Digestate Treatment Application

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Solutions for AD plants

EKOTON Industrial Group and our Partner Esmil have gained vast experience in the fi eld of digestate treatment. From bench scale studies, right the way through to full scale size plant we strive to off er BAT (Best Available Technology) using state of the art membrane separation and dewatering processes.

Process Description

Our digestate treatment system consists of 3 major process units and is able to produce a dry solid
cake and a highly quality treated water suitable for process reuse or disposal and a high nutrient concentrate.

ekoton solutions for AD plants

The first stage in our digestate treatment process is the separation of the solid and liquid fraction, otherwise known as digestate dewatering. For this we employ our highly effective Multidisc Screw Press Dehydrator  which with the assistance of a small dose of flocculant is able to remove the majority of solids from the liquor (sludge volume reduction of 6-10 times) and produce a dry cake with a dry solids content up to 40%.

ekoton solutions for AD plants

For the second stage, we use special vibratory membrane technology – VSEP (Vibratory Shear Enhanced Processing). This effectively works in the challenging feed conditions.

ekoton solutions for leachate treatment

Although the MDQ is able to remove the majority of the dry solids, some will remain along with other soluble contaminants. The dry solids may cause serious issues for standard membrane systems as they are highly susceptible to fouling. VSEP technology however, vibrates the membranes causing high shear forces at the membrane surface, greatly reducing the risk of fouling. Expected water recovery in this stage can be between 65-80%.

Our final stage of digestate treatment is a spiral-wound reverse osmosis membrane technology. This acts as a polishing stage further treating the permeate (treated water) from the VSEP units. Results have shown that a 95% reduction in COD concentration and 98% reduction of Ammonia can be achieved over the 2 passes of membrane treatment.

Technological stages were tried and are used on different ad plants:

  • 2013 – Kurana UAB, Grain Bioethanol, Lithuania (VSEP, RO)
  • 2017 – Wipptal Cow Manure, Italy (VSEP, RO)
  • 2018 – Quasar Energy Group LLC, Municipal Sludge, USA (MDQ)
  • 2018 – Renergy Inc., Wastewater Treatment Plant, USA (MDQ)
  • 2018 – KB BioEnergy Inc., Wastewater Treatment Plant, USA (MDQ)
  • 2019 – PowerCrop – Russi, Ravenna, Italy (VSEP + RO)

Process Efficiency

ParametrsUnitsVSEP (Pass-I)VSEP (Pass-II)
FeedConc.Perm.FeedConc.Perm.
Total CODmg/l13,08012,8007,9907,99031,960600
pH-5.685.65.75.76.15.9
Ammoniamg/l5,15011,3001,7601,7607,425100
Conductivityus/cm40,400-15,40015,40073,1001,389
Permeate/concentrate use:

- Anaerobic digester feed dilution;
- Plant washing/ cleaning operations;
- Boiler feed (may require additional polishing);
- Discharge to sewer at a very low cost;
- Low volume, high nutrient digestate product for soil conditioning.

Projected Operating Costs (for 15 m3/h)

MDQ - VSEP - ROCost £/m3
Power£0.46
Water£0.02
Chemicals£1.79
Replacements£0.99
TOTAL£3.29

Digestate Treatment Design Philosophy

As no two digestates are equal, it is essential to follow a number of steps to ensure that your tailored digestate treatment process performs as well and economically as possible to achieve your treatment goals.
  • Chemical testing to achieve best fl occulation at lowest dose rate.
  • Lab scale dewatering and membrane trial and selection to ensure process feasibility
  • Long term site pilot trial to allow for feed variation and data gathering
  • Extensive plant design and operating expense calculations]
  • Build, Installation and Commissioning
  • Comprehensive service support including maintenance and system upgrades