BIOPAQ^® CBD: continuous biological removal of both solids and COD

BIOPAQ® CBD (Clean Bottom Digester) is purpose-built for industries where high COD and high solids go hand in hand.

While most anaerobic systems require pre-treatment or clean influent, CBD efficiently treats wastewater with up to 150 g/L COD and 100 g/L TSS. It continuously removes heavy solids like sand, grit, and struvite to prevent accumulation and downtime.

• Handles what other systems can’t
  The only Paques reactor engineered to continuously remove inert materials — no manual cleaning or process shutdowns.
  (see system comparison)
• Designed for real-world wastewaters
  Ideal for streams from distilleries, waste-to-energy plants, and manure effluents where solids and grit are unavoidable.
• High-rate COD removal
  Non-granular anaerobic biomass and plug flow design ensure efficient conversion of organics to biogas, even at extreme loadings.
• No dead zones or scum
  Advanced hydraulic design prevents mixing problems, short-circuiting, and surface scum, common failure points in conventional anaerobic digesters.
• Simple, compact, and operator-friendly
  No internal mechanical mixers. All maintenance can be done externally without taking the system offline.
• Maximized uptime
  Continuous solids and grit removal eliminates process interruptions.

1. Influent and recirculation water are evenly distributed across the top of the reactor through nozzles that also break up any floating scum.
2. Biomass moves downflow, creating a stable plug flow regime for optimal COD conversion.
3. Heavy solids are collected by a bottom scraper and extracted from the reactor. Optionally, sand and grid are separated from the organic material using a special designed cyclone.
4. Biogas produced from the degraded organics exits the top of the reactor and is sent to downstream energy recovery.
5. Treated effluent is discharged for further treatment or reuse.

Plug Flow Activated Sludge Process

The BIOPAQ® CBD design draws inspiration from principles used in plug flow wastewater treatment. Particularly the plug flow activated sludge process and plug flow aeration tanks widely applied in municipal and industrial treatment.

In a plug flow reactor for wastewater treatment, influent travels in a linear path with minimal back-mixing, ensuring that the wastewater receives consistent treatment as it passes through the system. This flow regime promotes efficient substrate utilization and the lowest possible effluent concentration.

In the BIOPAQ® CBD, the downflow of biomass replicates plug flow behavior, enhancing the biological conversion of organic matter into valuable biogas while maintaining stable reactor performance. This approach optimizes COD removal efficiency and supports the reactor’s ability to handle variable loadings with minimal operational complexity.

BIOPAQ® CBD is the only anaerobic system that combines high-rate organic removal with continuous, automatic solids and grit handling. Where ICX, EGSB and UASB reactors require low solids influent or complex pre-treatment, CBD handles both COD and solids in one compact unit.

Biotech comparison for handling both COD and solids

While competing biological wastewater treatment technologies can handle either high COD or moderate solids/fats, the BIOPAQ® CBD stands out because:

• Continuous grit and heavy solids removal → prevents downtime and manual cleanouts
• Anaerobic biomass plug flow → maximizes COD conversion and TSS destruction
• No need for complex pre-treatment or hydrolysis → lower CapEx and OpEx

Most competing systems require either:

• Careful pre-treatment to avoid solids/grit overload
• Manual or batch grit removal that has accumulated in the reactor

Technology comparison

Get in touch with our experts to help you find out if BIOPAQ® CBD® is the right solution for your high-strength, high-solids wastewater challenges or that other systems or system combinations would work better for your plant’s demands.