Combined Packing for Sewage Treatment: 2026 Complete Guide to Biofilm Media for Food Plant Wastewater

Is your food plant wastewater treatment system struggling with biofilm growth and organic load reduction? Food processing wastewater contains high concentrations of organic matter, oils, and suspended solids that require effective biological treatment. The direct answer is: combined packing for sewage treatment provides an ideal biofilm carrier that maximizes microbial attachment and contact efficiency, achieving COD removal rates of 85–95% in food industry wastewater applications. The global food processing wastewater treatment market was valued at USD 12.3 billion in 2024 and is projected to reach USD 19.8 billion by 2034 (Grand View Research), driven by increasingly stringent discharge standards and growing food production demands. CHIWATEC has supplied wastewater treatment solutions for food processing facilities worldwide, integrating combined packing technology into customized biological treatment systems.

What Is Combined Packing for Sewage Treatment?

Combined packing (also known as composite packing or combined filler) is a specialized biofilm carrier media used in biological wastewater treatment processes. It combines the structural advantages of both soft and semi-soft packing materials into a single integrated design:

• Structure — The composite packing consists of fiber bundles, plastic ring sheets, sleeve components, and a center rope. The plastic ring sheets are pressed into double-loop large plastic rings, and aldehyde fibers or polyester filaments are uniformly distributed on the ring to create the fiber bundle structure.
• Design principle — The plastic ring serves as the rigid skeleton providing structural support, while the fiber bundles (typically vinylon yarn, polyester, or aldehyde fiber) provide a high-surface-area medium for biofilm attachment and growth.
• How it works — In biological contact oxidation tanks, the combined packing is suspended in the wastewater. Microorganisms attach to the fiber surfaces, forming a biofilm that consumes organic pollutants as they flow past. The open structure allows wastewater to contact the biofilm from all directions, maximizing treatment efficiency.

Combined packing is widely regarded as one of the most effective biofilm carrier materials for industrial wastewater treatment, particularly in food processing applications where organic loads are high and variable.

Key Characteristics of Combined Packing for Food Plant Wastewater

Combined packing for sewage treatment offers several distinctive characteristics that make it particularly suitable for food plant wastewater applications:

These characteristics make combined packing the preferred biofilm media for food processing wastewater treatment, where organic loads can spike during production hours and drop during cleaning cycles.

Product Specifications and Installation Parameters

Combined packing is available in standardized specifications to match different treatment system designs:

• Unit diameter — Common diameters include Φ150 mm, Φ160 mm, Φ180 mm, and Φ200 mm. The larger diameters provide greater void space for high-solids wastewater, while smaller diameters offer higher surface area for dilute effluents.
• Packing spacing — Standard spacing options are 80 mm and 100 mm between packing layers. Tighter spacing (80 mm) is recommended for high-concentration food wastewater to maximize contact time.
• Center rope material — Two options: plastic rope (standard, cost-effective) and fiber rope (higher tensile strength for deep tanks). For food plant applications with tank depths of 3–6 meters, fiber rope is recommended for its durability.
• Fiber material — Aldehyde fiber (standard) or polyester filament. Polyester offers better chemical resistance for wastewater with cleaning chemical residues.
• Installation density — Typical packing density ranges from 70–90 meters of rope per cubic meter of tank volume. Higher density is used for high-strength food processing wastewater.

For proper installation support, see how to maintain the integrated sewage treatment equipment sedimentation tank for guidance on integrating combined packing with other treatment unit operations.

Product Advantages Over Other Biofilm Media

Combined packing offers distinct advantages when compared to other types of biofilm carrier media used in food plant wastewater treatment:

• Versus soft packing — Soft packing (purely flexible fiber media) tends to compress and entangle under high flow conditions, reducing effective surface area. Combined packing’s plastic ring skeleton prevents compression, maintaining consistent treatment performance even during peak flow periods.
• Versus semi-soft packing — Semi-soft packing has limited rigidity and can deform over time. The double-loop large plastic ring design of combined packing provides superior structural integrity while maintaining the bio-affinity properties of semi-soft materials.
• Versus plastic media (MBBR) — While MBBR media offers high specific surface area, combined packing provides better bubble cutting and oxygen transfer enhancement, making it more energy-efficient for high-organic-load food wastewater. For more on biological treatment, see the introduction to biological aerated filter technology.
• Service life — Under normal operating conditions, combined packing lasts 3–5 years, significantly longer than purely soft packing (1–2 years) and comparable to high-quality MBBR media.

Application in Food Plant Wastewater Treatment Systems

Combined packing is integrated into biological treatment systems at food processing facilities through the following typical process flow:

1. Primary treatment — Screening and grease removal to remove large solids and FOG (fats, oils, and grease) before biological treatment.
2. Equalization tank — Flow and load equalization to smooth out production cycle fluctuations. Retention time typically 6–12 hours.
3. Biological contact oxidation tank — The main treatment zone where combined packing is installed. The tank is aerated from the bottom, and wastewater flows upward through the suspended packing media. COD removal of 80–90% occurs in this stage. For FRP integrated sewage treatment equipment, combined packing is often pre-installed in modular contact oxidation chambers.
4. Secondary sedimentation — Sludge settling and separation of treated effluent from biomass. The dispersion technology of domestic sewage treatment equipment ensures even flow distribution in the sedimentation stage.
5. Tertiary treatment (optional) — Advanced polishing, disinfection, or membrane filtration if required for discharge or reuse standards.

This process configuration is particularly effective for food plant wastewater from meat processing, dairy production, fruit and vegetable canning, beverage manufacturing, and snack food processing.

Operating Parameters and Maintenance Considerations

To achieve optimal performance from combined packing for sewage treatment in food plant applications, operators should monitor these key parameters:

• Dissolved oxygen (DO) — Maintain DO levels of 2–4 mg/L in the contact oxidation tank. Higher DO improves treatment efficiency but increases energy costs. The bubble-cutting effect of combined packing reduces the air flow requirement by 20–30% compared to conventional aeration.
• Sludge detachment — Periodically increase aeration intensity to slough excess biofilm. In food plant applications, this is typically needed every 2–4 weeks depending on organic loading rates.
• Temperature — Optimal biological activity occurs at 15–35°C. Food plant wastewater from cooking or sterilization processes may enter at higher temperatures; cooling to below 40°C before the biological stage is essential.
• pH control — Maintain pH between 6.5–8.5. Food processing wastewater can be acidic (fruit/vegetable processing) or alkaline (cleaning cycles), requiring pH adjustment before the biological treatment stage.
• Inspection frequency — Visually inspect packing condition quarterly for fiber loss, entanglement, or clogging. Replace sections showing more than 20% fiber degradation.

Frequently Asked Questions (FAQ)

What is the difference between combined packing and MBBR media?

Combined packing is a suspended biofilm carrier made of fiber bundles on a plastic ring skeleton, installed as fixed curtains in the treatment tank. MBBR media are small floating plastic carriers that move freely with aeration. Combined packing offers better bubble cutting and oxygen transfer, while MBBR provides slightly higher specific surface area.

What COD removal efficiency can combined packing achieve for food wastewater?

Combined packing in a well-designed biological contact oxidation system typically achieves 80–95% COD removal for food processing wastewater, depending on the organic loading rate and wastewater characteristics. For high-strength wastewater (COD above 3000 mg/L), two-stage biological treatment may be needed.

How long does combined packing last before replacement?

Under normal operating conditions with food plant wastewater, combined packing has a service life of 3–5 years. Fiber degradation occurs gradually due to biological activity and mechanical stress from aeration. Replace packing when fiber bundles show more than 20% breakage or when treatment efficiency drops significantly.

Can combined packing handle variable organic loads from food processing?

Yes. Combined packing’s biofilm structure adapts to fluctuating organic loads by adjusting the biofilm thickness. During high-load periods, the biofilm thickens and consumes more organic matter. During low-load periods, excess biofilm naturally sloughs off. This self-regulating characteristic makes it ideal for food plants with seasonal or daily production cycles.

Is combined packing suitable for dairy processing wastewater?

Yes, combined packing is highly effective for dairy wastewater treatment. The high fat and protein content in dairy wastewater is readily biodegradable, and the bubble-cutting effect of combined packing prevents grease accumulation on the media surface. For comprehensive food plant wastewater design, refer to the food factory wastewater treatment plant design engineering case.

Conclusion & Call to Action

Combined packing for sewage treatment offers food processing facilities a proven, cost-effective biofilm media solution that delivers 85–95% COD removal with 30–40% better oxygen transfer efficiency than conventional aeration systems. Its unique fiber-on-ring design combines the best properties of soft and semi-soft packing while overcoming their individual limitations, making it the ideal choice for the fluctuating organic loads typical of food manufacturing wastewater.

For expert assistance in designing or upgrading your food plant wastewater treatment system with combined packing technology, contact CHIWATEC today at [email protected] or [email protected].

Related Resources and Further Reading

• Food Factory Wastewater Treatment Plant Design: Complete Engineering Case Study
• Introduction to Biological Aerated Filter Technology
• How to Maintain the Integrated Sewage Treatment Equipment Sedimentation Tank
• How to Operate the Buried Sewage Treatment Equipment
• Wastewater Treatment System Product Range 2026 » CHIWATEC