From digestate, facilities can recover valuable nutrients, reduce pollution, and maintain compliance with environmental standards.

Treatment offers environmental and economic benefits

Digestate, a byproduct of wastewater treatment, plays a pivotal role in nutrient management and waste disposal. Technologies are available for treating digestate to maximize both environmental and economic benefits.

What is digestate?

Digestate is the treated effluent produced during the digestion of organic materials. Depending on the type of waste material, be it regional food waste, manure-based, industrial wastewater, or municipal biosolids, the quality of digestate can vary widely. Digesters are highly effective at reducing organic matter, but they leave behind a nutrient load. This nutrient-rich effluent generally has two parts:

• Solid phase is often used as biofertilizer because of its high agronomic value.
• Liquid phase is more challenging to manage because of its high volume, which can make disposal costly and logistically complex.

Handling digestate raises critical questions, including how to manage and treat it. Given the diverse applications and environments, digestate treatment strategies vary significantly.

Why Digestate Treatment Matters

Proper management ensures:

• Compliance with environmental regulations. It meets stringent requirements for discharge and nutrient content.
• Pollutant removal. It reduces contaminants in the effluent.
• Efficient nutrient capture. It supports nutrient recovery for biofertilizer production.
• Less strain on municipal infrastructure. It mitigates the load on public treatment facilities and minimizes landfill waste.

Types of Digestate Treatment Technology

Each technology employed to treat digestate offers unique benefits.

• Solids separation: Uses dissolved air flotation, clarification, and screw presses to divide digestate into solid and liquid fractions.
• MABR + Nitro: The membrane aerated biofilm reactor (MABR), combined with nitrification, offers energy-efficient nitrogen removal, suitable for low BOD ratios, using simultaneous nitrification and denitrification.
• Nitrosax: A modified SHARON (Suspended High Activity Ammonia Reduction Over Nitrate) process focusing on ammonia removal with minimal energy use, managing suspended growth to inhibit nitrite-oxidizing bacteria while promoting ammonia-oxidizing bacteria.
• Nitrostep: A conventional Modified Ludzack Ettinger process uses a two-stage setup of anoxic and aerobic tanks to efficiently handle the nitrogen cycle, allowing for stable and proven treatment.
• Precipitation: Techniques like Fostrex remove phosphorus by precipitating struvite or CaPO₄, a valuable step for resource recovery in digestate management.
• Filtration: Uses microbial bioreactors, ultrafiltration, and reverse osmosis for high-grade filtering and nutrient removal or recovery.

Each method and technology is tailored to the unique needs of the digestate source and quality, providing flexibility in managing output.

MABR: The Proven Solution in Digestate Treatment

MABR is among the most notable advances, with more than 300 installations globally. This system promotes aerobic biofilm growth within an anoxic environment using passive diffusion. This setup is particularly advantageous for achieving total nitrogen reduction with minimal energy, making it ideal for digestate from facilities with BOD ratios under 4:1.

Nitrosax and Nitrostep: Approaches to Nitrogen Removal

Nitrosax, a lesser-known SHARON process, provides rapid nitrogen reduction, converting ammonia directly to nitrogen gas. By optimizing pH and ORP, this system minimizes energy consumption while rapidly reducing nitrogen.

Nitrostep leverages a combination of suspended and attached growth systems to provide stable and efficient nitrification-denitrification. Its pre-anoxic phase reduces energy and chemical requirements, making it an economical choice.

Environment and Economics

Digestate management and treatment present unique challenges as well as significant opportunities. Facilities can recover valuable nutrients, reduce pollution, and maintain compliance with environmental standards. The choice of technology is often dictated by specific site needs, environmental regulations, and logistical factors, driving innovation in digestate processing and resource recovery.

Digestate treatment is not just a compliance measure. It’s an opportunity to turn waste into value, benefiting both the environment and the economy.

Ready to optimize your digestate treatment process? Contact us today to explore how our advanced technologies can help you achieve environmental sustainability and economic efficiency.