Liquid Manure Storage Treatment Options, Including Lagoons

A vital component of liquid livestock and poultry manure collection and handling systems is storage capacity for the collected manure and associated material(flush water, wasted feed, etc.). This manure storage capacity is typically in the form of under-floor pits or outside storage tanks or ponds and/or treatment lagoons. These structures accumulate collected wastes and allow the waste management system operator to move away from a “daily scrape (collect) and haul” situation. This reduces time and labor needed for final disposition (either land application or off-farm “value-added” processing) of these manure accumulations.

What Is a Liquid Manure System?

“Liquid” livestock manure collection and handling systems are actually “fluid” livestock manure collection and handling systems. These systems are selected based upon the consistency or “thickness” of the manure and its flow characteristics. Manure flow characteristics are highly dependent on “solids content” or “percent solids” of the manure volume.

Liquid manure storage volume size depends on the amount of time in a year that is not available for land application or other manure utilization strategies. This is the design storage period. Land application time depends on growing season of the target crop(s) and local weather. Manure storage volume should be emptied by the end of the design storage period to be able to hold the expected amount of manure accumulation during the next storage period.

Earthen storage structure with artificial liner (from Proper Lagoon Management to Reduce Odor and Excessive Sludge Accumulation).

This web page deals with two general categories of liquid systems:

  • Pits or slurry systems for storage only
  • Lagoons with both slurry/wastewater storage and treatment (see National Center White Paper summary, Manure Management Strategies).

Types of Manure

“As-excreted” livestock manure moisture content changes as it moves through the collection process into storage. Liquid collection and handling systems add waste drinking water, wash water, flush water, rain, and stormwater runoff, lowering solids content below the 15% level typically used to define “solid” manure. A manure volume of 5 to 15% solids is “slurry” manure, with consistency and flow characteristics similar to thick chocolate malt. Manure volumes with 0 to 5% solids content have consistency and flow characteristics similar to water.

What Is the Difference Between Storage and Storage With Treatment?

Contrasting storage and storage w/treatment, a manure containment structure which is emptied at the end of the storage period is essentially a storage structure. A lagoon has storage volume but will also have a permanent pool for residual treatment volume that provides a bacterial seed bed for continual bacterial action at an elevated level. This permanent pool is not considered in the design of a structure used for storage alone. Essentially whatever goes into a properly managed storage structure is what is pumped out. A lagoon, however, is designed to promote decomposition of organic matter entering the lagoon. For this reason, a lagoon is much larger than a storage pond.

Management of Lagoons

A manure containment structure which is not emptied at the end of the storage period is being operated as a lagoon, whether designed that way or not. Storage operated in this manner becomes a smelly, overloaded lagoon. Generally, when agitation is used to put settled or floating solids into suspension before pumping out the effluent, or the slurry, the structure is being operated as storage.

Digested solids do accumulate in a lagoon and should be removed once every ten or more years, or as specified by the system design to restore residual treatment volume. In rare circumstances, particular to specific lagoons approaching this restoration point, some engineers recommend some agitation during normal pumpout to remove some of this accumulation. Routine pumping from the storage volume portion of a lagoon involves only wastewater (<5% solids) and requires no agitation.

Related Web Pages

Recommended Educational Resources

National Center for Manure and Animal Waste Management white paper summary, Manure Management Strategies published by North Carolina State University. A two page Executive Summary is available. The full white paper can be ordered from Midwest Plan Service, Iowa State University.

Page Managers: Ted Tyson, Auburn University, and Saqib Mukhtar, Texas A&M University, .

Liquid Manure Treatment Lagoons

There are many options for the handling and storage of liquid manure. This page describes and differentiates some of the most common systems.

Anaerobic Treatment Lagoons Compared to Aerobic Lagoons and Storage Ponds

Most agricultural treatment lagoons are anaerobic lagoons. Anaerobic lagoons are earthen structures, which look at first glance like farm ponds. These lagoons are designed to provide biological treatment and long term storage of animal waste. Anaerobic lagoons are larger than manure storage basins, which do not provide significant biological treatment or long storage periods, but smaller than aerobic lagoons. Even though aerobic lagoons are designed to provide a higher degree of treatment with fewer odors, anaerobic lagoons decompose more organic matter per unit volume. Because of their treatment and storage capabilities anaerobic lagoons are a good compromise between storage basins and aerobic lagoons.

Anaerobic treatment of waste occurs without free oxygen to liquefy or degrade high BOD (biochemical oxygen demand) organic waste. With proper design and management the anaerobic lagoon can function for years. Odor from a well-designed and well-managed lagoon will be only slightly musty; foul odor indicates a malfunction requiring corrective action.

Advantages of Anaerobic Lagoons

Advantages of anaerobic lagoon systems are: manure can be handled with water flushing systems, sewer lines, pumps, and irrigation equipment; the high degree of stabilization reduces odors during land application; high nitrogen reduction minimizes the land area required for liquid effluent disposal, and long-term storage is provided at low cost.

Disadvantages of Anaerobic Lagoons

Disadvantages of anaerobic lagoons include: public perception that a lagoon is an open container of manure; offensive odors if improperly designed and maintained, and limited nitrogen availability if manure is used as a fertilizer. Lagoon design is based on the manure volume produced by the animals, plus any wash down water or wasted feed. An impoundment outside in the weather must also have space for runoff which may enter the impoundment, and rainfall less evaporation, that will occur over the storage area. Additional space for a 25-year 24-hour rainfall event and required freeboard is also necessary. Lagoons must have volume for all of the above plus the minimum pool or treatment volume to allow biological degradation, and in some cases, volume for sludge accumulation.




Figure 1. Single stage lagoon capacity Figure 2. Two-stage lagoon capacity

Contributed to eXtension CC2.5


Although emergency spillways as shown in the accompanying figures have the purpose of protecting embankments from overtopping and washing away during emergency weather situations (hurricanes, etc.), some states (i.e., Arkansas, at this writing) do not include these structures in lagoon and storage pond design requirements to save on construction costs.

Lagoons have been used extensively to treat swine manure and store wastewater prior to land application using normal irrigation equipment, Lagoon Design and Management for Livestock Waste Treatment and Storage.


Lagoon level gauge marker.jpg


Recommended Educational Resources

Research Summaries

National Center for Manure and Animal Waste Management white paper summary, “Manure Management Strategies” published by North Carolina State University. A two page Executive Summary is available. The full white paper can be ordered from MWPS, Iowa State University.

Page Managers: Ted Tyson, Auburn University, and Saqib Mukhtar, Texas A&M University, .

Role of Solid Liquid Separation in Manure Storage

There are benefits for manure storage systems in separating manure into solid and liquid components. Solid-liquid manure separation is also a desirable first step in many systems used for manure treatment (composting, anaerobic digestion, etc.)

Solids Accumulation

Waste solids, particularly those from dairy freestall housing bedding, can accumulate quickly in waste storage ponds. Solids accumulation requires longer, more thorough agitation at pump out time to re-suspend settled solids and special manure solids handling “chopper” pumps for transfer to tanker wagons or waste slurry irrigation systems.

Solids can cause pumping problems, and over time can greatly reduce usable storage pond volume. Serious consideration is usually given to the installation of solids separation equipment between animal housing, particularly dairy freestall barns, and the waste storage pond.

Mechanical separators are typically either rotating or stationary screens and generally remove 20 to 30 percent of the waste solids. These separators require little attention although operation in freezing weather requires special considerations. They produce manure solids that may be easily recycled as bedding or land applied off-farm with solid manure spreaders.

vibrating screen separator conveyor inclined screen separator typical two-cell settling basin

Settling Basins

Properly designed gravity settling basins can remove up to 50 percent of the waste solids but need enough elevation between the barn collection channel bottom and the maximum storage pond liquid surface height for installation of the settling basin and associated minimum 1% slope gravity in/out transfer lines. Gravity settling basins require periodic cleaning out with a tractor front end loader and work best when at least two are constructed side by side to allow alternating use and some manure solids drying out before cleaning.

Separated solids can be handled by conventional manure solids handling equipment. These nutrient-rich solids can be spread on distant fields and pastures as fertilizer and soil amendments, or sold for horticultural uses, with or without composting. Removing solids that retain their nutrients can help reduce nutrient loading on nearby fields, which are often irrigated from storage ponds or lagoons during the periodic pump outs required for proper management.

Related Web Pages

Page Managers: Ted Tyson, Auburn University, and Saqib Mukhtar, Texas A&M University, .