Granular sludge technology compounds already impressive benefits of anaerobic digestion

Anaerobic digestion is a robust process that transforms organic waste into valuable biogas for energy, as well as nourishing biosolids for agriculture. Applied in wastewater treatment, it also has the advantages of:

• Purifying even challenging, high-organic-load wastewater
• Lowering utility bills and increasing efficiency
• Bringing effluent into compliance with discharge limits

Adding to the win-win, granular sludge technology can now significantly improve the efficiency of the already-powerful process.

Anaerobic Digestion Challenges

Even with its significant benefits, anaerobic digestion does present perennial challenges. Solids retention time (SRT) and hydraulic retention time (HRT) — the amount of time solids and liquid sludge, respectively, spend in the digester – are often required to be weeks long to ensure complete digestion occurs, thus requiring large reactor volumes and site footprints.

Many operations that do not generate enough wastewater for a large reactor partner with nearby operations to pool waste for adequate feedstock, a practice called co-digestion. But such partnerships can be challenging, and there may not be enough of the right kinds of feedstock available.

The buildup of excess solids can necessitate frequent cleaning to maintain efficiency, and producing enough biogas can also be challenging, depending on design and feedstocks.

Granular Sludge Technology as a Solution

Game-changing granular sludge technology can overcome many of anaerobic digestion’s challenges. It decouples solids retention time from hydraulic retention time by developing and maintaining highly active and stable microbial granules inside the digester. By encouraging the formation of resilient granules in a specific size range, solids retention and methane production can be improved even in small reactors with shorter retention times.

That means granular sludge upgrades can boost reactors that were once too small to achieve high methane production into profitability. Where appropriate partners and feedstocks for codigestion are lacking, smaller operations can now become independent.

Additionally, granular sludge has superior settling properties that improve downstream solids separation.

Appropriate Applications for Granular Sludge

Anaerobic granular sludge technology excels particularly with wastewater streams that have high soluble organic loads of starches and sugars with COD values between 2,000 ppm and 30,000 ppm. Operations that stand to benefit from the technology include alcoholic and nonalcoholic beverage producers, fruit processors, producers of confectionary and baked goods, and other food and beverage manufacturing operations.

Enterprises considering adding granular sludge technology to anaerobic digesters can often make the upgrade with no break in production. The sludge and digestate of the granular sludge process differ from those of traditional anaerobic digesters, so a full Fluence upgrade typically includes additional recirculation piping, temperature and chemical control equipment, and a dewatering stage.

Upgrades can be delivered with traditional financing modes or Fluence’s Water Management Services. With the latter, a Fluence team handles long-term operations and maintenance, biogas production, and water reclamation.

Granular Sludge and Sustainability

While biogas produced by anaerobic digestion does contain carbon dioxide, it is considered a carbon-neutral fuel because the feedstock releases carbon whether or not it is captured. So, every unit of biomethane used to fuel human activities replaces a unit of fossil fuel.

Recovering energy through anaerobic digestion demonstrates a genuine commitment to sustainability on its own, and boosting biogas yields even further with granular sludge is the kind of sustainability practice that the ESG investment community notices in a world awash with confusing ESG claims.

The experts at Fluence are standing by to help you explore granular sludge upgrade options. Contact Fluence to learn more, including how Water Management Service agreements can deliver a quantum leap in the sustainability of an operation with no upfront investment and no long-term operations and maintenance.