United States Department of Agriculture 632-CPS-1

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NRCS reviews and periodically updates conservation practice standards. To obtain the current 

version of this standard, contact your Natural Resources Conservation Service State office or 

visit the Field Office Technical Guide online by going to the NRCS website at 

https://www.nrcs.usda.gov/ and type FOTG in the search field. 

USDA is an equal opportunity provider, employer, and lender.

Natural Resources Conservation Service 

CONSERVATION PRACTICE STANDARD 

WASTE SEPARATION FACILITY 

CODE 632 

(no)

DEFINITION 

A filtration or screening device, settling tank, settling basin, or settling channel used to partition solids

and/or nutrients from a waste stream. 

PURPOSE 

This practice is used to accomplish one or more of the following: 

• Improve or protect air quality 

• Improve or protect water quality 

• Improve manure handling methods or serve as a pre- or post-treatment for other processes 

CONDITIONS WHERE PRACTICE APPLIES 

This practice applies where the waste separation facility will— 

• Remove solids from a liquid waste stream as a primary treatment process and facilitate further

treatment processes. 

• Reduce problems associated with solids accumulation in liquid waste storage or treatment facilities. 

• Reduce solids content in a waste stream so liquids and solids can be recycled for other uses. 

• Reduce solids content in a waste stream to better facilitate land application of liquids using irrigation

techniques. 

• Assist with partitioning nutrients in a waste stream to improve handling and application. 

CRITERIA 

General Criteria Applicable to All Purposes 

Laws and regulations 

Plan, design, and construct the waste separation facility to meet all Federal, State, local, and Tribal

regulations. Notify landowner and/or contractor of their responsibility to locate all buried utilities in the

project area, including drainage tile and other structural measures. The landowner is also required to

obtain all necessary permits for project installation prior to construction. 

Safety 

Include appropriate safety features in the design to minimize the hazards of the facility. Provide warning

signs, fences, ladders, ropes, bars, rails, and other devices, as appropriate, to ensure the safety of

humans and livestock. Ensure that proper ventilation and adequate warning signage is provided for waste

separation equipment in an enclosed facility or confined area, as necessary, to prevent explosion,

poisoning, or asphyxiation. 
Location 

Position the waste separation facility so the waste stream can be safely routed to and from the facility.

Locate facilities outside the 100-year floodplain unless site restrictions require locating it within the

floodplain. If located in the floodplain, protect the facility from inundation or damage from a 25-year flood

event. Additionally, follow the policy found in the NRCS General Manual (GM) (Title 190), Part 410,

Subpart B, Section 410.25, “Flood Plain Management,” which may require providing additional protection

for structures located within the floodplain. 

Waste separator selection 

Base the type of waste separator, whether mechanical or nonmechanical, on site-specific data for the

waste stream and management conditions. A combination of separation unit processes may be necessary

to achieve the desired or required results. NRCS National Engineering Handbook (NEH) (Title 210), Part

637, Chapter 4, “Solid-Liquid Separation Alternatives for Manure Handling and Treatment,” provides

guidance on different types of solid/liquid separators available. Capture efficiency varies widely for each

type of separator depending on the type and consistency of the waste to be treated. 

Separation efficiency 

Base the volume or percentage of solids separated on estimates of daily waste water production, if

applicable, and the total solids capture efficiency for the type of separation device selected. Where

manufacturer information or local data concerning total solids capture efficiencies are not available for the

type of waste separation device selected, the efficiencies in 210-NEH-637-4 can be used to estimate the

amount of separated material that will be generated. 

Chemical amendments 

Chemical amendments, such as metal salts and polymers, can be used to treat manure to enhance the

separation process. The addition of chemicals to the liquid waste stream for improving total solids capture

efficiencies must be in accordance with manufacturer’s guidelines and requirements. 

Storage or treatment of separated solids 

Provide adequate storage for separated solids unless they are transported directly from the separator to

the final utilization location. Base the design for solid storage on the requirements in NRCS Conservation

Practice Standard (CPS) Waste Storage Facility (Code 313). 

Design treatment facilities in accordance with the appropriate practice standard for the treatment process,

such as NRCS CPS Composting Facility (Code 317) or other needed practice standards. 

Discharges 

Capture any discharge or runoff from the waste separation facility, the temporary solid or sand storage

area, or associated appurtenances in a waste storage or treatment structure. 

Conveyance system 

Design waste transfer components in accordance with requirements of NRCS CPS Waste Transfer (Code

634). 

Outlets 

Provide adequate outlet capacity for the waste separation facility to safely convey the design load to a

storage or utilization location. 

Outlets may include pipelines, perforated or slotted pipe risers, porous plank walls or dams, or screened

walls. Provide at least 10 percent open area for screening used to separate solids at the outlet of settling

basins. 

Use emergency overflow appurtenances, such as notched weirs, or pipe bypasses to control flows

exceeding design capacity. For separation facilities exposed to precipitation, design emergency overflow

appurtenances to pass and contain the contaminated runoff from the drainage area of the facility for a 25-

year 24-hour storm frequency plus the normal waste stream discharge. 

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Mechanical separators 

Manufactured separators are separators such as screen separators, centrifuges, hydrocyclones, and

presses (screw or belt type). 

Performance 

The performance of mechanical separators is generally reported for a given throughput or flow rate. If

different flow rates are required, obtain separator efficiencies from the manufacturer. 

Flow rate and velocity 

Follow manufacturer’s recommendations for the design flow rate and liquid waste stream velocity for

filtration and screening devices. 

For proper functioning of mechanical separation equipment, environmental conditions may require roofing

and/or building enclosure. Design roofs for enclosures in accordance with the requirements of NRCS CPS

Roofs and Covers (Code 367). 

Settling basins 

Construct the settling basin with a durable liner such as concrete, geosynthetic material, compacted soil,

or geomembrane liner that is adequate to support cleanout equipment 

Do not use the settling basin to store manure scraped from feedlots or other areas. Additional solid

storage should be used for scraped manure. If needed, leachate from solid storage area may be directed

to the settling basin. 

Velocity 

Do not exceed 1.5 feet per second liquid waste stream flow velocity through settling basins. 

Depth 

Provide sufficient depth for solid and liquid storage and for the depth of influent flow. Include a minimum of

1 foot freeboard. 

Base the minimum volume of the settling basin on a hydraulic retention time of at least 30 minutes. 

Bottom width 

Base the minimum bottom width for the settling basin on the cleanout equipment used, but not less than 4

feet. 

Access 

Establish the minimum top width of earthen embankments for settling basins at 15 feet when equipment

access is needed for cleanout. Where access to the settling basin is not required for cleanout, base the

minimum top width on the equipment used to construct the embankment or berm, but not less than 4 feet. 

Construct the side slopes of earthen embankments no steeper than 2 horizontal to 1 vertical (2:1). For

earthen embankments greater than 3 feet in height, construct the side slopes no steeper than 3:1 on the

outside and 2:1 on the inside of the embankment. 

Design access ramps to allow entry into the basin for cleanout by normal loading equipment at no steeper

than 10:1. Steeper access ramps are acceptable where special surfacing of the ramp is provided for

traction purposes and the equipment used can accommodate the increased slope, but no steeper than

4:1. 

Settling basins receiving lot runoff 

Settling basins used with or without screening to remove solids from process-generated liquid waste

streams (i.e., flush water from covered freestall barns or milking parlor waste water) that include

significant external drainage fall into this category. 

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Flow rate 

Base the minimum design flow rate for a settling basin that receives lot runoff on the normal liquid waste

stream from the operation plus the peak runoff from the 10-year 1-hour storm from the drainage area of

the basin. 

Volume 

Base the design volume for settling basins receiving lot runoff on the total depth needed for liquid and

solids storage and the minimum surface area required for the basin. Where no specific information is

available on sludge accumulation rates from lot surfaces, use 0.05 cubic feet per square foot of surface

area per month for unpaved lots and 0.01 cubic feet per square foot of surface area per month for paved

lots. Increase these values by 50 percent if lots are steep or poorly maintained. The minimum solids

accumulation storage period is 1 month. 

Settling basins that exclude lot runoff 

Settling basins used with or without screening to remove solids from process generated liquid waste

streams (i.e., flush water from covered freestall barns or milking parlor waste water) and do not receive

significant external drainage fall into this category. 

Flow rate 

Design the capacity for a settling basin that excludes lot runoff on the normal liquid waste stream from the

operation. 

Volume 

Base the design volume for settling basins that exclude lot runoff on the volume needed to provide solids

storage for a specified treatment period plus temporary liquid storage necessary during dewatering. Use a

minimum temporary liquid storage based on the volume of the liquid waste stream for 1 day. 

Sand separation and reuse 

Separation processes that remove sand from water and organic material fall into this category. 

Dilution 

Provide adequate dilution water for sand-laden manure to keep organic solids in suspension for proper

sand separation. Use a minimum water to sand-laden manure dilution ratio of 2:1 (volume basis). 

Capacity 

Design the system to provide adequate capacity to handle the required manure and sand loadings. 

Sand storage 

Provide storage of separated sand to allow additional time for liquid to drain from the sand. Collect the

drainage and route it back into the waste handling stream. 

Nonmechanical sand separation and reuse 

Sand separation techniques that rely on the velocity of the waste stream to settle out sand fall into this

category. 

Velocity 

Design the waste stream velocity between 1 and 2 feet per second. Base the flow velocity on the sitespecific sand gradation curve. 

Include a transition area between flush system or waste transfer system and the sand lane that will lower

the velocity to the design waste stream velocity that will allow the sand to settle out. Size sand lane outlets

large enough to prevent flow constriction that will cause excessive settling of organic solids. 

Volume 

Provide a minimum settling area storage volume based on the maximum time between cleanouts. Design

the bottom width to be compatible with the removal equipment, but not less than 8 feet. 

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Hydraulic retention time 

Design the hydraulic retention time of at least 3 minutes and not more than 5 minutes. Make adjustments

using the site-specific sand gradation curve. 

CONSIDERATIONS 

General Considerations 

Location 

When locating waste separation facilities, consider elevation and distance from the source of material to

be separated and the location of long-term liquid and solid waste storage facilities. Take advantage of

gravity flow wherever possible. Other considerations for locating waste separation facilities include vehicle

access, proximity to wells, wind direction, neighboring dwellings, proximity of streams and floodplains,

required setback distances, and visibility. 

Biosecurity 

Consider how waste separation facilities and the disposal of waste products will affect the biosecurity for

the farm and neighboring areas. 

Weeping walls 

To maximize drainage and solid-liquid separation, install weeping walls around the entire perimeter of the

waste to be treated and maintain drainage paths to and through the walls. Consider waste particle size,

particle size distribution, and length of flow paths when selecting screen opening size and spacing. Ensure

drainage is transferred to a liquid storage facility. 

Sand bedding 

When sand bedding is reused, select uniformly sized sand to improve separation efficiency. 

Solid/solid separation 

When separating poultry litter into fine and coarse fractions, a higher percentage of the nutrients are

partitioned with the fine fraction. The coarse material, consisting mostly of shavings and feathers, has a

lower nutrient content and can be reused as bedding or as an energy source. 

Visual screening 

Consider using vegetative screens or other methods to shield waste separation facilities from public view

for aesthetics. 

Precipitation 

Rainfall on the solids storage areas associated with waste separation facilities can result in increased

waste water discharge into the long-term storage facility. Consider covering solids storage facilities in high

precipitation areas. 

Sand system abrasion resistance 

Where sand is a major component of the liquid waste stream, consider the use of abrasion-resistant waste

transfer piping and pumps to increase the useful life and reduce frequency of repairs. 

PLANS AND SPECIFICATIONS 

Prepare plans and specifications that describe the requirements for applying the practice according to this

standard. As a minimum, the plans and specifications will include— 

• Plan view of the waste separation facility showing the entire waste management system, including

waste production facilities, waste collection points, waste transfer pipelines, waste treatment,

storage facilities, and related appurtenances. 

• Location of all inflow and discharge structures with a description of materials, sizing, profiles, and

critical elevations. 

• Detail drawings for all components to be constructed. 

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• Details of support systems for manufactured waste separation devices. 

• Fencing and signage as appropriate for safety purposes. 

• Written specifications describing installation requirements and operating characteristics, such as

design flow, volume, and/or retention time. 

OPERATION AND MAINTENANCE 

Develop and review an operation and maintenance (O&M) plan with the owner and operator prior to

constructing the waste separation facility. Ensure that the O&M plan is consistent with the purposes of the

waste separation device chosen, its intended life, safety requirements, and the criteria for its design. As a

minimum, include— 

• A description of the normal operation of the facility, safety issues, and normal maintenance items to

ensure that the owner and operator understand the level of O&M required for the separator to

operate as intended. 

• Operation instructions for any manufactured waste separation devices. 

• Alternative operation procedures in the event of equipment failure or other emergency. 

• Daily and/or periodic inspection of— 

• Separation device and support structure. 

• Screens and outlets. 

• Remaining capacity in storage facilities. 

REFERENCES 

Burns, R.T. and L.B. Moody. 2003. Development of a Standard Method for Testing Mechanical Manure

Solids Separators. American Society of Agricultural Engineers – CIGR Meeting Paper No. 034131.

American Society of Agricultural and Biological Engineers. St. Joseph, MI. 

Ford, M. and R. Fleming. 2002. Mechanical Solid-Liquid Separation of Livestock Manure Literature

Review. Ridgetown College – University of Guelph, Ridgetown. Ontario, Canada. 

Manure Management System Series – Outdoor Air Quality. 2002. MidWest Plan Services Handbook 18,

Section 3. MidWest Plan Service, Iowa State University. Ames, IA. 

Mukhtar, S., J.M. Sweeten, and B.W. Auvermann. 1999. Solid-Liquid Separation of Animal Manure and

Wastewater. Texas A&M AgriLife Extension Service. College Station, TX. 

Livestock and Poultry Environmental Learning Community. 2019. “Solid-Liquid Manure Separation.”

Accessed May 20, 2021. https://lpelc.org/solid-liquid-manure-separation/

USDA NRCS. 2019. National Engineering Handbook (Title 210), Part 637, Chapter 4, Solid-Liquid

Separation Alternatives for Manure Handling and Treatment. Washington, D.C.

https://directives.sc.egov.usda.gov/

USDA NRCS. 2012. National Engineering Handbook (Title 210), Part 651, Agricultural Waste

Management Field Handbook. Washington, D.C. https://directives.sc.egov.usda.gov/

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