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, tysontw@auburn.edu and Saqib Mukhtar, Texas A&M University, mukhtar@tamu.edu .

Liquid Manure Collection and Handling Systems

Handling and storage of liquid manure requires planning and consideration of the best fit for the entire system. Below are some descriptions of common liquid manure systems.

Systems Which Produce Liquid Manure

Liquid manure containing 5 percent solids or less generally results from the addition of washwater or rainwater to manure. Examples of liquid manure sources include lagoons, holding ponds and dairy parlor washwater.

Flush Systems

A typical example of a collection system resulting in liquid manure is the flush removal of manure from a dairy freestall barn. In this scenario dilute lagoon wastewater is pumped into flush tanks which in turn release the water into freestall alleys to wash the manure to the lagoon.

Flush water released into dairy freestall alleys dilutes manure and washes it to the lagoon.

Open Lots

Another form of dilute or liquid manure is runoff from lot surfaces. In these cases, most of the manure solids remain on the lot, or are removed by solids separation devices prior to a lagoon or holding pond that receives the runoff. The runoff then contains primarily fine suspended or dissolved solids that result in dilute liquid in the receiving basin.

Runoff holding ponds for beef feedlots typically contain dilute wastewater with less than 5% solids.

Equipment for Liquid Manure Handling

Liquid manure (less than 5% solids) is less difficult to handle hydraulically with pumps and pipes than the thicker slurry-type manure. Equipment designed to handle irrigation water is often suitable for handling the dilute wastewater found in liquid manure systems. However, operators often elect to use the same pumping and handling equipment for liquid manure as for slurry manure. This practice provides for the possible need to handle manure that may be occasionally thicker than anticipated and reduces the likelihood of plugging.

Irrigation

Conventional irrigation equipment may be suitable for handling dilute manure from certain lagoons or runoff holding ponds when the likelihood of encountering solids at problem levels is remote. In these cases, pumps designed for irrigation (typically more efficient than slurry manure pumps) will usually be acceptable for handling the wastewater.

Conventional irrigation pumps can handle manure wastewater with limited solids content.

Conventional irrigation application equipment can also be used to land apply dilute manure wastewater if solids levels are low enough to preclude plugging nozzles and orifices. Traveling guns have been used for many years for surface application of effluent from lagoons and runoff holding ponds. Traveling guns are applicable to small and irregular fields and thus find acceptance in areas where crop fields may be limited in size by terrain, timber or property boundaries. Center pivot systems are also able to handle dilute wastewater and are applicable where fields tend to be larger and reduced labor for land application is desired.

This traveling gun applies dilute manure wastewater to a growing crop as it travels across the field.

Center pivot irrigators can apply dilute manure wastewater with low labor input.

For additional information, see Liquid Manure Application and Irrigation Equipment

Authors: Charles Fulhage, University of Missouri, and Joe Harner, Kansas State University

Photos: CC 2.5 Charles Fulhage or Joe Harner

Liquid Manure Application and Irrigation Equipment

Liquid manure application to crop land

Direct injection of liquid animal manure
Direct injection of liquid animal manure

Liquid animal manure is land applied using liquid manure tankers or irrigation equipment. Liquid manure tanks are frequently pulled, much like a wagon, behind a tractor or mounted on a truck or other power source. Pull type tanks range in size from less than 1,000 gallons to over 8,000 gallons. Those that are mounted on a truck are generally between 3,000 and 6,000 gallons. Truck mounted tankers make over the road travel quicker and safer.

Drag-line direct injection of animal manure
Drag-line direct injection of animal manure

Liquid manure tankers generally discharge manure from the rear of the tank on the soil surface. Alternatively, various types of soil incorporation tools may be used and are generally mounted directly to the tanker. Manure from the tank is distributed through a series of hoses and discharges through the soil incorporation tool. Soil incorporation of liquid animal manure can minimize odors and conserve nutrients.

Irrigation of wastewater by hard hose traveling gun
Irrigation of wastewater by hard hose traveling gun

Land applications by sprinkler irrigation or by a drag-hose, tractor-mounted applicator are the current practical methods of applying large volumes of lagoon effluent or contained lot runoff. Drag-hose applicators can decrease odor problems and the loss of ammonia nitrogen to the air by incorporating the manure. The advantages of sprinkler irrigation include reduced cost because of lower energy and labor requirements.

Lagoon wastewater applied by pivot irrigation for hay production
Lagoon wastewater applied by pivot irrigation for hay production

Labor requirements can be further reduced by permanently installed underground pipes to sprinkler risers, center-pivot irrigators or hose attachment points for traveling guns or drag-hose applicators. However, land application of manure slurry and lagoon effluent with irrigation equipment requires a higher level of management than other methods of spreading to avoid pollution and nuisance problems.

Recommended Reading on Liquid Manure Application and Irrigation Equipment

Authors: Jon Rausch, Ohio State University and Ted Tyson, Auburn University

Costs of Liquid Manure Application and Transport

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What Systems Produce Liquid Manure?

Liquid manures are most common with pork production where the manure is flushed from the building and stored outside in lagoons. Liquid manures are mostly water with some organic matter and nutrients suspended in the water. Most of the organic matter decomposes in the lagoons and is not removed.

Options to Haul and Apply Liquid Manure

While some livestock producers haul liquid manure in tankers, it is usually considered cost prohibitive. The amount of water is so great that the hours spent distributing it and the resulting dollar cost exceeds the value of the manure supplied nutrients when using tankers.

Liquid manure is usually pumped through pipes and hoses to the land that will be accepting the manure. This means that loading costs and transportation costs are relatively low. Once the manure is at the field, it can be applied with a tractor that pulls the dragline hose through the field or via an irrigation system. The irrigation system can be a stationary sprinkler or a single big gun sprinkler that must be moved periodically by the operator.

Liquid manure can be land applied with a dragline hose.

Other options include, a big gun sprinkler or a center pivot irrigation system that move automatically through the field. The center pivot irrigation system is usually too expensive to own just for liquid manure distribution; it is usually part of an irrigation system that also pumps clean water. The stationary and big gun sprinklers are inexpensive and easy to use.

Authors: Ray Massey, University of Missouri and Josh Payne, Oklahoma State University

On-Farm Nutrient Management Research: Replacing Commercial Sidedress Nitrogen with Liquid Livestock Manure on Emerged Corn

This webinar highlights the on-farm research that has been done and is being planned in the state of Ohio to capitalize on the opportunity to apply in-season nutrients with manure application. This presentation was originally broadcast on May 19, 2017. More… Continue reading “On-Farm Nutrient Management Research: Replacing Commercial Sidedress Nitrogen with Liquid Livestock Manure on Emerged Corn”