The digestate treatment system, designed by Colloide, is built around the ultra-efficient Selective Vaporisation system.

Colloide's system is compact with a small footprint, and highly innovative with low energy and low chemical consumption.

Separated liquor or unseparated liquor and solids can be treated to selectively remove ammonia and only a small amount of water. The large energy consumption associated with the evaporation of bulk water is avoided.

Key outputs and benefits

  • Removal of ammonia from unseparated digestate (both solids and liquids) of up to 95%.

  • Enhanced solids removal from liquor.

  • Enhanced removal of phosphate from liquor up to 95%.

  • Efficient system – low energy and low chemical consumption.

  • The treated digestate can be land spread at a much higher density, therefore requiring a much smaller land bank for the AD operator.

  • The products from the treatment process are valuable resources that are easier to manage and can be used in other processes eg pure nitrogen organic fertiliser, soil conditioner, compost, land regeneration, solid fuel and building material.

  • The concentrated ammonia solution and solid fraction, ammonia free, dry cake are both suitable for industrial / commercial use.

  • The prevention of further damage to sensitive habitats due to recovering of condensates (reduction of ammonia emissions).

  • Possible reductions in transportation and storage costs by improved digestate processing.

Digestate treatment

Digestate enhancement and treatment technologies have become more important due to the increase in the number and capacity of AD plants and industrial processes. Due to growing environmental and regulatory concerns, there is a need to manage nutrients such as nitrogen, phosphorous and potassium in the digestate and how these are spread onto land.

Colloide has developed a digestate treatment system that not only targets effective management of ammonia emissions but, by recovering valuable resources, also enables a zero-waste solution. The recovered resources are products of agricultural value and present an opportunity to achieve a zero pollution digestate management system. The company has a wealth of experience in providing innovative solutions and upgrading existing systems. It's Digestate Treatment System is compliant with government regulations and codes of good practice. 

Colloide’s main methods are vaporisation (flash distillation / evaporation / stripping), reverse osmosis (including pre-filtration), chemical dosing (used in conjunction with other technologies) and a combination of SBR and MBR treatments.

Features

  • Enhanced solids separation and removal of suspended and dissolved solids.

  • Removal of COD, VOC, potassium and phosphorus.

  • Greenhouse gas reduction.

  • Vastly superior treated water quality and recovery of nutrients.

  • Flexible process can be tailored to meet specific requirements.

  • Capture or removal of ammonia for spreading on land, storage as concentrated fertiliser or exporting off site.

Applications

Physical treatment

Vaporisation: flash distillation / evaporation / stripping

These different methods of vaporisation ensure that ammonia is removed (>75%) from whole digestate, allowing the solids to be spread on land at a much higher coverage and approved for exporting off site. Alternatively, the ammonia can be captured as a liquid product for storage as a concentrated fertiliser, which can also be transported off-site for other markets. These systems help reduce the production of greenhouse gases, such as methane and CO2 and target the removal of suspended solids and VOC.

Reverse osmosis (including pre-filtration)

This treatment recycles the digestate wastewater into water (clean water recovery >75%), that can be re-used for washdown, irrigation, evaporative cooling or disposed directly to a watercourse, prolonging the availability of freshwater resources. It can remove microplastics, viruses, bacteria, pharmaceuticals and pesticides from treated water, as well as recovering specific nutrients. A pre-filter is installed before the reverse osmosis (RO) membrane and extends the life of the more expensive RO membrane, reducing overall operating costs. The treated effluent can be used as a concentrated liquid fertiliser for exporting from a digestor site.

Chemical treatment

Chemical dosing (used in conjunction with other technologies)

Colloide designs and builds customised chemical dosing systems for a wide range of chemicals and applications. These packages are tailored to suit clients’ requirements while adhering to European Standards, CIRIA and HSE guidance. The company's chemical dosing systems in conjunction with other technologies aid in the removal of chemicals such as phosphorus and ammonia. This treatment also enhances the separation of solids from liquid digestate and / or removal of suspended and dissolved solids as well as improving overall sterilisation.

Biological treatment

SBR and MBR 

The Sequential Batch Reactor (SBR) and Membrane Bioreactor (MBR) are extremely compact and flexible solutions to wastewater treatment. They offer an extremely high quality of treated effluent and both technologies achieve the removal of ammonia, suspended solids and COD. Colloide's specialist MBR systems can also remove microplastics. The liquid fraction of digestate from these processes can be disposed to sewers, land or pre-treatment for further technologies.