Biogas Plant Effluent (Nitrogen Removal)

Anaerobic digestion of manure, food processing byproducts, and other waste streams provides a source of low-cost, renewable energy but also generates a high-strength waste stream that contains high concentrations of nutrients, biomass, and organic matter. Processing this waste stream is so costly that it has prevented wider adoption of anaerobic digestion. However, BKT's solution allows the digestate to become a revenue stream by enabling the recovery of nutrients in the digestate as a marketable organic fertilizer. It also concentrates the solids in the digestate, reducing hauling costs for disposal.

BKT employs its anti-fouling FMX membrane filtration system as the basis of a treatment train for the recovery of nitrogen from anaerobic digester effluent (digestate) as a profitable liquid fertilizer. A sample process train is shown below.


Targeted Issues

  • Nitrogen and Phosphorus recovery from digestate & organic fertilizer production
  • Digestate volume reduction to reduce hauling costs

Digestate Treatment and Nutrient Recovery

Want to increase your digesters profitability? Turn your waste into liquid fertilizer!

A 6 megawatt anaerobic digester in the Netherlands installed 3 FMX units for the treatment of digestate. Prior to FMX, the facility had a tubular membrane system installed, but due to the difficult characteristics of the digestate, the tubular system was fouled beyond recovery within 3 months.
The first full scale industrial installation of its kind, the FMX has been proven to effectively and reliably treat digestate. At this installation the FMX is used as a pretreatment to remove suspended solids prior to a spiral RO system. The RO can then be used to provide clean water for reuse onsite, while concentrating the nutrients for sale as a fertilizer.

Not only does the FMX provide a reliable and consistent RO pretreatment, but the concentrated biomass from the FMX can be returned to the digester. By returning the FMX concentrate, the biogas facility has reported up to a 20% increase in biogas production. In addition, the returned biomass helps maintain a more stable digester, decreasing operational downtime of the whole operation.

  Full Scale Digestate Treatment with Nutrient Recovery

Full Scale Digestate Treatment with Nutrient Recovery


Digestate Treatment Pilot Test Video

Nutrient Recovery from Digestate

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