter BAF), but high cost and easy to clog.
Structure: PVC/PP made hexagonal honeycombs (e.g., honeycomb inclined tube fillers) or corrugated pipes, specific surface area 100-300 m²/m³.
Advantage: Uniform water distribution, suitable for low-load municipal wastewater (e.g., secondary treatment), but prone to sludge accumulation (requires regular backwashing).
Honeycomb/Tubular Fillers
Structured Packings
Random Packings
Characteristics: Combining biofilm with membrane separation, both biological degradation and filtration functions.
Typical Types:
Structure: Polyethylene hollow fiber bundles (inner diameter 0.1-1 mm), specific surface area 1000-2000 m²/m³.
Advantage: High membrane flux (10-20 L/(m²·h)), suitable for reclaimed water reuse (e.g., advanced treatment of municipal wastewater).
Structure: PVDF membrane sheets fixed on a support, forming a biofilm on the surface, pore size 0.1-0.4 μm.
Advantage: Excellent effluent quality (SS ≤1 mg/L), but membrane fouling requires regular chemical cleaning (CIP).
Flat Membrane Fillers
Hollow Fiber Membrane Fillers
Modified zeolite fillers: Adsorb ammonia nitrogen through ion exchange (adsorption capacity 5-10 mg/g), while providing attachment sites for denitrifying bacteria.
Iron-based fillers: Polymer fillers loaded with Fe³+, achieving synergistic phosphorus removal through chemical precipitation (Fe³+ + PO₄³- → FePO₄) and biological phosphorus removal, with phosphorus removal rate over 90%.
Activated carbon-loaded fillers: PE skeleton wrapped with activated carbon particles, adsorbing toxic substances like benzene series while domesticating toxic-resistant flora (e.g., phenol-degrading bacteria).
Magnetic fillers: PP + Fe₃O₄ composite material, enhancing filler recovery through magnetic fields, suitable for wastewater containing heavy metals (e.g., removal of electroplating nickel, cadmium).
Anaerobic granular sludge carriers: Macroporous polypropylene fillers (pore size 5-10 mm), promoting the formation of anaerobic granular sludge and increasing methane yield (e.g., UASB process improvement).
Anaerobic ammonium oxidation (Anammox) fillers: Rough surface (e.g., volcanic rock) accelerates Anammox bacteria biofilm formation, with nitrogen removal load reaching 1-2 kgN/(m³·d).
| Technical Direction | Innovations | Application Prospects |
|---|---|---|
| Nanomaterial Modification | Fillers loaded with nano-TiO₂/ZnO, photocatalytic degradation of organic matter (e.g., antibiotic wastewater), while inhibiting algae growth. | Advanced treatment of high-difficulty organic wastewater (pharmaceutical, pesticide). |
| 3D Printed Structured Fillers | Customized pore structures based on reactor flow fields (e.g., bionic coral skeletons), optimizing mass transfer efficiency (oxygen utilization increased by 30%). | Compact treatment of high-load industrial wastewater (e.g., beer brewing wastewater). |
| Degradable Environment-Friendly Fillers | Starch-based/polylactic acid (PLA) materials, naturally degrading after service life, avoiding secondary pollution. | Decentralized wastewater treatment in rural or ecologically sensitive areas. |
| Intelligent Responsive Fillers | pH/temperature-sensitive hydrogel coatings, adaptively regulating microbial activity (e.g., releasing enzyme-promoting factors at low temperatures). | Stable operation in winter for cold regions (e.g., northern municipal wastewater). |
Water Quality Characteristics: Choose suspended fillers (e.g., MBBR) for high-concentration wastewater, large-pore fillers (e.g., ceramsite) for wastewater containing suspended solids, and adsorption-biological composite fillers for toxic wastewater.
Process Type: Select fixed beds for aerobic processes (e.g., contact oxidation), macroporous suspended fillers for anaerobic processes, and modified inorganic fillers for nitrogen and phosphorus removal.
Economy: Prioritize low-cost materials (e.g., PE/PP) for municipal wastewater, and accept high-cost, high-performance fillers (e.g., activated carbon composite fillers) for industrial wastewater.
