top of page

Manure Separation: Fine Separation via Chemical Flocculation and Dewatering

alternative practice names:

Chemical-Assisted Fine Separation; Coagulation; Flocculation; Dissolved Air Flotation (DAF); Advanced Nutrient Recovery

Chemical-assisted fine separation enhances efficiency by using coagulants and flocculants to aggregate fine particles, making them easier to separate from the liquid fraction. This process improves the removal of suspended solids and phosphorus, resulting in a cleaner liquid effluent and a more concentrated solid fraction.


Coagulants, often referred to as "metal salts," are added to the liquid manure stream to change the charge on manure particles, causing them to attract to one another. Common coagulants include ferric chloride, ferric sulfate, and alum (aluminum sulfate). Flocculants—typically polymers with unique molecular weights, branching capabilities, and charge densities—cause manure particles to form larger clumps or "flocs" of solids. 


Once the flocs are formed, various methods can be used to remove the solids from the waste stream. One common technology is dissolved air flotation (DAF), where microscopic bubbles are introduced into the waste stream, causing the flocs to float to the surface. A skimmer is then used to remove the floating solids. Other separation technologies, such as belt presses or disc presses, can be used to dewater the solids.


The products of chemical-assisted fine separation include:


  • Liquid fraction: Fine separation produces a liquid fraction, often referred to as "tea water," that is rich in ammonia, nitrogen, and potassium with very little organic matter or potassium.

  • Solid fraction: The process also yields a solid fraction with 80% or more of the phosphorus as well a large portion of the potassium (Porterfield et al., 2020).

When used, in what regions in the U.S. is the practice found: 

Northwest, West, Upper Midwest, Southwest, Northeast, Southeast

FARM SIZE 

When used, typically found on farms of the following sizes:

Over 1000 cows

Case Studies.png

Practice Benefits 

Improved nutrient management: Separating fine solids concentrates phosphorus in the solid fraction, while the liquid fraction retains nearly all soluble nitrogen (ammonium, nitrates, nitrites) and potassium. This allows for more precise nutrient application, with different rates for solid and liquid portions, to better match crop needs.


Reduced odors: Fine solids separation technology helps remove solid particles that cause odors.


Prerequisite for advanced manure management technologies: Fine solid removal is essential for advanced manure management technologies such as ultra-filtration and reverse osmosis, which require a clean liquid fraction to operate effectively.


Compatibility with irrigation systems: Removing fine solids from the liquid waste stream improves waste application by reducing clogging in irrigation equipment. 

Practical Insights.png

Implementation Insights

Site-specific or Farm-specific requirements 

farm-icon.png
  • Manure handling: This practice is more applicable to farms that manage manure as a liquid or slurry.

Required Capital Expenditures (CapEx)

red-dollar-0.png
  • Manure pretreatment: Farm using sand for bedding will need a remove sand from the waste steam therefore they may need to invest in a sand seperation system.   In additional removal of coarse solids is necessary to improve system efficiency; see Manure Separation: Coarse Solid-Liquid Separation via Sloped Screens and Screw Press to learn about potential captial expenses. 

  • Engineering: Given the complexity of components involved in chemical application and separation processes, such as DAF and presses, all unit processes need to function cohesively as a system. A professional engineer or engineering firm must design this system to integrate seamlessly within the existing or proposed dairy operation.

  • DAF system: Several components are essential for the system's operation including a chemical dosing system designed, and vat to support proper mixing of chemicals and wastewater necessary to facilitate floc formation and removal. 

  • Building envelope: The chemical-assisted separation and fine solids collection system should be housed in a building to protect it from climatic conditions. This also provides a space for storing solids after separation and dewatering are completed.

  • Material handling: The farm may need multiple manure storage structures to accommodate manure, tea water, and sludge. Sludge, in particular, is often not stackable as it exits the system and will require an appropriate storage facility designed for its characteristics. 

Required Operational Expenditures (OpEx)

orange-dollar-0.png
  • Labor: Regular monitoring and adjustments to the chemical application rates may be required due to changes in the dairy operation. This may involve daily, weekly, or monthly inspections to ensure optimal performance.

  • Electricity: Adequate energy is needed to power the various unit processes involved in the system, as multiple technologies are typically used in conjunction with each other.

  • Chemicals: Ongoing costs for purchasing coagulants and flocculants are necessary to maintain proper chemical-assisted separation.

Implementation Considerations

implementation-complexity-1.png
  • System cohesion: To ensure optimal performance, all unit processes must operate in harmony. A comprehensive operation and maintenance plan, with scheduled inspections and upkeep, is essential to prevent breakdowns and maximize efficiency.

  • Connectivity for troubleshooting: Enabling internet connectivity for the chemical assist and separation systems allows the manufacturer to diagnose and troubleshoot issues remotely, reducing downtime and ensuring quicker resolutions for operational problems.

  • Chemical impact on solids: Overuse of chemicals can cause equipment corrosion and negatively impact nutrient uptake and plant growth after land application. It is crucial to follow recommended dosages carefully to minimize these risks while maintaining effective separation.

  • Ongoing monitoring and calibration: The system must be regularly monitored and calibrated to account for fluctuations in manure composition, system wear, and operational changes. This ensures consistent performance and prevents the overuse of energy, chemicals, and labor.

  • Regulatory compliance: Ensure that chemical usage, effluent disposal, and land application practices meet local environmental regulations to avoid potential fines or operational restrictions.

Financial Considerations and Revenue Streams

There are no federal cost-share programs or conservation funding for this practice.


FINANCIAL RESOURCES, TOOLS, AND CASE STUDIES

Research Results.png

Environmental Impacts

MAY REDUCE FARM GREENHOUSE GAS FOOTPRINT

Little scientific research directly evaluates the practice's impact on a farm's greenhouse gas (GHG) footprint. However, the removal of coarse and fine manure solids from liquid/slurry manure storage lowers the amount of organic matter and carbon available for methanogenesis, resulting in lower methane production potential. When the separated manure solids are stored in an environment that is predominately aerobic, farmers eliminate the anaerobic conditions necessary for CH production and thus decrease methane emissions.


IMPROVES WATER QUALITY

Advanced separation and nutrient recovery systems help farmers reduce the risks of nutrient run-off and leaching associated with nutrient overapplication. By separating the phosphorous-rich manure solids from the nitrogen-rich liquid fraction, farmers can apply different fractions at different rates to better match crop demands.

REFerences

farm-assessment.png

Alignment with FARM Program

This practice is not included in the FARM program.

Contents

farm-icon.png
farm-icon.png
farm-icon.png
farm-icon.png
farm-icon.png
farm-icon.png
farm-icon.png

We're always eager to update the website with the latest research, implementation insights, financial case studies, and emerging practices. Use the link above to share your insights. 

We're always eager to update the website with the latest research, implementation insights, financial case studies, and emerging practices. Use the link above to share your insights. 

Contents

farm-icon.png

Practice Overview

Case Studies.png
Practical Insights.png
dollar.png
reference,png
Research Results.png
farm-assessment.png

Chemical-assisted fine separation enhances efficiency by using coagulants and flocculants to aggregate fine particles, making them easier to separate from the liquid fraction. This process improves the removal of suspended solids and phosphorus, resulting in a cleaner liquid effluent and a more concentrated solid fraction.


Coagulants, often referred to as "metal salts," are added to the liquid manure stream to change the charge on manure particles, causing them to attract to one another. Common coagulants include ferric chloride, ferric sulfate, and alum (aluminum sulfate). Flocculants—typically polymers with unique molecular weights, branching capabilities, and charge densities—cause manure particles to form larger clumps or "flocs" of solids. 


Once the flocs are formed, various methods can be used to remove the solids from the waste stream. One common technology is dissolved air flotation (DAF), where microscopic bubbles are introduced into the waste stream, causing the flocs to float to the surface. A skimmer is then used to remove the floating solids. Other separation technologies, such as belt presses or disc presses, can be used to dewater the solids.


The products of chemical-assisted fine separation include:


  • Liquid fraction: Fine separation produces a liquid fraction, often referred to as "tea water," that is rich in ammonia, nitrogen, and potassium with very little organic matter or potassium.

  • Solid fraction: The process also yields a solid fraction with 80% or more of the phosphorus as well a large portion of the potassium (Porterfield et al., 2020).

Practices and technologies

Manure Separation: Fine Separation via Chemical Flocculation and Dewatering

alternative practice name:

Chemical-Assisted Fine Separation; Coagulation; Flocculation; Dissolved Air Flotation (DAF); Advanced Nutrient Recovery