BIOPAQ AFR - anaerobic COD removal of fat containing wastewater by Paques

Wastewater with fats, oil and grease and/or solids such as proteins and starch, can effectively be treated in the BIOPAQ®AFR. This anaerobic flotation reactor (AFR), with an effective sludge retention system, is an all-in-one system that converts organic compounds into valuable biogas. Wastewater from the food industry is especially suitable. The compactly designed bioreactor treats wastewater with a COD content from 5-70 g/l with vegetable or animal fats at hydraulically short retention times from 1-8 days.

The intensive contact between the open bacteria flocks and the organic compounds in combination with the biomass retention in the integrated flotation unit is the success factor for this technology.

Advantages of BIOPAQ®AFR

  • Considerably reduces discharge costs, with 90-95% COD removal in most cases
  • Produces valuable biogas
  • Combines the best characteristics of the compact high rate anaerobic reactors and the CSTR
  • Is a compact reactor: short hydraulic retention time and long biomass retention
  • Requires no acidification or solids separation up front
  • Has no odour emission because of its closed design
Typical influent characteristics
Characteristic Influent specification
Type of industry Food industry (dairy, vegetable oils, slaughter houses)
COD level 5 - 70 g/l
% of fats maximum 50% of total COD
BOD/COD 0.3 - 0.6
TSS load up to 70 g/l (solids must be largely biodegradable)

Working principle

Anaerobic bacteria (sludge) convert the organic compounds to biogas. The influent is pumped into the reactor, where biogas lifts mix it thoroughly with the sludge.

An integrated flotation unit retains the sludge in the reactor. The sludge is pumped continuously from the reactor to the flotation unit, where solids and fats are floated using biogas (so-called white water). The flotation layer falls back into the reactor for further digestion.

The purified effluent is extracted from beneath the flotation layer and contains virtually no solids. The generated biogas leaves the reactor through the top into a gas buffer.

The application of an integrated flotation unit results in high sludge concentrations and a long sludge retention time. The hydraulic retention time, on the other hand, is very short. The reactor design is therefore very compact.